Yield Responses of Upland Rice Varieties to Low N Conditions in Central Kenya

Growth, yield, and yield components of five upland rice varieties (MWUR 1, MWUR 4, NERICA 1, NERICA 4, and IRAT109) were evaluated under four different soil N conditions (0, 26, 52, and 78 kg N/ha) to identify the factors contributing to their adaptability to low soil-fertility. The results showed that MWUR 1, MWUR 4, and NERICA 4 had greater adaptability to low N conditions. Specifically, MWUR 1 showed the highest adaptability to low soil fertility. The greater low soil-fertility adaptability of these varieties was attributed to their ability to maintain dry matter production. Furthermore, their greater dry matter production under low N conditions could be attributed to the increased root length, which allowed improved soil nutrient absorption. Our findings suggest that rice grain yield was mainly restricted by sink size, particularly panicle number per plant under low N conditions. The higher grain yield of MWUR 1 under low N conditions could be attributed to greater tillering ability. Thus, MWUR 1 could be a good candidate for cultivation under nutrient-poor soil conditions.