Sky Journal of Agricultural Research Vol. 5(3), pp. 048 - 055, May, 2016 Available online http://www.skyjournals.org/SJAR ISSN 2315-8751 ©2016 Sky Journals
Full Length Research Paper
Long term effects of lime and phosphorus application on maize productivity in an acid soil of Uasin Gishu County, Kenya Kisinyo Peter Oloo School of Agriculture, Natural Resources and Environmental Studies, Rongo University College, P. O. Box 103-40404, Rongo, Kenya. E-mail:
[email protected]/
[email protected]. Tel.: +254723320168. Accepted 21 March, 2016
The study determined the individual and combined effects of lime and phosphorus (P) application on maize productivity and economic benefits on an acid soil of Uasin Gishu County, Kenya. Treatments were P fertilizer (0, 26 and 52 kg P/ha) and lime (0 and 6 tons/ha), all were applied once. All treatments, except control, received 3+ 75 kg N/ha. The soil was low in base cations, total N and available P but was high in exchangeable Al . Application of lime maintained soil pH above 5.5 for about four years only. The mean grain yield increment due to 26 kg P, 52 kg P and 6 tons lime/ha were 35, 61 and 29% respectively. In the second, third and fourth years, 75 kg N+52 kg P/ha produced economically viable returns with net financial benefits of (NFBs) of USD 942, 1802 and 2540, respectively. Application of 52 kg P/ha together with 75 kg N and 6 tons of lime/ha produced economically viable returns with NFB of USD 2732 during the fourth year. Therefore, farmers can obtain long term economically viable maize grain yield with application of lime and P fertilizer on low P acid soil of the region. Key words: Soil acidity, lime, phosphorus, maize yield, economic benefits.
INTRODUCTION Soil acidity is a major constraint for crop production in tropics, due to low soil pH and poor availability of plant nutrients, such as phosphorus (P), calcium (Ca), magnesium (Mg) and potassium (K). It leads to poor soil biological activity, hindering organic matter mineralization and therefore, nitrogen availability (Baligar and Fageria, 1997; Kamprath, 1984). In Kenya, acid and low-fertility soils particularly low available P and N are the major causes of low and declining maize yields (Kanyanjua et al., 2002; Ayaga, 2003). Acid soils which cover 13% of the Kenyan land area (Kanyanjua et al., 2002) are found in areas of high rainfall and are potentially suitable for maize production (Muhammad and Underwood, 2004). Most Kenyan acid soils have aluminum (Al), hydrogen (H) and iron (Fe) toxicities with low levels of P, Ca, Mg and K (Kisinyo et al., 2013; Obura, 2008). The acidity is attributed to their development from acid parent materials, high rainfall, leading to leaching of bases and in some cases, application of acid forming fertilizers (Jaetzold and Schmidt, 1983; Kanyanjua et al., 2002).
Like many tropical soils, phosphorus deficiency on Kenyan acid soils is due to inherent low soil available P, its P fixation by Al and Fe oxides and insufficient fertilizer use (Okalebo et al., 2006; Obura, 2008; Kisinyo et al., 2013, 2014; Sanchez et al., 1997). In tropical Africa, soil acidity related constraints reduce grain yields by about 10% (Sierra et al., 2003). On Kenyan acid soils, Al toxicity reduce maize grain yield by 16% and low soil available P by 30% (Ligeyo, 2007). Given the effect of soil acidity related constraints on food production, there is need to find along lasting solution. Use of lime and P fertilizer is recommended for the management of P deficient acid soils (Kanyanjua et al., 3+ 2002; Kisinyo, 2011). Lime reduces exchangeable Al 3+ and Fe in acid soils resulting to reduction in Al toxicity and P sorption. This creates a conducive environment for root growth and also makes both the applied P fertilizers and the native soil P available for plant uptake (The et al., 2006). The importance of application of P fertilizer in increasing crop productivity in Kenya has been
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Table 1. Cost and benefits in USD used during the cropping period (year 2005- 2008). Year First rate of TSP fertilizer was 26 P/kg/ha Second rate of TSP fertilizer 52 P/kg/ha CAN applied at 75 N/kg/ha Rate of lime applied in tons/ha Price of TSP/kg Price of 1.0 kg CAN fertilizer Cost of transporting 50 kg fertilizer to homestead Factory price of 50 kg of lime Transport cost of 50 kg bag of lime from factory to the farm Cost of a 90 kg maize grain storage bag Labour costs Cost of applying 50 kg bag lime Cost of applying 50 kg TSP or CAN fertilizer Cost of harvesting 90 kg bag of maize cobs Cost of shelling 90 kg dry maize grain Price of 1.0 kg of maize grain Opportunity cost of Capital per year (%)
2005 127.2 254.4 277.8 6.0 0.37 0.35 0.26 1.12 0.64 0.19
2006 277.80 0.48 0.32 0.24
2007 277.8 0.54 0.36 0.29
2008 277.8 0.62 0.41 0.28
0.26 0.51 0.19 0.26 0.17 20
0.63 0.24 0.32 0.22 20
0.68 0.29 0.29 0.29 20
0.82 0.28 0.41 0.31 20
Note: 2.5 bags of maize cobs is equivalent to 90 kg maize grain bag.
