Sugarcane/soybean intercropping enhances crop productivity, nutrient uptake, and net economic return with reduced inputs

Context: Global pressures on the land require a shift to efficient land uses that meet economic and dietary demands and are within planetary boundaries. Important anthropogenic emissions from sugarcane fields around the world and sluggish consumption of resources during the initial canopy growth of this crop provide a chance to leverage the potential of intercropping to make better use of the available resources. Objective: We conducted this study to test whether intercropped soybean with appropriate spatial arrangements have the potential to yield near to its sole system by taking up the under-utilized land and nutrients during the initial 3-4 months of the sugarcane growth. Methods: A three-year field study (2020-2022) was conducted to analyze the effects of different spatial arrangements on sugarcane/soybean intercropping (two soybean rows intercropped between every two sugarcane rows; 2S2Sc, and three soybean rows intercropped between every two sugarcane rows; 3S2Sc) and compare them with corresponding sole systems in terms of crop growth, nitrogen (N) and phosphorus (P) uptake, grain/cane yields, land productivity, and economic returns. Results and conclusions: Results showed that intercrops achieved 91-94% of sole cane yield and 66-81% of sole soybean grain yield, which was mainly due to the improved canopy cover resulting from soybean intercropping during the early cane growth in 2S2Sc and 3S2Sc. The land productivity and nutrient use advantage under sugarcane/soybean intercropping, estimated as the total land equivalent ratios for land, N, and P, were 1.58-1.75 (LERL), 1.72-1.87 (LERN), and 1.38-1.67 (LERP), respectively, which in turn substantially increased the net profit of 2S2Sc (USD 2191, 1426, and 1014 ha-1) and 3S2Sc (USD 1888, 1190, and 780 ha-1) compared to sole sugarcane (USD 1752, 967, and 575 ha-1) in 2020-21, 2021-22, and 2022-23, respectively. The increase in net profit under intercropping was mainly due to the additional soybean grain yield that was obtained from the capture of resources that are not used by sugarcane during its early canopy development phase, most importantly, without investing any extra capital on land preparation, irrigation, labor, and fertilizers. Significance: Our results show that sugarcane/soybean intercropping could be adopted as a potential cropping system for obtaining higher yields with reduced cultivation and anthropogenic inputs (N and P), and it will put