EFFECTS OF MINERAL FERTILIZER RATES ON YIELD COMPONENTS AND GRAIN YIELD OF IRRIGATED WINTER WHEAT IN THE SOUTH OF KARAKALPAKSTAN

The response of winter wheat (Triticum aestivum L., cv. Krasnodarskaya-99) to mineral fertilizer levels viz. N0P0K0, N120P80K60, N180P120K90 and N240P160K120 kg ha-1 was studied under the conditions of newly irrigated soils in Yanbashkala, south Karakalpakstan, Uzbekistan. Two years data during winter wheat season in 2013/14 and 2014/15 indicated that yield components and grain yield adversely affected by low soil fertility and no fertilizer application. External nutrient input as application of N180P120K90 kg ha-1 substantially increased spike length (SL), number of spikelet spike-1 (SNS), number of grain spike-1 (GNS), grain weight spike-1 (GWS) and 1000-grain weight (TGW) and grain yield. Further elevation of mineral fertilizer rate up to N240P160K120 kg ha-1 did not increase grain yield and improve yield components except GNS. Application of N240P160K120 kg ha-1 resulted in the highest GNS but decreased TGW in 2013/14 but these were not corroborated in 2014/15. Regression analysis of yield component and grain yield data revealed that among all variables investigated only GNS was significant at p<0.05. Regression model was developed to predict grain yield as a function of number of kernels spike-1 . Mineral fertilizer of N180P120K90 kg ha-1 was found to be an optimum r