Centre for Earth Observation Science, Geography Department, University of Manitoba, Winnipeg,. Manitoba, Canada R3T 2N2; Current address: IUCN-ROSA ...
Biodiversity and Conservation 11: 1327–1359, 2002. 2002 Kluwer Academic Publishers. Printed in the Netherlands.
Contribution by farmers’ survival strategies to soil erosion in the Linthipe River Catchment: implications for biodiversity conservation in Lake Malawi / Nyasa F.X. MKANDA Centre for Earth Observation Science, Geography Department, University of Manitoba, Winnipeg, Manitoba, Canada R3 T 2 N2; Current address: IUCN-ROSA ( International Union for the Conservation of Nature–Regional Office for Southern Africa), 6 Lanark Road, Belgravia, P.O. Box 745, Harare, Zimbabwe (e-mail: francism@ iucnrosa.org.zw; fax: 1263 -4 -720738) Received 24 November 2000; accepted in revised form 27 July 2001
Key words: Agriculture, Biodiversity, Contribution, Erosion, Implications, Survival Abstract. Sediment discharge into Lake Malawi is threatening its ecological importance, thereby inflicting serious socio-economic consequences upon people dependent on this ecosystem. The discharge is attributed to high rates of erosion in the Lake’s catchment, principally occurring on agricultural land. This study examines how survival strategies, such as expansion of cultivated farmland and use of low fertilizer application rates, enhance the likelihood of erosion in the Linthipe River Catchment – one of the Lake’s important river catchments. As such, it shows that the magnitude of erosion is significantly correlated to the amount of farmland cultivated by estate farmers and smallholders (r 5 0.18, P 5 0.03, and r 5 0.19, P 5 0.003 respectively). The low correlation coefficients uphold the long-established fact that physical variables such as soil erodibility (vulnerability of soil to erosion), rainfall erosivity (the potential of rainfall to cause erosion), and topography, also play major roles in erosion processes. Nonetheless they do show that area of cultivated land contributes to erosion. Additionally, the study shows that yields of important crops such as maize and tobacco are low because of insufficient use of fertilizers. To compensate for the low yields, farmers rely on extending sizes of land that they cultivate thereby exposing more land to erosive forces of rainfall. The study, therefore, concludes that Lake Malawi’s biodiversity is under threat. In order to sustain the biodiversity, it is necessary to eliminate the need to increase farmland by means of agricultural intensification that incorporates appropriate soilconservation measures.
Introduction The Lake Malawi Biodiversity Conservation Project (LMBCP)1 seeks to understand the relationships between agricultural practises, soil conservation, erosion, sedimentation and associated downstream effects of sediments on fish communities of Lake Malawi / Nyasa (hereafter referred to as Lake Malawi). The purpose is to develop a management strategy (Ribbink and Barber 1996, p. 7), a necessity that is 1 The project involved the three riparian states, namely: Malawi, Tanzania, and Mozambique with development of a biodiversity atlas, a fish identification guide, and a management strategy as principal objectives. To this end, the project conducted taxonomical, ecological, limnological, and geographical (including this one) studies.
1328 underpinned by three compelling reasons. First, Lake Malawi (Figure 1) is one of the richest and most diverse in terms of fish species in the world (Hecky 1993). There are over 600 fish species, 99% of which are endemic, suggesting that speciation took place within the Lake (Ribbink 1994). Furthermore, Cohen et al. (1996, p. 580) have claimed that the Lake’s endemic species represent hotspots of biodiversity for the planet, and as such, play an important role in understanding evolutionary processes. Secondly, fish provide nearly 75% of the animal protein intake by Malawians (Ribbink 1994), while fishing is a significant source of employment to 32 000 fishers and 200 000 fish-processors and mongers (Munthali 1997). Thirdly, the Lake has a thriving ornamental fish trade that in 1988 accounted for 66% of the earnings from fish export (Malawi Government 1988, p. 100). This trade has been, and continues to be, a source of foreign exchange. Undoubtedly, the Lake is an ecological and socio-economic asset for Malawi, Mozambique and Tanzania; one that must be conserved not only for the benefit of the people who depend upon it, but for the scientific community to investigate thoroughly. This important resource, however, is under pressure from over-fishing and impacts of sediments that emanate from the Lake’s catchment (Bootsma and Hecky 1993; Hecky 1993; Munthali 1997). Previous work has estimated that up to 143.2 g m 22 (Kingdon et al. 1999, p. 52) or about 4.97 t ha 21 yr 21 of suspended sediments are being discharged into Lake Malawi. The fate of a pollutant entering a lake depends on a variety of processes including degradation, sedimentation, volatilisation, resuspension, and flushing (Bootsma and Hecky 1993). The relative importance of each process depends on the nature of the pollutant and physico-chemical conditions, but flushing rate is the dominant factor (Bootsma and Hecky 1993). In the case of Lake Malawi, the flushing time is about 750 years (Bootsma and Hecky 1993), which implies that sediments progressively accumulate before being removed. Although the effect of sediment on the aquatic environment of Lake Malawi is not yet fully understood, evidence of sediment impacts on fish habitats provides a basis for the concern about sustainability of biodiversity. Suspended sediments cause turbidity, thereby limiting penetration of light, which is essential for primary productivity (Bootsma and Hecky 1999, p. 1). Actually, a decline in rock-algae production has been observed where sediments cover the rock sub-stratum in the Lake (Munthali 1997). Generally, the temporal effect of such a decline is disruption of the littoral food web (Worthington and Lowe-McConnell 1994). Additionally, sediments seal holes in which most of the rock-dwelling cichlids such as the ‘Mbuna’, that comprise almost 50% of all fish species in the Lake, breed (Reinthal 1993; Munthali 1997). Therefore sedimentation is having a negative effect on the feeding and breeding behaviour of the fishes in the Lake. Furthermore, large silt loads that are washed down from cultivated steep marginal lands and catchment areas after heavy rains have destroyed habitats of gravel spawners (Tweddle 1992). Consequently, most of the popular fish species found in the rivers and streams of the Lake Malawi catchment are in decline, for example Opsaridium microlepis, O. microcephalus, Barbus johnstoni, B. eurystomus, B. litamba and Labeo mesops. Since fish communities of Lake Malawi are predominantly in habitats such as rocky
1329
Figure 1. Lake Malawi Catchment showing major riverine inflows, and the Linthipe River including administrative headquarters of districts and Agricultural Development Divisions covered by the catchment (Environmental System Research Institute 1999).
