Long-term farmyard manure application effects on ...

Soil & Tillage Research 94 (2007) 386–396 www.elsevier.com/locate/still

Long-term farmyard manure application effects on properties of a silty clay loam soil under irrigated wheat–soybean rotation Ranjan Bhattacharyya *, S. Chandra, R.D. Singh, S. Kundu, A.K. Srivastva, H.S. Gupta Vivekananda Institute of Hill Agriculture, Almora 263601, Uttaranchal, India Received 13 April 2005; received in revised form 22 August 2006; accepted 28 August 2006

Abstract Increasing importance has been placed on the use of agricultural soils for the mitigation of atmospheric CO2 through sequestration of soil C. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, little information is available on C sequestration, C content in different aggregate size fractions and soil water transmission properties (infiltration and saturated hydraulic conductivity) as affected by long-term manure addition. We analyzed results of an 8-year experiment, initiated in 1995–1996 on a silty clay loam soil, to determine the influence of fertilizer and fertilizer + farmyard manure (FYM) application on those important soil properties. The overall increase in soil organic C (SOC) content in the 0–45 cm soil depth in NPK + FYM treatment as compared to NPK and control treatments was 11.0 and 13.9 Mg C ha1 at the end of 8 years, respectively. Application of FYM significantly reduced soil bulk density and increased mean weight diameter (MWD) and SOC contents in different aggregate size fractions. Soil organic C content in macroaggregates was greater than in microaggregates. The response of SOC content to FYM application was dependent upon inorganic fertilization and more upon balanced application of NPK than N only. Steady state infiltration rate under NPK + FYM (1.98 cm h1) was higher than under unfertilized (0.72 cm h1) and NPK (1.2 cm h1). Soil water sorptivity (calculated from Philip’s equation) under NPK + FYM (1.06 cm min0.5) was higher than under NPK (0.61 cm min0.5). We conclude that hill farmers in northern India should be encouraged to use FYM along with chemical fertilizers to increase SOC content and improve soil physical properties. # 2006 Elsevier B.V. All rights reserved. Keywords: Soil organic C; Aggregate stability; C contents in aggregates; Farmyard manure; Bulk density; Infiltration rate; Wheat–soybean cropping

1. Introduction Soil organic matter (SOM) and various physical properties have been proposed as indicators of soil quality (Doran and Parkin, 1994). Maintenance of soil organic C (SOC) is considered essential for long-term

* Corresponding author. Tel.: +44 7852609026; fax: +01902 323316. E-mail address: [email protected] (R. Bhattacharyya). 0167-1987/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2006.08.014

sustainable agriculture, since declining SOC levels generally lead to decreased crop productivity (Allison, 1973). Soil organic matter and structure, which determine to a large extent soil workability and availability of water and nutrients to crops, are greatly influenced by management practices. Continuous cultivation in most irrigated lands has resulted in the decline of soil physical condition in general, and SOC content in particular. Soil organic matter and soil structure are strongly related: organic matter binds mineral particles into aggregates and reduces the

R. Bhattacharyya et al. / Soil & Tillage Research 94 (2007) 386–396

susceptibility of soil to erosion (Tisdall and Oades, 1982). In turn, stable aggregates may enhance physical protection of SOM against decomposition under managed compared with unmanaged systems (Six et al., 1998). Thus, a decline in SOM may result in poor physical fertility of soil (Sharma et al., 2003). To evaluate the impact of management practices on soil quality it is necessary to quantify modifications to soil structure in general and SOC content in different aggregate sizes in particular. Comparison of SOC content in different sized water stable aggregate classes shows that macroaggregates are the source of highly enriched and most labile fraction of SOC (Cambardella and Elliott, 1994). Macroaggregates have wider C:N ratio than microaggregates (Whalen et al., 2003). Farmyard manure reduces dispersion in soil, thereby increasing macroaggregates in soil (Ray and Gupta, 2001). Chardravansi et al. (1999) reported that increase in mean weight diameter (MWD) with addition of N or FYM was due to higher percentage of macroaggregates in soil. Knowledge of SOC sequestration and turnover helps in understanding the contribution of soils to greenhouse gas emission (Powlson et al., 1987). Management systems to increase distribution of organic C in stable macroaggregates deserve to be studied in detail so as to increase the labile and protected SOC and reduce CO2 emissions (Tripathi and Singh, 2004). Several studies have shown that regular application of fertilizers for many years leads to an increase in SOC (Reeder et al., 1998; Kundu et al., 2001). Fertilization stimulates biomass production, and therefore, enhances C accumulation (Schuman et al., 2002). In general, the use of organic manures and compost enhances SOC more than application of the same amount of nutrients as inorganic fertilizers (Gregorich et al., 2001). Reduction in bulk density, increase in SOC content, increase in hydraulic conductivity and improved soil structure along with improved microbial communities were observed through the application of FYM plus inorganic N under irrigated systems (Sharma and Sharma, 1993; Katyal et al., 1997; Schjonning et al., 2002; Munkholm et al., 2002). Similar increases in SOC content due to addition of FYM in irrigated system were also observed by Swarup and Yaduvanshi (2000) and Yadav et al. (2000) in India. Smith and Powlson (2000) estimated that if all manures were incorporated into arable land in the European Union, there would be a net sequestration of 6.8 Tg C year1, which would be equivalent to 0.8% of the 1990 CO2-C emissions for the region. Application of N fertilizer is important to obtain high yields, but may have little impact on SOC concentration