demonstrated by many researchers (Kisinyo, 2011; Opala et al., 2010). In addition, both lime and P fertilizers have residual effects on soils (Kisinyo, 2011, Kisinyo et al. 2014; Sanchez, 1976) which attracts farmers to use them during crop production. The objectives of this study were therefore to determine:- i) the long term effects of lime and P fertilizer on some soil chemical properties and maize grain yield and ii) the economic benefits of lime, N and P fertilizers on maize production in Uasin Gishu County, Kenya.
consisting of three levels of P fertilizer (0, 26 and 52 kg P/ha ) applied as triple super phosphate (TSP) and two levels of lime (0 and 6 tons/ha). 26 kg P/ha is the recommended P fertilizer rate for maize production in Kenya (Kenya Agricultural Research Institute, 1994). Burnt lime with 92.5% calcium carbonate equivalent was used as lime source. Lime requirement was calculated using the equation of Cochrane et al. (1980) with the aim to reduce percentage Al saturation to a level that is commensurate with crop Al tolerance was used:
MATERIALS AND METHODS
Ca(cmol/kg soil) = 1.5[Al − RAS (Al + Ca + Mg)/100
Site characteristics and soil sampling
where Al = cmol/kg soil in the original exchange complex, RAS = required percentage Al saturation, Ca = cmol/kg soil in the original exchange complex and Mg = cmol/kg soil in the original exchange complex.
A field experiment was conducted on a smallholder o farmer (SHF) field in Uasin Gishu with longitude 0 o 36.781’’N and latitude 35 18.280’’E in Kenya with an acid soil classified as orthic Ferralsol. The site is situated at an elevation of 2100 m above sea level. The average 10 years of rainfall for the study site is 900 mm per year, with unimodal distribution pattern with peaks in April and August (Jaetzold and Schmidt, 1983). Prior to lime and P fertilizer applications, nine surfacesoil samples were taken in a random manner with a soil auger from the top 0–20 cm (Okalebo et al., 2002). They were mixed thoroughly and about 1.0 kg composite sample packed in a polythene bag and analyzed in the laboratory. Post-treatment application soils were also analyzed for interpreting the results. Experimental design and layout The experiment was conducted in a 3 × 2 factorial in randomized complete block design replicated three times,
(1)
The approximate lime requirement (tons CaCO3/ha) was calculated by multiplying the Ca cmol/kg by the soil specific gravities. RAS value of 20% was used since most maize germ plasm grown by Kenyan farmers are sensitive to >20% Al saturation found in most maize growing areas (Ligeyo, 2007). Initial soil characterization data (Table 1) was used to determine lime requirement and the calculated lime requirement was approximately 6.0 tons/ha. Agronomic practices 2
After ploughing and harrowing, 20 m (5 x 4) plots were demarcated and the plots were separated from each other with a guard row 1.0 m apart. Prior to planting, lime was broadcast evenly and thoroughly mixed with the soil, about a month prior to sowing. Phosphorus fertilizer was
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also broadcasted and thoroughly mixed with the soil during planting. Lime and P fertilizer were applied once in the year 2005. All plots except the absolute control, received 40 and 60% of N fertilizer during planting and top dress, respectively in form of calcium ammonium nitrate at 75 kg N/ha which is the recommended rate for maize production in Kenya (Kenya Agricultural Research Institute, 1994). Plant spacing of 25 cm within rows and 75 cm between rows, planted with maize hybrid H614, two seeds in each hole which were thinned leaving one seedling in each hole, 2 weeks post emergence. Plots were weeded using a hand hoe while pests and diseases were managed as necessary. Maize cobs from each plot was harvested at physiological maturity and their weights recorded. Representative sample of cobs were taken from each plot and their weights recorded. They were airdried until a constant weight was obtained, shelled and dry grain weight recorded. The flowing formulae were used to determine grain yield:Yield (kg) per plot = Total Fresh Weigh(kg) x Sample Dry Weight (kg) Sample Fresh Weight (kg)
(2) Yield (kg/ha) = Yield per plot x 10,000 m 2 Effective Area (m )
2
(3)
Where effective area is harvested plot excluding the guard row and plants at the end of each row.
