Effects of Nitrogen Rates on Morphological Development of Upland Rice Varieties in Mwea, Kirinyaga County, Kenya

Rice is the third most important cereal in consumption after maize and wheat in Kenya. It has been grown as a commercial food crop under irrigated and rain fed ecologies. Low soil Nitrogen (N) fertility is a major constraint to upland rice production in smallholder farmers mostly under rain fed agriculture. This study evaluated the morphological development of upland rice varieties as influenced by different N fertilizer treatments. A field study was carried out at the Kenya Agricultural and Livestock Research Organization experimental farm in Kirinyaga County for two seasons. The experiment was laid down as a randomized complete block design (RCBD) in split-plot arrangement in three replications. The main plot factors were the five upland rice genotypes, MWUR1, MWUR4, NERICA4, NERICA10 and IRAT109, while the subplots factors were the four N rates, 0, 26, 52 and 78 kg N ha-1. In addition calcium ammonium nitrate (26% N) was top-dressed in two equal splits at 21 and 45 days after sowing. Data on plant growth parameters was collected at fortnight interval. The analysis of variance revealed significant (p < 0.05) variation on plant height and tiller numbers due to N rates. However, there was no significant variation in plant height and tiller numbers due to variety. In addition, shoot and root dry weight and leaf area were significantly different due to variety and N rates in both seasons. Finally root dry weight was not significantly different due to variety and N-rates in the two seasons. The current study has shown that increase in nitrogen level lead to significant increase in plant height, tiller numbers, shoot dry weight and root dry weight. The study recommends the use of N fertilizers for rice cultivation to increase N supply in the soil.