Optimizing Upland Rice–soybean Intercropping for Enhanced Productivity, Resource Use Efficiency, and Farmer Income

Abstract

MAK 4 soybean, a widely grown and early maturing variety, offers potential compatibility with upland rice due to its growth habit and soil fertility benefits. The study aims to assess the growth and yield performance of different upland rice varieties when intercropped with MAK 4 soybean.  A field experiment was conducted during the first and second rainy seasons of 2024 and 2025 at the Buginyanya Zonal Agricultural Research and Development Institute, Ikulwe satellite station in Eastern Uganda. The experiment was laid out in a randomized complete block design with three replications, consisting of eleven treatments combining five rice varieties (NERICA 1, NERICA 4, NERICA 10, NamChe 3, and NamChe 5) grown as sole crops and intercropped with soybean (MAK4), alongside a sole soybean control. Plant height and leaf length of intercropped rice were significantly (P≤0.05) greater than those of sole crops, except for NERICA 1 + soybeans. Plant height and leaf length of intercropped rice were significantly (P=0.05) greater than sole crops except for NERICA 1 + soybean. Rice leaf length increased notably in 2024 due to soybean introduction, except for NERICA 10.  Intercropping did not affect MAK4 soybean height, pods per plant or grain yield significantly (P=0.05), over the two years, but reduced soybean pods by 0.08-30% while increasing rice height (0.004-12%) in 2024. Tiller and panicle numbers were unaffected in both years. The combined land equivalent ratio of rice + soybean was 1.75 & 1.68 for NamChe 3 and 1.87 & 1.75 for NamChe 5 + MAK 4 soybean, indicating high land use efficiency. High LEC and REY values occurred with Soybean + NamChe 3 and Soybean + NamChe 5, while low ATER values were observed for the same treatments. TRGYE scores were higher under intercropping than sole rice in both years, with the highest values in 2025. The competition ratio was significantly high (<0.001) under NERICA 1 + soybean (1.98 & 1.34) and low under NamChe 5 (0.83 & 0.85) and NamChe 3 (1.27 & 1.26). The study concludes that NamChe 3 + MAK 4 soybean and NamChe 5 + MAK 4 soybean are sustainable intercropping systems for maximizing land productivity and farmer income in upland systems.