AERIAL ACCUMULATION AND PARTITIONING OF NUTRIENTS BY HARD RED SPRING WHEAT

Periods of maximum hard red spring (HRS) wheat (Triticum aestivum L.) nutrient demand need to be determined in order to develop best nutrien t management practices, and to provide data for nutrient uptake modeli ng. Aerial (aboveground biomass) whole plant samples of irrigated HRS wheat were collected from the field at 16 growth stages and separated into leaves, stems, heads, and grain for dry matter determinations and analyzed for N, P, K, Ca, Mg, S, Cl, Zn, Mn, Fe, and Cu concentration s. Accumulation curves were computed for each plant part for the growi ng season from compound cubic polynomial models based on accumulated g rowing degree units (GDUs). Total aerial accumulations of dry matter, N, P, K, Ca, Mg, S, Cl, Zn, Mn, Fe, and Cu were 14400, 116, 30.8, 103, 9.2, 9.3, 15.2, 32.3, 0.18, 0.58, 2.05, and 0.045 kg/ha, respectively . Grain at maturity accumulated greater than 78% of the total aerial N , P, and Zn, while it contained less than 20% of the aerial accumulate d K, Ca, Cl, and Fe. Nitrogen and Fe were rapidly accumulated near 200 GDU, while P, K, Ca, Mg, S, Cl, Zn, Mn, and Cu were most rapidly accu mulated near 600 GDU. Accumulation rates were 183, 2.9, 0.90, 0.72, 0. 008, 1.41, 0.29, and 0. 12 kg/ha/d for dry matter, N, P, K, Ca, Mg, S, and Cl, respectively, and 136, 1.7, 0.48, 0.13, 0.004, 0.78, 0.20, an d 0.02 g/ha/d, respectively, during grainfill. This plant information suggests the timing of in-season nutrient applications, and when integ rated with other agronomic practices could improve overall nutrient ma nagement for HRS wheat in the northern Great Plains.