Intercropping and mulching in rain-dependent cotton can improve soil structure and reduce erosion

Transgenic Bt (Bacillus thuringiensis) cotton (Gossypium spp.) hybrids are grown at wide-row spacing in India. Farmers practice traditional methods of cultivation that involve excessive inter-row cultivations. These practices exacerbate soil erosion and run-off ultimately leading to land degradation. Growing a cover crop between the cotton rows and retaining its residues in situ can reduce erosion and runoff, and improve soil productivity. We compared the effects of growing an intercrop {sorghum (Sorghum bicolor), sunnhemp (Crotolaria juncea) or sesame (Sesamum indicum)} in between the cotton rows and retaining its residues as in situ mulch, vis-à-vis plastic, newspaper mulch and the traditional farmers’ practice (FP) on the soil physical properties (soil microstructure, porosity, water stable aggregates, infiltration rate, soil erosion and soil loss) of a Vertisol near Nagpur in central India. Digital image analysis of the micrographs obtained by a scanning electron microscope indicated porosities were highest with intercropping (53–58%) and the least with the FP and plastic mulching (35–36%). Infiltration rate was in the order of intercropping (19.4–22.6 mm h−1) > newspaper mulch (14.5 mm h−1) > FP (13.8 mm h−1) > plastic mulch (12.3 mm h−1); while the reverse occurred with respect to run-off. Although run-off was the greatest (577 mm) in the plastic mulched plots, soil loss was negligible (0.58 Mg ha−1). Intercropping resulted in 35% less soil loss than FP (6.7 Mg ha−1). This study pointed out that growing an intercrop and retaining its residues as in situ mulch between the cotton rows can improve soil condition by increasing soil microstructure, water stable aggregation and infiltration rate, and reducing run-off and soil loss