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under rainfed conditions unless used in conjunction with no-till and residue management (Dalal et al., 1995; Havlin et al., 1990; Robinson et al., 1996). However, it might be possible that long-term manuring practices and balanced fertilization under rainfed conditions could sequester SOC as well (Ryan, 1998). In India, Gupta and Venkateswarlu (1994) observed that application of manure at 10 Mg ha1 increased SOC concentration. Thus, recycling of organic materials is of utmost importance to maintain SOC and soil physical properties. Due to poor socio-economic conditions of local farmers in the hill region of northern India, livestock rearing is given high importance. Farmers get reasonably good quantity of fodder from uncultivated lands (except during winter months) and use rice (Oryza sativa L.) and wheat (Triticum aestivum L.) straw to feed their livestock. Hence, the most commonly used organic material by local farmers is FYM (Mishra and Sharma, 1997). To maintain soil productivity, farmers of this region invariably apply FYM along with occasional dose of N to cereal crops. Wheat–soybean [Glycine max (L.) Merr.] rotation is one of the profitable agricultural production systems in the Indian Himalayas (Kundu et al., 1990). The crops are grown under irrigated conditions in some pockets of the region to get better productivity, especially with fine textured soil. Results of field experiments clearly indicate that with the adoption of high yielding cultivars and adequate use of mineral fertilizers, yield of wheat– soybean cropping system under irrigated conditions could be increased from subsistence level to economically profitable level (Ved Prakash et al., 2002). Even if soybean were grown on residual fertility of wheat, system productivity would be economical (Ved Prakash et al., 2002). But in this region, due to various socioeconomic constraints, the use of chemical fertilizers is far from satisfactory. In Uttaranchal, India, for example, where the present study was undertaken, the average annual fertilizer use in soybean–wheat does not exceed 30 kg ha1, and the ratio of N:P:K used by farmers is 9:2:1 (Sharma et al., 2003), against the recommended ratio of 4:2:1. Although crop productivity is sustained mainly through the application of FYM in the Indian Himalayas, little information is available on the effect of FYM on SOC storage and the distribution of SOC content in different aggregate sizes. Hence, our hypothesis was that the concentration of SOC in different aggregate size fractions and soil aggregation and water transmission would be influenced by the application of fertilizers alone and with manures. The

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objectives of the present study were (i) to assess the effect of mineral fertilizer and FYM addition on the changes in SOC content in whole soil as well as in different aggregate sizes, and (ii) to investigate the effects of long-term manure and fertilizer application on water infiltration, sorptivity and saturated hydraulic conductivity in a silty clay loam soil (Alfisol) under sub-temperate Indian Himalayas in an irrigated wheat– soybean cropping system. 2. Materials and methods 2.1. The experiment The experiment was initiated during rabi (winter) 1995–1996 at Vivekananda Institute of Hill Agriculture, Almora (298360 N and 798400 E, 1250 m a.m.s.l.), Uttaranchal, India. The climate of the region is subtemperate. During the last 30 years the average daily maximum and minimum air temperatures ranged from 31.7 to 20.6 8C (June) and 17.8 to 1.1 8C (January). The mean annual rainfall was 1058 mm. Approximately, 70% of the total precipitation occurred during the rainy season (June–September). Initial soil characteristics are shown in Table 1 and the climatic properties during the experimental period are shown in Table 2. The experiment included two crops per year, wheat (November–April) and soybean (June–October) with six treatments arranged in a randomized complete block design with four replications. The treatments were no fertilizer and no manure (unfertilized control); 120 kg N ha1 (N); FYM at 10 Mg ha1 (FYM); 120 kg N ha1 + 26 kg P ha1 + 33 kg K ha1 (NPK), 120 kg N ha1 + FYM at 10 Mg ha1 (N + FYM) and NPK + FYM at 10 Mg ha1 (NPK + FYM). The individual plot size was 17.5 m2.