1330 zones, vegetated areas, and open waters near the shore (Ribbink 1994), they are inevitably impacted by the high rates of sediment discharge because these habitats are frequently near the mouths of rivers. Agriculture as a sediment source Erosion potential in the catchment of Lake Malawi derives from its steep topography (Kettlewell 1965) and erosive rainfall (Malawi Government 1974, p. 1-6). The intrinsic potential, however, is accelerated by human activities such as deforestation and agriculture. The decline in forested area associated exclusively with agricultural clearing for the past 50 years or more has been 1.5% per annum (Orr et al. 1998, pp. 28 and 29). Agriculture is the backbone of Malawi’s economy and the mainstay of the population (Sahn and Arulpragasam 1991). It comprises about 33–45% of the nation’s gross domestic product (GDP), employs 80% of the labour force, and generates 90% of export earnings (Food and Agricultural Organisation 2000; World Bank Group 2000). Agriculture’s prominence in Malawi’s economy is further illustrated by the amount of land under estate and customary tenure (7.43 million ha out of the total 9.4 million), the balance being occupied by protected areas, cities and other urban areas (Orr et al. 1998, p. 19). Agricultural systems in Malawi are characterized by smallholder and estate farming, which are distinguished by land tenure, cropping emphasis, and size of holdings (World Bank 1991, p. 10). Smallholder farming provides 70% of domestic food production (World Bank Group 2000). This category of farming is undertaken on land that is held, used, or occupied under customary law (Mkandawire et al. 1990, p. 8), and its nomenclature is associated with communal type of tenure. According to Lorkeers and Venema (1991, p. 54), smallholder farming can be subdivided into three groups according to holding sizes (,0.7, 0.7–1.5, and .1.5 ha) and related socio-economic aspects. In general, smallholders grow subsistence food crops, especially maize (Zea mays), and depend on off-farm cash income, but some of them grow cash crops such as tobacco (Nicotiana tabaccum). Estate farming, on the other hand, is principally concerned with tobacco (N. tabaccum), tea (Camellia sinensis), and sugar production (World Bank 1991, p. 11). It provides about 90% of the export trade (Malawi Agroforestry Extension Project 1995, p. 3). Estate farmers also grow maize (Z. mays) as a food crop for labourers (Lorkeers and Venema 1991, p. 61). This farming system is exemplified primarily by leasehold tenure (World Bank 1991, p. 11) and larger holdings than those owned by smallholders. Mkandawire et al. (1990, p. 15) classified the estate sub-sector as small-scale estates (,30.0 ha), medium-scale (30.0–100.0 ha), and large-scale (.100.0 ha). Both farming systems contribute to soil erosion because of several sub-optimal land use practices that include improper alignment of contour ridges, and failure to control gully formation (World Bank 1991, p. 12). Among estate farmers, suboptimal practices are common among the new group that emerged in the 1970s when about 1.1 million ha were converted from customary land into leasehold
1331 estates because the latter were viewed as a potentially more reliable source of growth and revenues than smallholder agriculture (Mkandawire et al. 1990, p. 18). In fact the Malawi Government (1998, p. 33) states that despite intensive campaigns, only about 12% of the cultivated land in Malawi can be said to have true ridges on contours. Aggregate soil loss on arable land in Malawi is in the order of 20 t ha 21 yr 21 (World Bank 1991, p. i), while rates as low as 0.03 t ha 21 yr 21 have been observed under Eucalyptus plantation (White 1988). This rate of soil loss from arable land is almost two times higher than the maximum permissible limit of approximately 5 acre 21 yr 21 or 12.7 t ha 21 yr 21 , which is balanced by the rate of soil formation from below (Shaxson 1970). Soil is therefore being removed by erosion at a faster rate than that of soil formation, thereby undermining the longterm sustainability of agriculture and, at the same time, of aquatic biodiversity. Although economic growth in Malawi is contingent on increasing agricultural production, yields of both its staple crop, maize (Z. mays) and export cash crop, tobacco (N. tabaccum) are lower than their estimated potentials. For instance, the average yields of local and hybrid maize are 1.3 and 3.0 t ha 21 respectively, in contrast to the government-proclaimed potential outputs of 3.0 and 8.0 t ha 21 for these varieties assuming farmers adhere to recommended farming practices (Malawi Government 1992, p. 41)2 . Potential yield of burley tobacco, which is most commonly grown in Malawi, is 4 t ha 21 , yet the average yield is approximately 1.5 t ha 21 (Malawi Government 1992, p. 41). To achieve their farming goals, which are food sufficiency and profit optimization, farmers have to cultivate additional land. Chipande (1988, p. 166) reported that the annual growth rates of 1 and 11.1% attained in the agricultural sector by smallholders and estate farmers between 1964 and 1978 were more a result of expanding the area of cultivation than intensifying production. This practice inevitably involves cultivating land of marginal quality, invariably with steep slopes. Once under cultivation, these steep slopes are prone to high rates of erosion (Cohen et al. 1996, p. 578). It is common knowledge that steep land is potentially more vulnerable to water erosion than flat land for the obvious reason that erosive forces such as splash, scour, and transport, all have a greater effect on steep slopes (Hudson 1995, p. 98). Consequently, there is markedly greater erosion on slopes of 5–10% compared to erosion on gentler slopes (Evans 1980, p. 122). The Ministry of Agriculture advocates use of various conservation measures to address the soil-erosion problem. The measures fall into four categories: agronomic practices; land-use planning; soil management; and mechanical measures (Malawi Government 1974, p. 2-1; 1998, p. 33). The fact that rates of soil loss in the catchment and the ensuing sediment discharges into Lake Malawi are high is evidence that erosion continues, notwithstanding this variety of soil-conservation options. With such high rates of erosion and sediment discharge, the need for study and conservation is as pressing as the severity of the problem. In view of the situation described above, this study examines the hypothesis: that 2 Latest issue of Guide to Agricultural Production made available to the author by staff at the Salima Agricultural Development Division.
1332 although farmers in Malawi recognize soil erosion as a problem, they do not regard soil-conservation measures to be of sufficiently high priority in light of the potency of survival strategies confronting their farming activities, hence there continues to be soil loss from their farms. Its principal focus is to illustrate how expansion of cultivated land into areas of steep gradient and use of low fertilizer-application rates, as survival strategies, influence erosion processes in the Linthipe River Catchment – one of the Lake’s important river catchments. Information obtained from this study can be used to develop and implement a more effective soil- and biodiversityconservation strategy.
Study site The Linthipe River Catchment (Figure 2) has an advantage as a study site because it drains a large area (8641 km 2 ) within which there is widespread farming that has resulted in a forest cover of only 30% and surface-runoff rates of 41 m 3 s 21 (Malawi Government 1994, p. 30). Soil loss in the Salima, Kasungu, and Lilongwe agricultural development divisions (ADDs), parts of which lie within the Linthipe catchment area (Figure 1), are 16, 20 and 22 t ha 21 yr 21 respectively (World Bank 1991, p. 13). These soil-loss rates result in a sediment-discharge rate of about 94.4 g m 22 (3.28 t ha 21 yr 21 ) at the river mouth, which is only surpassed by that of the Ruhuhu River (143.2 4 g m 21 or 4.97 t ha 21 yr 21 ) on the Tanzanian side (Kingdon et al. 1999, p. 52). Therefore, the Linthipe is an ideal site in which to investigate what happens to a large catchment when it is extensively utilized for agriculture. Proximity to the LMBCP research station at Senga Bay, Salima also made the Linthipe a logistically convenient study area. Physical characteristics of the Linthipe catchment The Linthipe River catchment can be categorized into five geographic regions (Figure 2) on the basis of landscape, geology, soils, climate, and drainage (Rimmington 1963; Malawi Government 1986, pp. 4.4.4–4.4.6). The regions are: the Dzalanyama Range, Lilongwe Plain, Dowa / Dedza hills, Rift Valley Scarp, and Lakeshore Plain. Elevation ranges from 500 m above mean sea level in the Lakeshore to 1500 m (Dzalanyama). The eastern and central parts of the catchment comprise the Lilongwe Plain, which is undulating with broad marshy valleys. South-western of the Lilongwe Plain is the Dzalanyama Range with high and massive ridges covered by forest reserves. On the east of the Lilongwe Plain are the Dowa / Dedza Hills, with moderate to high relief extending north to south of the catchment. East of this region lie the Rift Valley Scarp, and Lakeshore Plain consecutively. Slope gradient is gentle (1–6%) in the Lilongwe and Lakeshore Plains, moderate to steep (6.1–50%) in the Scarp and Dowa regions (Mkanda and Barber 1999, p. 117). The geology of the Lilongwe Plain, Dowa / Dedza Hills and Scarp regions belongs to the basement complex of Precambrian age, consisting mainly of
1333
Figure 2. Geographic regions of the Linthipe River Catchment, Malawi; regional boundaries are approximate (Rimmington 1963; Malawi Government 1986; Lorkeers and Venema 1991).
