MODELING MAIZE GRAIN YIELD DEPENDING ON RATES AND RATIOS OF MINERAL FERTILIZERS ON SALINE SEROZEMS OF SOUTHERN KAZAKHSTAN

The article presents the results of a study of various doses and ratios of mineral fertilizers on old-irrigated saline gray soils of the Shaulder massif in the Turkestan region on corn grown for grain, to optimize the mineral nutrition of plants and model the formation of biomass and yield. An analysis was made of the dynamics of accumulation of raw biomass and the formation of yield, as well as the economic efficiency of using fertilizers (nitrogen, phosphorus, potassium) for corn grain on saline gray soils. The study was based on the principles of multivariate field experiments using stepwise regression analysis. Studies have shown that on saline gray soil, the biomass of corn increases with increasing doses of fertilizers, especially nitrogen. Without fertilizers, the biomass of one plant is 328 and 408 g in the flowering and ripening phases, and with maximum doses of N200P150K150, it reached 641 and 907 g, respectively. In the flowering phase, as shown by the regression equation with a high coefficient of determination (R²=0.963), there is a positive effect of nitrogen and phosphorus, with the former having the greatest effect, and the effect of potassium was insignificant (P>0.05). Processing the results for the ripening period made it possible to obtain a multiple regression model with a high coefficient of determination (R²=0.979), confirming that fertilizers are responsible for 98% of the variability of biomass in the ripening phase, where all three nutrients in unilateral action and nitrogen in interactions with potassium have a positive effect influence. The regression equation describing the dependence of corn grain yield with high accuracy (R²=0.979) indicates the leading positive role of nitrogen and phosphorus, but the interaction of nitrogen with potassium had a negative effect on productivity. The yield in the variant without fertilizers is 6.3 t/ha, and in the variant with doses of N200P150K150 - 13.0 t/ha, while the cob length is 16.2 and 23.9 cm, width is 4.2 and 5.2 cm , the number of grains in the cob is 375 and 593 pieces, the weight of 1000 grains is 303 and 427 g, respectively. A regression model with a high coefficient of determination (R²=0.849) shows that phosphorus stimulates grain formation, and excess nitrogen can reduce it against the background of the toxic effect of soil salinity. The most economically beneficial are moderate doses of fertilizers - N120P90K0 and N160P120K30, which provide a balance of yield and costs with a profitability of 119 and 107%, respectively. The maximum income (1167 thousand tenge/ha) obtained when applying doses of N200P150K150 is accompanied by high costs (699 thousand tenge/ha). Thus, moderate doses of fertilizer are more effective in increasing corn yield on saline soils.