cropping season cost of farm inputs, labour wages for farm operations and storage bags were determined through market survey. To equate the obtained maize grain yield with what a farmer would get, the obtained yield was adjusted downward by 10%. Discounted rate of capital was only applied to cash costs the rate of 20% per year. Both the costs and benefits were converted to monetary values in USA dollars (USD) and reported per ha. Table 1 shows a list of cost and benefit values used. Treatments net financial benefits (NFBs) and TCV were compared using dominance analysis following the two steps described below. The first step was the calculation of the NFBs as shown in the formula below:NFB = (Y x P) – TCV
(4)
where Y x P = Gross Field Benefit (GFB), Y = Yield per ha and P = Field price per unit of the crop. Secondly, treatments TCV were listed in increasing order in accordance with dominance analysis. All treatments which had NFB less than or equal to treatment with lower TCV were marked with a letter “D” since they were dominated and eliminated for any further analysis. Undominated treatments were subjected to Marginal rate of return analysis (MRR) (CIMMYT, 1988) in stepwise manner, moving from lowest TCV to the next as shown below:
Laboratory analyses All the soil samples were air- dried. Soil samples taken prior to lime and P fertilizers treatments were analyzed 1 for pH (1: 2 /2; soil: water), bicarbonate extractable P, exchangeable base cations, exchangeable Al, organic carbon, total N and specific gravity (Smith, 1981; Okalebo et al., 2002). Soils sampled taken after lime and fertilizer applications were analyzed for soil pH and bicarbonate extractable P. Statistical analysis of data General Statistics (GenStat, 2010) was used to analyze maize grain yield data. To compare differences as result of treatment applications standard error of difference (SED) at significance level of 5% was used.
MRR (%) = Change in NFB (NFBb- NFBa) x 100 Change in TCV (TCVb- TCVa)
(5)
where NFBa = NFB with the immediate lower TCV, NFBb = NFB with the next higher TCV, TCVa = the immediate lower TCV and TCVb = the next highest TCV. Changes in NFB is referred to as marginal benefits while those in TCV as marginal costs. MRR shows the average gain(s) a farmer would expect from an investment that requires an increase in cost. For investments that require change in the use of technology, minimum rate of return of 50-100% is gratifying to farmers (CIMMYT, 1988; Dillion and Hardaker, 1993). This study did not require use of new knowledge; therefore, minimum rate of return was set at 50% (CIMMYT, 1988). Therefore, all treatments that gave MRR more than 50% were considered to be ideal investment by farmers.
Economic analyses of the grain yield data RESULTS AND DISCUSSION The economically acceptable treatment(s) were determined by partial budgeting analysis to estimate the gross value of the grain yield by using the adjusted yield (CIMMYT, 1988) at the market value of the grain and inputs during the cropping period. Only total costs that vary (TCV) were used to compute costs. For each
Initial soil characteristics of the study site The initial soil was strongly acidic with high Al and low level of basic cations, except K. The level of P, N and
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Figure 1. Effect of lime on soil pH; d = days from the time of lime application and error bars indicate SE.
