Intercropping Legumes with High-Density Cotton to Improve the Land Use Efficiencies of Rainfed Vertisols of India

Cotton (Gossypium hirsutum L.) is typically grown with wide-row spacing (0.6–1.5 m), offering an opportunity for intercropping. It is hypothesized that incorporating a legume could enhance system productivity or cotton equivalent yield (CEY). However, there is limited knowledge about intercropping legumes in cotton at high density (HD) on rainfed Vertisols. During the 2015–2017, field experiments were conducted to identify efficient nitrogen (N)-fixing legumes [blackgram (Bg), green gram (Gg), cowpea (Cp), soybean (Sb), cluster bean (Cb), pigeon pea (Pp), dolichos (Dc), and groundnut (Gn)] as intercrops in additive series (1 + 1) with cotton grown at a row spacing of 0.90 m compared to sole cotton (Cs). Cotton at a spacing of 0.45 m was also included (Cd). Based on the results of 2015–2017, another study (2017–2020) was conducted with different duration (short, medium, and long) of six legume (Bg, Gg, Cp, Sb, Cb and Gn) cultivars to assess the feasibility of cotton and legume intercropping (CLI) systems. During 2015–2017, Pp and Dc intercrops reduced cotton yield (10–11%) than Cs. However, CEY results indicated that CLI, under rainfed conditions, had higher productivity (30%) than Cs, except Pp. Positive values (1.40–1.78) of land equivalent ratio demonstrated the benefits of CLI compared to Pp (0.74–0.69) or Cs (1.00). Legumes also enhanced area-time equivalent ratio by 14–28% and land use efficiency by 97% compared to Cs. Competitive ratio or aggressivity of cotton was not observed between CLI, except Pp. All the indices indicated that pigeon pea and dolichos are not suitable for intercropping in additive series. Among the legume durations, the indices indicated that maximum gains were observed with the short-duration legumes suggesting the possibility of CLI technology for sustainable production in rainfed areas.