Effects of Watering Regimes, Fertilizer Levels on Nutrients Uptake, Growth and Yield of Upland Rice in Mwea, Kenya
Kirambia, Rosemary Karimi
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Upland rice contributes substantially to food and nutritional security in many African countries. Introduction of NERICA cultivars was meant to boost the production and hence area under upland rice. Factors such as poor soils and inadequate rainfall limit both the quality and achievement of yield targets. The research aimed to establish the impact of water levels, fertilizer rates on nutrients uptake and performance of NERICA 1 rice variety. It was carried out in a greenhouse setting in 2017 for two seasons and a field experiment at Kirogo farm at KALRO-Mwea. The treatments were; two water rates; 3.5 mm day-1 and 7.0 mm day-1; four rates of Phosphorus from Triple superphosphate applied at a ratio of 0, 20, 40, 60 kg ha-1 P2O5 and 4 rates of Potassium (K2O) at 0, 10, 20, 30 kg ha-1 applied as murate of potash. 60 kg ha-1 of N was applied in all treatments. Experimental set up was arranged in split plot layout replicated three times, whereby water levels were assigned in the main plot while fertilizer rate in sub-plot. Plant height, number of tillers and leaves, were growth parameters measured while yield components included weight of panicle, percentage of filled grains, weight of 100 dry grains, grain width/length ratio and overall grain yield ha-1. Details of nutrients uptake (NPK) in straw and crude protein in grain, and soil analysis were recorded. The data was subjected to F-Test at 5% significance level using SPSS version 23 and means separation done using LSD, DMRT and T-test. Water levels had significant effect at p= 0.05 on growth parameters, yield of crop and WUE. Maximum grain yield of 4,535.6 kg ha-1 and 2,705.1 kg ha-1was achieved with 7.0 mm day-1 in season one and two respectively while top most crop yield of 3,745.4 kg ha-1 was attained by P1K2 (0 kg ha-1 P2O5+0 kg ha-1 K2O) fertilizer level, being average of two seasons. In second season, fertilizer levels had significant effect (p= 0.05) on WUE with P1K2 (0 kg ha-1 P2O5+0 kg ha-1 K2O) giving highest value of 0.66.00 kg ha-1m-3,whereas P4K4 (60 kg ha-1P2O5+30 kg ha-1 K2O) gave lowest yield of 0.36 kg ha-1m-3, as an average for the two seasons. P3K3+W2 (40 kg ha-1 P2O5+20 kg ha-1 K2O -7.0 mm day-1 water fertilizer interaction had highest yields of 4,603.6 kg ha-1 whereas P4K4W1 had the least crop yield of 1,832.4 kg ha-1. Significant interaction effect (p= 0.05) was observed in water regimes and fertilizer rates on WUE in both seasons. Greatest WUE of 0.86 kg ha-1m-3 was achieved in the P1K2W1 (0 kg ha-1 P2O5+10 kg ha-1 K2O) interaction while the lowest (0.30 kg ha-1m-3) was attained by P4K4W2 (60 kg ha-1 P2O5 +30 kg ha-1 K2O+ 7.0 mmday-1). Percentage NPK uptake in straw and crude protein in grain increased with increase of P2O5 and K2O levels up to 20 kg ha-1 above which it dropped. For profit, efficient water use, and good performance of NERICA 1, use of P1K2 (0 kg ha-1 P2O5 + 10 kg ha-1 K2O) with 3.5 mm day-1 while for quality parameters, P2K2 (P2O5, 20 kg ha-1 and K2O -10 kg ha-1) plus 7.0 mm day-1 seems to be the sustainable choice for production of the variety in Kirogo –Mwea soils.