organic carbon were low. Acid soils with high Al levels and with low basic cations in the soil makes it unsuitable for maize production (Kanyanjua et al., 2002; Kisinyo et al., 2013 Landon, 1984; Ligeyo, 2007). Toxic levels of Al 2+ 2+ with low exchangeable Ca and Mg levels, available P and soil acidity are the major soil-related constraints identified in the soil. Long term effect of lime on soil pH The effect of lime on soil pH is indicated on Figure 1. Lime gradually increased soil pH up to a maximum peak of pH 7.0 in 415 days. This was followed with a gradual decline for the rest of the cropping season maintaining soil pH above the critical level (pH≤ 5.5) below which 1 liming is necessary for more than 1284 days (≈ 3 /2 years) after its application. Lime’s gradual effect was due 2+ 2+ to its very slow reactivity to release Ca and/or Mg ions and as a result its effects last longer compared to other organic and inorganic inputs (Sanchez, 1976; Kisinyo et al., 2014). The observed increase in soil pH was probably 3+ 3+ 4+ as a result of Al , Fe and Mn ions precipitation and + 2+ 2+ H ions neutralized by Ca and Mg contained in lime (Kanyanjua et al., 2002; Kisinyo, 2011; The et al., 2006). In a similar trial, 2, 4 and 6 tons lime/ha kept soil pH above the critical level for approximately 2, 3 and 4 years, respectively on a Kenyan acid soil (Kisinyo et al., 2014). 3+ The authors attributed this to its effects on controlling Al ion level resulting to increase in soil pH. Abruna et al. (1964) reported similar long term effect of lime on soil pH on tropical acid soil. Long term effect of lime and P fertilizer on soil available phosphorus The effect of lime and P fertilizer on soil P availability is indicated in Figure 2. Phosphorus fertilizer rapidly increased the soil P availability to the highest peak in about 64 days following its application. This was primarily
due to the release of P from TSP. Rapid reactivity of P fertilizer to release P has earlier been reported by several workers (Kisinyo, 2011; Tisdale et al., 1990). The availability of P increased with the rate of P-fertilizer application. Similar results have been reported on P deficient acid soils (Kisinyo et al., 2014; Weisz et al., 2003; Tisdale et al., 1990). Where both P fertilizer and lime were applied, soil P availability was higher than where either of them was applied alone. This was because lime reduced P sorption making both the native and phosphorus fertilizer available for plant absorption (Kisinyo et al., 2013; The et al., 2006). It is therefore apparent from this study that both P fertilizer and lime application are important for long term management of soil P deficient acid soils. Long term effect of lime and P fertilizer on grain yield Table 2 indicates the effect of lime and P fertilizer on a 4year average grain yield. Both treatments had significant effects on grain production. The mean maize grain production increased above the unfertilized plot, from 26 kg P, 52 kg P and 6 tons lime/ha was 35, 61 and 29%, respectively. A combination of lime and phosphorus fertilizer resulted in higher grain production than that with lime or P used independently. Treatment effectiveness on grain production generally increased in the order: control → lime → P fertilizer → P fertilizer + lime. This was due to the fact that, lime alleviated plants from Al toxicity, reduced P fixation and increase Ca and P availabilities leading to higher grain production (The et al., 2006). The effect of lime and P fertilizer on annual maize grain production during the cropping period is shown in Figure 3. Both lime and P fertilizer significantly increased grain production. Grain production was highest immediately after lime and phosphorus application and declined gradually over the years. In the year 2006, grain yields were lower than 2007 as a result of low and poor rainfall distribution during the cropping season.
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Figure 2. Effects of P fertilizer and lime on soil P availability; d = days from the time of lime application and error bars indicate SEM. P fertilizer was applied during planting.
Table 2. Initial Soil chemical characteristics of the study site. Parameter Soil pH (1: 2.5 (soil: water) Bicarbonate extractable P (mg/kg) Total N (%) Organic Carbon (%) Exchangeable Ca (cmol/kg) Exchangeable Mg (cmol/kg) Exchangeable K (cmol/kg) Exchangeable Al (cmol/kg) ECEC (cmol/kg) % Al saturation Sand (%) Clay (%) Silt (%) Textural Class Specific gravity
Therefore, plants suffered drought stress during their vegetative growth which resulted in low grain production (Kisinyo, 2011). Higher grain yield as a result of similar treatments have been reported on P deficient tropical acid soils (Kanyanjua et al., 2002; Kisinyo et al., 2014; Opala et al., 2010; Sierra et al., 2003; The et al., 2006). Maize grain production declined during the cropping
and
physical
Value 4.84 4.44 0.23 1.33 2.01 0.38 1.28 2.28 6.05 39.4 46 38 36 Clay loam 2.58
period with corresponding decrease on soil pH and P availability as has been the case on other tropical soils (Ayaga, 2003; Sanchez et al., 1997). In the acid soils of the Kenya highlands, the average grain yield declined from 3 to 1 ton/ha during 18 years of continuous cropping without P and N fertilizers replenishments (Qureshi, 1991). The results of the present study further confirms
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Figure 3. Seasonal effects of P fertilizer and lime on maize grain yield during the cropping period; P = kg P/ha.