undifferentiated paragneisses, schists and granulites. The area along the Lakeshore belongs to the quaternary period with superficial deposits. Soils in the Lilongwe Plain are mostly ferallitic or ferruginous, while lithosols are dominant in the Dzalanyama Range as well as the Scarp region. Soil associations like ferruginous soils and lithosols, then ferallitic soils and lithosols are found in the Dowa and the Dedza Hills. Calcimorphic alluvial soils exist in the Lakeshore plain. Erodibility factors of these dominant soils in the catchment range between 4.5 and 5.5 (Paris 1990, p. 5; Lorkeers and Venema 1991, p. 18; Lorkeers 1992, p. 18). Given that Elwell and Stocking (1982) rated soil erodibility on a scale of 1.0–10, the erodibility factors of the Linthipe catchment soils imply that they are mostly moderately vulnerable to erosion apart from those in the Dzalanyama and Scarp regions. Low erodibility values indicate highly erodible soils (Chakela and Stocking 1988). The greater part of the catchment, mainly the Lilongwe Plain, receives an annual rainfall ranging from 800 to 1000 mm. In the Lakeshore, around the Linthipe river estuary, the rainfall increases up to 1400 mm. The resultant rainfall energy, an important factor in soil-particle detachment and entrainment (Hudson 1995, p. 73), is high; it ranges from 15 000 j m 22 in the Lilongwe Plain to 18 000 j m 22 in the Lakeshore (Mkanda and Barber 1999, p. 117). Most of the catchment’s
1334 drainage system lies in the Lilongwe Plain, the main tributary being the Lilongwe River (Figure 1). Farmer distribution For purposes of distinction, the three categories of smallholders are referred to as smallholder 1, smallholder 2, and smallholder 3, respectively. Farmer distribution (Table 1), that is, more smallholders than estate farmers, is reflective of the general situation in Malawi; by 1991 over 1.6 million families practised smallholder farming (World Bank 1991, p. 10). The number has most likely increased alongside the human population growth of between 2 and 3.7% since 1966 (Malawi Government 2001). To the contrary, estate farmers are a minority. Although the number of estates has also been increasing from 229 in 1970 (Mkandawire et al. 1990, p. 13) to 15 000 farms (World Bank 1991, p. 11), it is likely that smallholders have retained their numerical superiority. The occurrence of more small-scale estate farmers than the other categories of the estate sub-sector is an indication of declining farm sizes since the emergence of the new group of estate farmers. Mkandawire et al. (1990, p. 13) estimated that in 1970 the mean size of states was 345 ha, but by 1989 it had declined to about 26 ha, even after converting over 1.1 million ha from customary land. Causes of the regional variations in the number of farmers, such as most of the smallholders being in the Lakeshore while estate farmers are mainly in the Lilongwe Plain (Table 1), were not examined because an analysis of that kind is beyond the scope of this study. However, it is asserted that catchment relief and concerted efforts on the part of the Malawi Government to promote estate agriculture may have influenced farmer distribution. Catchment relief influences preferences for settlement and agricultural activities in the sense that low relief areas are preferred over steep slopes. Bootsma and Hecky (1993) have stated that catchment basin morphology is one of the major determinants of the potential for human habitation and basin development. While the foregoing explanation may be applicable to the two major farmer Table 1. Distribution of estate farmers by region, Linthipe River catchment, Malawi, 1998. Farmer type
Estate Small Medium Large Total Smallholders 1 2 3 Total
No. of farmers by geographic region
Total
% Total
Dowa
Lakeshore
Lilongwe
Scarp
11 7 4 22
6 0 2 8
51 1 0 52
42 2 0 44
110 10 6 126
87.3 7.9 4.8 100
6 25 37 68
16 32 34 82
2 22 14 38
28 11 7 46
52 90 92 234
22.2 38.5 39.3 100
1335 categories, the market-oriented development economy played a role in the distribution of estate farmers. Kydd and Christiansen (1982) stated that there has been preferential land allocation to estate agriculture because of its importance in terms of export earnings. Individuals and corporations were accorded the opportunity to lease large tracts of land at very little cost, land tax was not imposed, and land rents were set at nominal levels and frequently went unpaid (Mkandawire et al. 1990, p. 18). This preferential allocation, therefore, meant that estate farmers must have chosen any land that suited their requirements irrespective of geographic region, and it partly explains why the Lilongwe Plain, which is one of the most fertile areas in Malawi (Kettlewell 1965), has the highest number of estate farmers.
Methods Survey questionnaire A survey questionnaire, which included reliability questions in order to crosscheck farmers’ responses, was used to examine socio-economic issues of soil erosion in the study area. Variables in this survey fall under four major headings: farmers’ background, farming practises, farm inputs, and farm output. For purposes of verifying the study’s hypothesis, however, only a subset comprising variables such as degree of erosion, erosion-control measures, farm size, fertilizer use, and crop yields is used. Degree of erosion was considered in order to get a scale of the severity of erosion and how it relates to farm size, which for purposes of this paper constitutes cultivated and uncultivated land, and number of fragments occupied by a farmer irrespective of tenure. Fragments are defined as separate pieces of land cultivated by one family or individual. They are a common feature of smallholder farming in Malawi (Rimmington 1963; Kettlewell 1965), hence worth considering because they place additional demand on labour (Edwards 1961, p. 114), which is an essential input in soil conservation (Stocking 1992, p. 213). Erosion-control measures were examined to ascertain the degree to which farmers employed the methods that the Ministry of Agriculture has been advocating since the 1970s when it undertook a major review of its activities including soil-conservation practices (Douglas 1988, p. 217). Farm size was identified because it has been found to be a key variable in explaining the degree of importance farmers attach to soil-conservation programmes (Christensen and Norris 1983). Farmers occupying large holdings were found to be more concerned with soil conservation than those who had small sized holdings. Fertilizers improve soil fertility thereby enhancing plant nutrition, canopy cover, and yield (Shaxson 1970; Malawi Government 1992, p. 24), hence they were considered to find out if farmers followed the application rates recommended by the Ministry of Agriculture. Yields of maize and tobacco crops were assessed to find out if, in the study area, they were indeed lower than their estimated potentials.
1336 In order to reflect the dualism in Malawi’s farming system, the stratified random sampling method was employed so that both categories had equal probability of being sampled (Fowler and Cohen 1992, p. 5; Mead et al. 1993, p. 393). Only four (Dowa, Lilongwe, Scarp, and Lakeshore) of the five geographic regions were used to stratify the study area because the Dzalanyama Range is covered by gazetted forest reserves. Three-hundred-and-sixty farmers, 90 in each region, were subjected to the questions and interviewed in Chichewa, the lingua franca in the area. Before commencing the interview, the purpose of the study was explained to the subjects, and their consent was obtained. All data were acquired directly from farmers’ responses, but farm-size estimates were also provided by agricultural extension workers in cases where farmers did not know the area of land they were cultivating. Erosion assessment The extent of erosion was examined in terms of degree of erosion as perceived by farmers because the large sample size (360 farmers) precluded installation of runoff and sediment collection pits in fields of all farmers. To this end, degree of erosion was scored on an ordinal scale of 1–3, where: 0 5 none, 1 5 low, 2 5 moderate, and 3 5 severe. To validate farmers’ perception of the magnitude of erosion, however, 22 sediment and runoff plots, each one measuring 5 3 5 m, were installed in sub-catchments following the methods used by other authors (Weil 1982; Mwendera and Saleem 1997). In addition, eight control plots were installed in natural vegetation. Each site had a standard rain gauge so that the amount of soil lost could be related to rainfall, besides the other physical factors such as slope and soil characteristics. All plots were bounded with wooden planks (about 45 cm high) to keep outside runoff from entering the plots. Two important considerations were made when locating a plot at each site. These were availability of labour to help with data collection, and safety of the monitoring equipment. The result of using these criteria is that the number of plots varies between the different types of vegetation cover and regions. This variation, however, does not affect the results negatively as they are comparable to those of the Lilongwe and Salima ADD (World Bank 1991, p. 13). In natural vegetation, four of the eight sub-catchments were in Brachystegia / Isoberlinia /Julbernadia woodland. Four plots were established in Lilongwe and Lakeshore, two in each region. The remaining four plots were in tall grass / scrub vegetation dominated by grass of the genera Hyperrhania. Of these, two plots were in the Scarp, and the remainder were installed in Dowa. All sub-catchments sampled among smallholders were in maize fields that had been prepared early, and planted with the first rains. All of the farmers employed contour ridging as a mechanical conservation measure. Other practices were also used, but they varied between individuals. For example, four plots were in Dowa: one of them had pumpkin as an intercrop, but it also had contour-vegetation strips planted with vetiver (Vetiveria zizanioides) grass as an agronomic measure. The second field used contour-vegetation strips planted with vetiver; the third site had