Table 1 Initial soil properties at 0–15 cm soil layer Properties

Values

Texture Bulk density (Mg m3) pH (1:2.5, soil:water) CEC [cmol (p+) kg1] EC (dS m1) Total soil organic C (g kg1) Total N (g kg1) Available N (mg kg1) Available P (mg kg1) Available K (mg kg1)

Silty clay loam 1.36 6.4 13.5 0.12 7.31 0.82 102 5 82

CEC: cation exchange capacity; EC: electrical conductivity of soil solution.

2.2. Crop management Pre-sowing irrigation was given in wheat to facilitate field preparation and crop establishment in all years except in 1997, as rainfall received in early November was adequate. Three days after irrigation, FYM was applied on a fresh weight basis in plots under respective treatments and incorporated in the soil with a spade during field preparation. In this region, due to small, scattered and sloping lands, most of the operations to prepare the cultivated plots are carried out manually. The advantages of manual tillage include lower soil erosion and compaction compared to tillage with the help of heavy machineries. Fertilizers were applied before last plowing to wheat crop every year. Full rate of P as single super phosphate and K as murate of potash was applied at the time of land preparation. Nitrogen was applied in three equal splits: at the time of field preparation, at crown root initiation and at tillering stage. Fields were tilled by hand with a spade to 15 cm soil depth and leveled properly. Wheat cultivar VL-616 was sown (100 kg seed ha1) in rows 20 cm apart at a depth of 5 to 6 cm manually. Based on our analysis of every alternate year we found that FYM had 370 g moisture kg1 and contained 7.0 g N kg1, 1.9 g P kg1 and 5.8 g K kg1 (oven-dry weight basis) and the C:N ratio of the applied FYM was 29:1. Isoproturon [3,-(4-isopropylphenyl) 1,1-dimethyl urea] was sprayed at 1 kg a.i. ha1 35 days after sowing of wheat to control weeds. Wheat was harvested manually 5 cm above the ground using sickles and aboveground biomass was removed from the field. Soybean (80 kg seed ha1) was sown in the second week of June each year. Before seeding, the land was tilled twice by hand with a spade to 15 cm soil depth. Soybean cultivar VLS 2 was sown in rows 40 cm apart at a depth of 4–5 cm by hand. Both wheat and soybean cultivars used in this study were very much in use at our farm and are popular among the local farmers of this region. After seeding, a light roller was dragged to cover the seeds. To control weeds in soybean, Alachlor [2chloro-N-(2,6-diethylphenyl)-N-(methoxy-methyl) acetamide] at 2.0 kg a.i. ha1 was sprayed as preemergence followed by one manual weeding 40 days after sowing. Generally no disease infestation was observed in soybean. However, frog-eye spot disease caused by Cercospora sp. affected the crop in 1998, 2000 and 2003 and was well controlled by two foliar sprays of 0.2% Mencozeb. In irrigated conditions, farmers of this region also apply pesticides depending upon the economic loss likely to be caused by pathogens/insects.


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Table 2 Climatic pattern observed during the crop growing seasons of 1995–2003 Minimum temperature (8C)

Maximum RH (%)

Minimum RH (%)

Wheat growing season November 23 December 20 January 18 February 20 March 24 April 29

4 0 0 3 6 10

95 96 83 82 77 70

37 37 35 35 32 27

Soybean growing season June 30 July 30 August 29 September 28

19 21 21 18

75 79 80 81

50 57 59 54

Months

Maximum temperature (8C)

Evaporation (mm day1)

Sunshine (h)

8 17 56 56 34 50

2.0 1.4 1.3 1.8 2.9 4.1

7.9 7.2 6.7 6.8 7.8 8.9

139 193 194 99

4.3 3.5 3.0 3.0

6.8 5.2 4.7 5.8

Rainfall (mm)

passed through a 2 mm sieve and the other portion (