RESPONSE OF SPRING WHEAT AND BARLEY TO NITROGEN, PHOSPHORUS AND POTASSIUM

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Abstract
Fertilizer trials with spring wheat and barley were conducted at a total of seven and nine locations, respectively, during a three-year period. Treatments consisted of three rates of N, of P and of K in all possible combinations. Although the soils varied in their chemical properties, grain yields increased with the second increment of N in some years and the crude protein content of the grain increased with the third increment in all years. Grain yields were not increased by the second increment of either P or K. Although the effects of increasing rates of N, P and K on the levels of these nutrients in plant tissue were predominantly linear, increases in N levels were of much greater magnitude than increases in either P or K levels. The results indicate that N, P and K at approximately 135, 39 and 37 kg/ha, respectively, should be generally adequate.