1337 crop residue incorporated into the soil; and the last one also had pumpkin as an intercrop. Only two plots were in Lilongwe on fields that had vetiver strips. Three sub-catchments were used in the Scarp; all of them had contour ridges consolidated with box ridges. Only one plot was located in the Lakeshore on a farm that did not use any additional conservation measure. On estates, all sub-catchments were in fields that were also prepared and planted early. As in the case of smallholders, contour ridging was the standard mechanical measure used by all of the farmers, but this was complemented by various other measures. Two of the fields in Dowa were planted to tobacco and had vetiver strips. In Lilongwe, a set of two plots was in maize fields without additional defence apart from the usual contour ridges. In the Scarp, two plots were established in a tobacco field that did not have any additional practices either. In the Lakeshore region, two plots were in tobacco and two others were in maize fields. All the fields had contour and box ridges in place. Metal drums measuring about 7.15 m 3 were inserted into pits so that they could trap runoff and sediments from the plots. To this end, the drums were located at the bottom of each plot. Surface runoff was recorded storm by storm as done by Shakesby et al. (1996). To determine sediment content, water samples were collected after thorough agitation of the runoff to ensure suspension of soil particles. Agitation was done by stirring ten times in one direction and ten times in ¨ the opposite direction as done by Zobisch et al. (1996). One litre water samples were collected, then the pits were emptied in preparation for the next storm. The samples were filtered and dried in desiccators until they reached constant weight. The dry weight of sediments from each pit was converted to soil loss (t ha 21 yr 21 ). Data analysis Erosion degree and control measures The number of farmers in each category was determined for each class of perceived degree of erosion and region. The observed soil-loss range was divided into five categories that were ranked using the terms adopted from the Southern African Regional Commission for the Conservation and Utilization of the Soil (1981, p. 3) as follows: ,3.0 5 low; 3.1–12.7 5 moderate; .12.8–19.0 5 severe. Means of the observed rates of soil loss were calculated to identify the centres of distribution of observations (Fowler and Cohen 1992, p. 26) in each farmer category. However, statistical testing to find out if the differences in rates of soil erosion were significant between the regions and farmer category was not done in view of the small sample sizes. Commonly employed erosion-control measures were grouped under the headings used by the Ministry of Agriculture (Malawi Government 1974, p. 2-1; 1988, p. 33). Agronomic measures mentioned by farmers during interviews included crop rotation, intercropping, timely planting, and correct plant spacing; soil management incorporated practices such as use of crop residues, and application of inorganic and organic fertilizers; land-use planning considered avoidance of
1338 watercourses and slopes for regular cultivation; and mechanical measures took into account structures such as contour ridging, use of artificial waterways, and banking. These measures were ranked, according to the extent of control they have over soil-particle detachment and sediment transport, adopting the approach used by Morgan (1986, p. 165). The ranking was from 1 to 4, where: 1 5 very strong, 2 5 strong, 3 5 moderate, and 4 5 low. To this end, land-use planning was scored as 1 because planning entails avoiding watercourses and slopes for regular cultivation; its purpose is to optimize use of the land in accordance with the land’s capabilities for sustained production (Malawi Government 1974, p. 2-1). In fact this tool is considered as the second crucial step in soil conservation because it logically follows a thorough assessment of erosion risk (Morgan 1986, p. 166). The implication is that land-use planning has to be conducted even before subjecting any land to agricultural use. Agronomic practises produce vigorous crops that provide increased ground cover, thereby diminishing the amount of bare ground exposed to rainfall impact (Shaxson 1981, p. 389); hence they were considered to have strong control over erosion processes. Soil management was ranked as 3 because it improves soil structure so that it is more resistant to erosion, and promotes dense vegetative growth (Morgan 1986, p. 164). Mechanical measures were scored as 4 because they have no control over soil-particle detachment. Their main role is to supplement agronomic measures, being used to control the flows of any excess water and wind that arise (Morgan 1986, p. 165). In most cases, farmers integrated different practises that fall under the four major headings, hence the total scores were averaged for each farmer, and the number of farmers using different permutations was calculated to distinguish between the most and least preferred methods. To ascertain if farmers with bigger farms attached more importance to erosion than those with small holdings, the Pearson x 2 test (Sall and Lehman 1996, p. 205) was used to determine how response probabilities varied between estate farmers and smallholders within each region. These variables were also tested using the Correspondence Analysis to ascertain if response probabilities varied between the regions across each farmer category. The Correspondence Analysis is similar to the x 2 test, but it is more useful for data with many levels (Sall and Lehman 1996, p. 215), in this case four geographic regions, four levels of erosion degree, and different combinations of erosion-control methods. All statistical analyses were done using the JMP Start Statistics software (Sall and Lehman 1996). In view of small sample sizes in certain regions (Table 1) and lack of representation in others, large-, medium-, and small-scale estate farmers were grouped together as ‘estate farmers’ while the three categories of smallholders were also grouped together for purposes of statistical comparison between these two major farmer groups. Farm size Farm size was examined in terms of the elements it consists of, such as cultivated and uncultivated land, and fragments. To determine the distribution of estate farmers in each land use (cultivated or uncultivated), they were grouped by region
1339 and category according to the farm-size classes described by Mkandawire et al. (1990, p. 15). Smallholders were grouped in a similar manner following the farm-size categories (,0.7, 0.7–1.5, and .1.5 ha) described by Lorkeers and Venema (1991, p. 54). As land under cultivation is more vulnerable to erosion than uncultivated land, focus is given to the former by relating it to the other variables such as yield, erosion degree, and erosion-control measures. Means of farm size, cultivated and uncultivated land as well as fragments were calculated. Since the numbers of estate farmers (126) and smallholders (234) were unmatched, the nonparametric Mann–Whitney U-test (Sall and Lehman 1996, p. 12) was employed to confirm statistically the superiority of estate farmers over smallholders in terms of farm size. Another nonparametric test, the Kruskal– Wallis, was used to compare, for each farmer category, any significant differences between the regions. Crop yields Yields of maize and tobacco were estimated as tonnes per hectare, taking into account factors such as area of cultivated farmland, potential yield, fertilizer type, and fertilizer-application rates as recommended by the Ministry of Agriculture (Malawi Government 1992, pp. 45, 87, and 88). In the study area, hybrid is the popular maize variety, cultivated by approximately 67 and 82% of smallholders and estate farmers respectively. Local maize is grown by the remaining percentage of farmers. The frequently grown tobacco variety is burley, which is produced by about 83% of the estate farmers. Certain farmers, however, also grow other varieties such as Northern and Southern division fire-cured. Types of fertilizers commonly applied to maize are 23:21:014S and Calcium Ammonium Nitrate (CAN) as basal and top dressing respectively. Basal dressing fertilizer is applied either at the time of planting or when the crop has at least three leaves (Lorkeers and Venema 1991, p. 58). Top dressing fertilizer is the second application done 3–4 weeks after basal dressing. The recommended rates for hybrid maize are 200 kg ha 21 of 23:21:014S, and 290 kg ha 21 of CAN, but for the local variety they are 50 kg ha 21 of 23:21:014S and 130 kg ha 21 of CAN. In tobacco, Super mixture and Ordinary mixture fertilizers are mostly used as basal dressing and CAN is the top fertilizer. The basal dressing rate is 450 kg ha 21 of Super C or D, or 600 kg ha 21 of Ordinary mixture, while the rate of CAN ranges from 150 to 450 kg ha 21 . Application rates of fertilizers were estimated from the number of bags of known weight that farmers claimed to have applied to their fields. The area under cultivation, and potential yields were multiplied by amounts of fertilizers. The derived yields of different varieties of maize or tobacco were aggregated. Mkanda (1992) used this approach to assess the amount of crop damage by wildlife in communities neighbouring Kasungu National Park (Malawi), and found that estimated yields of tobacco and maize were close to the actual yields realized by farmers. To determine the number of farmers in different yield classes, three categories were derived from the potential yield levels of maize and tobacco. The yield classes for maize were as follows: #3.0, 3.1–6.0, and 6.1–8.0 t ha 21 using
1340 the potential yield of local maize as the minimum and that of the hybrid variety as the maximum. Tobacco yield classes were as follows: #2.0, 2.1–3.0, and 3.1–4.0 t ha 21 using the potential yield of the fire-cured varieties as the minimum and that of burley tobacco as the maximum. Relationship between variables Correlation coefficients (Sall and Lehman 1996, p. 142) were calculated in order to test the significance of associations between cultivated farmland, crop yields, erosion degree, and erosion-control measures. Similar coefficients were also computed for farm size and cultivated area to test whether or not the latter was significantly dependent on the former.
Results Perceived degree of erosion The proportions of estate farmers and smallholders in the different classes of erosion suggest that these two groups had similar perception as to the magnitude of erosion on their properties (Table 2). This similarity is confirmed by the lack of any significant association (X 2 5 5.9, P 5 0.11) between erosion degree and farmer type, and it is attributed to the high representation (87.3%) in the sample by small-scale estate farmers who, like smallholders, use soil-conservation measures sub-optimally. In view of this similarity in farmers’ perception of erosion degree, it is deduced that estate farmers, especially the small-scale ones, did not necessarily attach more importance to soil conservation than smallholders. Clear distinctions in erosion degree between the geographic regions are, however, evident (Figure 3a and b). For example, the Scarp and Dowa regions are associated with average and high magnitude of erosion regardless of farmer category. The Correspondence Analysis plot shows that this association is highly Table 2. Perceived degree of erosion by farmers in the Linthipe River catchment, Malawi, 1998. Farmer
Estate
Smallholders
Erosion degree
None Low Moderate Severe Total None Low Moderate Severe Total
No. of farmers by region Dowa
Lilongwe
Lakeshore
Scarp
1 – 2 19 22 8 – 16 44 68
15 3 20 14 52 11 5 15 7 38
2 2 0 4 8 30 13 10 29 82
5 6 29 4 44 9 7 25 5 46
Total
% Total
23 11 51 41 126 58 25 66 85 234
18.3 8.7 40.5 32.5 100 24.8 10.7 28.2 36.3 100
1341
Figure 3. Correspondence Analysis of perceived erosion degree by geographic region in the Linthipe River catchment, Malawi: (a) estate farmers; and (b) smallholders.
