Crop rotation - an alternative to mechanical subsoiling for rainfed cotton of central India

Soil compaction issues are increasing with greater use of heavy farm machinery for field operations. Although subsoiling can alleviate soil compaction, it is an energy-intensive and costly process. Therefore, we tried an alternative approach of cotton crop rotation with deep-rooted annual field crops and cover crops. Thus far, no information is available on these strategies for rainfed cotton grown on the rainfed Vertisols of central India. Field experiments were conducted from 2017-18 to 2021-22 involving deep and shallow subsoiling compared with cotton crop rotation with field crops (pigeonpea, radish or mustard, soybean), cover crops (sunnhemp, sesbania) and control (no subsoiling and no cover crops). We measured the effects of these treatments on the penetration resistance (PR), soil organic carbon (SOC), labile (C L ), nonlabile C (C NL ) and seedcotton (SCY) yield. Across treatments, PR decreased up to 0.30 m, followed by an increase at 0.45 m soil depth. Treatments with deep subsoiling, averaged across soil depths and rows, recorded the least PR values (0.37 MPa) followed by the crop rotation treatments (0.45 to 0.49 MPa) while the control plots had the highest PR (0.72 MPa). The rotation plots had significantly higher SOC content (6.3 to 6.5 g kg -1 ) than the subsoiling and control treatments (5.0 g kg -1 ). The C L content was significantly greater in the sesbania and sunnhemp, followed by the soybean and pigeonpea rotated plots. Averaged over four seasons (2018-19 to 2021-22), SCY was significantly (p<0.01) greater in the treatments involving rotation with field crops (2463 to 2537 kg ha -1 ) than those with cover crops (2086 to 2253 kg ha -1 ), subsoiling treatments (1780 to 1985 kg ha -1 ) and the control (1681 kg ha -1 ). Our results suggest that rotating cotton with deep-rooted annual field crops is an effective strategy for improving cotton productivity through possibly breaking hardpan and improving soil quality. • Deep-rooted annual crops and cover crops were evaluated as an alternative to subsoiling • Subsoiling reduced penetration resistance and improved cotton root growth • Cotton yield was higher after radish/mustard, pigeonpea or soybean than after subsoiling • Cover crops improved the organic C content and had a higher proportion of labile C fraction