THE EFFECT OF FALL-APPLIED N AND P FERTILIZER AND TIMING OF N APPLICATION ON YIELD AND PROTEIN CONTENT OF WINTER WHEAT GROWN ON ZERO-TILLED LAND IN MANITOBA

Field studies were conducted to evaluate the effect of the rate and timing of N application and the amount of seed-placed P on grain yield and protein content of winter wheat grown on zero-tilled and conventionally tilled land in Manitoba. Yield increased with increasing amounts of fall-applied N and P. Yield, as affected by time of N application, decreased in the order: spring, freezeup, seeding, and applied on snow in winter. Split application of N resulted in yields comparable to that obtained with N applied at seeding. Protein concentration in grain decreased when small amounts of N led to large increases in dry matter but increased when sufficient quantities of N fertilizer were added to meet the requirements for both yield and protein. The amount of fertilizer N recovered in the grain did not differ with time of application in 1979–1980. However, in 1980–1981, N recovery was consistently higher with spring applications of N than with applications at any other time. Differences between the two seasons reflected the higher moisture availability for crop growth in 1980–1981 as compared to 1979–1980. Key words: Winter wheat, zero tillage, nitrogen, phosphorus, protein