significant for estate farmers and smallholders (inertia 5 99.9%, X 2 5 50.71, P , 0.0001; inertia 5 99.5%, X 2 5 67.94, P , 0.0001 respectively). The inertia represents a measure of dispersion of points in space, and a high proportion means
1342 that high confidence can be placed in the plot of variables on the coordinate plane of the first two principal axes (Keen 1997, pp. 91 and 95). The regional variations in erosion degree are reflective of the variations in physical factors such as rainfall, soil erodibility, and slope gradient (Table 3), suggesting that whatever measures farmers had in place were not effective. Although these factors interact to cause erosion, it appears they have varying influences on the erosion processes in different geographic regions. For instance, in the Scarp, the highly erodible soils, steep slopes, and high rainfall are clearly the important determinants of soil loss. In the Dowa and Lilongwe regions, which have similar soil-loss rates and soil characteristics, slope and rainfall, respectively, seem to be more influential than soil erodibility. In the Lakeshore region, it seems that all the physical factors exerted equal influence on the erosion process. Observed soil erosion Farmers’ perception of the extent of erosion is supported by the observed soil-loss data (Table 3). In regions of steep gradient, for example the Dowa Hills and Scarps, soil loss generally ranged from moderate (3.1–12.7 t ha 21 yr 21 ) to very severe (19.1–29.0 t ha 21 yr 21 ). That the observed soil-loss rates are generally consistent with farmers’ assessment of erosion gives confidence in the use of the questionnaire survey in this study, despite the criticism by other researchers that questionnaires are subject to the vagaries and inaccuracies of people’s memories (Grundy et al. 1993; Vermeulen et al. 1996). The fact that soil loss in natural vegetation was lower than on cultivated farmland emphasizes the importance of retaining cover vis a` vis opening more land for agriculture; natural vegetation intercepts raindrops better than maize and tobacco (Paris 1990, p. 6). Comparison of soil loss on agricultural land, irrespective of region, shows that higher rates of soil erosion were recorded in tobacco than in maize because the latter provides better cover (Paris 1990, p. 6). Table 3. Estimated soil erosion rates by region and land use in the Linthipe River catchment, Malawi, 1998 / 99 rainy season. Variable
Geographic region Dowa
Rainfall (mm) 825.42 % Slope (range) 6–50 Soils erodibility a 4.5–5.5 Soil loss (t h 21 y 21 ) by land use b Brachystegia – Grass / shrub 13.98 Maize (smallholders) 13.9 Maize (estate) – Tobacco 20.36
Mean
Dzalanyama
Lakeshore
Lilongwe
Scarp
1363 13–25 4.5–5.5
867.64 2–6 4.5–5.5
1101.24 2–13 4.5–5.5
1072.33 6–55 4.5–5.5
1045.92 2–55 4.5–5.5
1.04 – – – –
1.37 – 12.05 11.71 19.27
– – 7.07 7.76 23.1
– 6.00 16.78 – 24.73
1.20 9.99 12.44 9.73 21.86
a Dominant soil groups only. b ,3.0 – low; 3.1–12.7 – moderate; .12.8–19.0 – severe; 19.1–29.0 – very severe; and .29.0 – extremely severe.
1343 The other reason for the high soil loss observed on tobacco estates is that all of them use the ‘visiting-tenant’ system. Kydd and Christiansen (1982) defined this system as a share-cropping arrangement under which some families obtain land on estates on the condition that they grow a cash crop that is sold to the estate at a price determined by the estate owner. Under this type of arrangement, the visiting-tenant farmers cannot be expected to be committed in implementing soil-conservation practises, least of all to pay for them since the costs incurred would reduce their financial gains. Erosion-control measures Responses from the survey questionnaire indicate that the most preferred approach by estate farmers is to integrate agronomic, mechanical and soil management, while smallholders generally included land-use planning besides these three methods (Table 4). The least used approach by both groups is blending of agronomic, land-use planning, and mechanical measures. There are differences in measures used by smallholder and estate farmers in Dowa and Scarp, but not in Lilongwe. Smallholders are more associated (X 2 5 9.0, P 5 0.02) with all of the four measures in Dowa than estate farmers. In the Scarp region estate farmers are more associated with four measures, while smallholders mostly used only three methods (X 2 5 10.1, P 5 0.01). The differences between smallholders and estate farmers in use of conservation measures may have been caused by various factors, among which are farmers’ education level and labour availability, both of which affect farmers’ ability to deal with soil-conservation issues. For example, higher education level is linked to greater knowledge of conservation issues and problems (Infield 1988). Hence it is possible that irrespective of category, those farmers using more measures are better educated than those using fewer measures. On the other hand, labour is considered as one of the critical socio-economic constraints in agriculture, as its availability is Table 4. Erosion-control measures commonly used by farmers in the Linthipe River catchment, Malawi, 1998. Farmer
Estate
Smallholders
Measures
Ag / fp / mm Ag / fp / mm / sm Ag / mm Ag / mm / sm Total Ag / fp / mm Ag / fp / mm / sm Ag / mm Ag / mm / sm Total
No. of farmers by geographic region Dowa
Lilongwe
Lakeshore
Scarp
3 14 1 4 22 13 49 5 1 68
0 3 2 47 52 0 3 2 33 38
1 4 1 2 8 6 28 24 24 82
6 15 10 13 44 6 4 11 25 46
Total
% Total
10 36 14 66 126 25 84 42 83 234
7.9 28.6 11.1 52.4 100 10.7 35.9 17.9 35.5 100
The codes are as follows: Ag – agronomic; fp – land-use planning; mm – mechanical; and sm – soil management.
1344 a principal factor in the acceptance or rejection of soil conservation (Stocking 1992, p. 213). Therefore there is a possibility that farmers using fewer methods were facing labour constraints. Highly significant associations (inertia 5 99.9%, X 2 558.9, P , 0.0001 for estate farmers, and inertia 5 96.9%, X 2 5 122.6, P , 0.0001 for smallholders) are also observed between regions and erosion-control measures (Figure 4a and b). The regional differences in the number of control measures used by farmers indicate that there is some sense of rationality in their use. For instance, both farmer groups used all the available measures in Dowa, while those in Lilongwe and Lakeshore used only three and two methods, respectively. Most likely farmers realize that integrating more methods in regions with steep gradient such as the Dowa and Scarp may afford better protection against erosion than using fewer practises. On the other hand, only two measures were significantly associated with the Lakeshore Plain, where slope gradient is gentle. Hence the farmers’ perspective is that there is no need for employing all the methods in Lilongwe and the Lakeshore regions. Since all farmers (Table 4) applied erosion-control measures, it can be inferred that they were effective on very few estates and smallholder farms where there was either no erosion or where erosion occurred to a low degree (Figure 4a and b). The fact that the majority of farmers experienced average and high erosion suggests that these control measures were indeed not effective in reducing erosion on most of the farms. This assertion is supported by the fact that only 37 and 47% of estate farmers and smallholders, respectively used land-use planning, which was ranked as having very strong control over soil-erosion processes. Had this practice been widely applied, only few farmers would have perceived average to high magnitude of erosion. Additional support to the contention that measures were ineffective is rendered by farmers’ claims that they used agronomic measures, which are 90% effective in minimizing soil-particle detachment by rainfall impact (Malawi Government 1974, p. 2-6). Also, had the majority of the farmers employed these measures, only few of them, or none at all, could have experienced high soil loss. In this case, however, about 73% of estate farmers, and 65% of the smallholders experienced average to high magnitude of erosion. Farm size Cultivated and uncultivated land The general pattern in land use is that in the Scarp and Dowa regions, farmers owned, cultivated, and kept more land uncultivated (Table 5). The Kruskal–Wallis test confirms that regionally, estate farmers in Dowa owned, cultivated, and left areas of uncultivated land that were significantly larger than those in the other regions (X 2 5 47.6, P , 0.001; X 2 5 13.2, P 5 0.004; and X 2 5 56.0, P , 0.001, respectively). Among smallholders, there were also significant differences between farmers on the Scarp and in Lilongwe; owned (X 2 5 50.4, P , 0.001), cultivated (X 2 5 56.07, P 5 0.0001), and pieces of land uncultivated (X 2 5 14.3, P 5 0.002) that were significantly smaller than those in Dowa and Lakeshore. The
1345
Figure 4. Correspondence Analysis of erosion-control measures by geographic region in the Linthipe River catchment: (a) estate farmers; and (b) smallholders.
