Irrigation Scheduling And Phosphatic Fertilizer On Growth, Yield, And Yield Components Of Nerica Rice In Kirinyaga County, Kenya

ABSTRACT

Rice is an increasingly important cereal crop in Kenya with the major production being done in Mwea, Kirinyaga County. Rice farming faces notable challenges such as; erratic rainfall, waterscarcity, mismanaged irrigation and low soil phosphorus. In that view, therefore, an experiment was conducted at KALRO-Mwea for two seasons to investigate the effect of irrigation scheduling and phosphorus levels on growth, yield and yield yield components of two Nerica rice varieties. The experiment was laid out in RCBD in split-split plot arrangement replicated thrice. Four irrigation schedules (Daily, Every 3 days, Every 5 days and Weekly) formed main plots, two rice varieties (Nerica 4 and Nerica 11) constituted the sub plots and four phosphorus levels (0 kg P haˉ¹, 25 kg P haˉ¹, 50 kg P haˉ¹ and 75 kg P haˉ¹) the sub-sub plots. Data was collected in both seasons on plant height, tiller number, leaf number, leaf fresh weight, leaf dry weight, SPAD readings, panicle length, panicle number, root biomass, shoot biomass, mature panicle number, filled grain number, unfilled grain number, 1000-grain weight, net plot grain weight, grain moisture content and on grain yield. Soils were also sampled for phosphorus determination and effect on the selected soil properties in the plots before planting and at harvest. Shoot biomass samples were also obtained from the plots at harvest, and nitrogen uptake and phosphorus in plant tissues was determined through nitrogen and phosphorus tissue analysis. Data collected were subjected to analysis of variance (ANOVA) using GenStat version 15.1 and means separated using Fischer‟s Protected LSD test. Results revealed significant differences (P≤0.05) amongst irrigation schedules regarding 1000-grain weight in season 1, where highest (55.92g) and least (41.0 g) in Nerica 4 under every 3 days‟ and weekly schedules in season 1 respectively. Significant effect was also elicited on unproductive tillers in season 2 where highest (1.783 per hill) in Nerica 11 under every 5 days‟ schedule, and least (1.0 per hill) in Nerica 4 under weekly irrigation schedule was recorded. Phosphorus levels significantly influenced 1000-grain weight, where highest (76.3 g) in Nerica 4 under 50kg P haˉ¹ in season 1 and least (19.6 g) in Nerica 11 under 25kg P haˉ¹ / 75 kg P haˉ¹ in season 2 were recorded. Phosphorus level treatments also significantly influenced number of panicles per hill, where highest and least panicles of 17.3 per hill under 50kg P haˉ¹ in season 1 and least of 8.7 per hill in Nerica 11 under control in season 2 were recorded. There were no interactions between irrigation schedule and phosphorus level on all the parameters. Phosphorus level led to decreases in soil pH, CEC, Soil Phosphorus and increase in soil nitrogen. Inferentially, the weekly irrigation schedule on growth parameters, yield components and yield of Nerica 4 proved best for water-use efficiency by the crop, at the same time water that would have gone to waste would be saved for more crop production in the expanded land. The 50 Kg P haˉ¹ level on growth parameters, yield components and yield of Nerica 4 was the most superior in the experiment undertaken. Further, the effect of 50 Kg P haˉ¹ level acidifed the soils more and reduced the soil cation exchange capacity as well. The 75 Kg P haˉ¹ level led to more accumulation of phosphorus in the soils, and the increase of total soil nitrogen at harvest. Lastly, the 75 Kg P haˉ¹ level proved to have contributed to the plant-tissue phosphorus and plant-tissue nitrogen on Nerica 4 and Nerica 11 respectively. It is therefore recommended that farmers grow Nerica 4 under irrigation once a week and utilize 50 Kg P haˉ¹ as these gave the highest rice yields.