that soil fertility depletion is the cause of low and decline in the per capital food production in tropical Africa. In this region, several years of nutrient depletion has made originally fertile soils which produced between 2 and 4 tons/ha of cereal grain into unfertile soils, that produce less than 1.0 ton/ha (Sanchez et al., 1997). Economic benefits of long term lime and P fertilizer application in maize production The analysis of benefits, variable costs and marginal rate of returns are presented in Table 3. Majority of treatments did not produce economically viable returns because MRR accrued by changing from an undominated option with lower cost of production to the next produced less than 50% MRR considered sufficient for an investment. As a result, majority of treatment combinations did not produce economically viable returns suitable for adoption by farmers. No farmer would be willing to invest more and get less benefit compared to the ones with lower cost of production. It has been reported in Kenya that high cost of organic and inorganic inputs results in low farm profits (Kisinyo et al., 2015; Makinde et al., 2007). For example, in Kenya, the recommended inorganic fertilizer rates (75 kg N + 26 kg P/ha) for maize production (Kenya Agricultural Research Institute, 1994) is no longer profitable as observed in this study. None of the inorganic inputs realized economically viable returns in the first year. During the second and third year, only 75 kg N + 52 kg P/ha, with NFBs of USD
942 and 1802, respectively was economically viable. During the fourth year, 75 kg N + 52 kg P/ha and 75 kg N + 52 kg P + 6 tons lime/ha with NFBs of USD of 2540 and 2732, respectively were economically viable. It is interesting to note that lime and phosphatic fertilizer application had additive effects on acid soil. This benefitted maize productivity by improving soil health due to increase in soil pH, enhancing P availability to crops and reducing adverse impacts of soil acidity.
Conclusion The soil was strongly acidic, with Al toxicity and low 2+ 2+ exchangeable Ca & Mg and poor availability of P. Maize yields were poor due to these soil related constraints. Lime gradually increased soil pH to a maximum of pH 7.0 in 415 days and thereafter, there was a gradual decline, maintaining the pH above the critical 1 level (pH≤ 5.5), for approximately 3 /2 years. A combination of lime and P fertilizer had additive effect on soil P availability and grain production compared to either of them alone. This was due to the fact that lime reduced P sorption increasing soil P availability for plant absorption. In the second and third year of cropping, only 75 kg N + 52 kg P/ha with NFBs of USD 942 and 1802, respectively was economically viable. During the fourth cropping season, 75 kg N + 52 kg P/ha and 75 kg N + 52 kg P + 6 tons lime/ha with NFBs of USD of 2540 and 2732 were economically viable. Therefore farmers can obtain long term economic gain with one-time application
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Table 3. Gross field benefits, total costs that vary, net financial benefits and marginal rate of returns analysis of treatments during year 2005 to 2008.
Treatments Control 75 kg N + 26 kg P/ha 75 kg N + 52 kg P/ha 75 kg N + 6 tons lime/ha 75 kg N + 26 kg P + 6 tons lime/ha 75 kg N + 52 kg P + 6 tons lime/ha
GFB (USD) 420 521 702 506 654 786
Year 2005 TVC NFB (USD) (USD) 28 392 200 320 266 435 412 94 476 178 539 248
MRR (%) D 18 D D D
Cumulative (Years 2005 2006) GFB TVC NFB MRR (USD) (USD) (USD) (%) 780 51 729 1120 392 728 D 1407 464 942 52 1017 598 419 D 1362 674 688 D 1567 742 826 D
Cumulative (Years 2005 2007) GFB TVC NFB MRR (USD) (USD) (USD) (%) 1406 86 1320 D 2075 616 1460 26 2497 696 1802 428 1895 817 1078 D 2442 905 1537 D 2823 982 1841 14
Cumulative (Years 2005 2008) GFB TVC NFB MRR (USD) (USD) (USD) (%) 1984 118 1866 2865 856 2009 19 3487 947 2540 585 2669 1057 1612 D 3427 1156 2271 D 3974 1242 2732 65
GFB = Gross field benefits, TCV = Total costs that vary, NFB = Net financial benefits, MRR = Marginal rate of returns and bolded indicates viable investments.
of lime and P fertilizer on P deficient acid soil of the region.
Acknowledgements I am grateful to The McKnight Foundation for funding this research work. I am also very thankful to the farmer, Mrs. Rebecca Soy for allowing me conduct the research on her farm. REFERENCES Abruna F, Vicente-Chandler J, Pearson RW (1964). Effects of lime on yield and composition of heavily fertilized grasses and soil properties under humid tropical conditions. Soil Sci. Soc. Am., Proc. 28: 657–661. Ayaga GO (2003). Maize yield trends in Kenya in the last 20 years. A keynote paper. In Proceedings of a Workshop on Declining Maize Yield Trends in Trans Nzoia District Conference, Kitale, Kenya. May 22–23, 2003, Moi University, Eldoret, Kenya. Pp. 7–13. Baligar VC, Fageria NK (1997). Nutrient use efficiency in acid soils: Nutrient management and plant use efficiency. In: Moniz AC, Furlani AMC, Schaffert RE, Fageria NK, Rosolem CA, Cantarella H (Eds.). Plant
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