Application of Nitrogen Fertilizer in Dual-Purpose Wheat (Triticum aestivam L.)

Abstract

In the Southern Great Plains winter wheat (Triticum aestivum L.) is mostly used as a dual purpose grain crop and forage crop. Wheat pasture is considered as a valuable source of high-quality forage during the late fall or early spring, when there is no other good quality source of forage available. Pre-plant nitrogen plays an important role for the growth and development of wheat forage. The cost of nitrogen fertilizer has increased significantly in the past few years. Knowledge about the optimal nitrogen level for fall forage production in wheat would allow dual-purpose wheat producers to minimize fertility costs. This study was conducted to evaluate the forage response of the wheat varieties (Jagger, Jagalene, 2174 and OK 102) to pre-plant nitrogen fertilizer. The study was conducted in 2004, 2006 and 2007 in Stillwater, OK. Six levels (0, 30, 60, 90, 120, 150 kg ha^-1) of pre-plant nitrogen fertilizer were applied in a split-block design with four replications. In 2004, N rate of 90, 120 and 150 kg ha-1 produced more forage than other rate of N, but there was no significant difference among N rate. In 2007, N rate of 90 and 150 kg ha^-1 produced more forage than other rates of N and there was no significant difference between these two N rates, whereas, in 2006, it took 150 kg ha^-1 to optimize forage production. So, overall 90 kg ha^-1 was sufficient to optimize agronomic forage production. The variety OK 102 produced the least forage but there were no large difference in the production of forage among other three varieties. This experiment indicates that when residual N (28 kg ha^-1) is present in the soil profile, farmers can maximize net returns without application of additional N for forage production.