Overcoming Competition from Intercropped Legumes on upland Rice (Oryza sativa L.)with Seeding Rates and Suitable Legume

Upland rice (Oryza sativa L.) is a staple cereal in upland farming systems; however, its inherently low productivity often necessitates intercropping to enhance overall land use efficiency.Among intercropping strategies, integration with legumes has shown promise due to their nitrogenfixing ability and contribution to system sustainability.Nevertheless, most existing studies have primarily emphasized total system productivity, with legume yield often disproportionately influencing outcomes.The present study aimed to improve the performance of upland rice by evaluating increased seeding rates and identifying the more suitable legume intercrop for optimizing both rice yield and system productivity.A two-factor experiment was conducted using a Randomized Complete Block Design (RCBD) with three replications.Factor A consisted of varying seeding rates of rice, while Factor B represented two intercropping systems: rice intercropped with mungbean (Vigna radiata, CS-M) and rice intercropped with cowpea (Vigna unguiculata, CS-C).The data collected for both rice and legumes included the leaf area index (LAI), the dry matter yield (DMY), and the land equivalent ratio (LER).For rice, it also included the harvest index (HI), the number of panicles, the number of filled grains per panicle, the weight of 1000 seeds, and the grain yield.For legumes, it also included the number of branches and pods per plant, the number of seeds per pod, the weight of 100 seeds, and the seed yield.The results showed that CS-C at a rate of 75kgha (SR-2) gave the most rice grain production and Land Equivalent Ratio of 1.18.These results were attributed by higher 1000-seed weight and grain yield of rice, and high harvest index.In contrast, rice yields under the CS-M and CS-C systems were 60% and 38% lower, respectively, compared to sole rice cultivation, regardless of seeding rate.The reduced yield in the CS-M system was likely due to excessive shading caused by the dense branching of mungbean plants, which suppressed rice growth.Overall, the study suggests that intercropping upland rice with cowpea at a seeding rate of 75kgha offers a more effective strategy to enhance rice productivity and land use efficiency.These findings highlight the importance of selecting appropriate legume species and optimizing planting density to improve the performance of upland rice-legume intercropping systems.