Effect of row-orientation and NPK fertilizer levels on the performance of maize-soybean intercropping system

Monoculture has been recognized as a major threat to sustainable maize production, driven by the depletion of soil organic matter and the reduction of agrobiodiversity. Maize-legume intercropping is an established practice that can effectively improve resource use efficiency and land productivity. However, current research remains limited regarding the combined effects of row orientation and balanced NPK fertilization on intercropping systems. This study was carried out to investigate the impacts of row orientation and NPK application rate on the agronomic performance, productivity and economic return of a maize-soybean intercropping system under the agroecological conditions of Bangladesh. A field experiment was conducted using a split-plot design, with two row orientations [North-South (N-S) and East-West (E-W)] arranged as main plots, and four NPK application rates [0% (F 0 ), 75% (F 1 ), 100% (F 2 ), and 125% (F 3 ) of the locally recommended NPK rate] arranged as subplots. We measured a range of indicator parameters including plant growth traits, yield components, grain yield, land equivalent ratio (LER), maize equivalent yield (MEY) and economic returns. The results showed that row orientation had negligible effects on maize growth and grain yield, but exerted a significant influence on soybean performance. Compared with the E-W orientation, the N-S orientation produced higher soybean grain yield (1.11 t ha -1 ), higher harvest index, and higher maize-equivalent yield (12.25 t ha -1 ). Increasing NPK application rate significantly promoted the growth, yield components, grain yield and stover yield of both maize and soybean. The highest grain yields of maize (12.68 t ha -1 ) and soybean (1.47 t ha -1 ) were recorded in the F 3 treatment. The highest LER (2.25) was observed in the N-S × F 3 combination. Economic analysis further demonstrated that the F 3 treatment achieved the optimal economic performance, with the highest gross return (BDT 480,537 ha -1 ), net return (BDT 233,124 ha -1 ) and benefit-cost ratio (1.94). This study concludes that the highest agronomic performance, land use efficiency and economic return of maize-soybean intercropping in the study region can be achieved when adopting North-South row orientation and applying 125% of the recommended NPK fertilizer rate.