Yield gains and resource use advantages driven by legume choice and row ratio in cotton/legume intercropping under arid-irrigated conditions

Context

Intercropping ensures stable yields and aboveground productivity through efficient resource consumption by exploiting species complementarities. Tthe wide space between cotton rows and inefficient resources utilization presents an opportunity to leverage intercropping to optimize resource use.

Objective

We hypothesized that cotton/legume intercropping could (i) achieve higher land and nutrient productivity than sole cotton and (ii) produce additional legume (soybean/mungbean) yield while maintaining cotton cultivation area and yield with reduced land and anthropogenic inputs (nitrogen; N, and phosphorus; P).

Methods

This three-year field study (2022–2024) on cotton/legume intercropping, with varying legume row ratios (two (2LRs) or three (3LRs) rows of legumes planted between every two rows of cotton), was conducted in arid-irrigated conditions. Growth indices (leaf area index and dry matter accumulation), N and P uptake, seed cotton/seed yield, system level land- and nutrient-use advantages, measured as land equivalent ratios (LER) for land (LER_L), N (LER_N), and P (LER_P), and economic returns were compared between sole cotton and cotton/legume intercropping systems.

Results

Intercropping with 2LRs achieved higher growth indices, nutrient uptake, and yields than with 3LRs. With 2LRs, intercropped mungbean and soybean achieved 64 % and 79 % of their sole yield; intercropped cotton produced 87 % and 83 % of their sole yield in cotton/mungbean and cotton/soybean intercropping, respectively. Similarly, with 2LRs, the total N and P uptake, calculated as cotton N/P uptake + legume N/P uptake, was 31 %-36 % higher for N and 9 %-15 % higher for P in cotton/legume systems compared to the corresponding values in sole cotton. Overall, the LER_L, LER_N, and LER_P, ranged from 1.34 to 1.63, 1.44–1.70, and 1.22–1.54, respectively, in cotton/legume intercropping, which increased the net economic profit of cotton/mungbean intercropping with 2LRs (USD 472 ha⁻¹) and 3LRs (USD 290 ha⁻¹) by 122 % and 37 %, and cotton/soybean intercropping with 2LRs (USD 692 ha⁻¹) and 3LRs (USD 444 ha⁻¹) by 226 % and 109 %, respectively, than sole cotton (USD 213 ha⁻¹). This improvement in economic returns was primarily due to the additional legume yield obtained from the efficient resource utilization between intercrops, which was not fully utilized by cotton in sole cropping— notably, without extra expenditure on land preparation, irrigation, or fertilizers.

Significance

Our study suggests that cotton/legume intercropping could be adopted as a productive strategy to achieve higher and stable yields with less land and fewer nutrient inputs, promoting economic sustainability for resource-poor cotton farmers while reducing environmental footprint compared to a sole cotton cropping system.