trend in regional variability of farm size is also evident in mean cultivated farmland because these variables are highly correlated (r 5 0.73, P , 0.0001 for estate farmers, and r 5 0.76, P , 0.0001 for smallholders). On the other hand, the
1346 Table 5. Mann–Whitney U-test comparing mean farm size, cultivated land, uncultivated land (ha), and fragments between estate farmers and smallholders, Linthipe River catchment, Malawi, 1998. Geographic region
Variable
Estate
Smallholder
z
P
Dowa
Farm size Cultivated Uncultivated No. of fragments Farm size Cultivated Uncultivated No. of fragments Farm size Cultivated Uncultivated No. of fragments Farm size Cultivated Uncultivated No. of fragments
47.7 9.69 37.99 5.86 4.24 2.53 1.71 2.11 308.7 40.16 260.84 2.12 7.2 3.41 3.80 2.61
3.47 1.74 1.73 1.36 1.2 1.1 0.1 1.52 1.4 0.9 0.5 1.86 0.9 0.6 0.3 2.08
6.76 4.9 7.0 5.4 24.1 24.8 22.4 22.6 – – – – 7.5 2.3 4.7 2.0
,0.0001 ,0.0001 ,0.0001 ,0.0001 ,0.0001 ,0.0001 0.01 0.007 – – – – ,0.001 0.017 ,0.0001 0.04
Lilongwe
Lakeshore
Scarp
Mann–Whitney U-test shows that overall, there are significant differences in farm size, cultivated land, and uncultivated land between smallholders and estate farmers (Table 5), thereby confirming superiority of estate farmers over smallholders in these respects. These results indicate that human population growth and slope gradient have played a role in influencing the regional variations in the amount of cultivated and uncultivated land. As human population pressure has increased, farmers have shifted from the low relief areas and resorted to occupying and cultivating fragile steep slopes. Population pressure in these steep regions is certainly not as acute as in the low-lying areas; hence farmers tend to own large holdings. In Malawi the dividing line of arable and non-arable land is a slope of 12% (Khonje and Machira 1987, p. 2). By cultivating large areas in the Dowa and Scarp regions where slopes are steep, agriculture is, therefore, contributing to soil erosion because such areas are rendered vulnerable to erosive rains, which comprise 40% of the rainfall in Malawi (Malawi Government 1974, p. 1-6). An increasing population requires larger amounts of resources to satisfy both tangible and intangible needs, most particularly food production (Shaxson 1970). Hence consequent upon population increase and expansion of land under cultivation, the limited area of potentially cultivable land, which is estimated to be 5.3 million ha (Malawi Government 1988, p. 77), has come under pressure resulting in smaller per capita size of holdings. For example, a sample survey of smallholder agriculture conducted in the 1968 / 69 cropping season indicated that the average holding size on customary land was 1.54 ha per capita (Chipande 1988, p. 164). Mean holding sizes among smallholders in three of the regions in the study area range between 0.6 and 1.1, suggesting a decline over the national average for the past three decades, hence these areas are more intensively cultivated.
1347 The disadvantage with small holdings is that they prevent farmers from practising sound soil-conservation practices such as crop rotation, which helps to minimize erosion (Malawi Government 1974, p. 2-2). The limitation of cultivated farmland in erosion control has been well articulated by Douglas (1988, p. 216). Considering that the principal goal of smallholder farmers is to satisfy their families’ food needs, such farmers are rarely able or willing to adopt improved conservation and land-use practices solely for the sake of soil conservation, as most of the standard soil-conservation recommendations require farmers to forego short-term benefits for the sake of long-term sustainability. For example, the priority of farmers with only 1 or 2 ha of land is to grow food for the family, not crop rotation. In the case of class C arable land, which is inevitably cultivated in the Dowa and Scarp regions, at least 40% (Douglas 1988, p. 216) of the land would be required to be under perennial crops at any one time. Class C arable land is equivalent to land capability class III in the American system. This class has an increasing erosion hazard, and hence is recommended for limited or moderate cultivation (Brady and Weil 1999, p. 713). The requirement to conserve such land, however, diminishes the farmers’ capacity to produce food. Mechanical conservation structures such as artificial waterways and storm drains, if installed, would similarly remove some land from food production. Farmers would rather commit as much land as necessary to food crop production. Under such circumstances erosion occurs with less than optimal conservation measures in place. Limitations of sizes of cultivated holdings (Table 5) must be the cause of the ineffectiveness of the soil-conservation measures, and the resultant average to high degree of erosion perceived by farmers. The proportions of farmers claiming to have used crop rotation in each farmer category support this deduction. A close scrutiny of the agronomic measures data reveals that only 48% of smallholders used crop rotation compared to 70% of the estate farmers. Another problem stemming from the size of small holdings is that it limits access to cultivable land, especially under the customary tenure system where the chief may reallocate uncultivated land, away from a household that is unable to cultivate it, to those in need of more land (Chipande 1988, p. 163). The consequence of this practice is that subsequent generations inherit very small pieces of land that may neither provide enough subsistence in a situation of static technology (Chipande 1988, p. 163), nor offer opportunities for soil conservation. While farming has the propensity to accelerate erosion, by keeping parts of their land uncultivated, however, farmers help to conserve soil, a point clearly illustrated by the soil-loss data from natural vegetation (Table 3). Three reasons are advanced to explain why estate farmers leave parts of their land uncultivated. First, the low lease charges mean that farmers can afford to keep their land undeveloped without incurring any losses as a result of taxation on idle land. In certain cases, leaseholders have acquired leases in other locations, not intending to develop the land, but merely wishing to obtain an additional tobacco quota 3 whose 3 Tobacco sales quotas were introduced following the excess production of burley tobacco in 1981 / 82.
1348 level is met by production from the already existing estate (Mkandawire et al. 1990, p. 23). Thirdly, to estate farmers who realize high tobacco yields, the quota system has proved to be a binding constraint in utilizing their land. Among smallholders on the other hand, production constraints, particularly labour availability, limit full utilization of land (Chipande 1988, p. 166). On account of the amount of uncultivated land, therefore, estate farmers generally conserve soil better than smallholders. From the differences in the amount of uncultivated land between geographic regions (Table 5), it is inferred that estate farmers and smallholders in Dowa and Lakeshore conserved soil better than their counterparts in the other regions. While keeping land uncultivated is conserving soil on an individual’s property, the overall benefit on catchment scale, however, is diminished by the fact that smallholders, who are the majority, either cultivate all their land or leave very little land uncultivated (Table 5). Fragmentation Concomitant with shrinkage of cultivated land being a constraint in soil conservation, there is the problem of fragmented holdings, which not only renders different patches of land vulnerable to erosion due to cultivation, but also limits implementation of soil-conservation measures. While fragmentation has been a predominant feature of smallholder farming (Rimmington 1963), it is also common among estate farmers in the study area, especially among the small-scale estate owners because these farmers merely converted their customary land into leasehold estates. In doing so they merely registered their fragmented holdings as estates. Actually, Mkandawire et al. (1990, p. 23) state that smallholder farmers were prompted to register their customary land as estates in order to obtain a licence and quota to produce burley tobacco and also as a consequence of perceived or real threat of insecurity in the face of large-scale estates alienating customary land around them. As sometimes farmers have to walk long distances from their homes to go to work on their holdings, the chances are that distant fragments receive less attention in terms of soil-conservation measures, hence the average to high magnitudes of erosion perceived by the farmers. It has been suggested that from a technical point of view, planning conservation in the framework of a catchment consisting of consolidated holdings might seem tempting (Douglas 1988, p. 218). However, attempts to realign farm and field boundaries with strict reference to contours of the land, in the interest of better erosion control, may cause considerable disruption of farming activities, and engender much argument (Shaxson 1981, p. 386). Individual catchments are likely to include many farmers with separate holdings and marked differences in farming skills, education, interests, and needs (Douglas 1988, p. 218). A situation like this makes it difficult for farmers to work together and conserve resources because conserving a catchment is not solely an individual farmer’s responsibility. Crop yields Maize The total mean yield of maize by estate farmers is significantly higher than that
1349 Table 6. Mann–Whitney U-test comparing maize yield between farmer categories in the Linthipe River catchment, Malawi, 1998. Geographic region
Dowa Lakeshore Lilongwe Scarp Total
Mean yield (t ha 21 ) by farmer group Estate
Smallholders
1.29 1.55 1.41 1.6 1.46
0.94 0.78 0.11 1.79 1.08
z
P
4.35 – 21.43 20.16 4.63
0.15 – ,0.01 0.87 ,0.0001
achieved by smallholders (Table 6). At the same time, results of the Kruskal– Wallis test show that between the regions, estate farmers in Lilongwe had significantly lower yields than the rest (X 2 5 18.73, P 5 0.0003). On the other hand, smallholders in the Scarp achieved significantly higher yield than in the other regions (X 2 5 45.49, P , 0.0001). However, the yields realized by both farmer categories are low. Estate farmers’ mean yield is about 1.46 t ha 21 , which is 26.54% of the potential aggregated yield of hybrid and local varieties (5.5 t ha 21 ), while smallholders achieved only 1.08 t ha 21 or 19.6%. Farmer distribution in the different maize-yield classes (Table 7) shows that almost 73% of estate farmers, and about 86% of the smallholders realised #3.0 kg ha 21 , which is about 55% of the aggregated potential yield. The difference in maize yield between farmer groups is attributed to the larger areas of land cultivated by estate farmers than smallholders and the significantly higher amounts of fertilizers that the former applied (Tables 5 and 8). Although estate farmers applied more fertilizers than smallholders (Table 8), and those in the other regions applied higher (total) fertilizer rates than in Lilongwe, the quantities used were lower than recommended. For instance, the mean rate of 23:21:01S ranges from about 47% of the recommended amount in the Scarp to 65% in Dowa, while that of CAN varies from 17% in Lilongwe to 70% in the Lakeshore region. The differences in mean quantities of fertilizers applied in the regions seem to be consistent with mean sizes of cultivated land (Tables 5 and 8), suggesting that farmers who cultivated bigger areas attempted to apply more Table 7. Farmer distribution in different maize yield classes in the Linthipe River catchment, Malawi, 1998. Farmer
Estate
Smallholders
Yield class (t ha 21 )
,3.0 3.1–6.0 6.1–8.0 Total ,3.0 3.1–6.0 6.1–8.0 Total
No. of farmers by geographic region Dowa
Lilongwe
Lakeshore
Scarp
15 5 2 22 60 8 0 68
44 8 0 52 37 1 0 38
4 2 2 8 77 4 – 82
29 11 4 44 28 14 4 46
Total
% Of total
92 26 8 126 202 27 5 234
73.0 20.6 6.4 100 86.3 11.5 2.2 100
1350 Table 8. Mann–Whitney U-test comparing application rates of basal and top dressing fertilizers used by farmers in maize, Linthipe River catchment, Malawi, 1998. Fertilizer type
23:21:01S
CAN a
a
Geographic region
Dowa Lilongwe Lakeshore Scarp Total Dowa Lilongwe Lakeshore Scarp Total
Mean rate (kg ha 21 ) by farmer group Estate
Smallholders
81.54 64.96 78.12 58.61 66.48 102.58 44.41 181.25 170.92 107.43
33.96 36.38 19.38 99.63 42.15 37.87 36.0 56.01 165.15 68.95
z
P
2.67 21.42 – 20.70 3.08 4.0 21.17 – 20.27 3.68
0.007 0.15 – 0.47 0.002 ,0.0001 0.24 – 0.78 0.0002
Calcium ammonium nitrate.
