Medium-term impact of resource conservation technologies on physical environment of soil in rice-wheat system
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Rice-wheat system is a predominant cropping system in India in general and Punjab in specific. Repeated puddling for rice cultivation and extensive tillage during wheat has adversely affected the physical environment of soil. Keeping in view the long-term sustainability of the conventional rice-wheat systems, there has been more emphasis nowadays on adopting and promoting resource conservation technologies. Therefore, a medium term study was conducted to evaluate the impact of tillage, mulch and establishment methods on soil physical, biochemical and microbial characteristics of sandy loam and loam soil. In sandy loam soil the experiment started in year 2010 with four treatments i.e. conventional tillage both in wheat and direct sown rice (CTDSR/CTW), zero tillage both in wheat and direct sown rice (ZTDSR/ZTW), conventional tillage both in wheat and direct sown rice with mulch (CTDSR/CTW+M) and zero tillage both in wheat and direct sown rice with mulch (ZTDSR/ZTW+M) and in loam soil the experiment started in year 2011 with two treatments i.e. zero tillage both in wheat and direct sown rice (ZTDSR/ZTW) and conventional tilled wheat followed by transplanted rice (PTR/CTW). In mulch treatments, rice residues were retained in wheat and in without mulch treatments, rice residues were removed. Soil physical characteristics like water stable macro aggregates > 0.25 mm (WSMacA), water stable micro aggregates (WSMicA), mean weight diameter (MWD), bulk density (BD), infiltration rate (IR), soil moisture characteristics, soil organic carbon (SOC), soil enzymatic activities (dehydrogenase, alkaline and acid phosphatase and urease), microbial biomass carbon and soil respiration were evaluated. In sandy loam soil, in zero tillage treatments in the surface layer (0-15 cm), the soil physical characteristics like WSMacA were 8.2% higher, MWD was 31.8% higher and BD was 4% higher as compared to conventional tillage. In the sub- surface soil layer (15-30 cm), WSMacA and MWD showed the similar trend, but BD was lower (5.6 %) in zero tillage treatments. With addition of mulch, WSMacA increased by 16%, MWD by 39% and BD decreased by 2 % in the surface layer. The SOC increased by 9 % at 0–15 cm, and 25% at 15–30 cm soil depths with ZT over CT. Mulched plots showed significant increase in SOC by 18% than CT. Higher steady state IR was observed under zero tillage plots, in spite of the fact that surface soil layer was having high BD in these treatments, which show the predominant effect of higher SOC in these treatments. Higher values were observed for soil enzymatic activities (dehydrogenase, akaline and acid phosphatase and urease), microbial biomass carbon and soil respiration in the conservational agriculture based treatments (ZT and mulching). In loam soil, physical and biological characteristics of soil after 5 years of continuous ZT and CT in rice- wheat system were analyzed. BD was higher in surface layer under ZTDSR/ZTW than PTR/CTW and showed significant decline in sub-surface soil layer. SOC, WSMacA, IR, soil water retention at different soil matric potentials, soil enzymatic activities (dehydrogenase, akaline and acid phosphatase and urease), microbial biomass carbon and soil respiration showed significant improvement under ZTDSR/ZTW as compared to PTR/CTW. Thus our medium- term study on both sandy loam and loam soils suggest that resource conservation technologies like direct dry-seeded rice (DSR), zero tillage (ZT) and mulching improves soil physical characteristics and these needs to be promoted for sustainable soil health.