fertilizers than those cultivating small holdings. Since use of manure is limited, used only by 12 estate farmers and nine smallholders respectively in the sample, soil fertility was low, hence the low yield. These low yields have implications for soil conservation. First, since yield is related to crop cover, it is obvious that cover on maize fields was generally low, hence the observed high rates of erosion. The other implication is the reduction of labour on those farms whose owners hire out family members to better off farmers for payment in kind or cash, which is a common practice among smallholders (Chipande 1988, p. 169). The necessity to hire out labour is especially acute between December and January, which is also the critical period for soil erosion because crops do not have enough cover to protect the soil against raindrop impact. As labour is one of the crucial inputs in soil conservation, it means that those farmers who are forced to hire out their labour pay little attention to erosion control. Tobacco The estimated mean tobacco yield (Table 9) among estate farmers was about only 1.18 t ha 21 or 39% of the potential aggregated yields of burley and fire-cured Table 9. Estimated mean yield of tobacco among farmers in the Linthipe River catchment, Malawi, 1998. Geographic region
Dowa Lilongwe Lakeshore Scarp Total
Mean yield (t ha 21 ) by farmer group Estate
Smallholders
1.46 0.71 1.09 1.62 1.18
0.35 0.06 – 0.12 0.14
1351 Table 10. Fertilizer application rates used in tobacco by farmers in the Linthipe River catchment, Malawi, 1998. Farmer
Estate
Smallholders
Mean rate (kg ha 21 ) by geographic region
Fertilizer
Super mixtures Ordinary mixtures CAN Super mixtures Ordinary mixtures CAN
Total
Dowa
Lakeshore
Lilongwe
Scarp
207.81 168.8 205.75 46.01 223.1 54.12
151.91 187.5 155.81 0 – –
126.51 174.8 91.66 13.15 500.0 13.15
249.21 – 209.72 17.66 – 17.66
185.17 177.0 156.88 18.98 361.6 21.33
varieties (3.0 t ha 21 ). The mean yield of tobacco by smallholders was even lower, approximately 0.14 t ha 21 or 4%. A comparison between the regions using the Kruskal–Wallis test indicates that Lilongwe estate farmers had significantly lower yields than those in Dowa and Scarp (X 2 5 18.52, P 5 0.0003). Farmer distribution (Table 10) in different tobacco yield classes shows that approximately 82% of the tobacco growers yielded #2.0 t ha 21 , or about 66% of the aggregate potential yield. These differences in tobacco yields are also a function of size of cultivated land and quantities of fertilizers applied by farmers (Tables 5 and 11). Again, the amounts of fertilizers applied seem to be dependent on farm size in that the larger the area of cultivated land, the higher the rates of fertilizers applied (Tables 5 and 11). Overall, however, these rates were lower than recommended. For example, only about 126.51 kg ha 21 or 25% of the aggregate recommended rates of basal fertilizers were applied in Lilongwe, while the highest rate was only 47% or 249.21 kg ha 21 , as was the case in the Scarp. Similarly, in Lilongwe the rates of CAN used were only 91.66 kg ha 21 or 31% lower than the recommended quantities, and only 209.72 kg ha 21 or 63% in the Scarp. The regional differences in farm sizes and fertilizer rates also explain the differences in tobacco yields among smallholders. However, these regional differences are of little consequence in as far as soil erosion is concerned because the yield was low overall, suggesting that the protective effect of tobacco, which is considered as a low-cover crop, was Table 11. Farmer distribution in different tobacco yield classes by region in the Linthipe River catchment, Malawi, 1998. Farmer
Estate
Smallholder
Yield class (t ha 21 )
#2.0 2.1–3.0 3.1–4.0 Total #2.0 2.1–3.0 3.1–4.0 Total
Number of farmers by geographic region Dowa
Lilongwe
Lakeshore
Scarp
18 1 3 22 14 2 2 18
48 2 2 52 1 1 0 2
7 0 1 8 2 0 0 2
29 11 4 44 13 0 0 13
Total
% Total
102 14 10 126 30 3 2 35
80.9 11.1 8.0 100 85.7 8.6 5.7 100
1352 Table 12. Correlation coefficients of erosion degree, cultivated farm size, crop yields, and control measures in the Linthipe River catchment, Malawi, 1998. Farmer
Variable
Farm size variable
r
P
Estate
Erosion degree Control measure Erosion degree Erosion degree Erosion degree Tobacco yield Maize yield Erosion degree Control measure Erosion degree Erosion degree Maize yield
Cultivated land Cultivated land Control measure Tobacco yield Maize yield Cultivated land Maize yield Cultivated land Cultivated land Control measure Maize yield Cultivated land
0.18 0.16 0.02 20.06 20.16 20.19 0.003 0.19 0.06 0.11 20.10 20.09
0.03 0.07 0.79 0.49 0.49 0.02 0.96 0.003 0.3 0.07 0.09 0.16
Smallholders
further diminished, thereby rendering the soil vulnerable to detachment by rain splash and surface runoff.
Relationship between variables Erosion degree is significantly correlated with the amount of cultivated farmland (Table 12), indicating that indeed as more land is cultivated, especially on steep slopes, susceptibility to erosion processes is accelerated. The low correlation coefficients illustrate the roles played by other factors that also contribute to erosion, such as soil erodibility, rainfall erosivity, and topography (Shaxson 1970). Nevertheless, these correlations illustrate that the amount of cultivated land does contribute to erosion. The fact that degree of erosion as perceived by farmers is not significantly correlated to the yields of maize and tobacco confirms that cover, an important factor in minimizing raindrop impact, was inadequate, hence the perception of average and high degree of erosion by most of the farmers. Besides, the negative, albeit insignificant correlations between tobacco or maize yield (Table 12) and the amount of cultivated land are further indications that indeed farmers have to open up more land to optimize production. The fact that there is no significant relationship between cultivated farmland and erosion-control measures (Table 12) is additional evidence of the ineffectiveness of the control measures. The insignificant correlations for both estate farmers and smallholders suggest that farmers who cultivated large farms did not necessarily use more measures than those with small farms. Therefore, on account of cultivated farmland, estate farmers are just as ineffective as smallholders at controlling erosion because they cultivate large farms while their soil-conservation practices are sub-optimal.
1353 Discussion The foregoing results help to verify the study’s hypothesis. That farmers use soil-conservation methods is evidence of their recognition of soil erosion as a problem. Efforts to control erosion are also an indication of willingness on the part of farmers to fulfil one of the Malawi Government’s agricultural objectives, which is ‘‘to conserve the natural resources, especially soil, water and trees in order to improve and maintain the productivity of the land’’ (Malawi Government 1992, p. 7). In a country where agriculture is a prominent socio-economic activity, it is no surprise that farmers recognize the importance of erosion. In fact farmers have long recognized this problem, which they controlled by using appropriate indigenous practices whose salient feature was to retain soil fertility by using maize–legume (groundnuts Arachis hypogea or beans) rotation (Wilson 1941). While hoeing, the main idea was to turn the sod and bury the grass and crop residue to enhance decomposition. These practices meant that erosion problems rarely confronted the indigenous population (Harper and Gibson 1959), and they had undoubtedly evolved through a long course of experience and adaptation to their natural surroundings (Wilson 1941). These practices prevailed for countless generations until the arrival of European settlers. With the arrival of settlers, a subtle change in land use and conservation began. The old ways of the indigenous people changed slowly. In 1902, when there was general setting aside of land as native reserves, the first mistake that was to result in general land misuse in many areas was made (Harper and Gibson 1959). Under the more settled conditions, the population pressure of local people on land increased. Use of machinery in areas farmed by the settlers, injudicious bush fires, monocultural agriculture, and persistent overgrazing brought about soil erosion on a large and ever increasing scale (Harper and Gibson 1959). In response to these problems, soil conservation became a land-use policy. The first soil-conservation officer was appointed in 1936, and in 1946 the first Natural Resources Ordinance was enacted to provide for the conservation and improvement of natural resources (Harper and Gibson 1959; Kettlewell 1965). Introduction of non-indigenous soil conservation practices, and their continued advocacy by the Government have, therefore, merely augmented farmers’ awareness of soil erosion. Although farmers recognize the need to conserve soil, and they are willing to do so, the need to survive undermines their recognition of the problem and willingness to control it. Therefore, they have developed different survival strategies that include hiring out of labour, and leasing of different pieces of land. The strategies that contribute to erosion, confirmed by the data collected by this study, are application of low amounts of fertilizers and expansion of cultivation into marginal land. Douglas (1988, p. 222) states that the cost of fertilizers has increased, partly due to removal of government subsidies (Sahn and Arulpragasam 1991), but also due to the consistent decline in the value of the local currency. According to the World Fact Book (Central Intelligence Agency 2000), the exchange rate was Malawian
1354 Kwacha (MK) 46.35 per US$ 1.00 by December 1999, while in 1995 the rate was MK 15.28 to US$ 1.00. The decline has inevitably in turn caused costs of importing fertilizers to rise, a situation that has made it even more difficult for farmers to procure this crucial input. Therefore to beat the odds of realizing even lower crop yields, which would be the case if they did not apply any fertilizers, farmers instead would rather apply small quantities that minimize costs. Also, in view of the rising fertilizer costs, farmers consider the available uncultivated land, even if its quality is marginal, as an alternative to purchasing inputs. To alleviate the problem of input availability, the Malawi Government’s structural adjustment policies of the 1980s focused on stimulating smallholder agriculture (Sahn and Arulpragasam 1991). Hence the Government either facilitated or provided farm inputs such as fertilizers and improved seed on credit in order to improve agricultural productivity (Chipande 1988, p. 165; Sahn and Arulpragasam 1991). Farmers who have access to credit (based on their ability to pay), and hence can afford to use innovations such as fertilizers and improved seed, have improved their farm productivity (Chipande 1988, pp. 168 and 169). Therefore, the pressure for such farmers to cultivate more land in order to increase farm output is diminished. On the other hand, farm output has stagnated among those farmers who are unable to acquire inputs on credit (Sahn and Arulpragasam 1991). Stagnation is particularly common among the majority of smallholder farmers because they are disadvantaged by one of the credit criteria, which implies that farmers must first of all produce surpluses and sell them in order to qualify for credit. As smallholders are the ones who often face food deficits (Chipande 1988, p. 170), and so do not warrant consideration for loan, they have little alternative but to bring more land into cultivation. Despite the fact that farmers perceive average to high degrees of erosion, it is evident that they have been using these survival strategies to achieve their agricultural goals for decades, and it is likely that they will continue using them. For example, present cultivation of marginal land clearly shows that the strategy of opening up more land for cultivation is still the key to increasing agricultural productivity. Orr et al. (1998, p. 19) reported that of the total (2.5 million ha) cultivated estate and customary land, 296 000 ha (about 12%) are unsuitable for agricultural use. This practice is definitely at the expense of soil conservation. The impacts of these survival strategies, which are excessive erosion in the catchment and sediment discharges into Lake Malawi, undoubtedly have ramifications for biodiversity conservation in Lake Malawi. It is deduced that the observed impacts on the fish communities may lead to further decline of fish species, thereby diminishing both the ecological and socio-economic integrity of the Lake. To protect the biodiversity from further impacts associated with cultivation, agricultural intensification has to increase by means of providing a social and economic environment that will enable farmers to use high yielding varieties and fertilizers. In view of the limited access to credit by smallholders, it would be appropriate for the Ministry of Agriculture to explore means of providing favourable terms of credit to the disadvantaged farmers. Additionally, since the
1355 problem at hand is primarily that of survival, involving the need for sustainable agriculture and to conserve the biodiversity of Lake Malawi, a multi-faceted approach to resolving it is advocated. Involvement of all relevant government agencies and other institutions would, therefore, be pertinent. This approach befits a problem of this magnitude, which transcends the official jurisdiction and mandate of a single government institution. In this regard, it is suggested that both the Ministry of Agriculture and Department of Fisheries, besides other stakeholders and credit institutions, be involved in formulation of credit criteria that are favourable to the socio-economic situation of farmers, especially smallholders. An improved socio-economic environment would help eradicate, or at least minimize, the need on the part of farmers to extend farmland and cultivation of steep slopes as a means of improving productivity. Increased use of fertilizers may also aid soil conservation by improving plant health and cover that is essential in minimizing raindrop impact. The impact of increased nutrient input on farmland, and subsequent discharges into the Lake, however, would need investigating. Bootsma and Hecky (1999, p. 2) have shown that the quality of water in Lake Malawi may be changing as a result of nutrient input from the catchment. Therefore creation of another problem in the course of resolving the current one must be avoided.
Conclusions This study illustrates how survival strategies such as low fertilizer-application rates, and cultivation of marginal land, contribute to erosion in the Linthipe River catchment, and subsequently to sediment discharge into Lake Malawi. As such, it shows that crop yields are low because of insufficient amounts of fertilizers that are used by farmers. Consequently, these farmers are forced to cultivate even marginal land in order to increase crop yield. In that way, cultivated farm land contributes in three different ways: large cultivated areas are exposed to raindrop impacts in view of the sub-optimally applied soil-conservation measures; small cultivated areas limit effective use of soil-conservation practises, and cultivation of different fragments exerts competition for labour. Therefore, Lake Malawi’s biodiversity is threatened by sedimentation ensuing from excessive erosion on cultivated land. This impact may lead to impoverishment of fish species diversity. To sustain the Lake’s biodiversity, it is necessary to eliminate the need to increase farmland.
Acknowledgements I am indebted to several institutions and individuals (both in Malawi and Canada) who made this research possible. Firstly, I wish to thank the Malawi Government, especially the Department of National Parks and Wildlife for providing clearance
1356 for this study to take place in Malawi. The SADC 4 Global Environment Facility (LMBCP), and the Canadian International Development Agency jointly funded the study and their sponsorship is gratefully acknowledged. Without the farmers’ cooperation, this study would not have been undertaken. Therefore I would like to thank all the farmers who participated in the survey. Miston Whayo of the LMBCP, and the Agricultural Extension Workers (too many to list) provided valuable support during the field survey. Dr. Anthony Ribbink, who was the project manager of LMBCP, provided much administrative support by providing vehicles for administration of the questionnaire. At the University of Manitoba, I acknowledge the Ethics Review Committee in the Faculty of Arts for approving this research. Dr. J.S. Brierley, of the Department of Geography, kindly helped with questionnaire design and reviewed the draft of this paper. Members of staff at the Centre for Observation Science (CEOS) provided all the logistical support for this study. Their role is highly appreciated. Special thanks go to Dr. David G. Barber, the director of CEOS, for reviewing the draft of this manuscript, and to Douglas Fast for the cartographic work.
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