Nitrogen fertilization of dryland grasses in the Northern Great Plains.

Abstract

Dryland grass production is an important agricultural commodity in the Northern Great Plains. Nitrogen (N) fertilizer can increase dry matter production and forage quality, yet there are relatively few rangeland and improved pasture managers who utilize fertilization practices to optimize production. Two trials (1972-1975 and 1978-1981) with 10 common grass species used a single application of 0, 56, or 112 kg N ha-1 and 0, 112, or 224 kg N ha-1 to evaluate long-term grass performance to N fertilization. Dry matter production in each trial was measured annually for 4 years. Yields increased on average 1,340 kg ha-1 with the application of 56 kg N ha-1, and 1,662 kg ha-1 with 112 kg N ha-1 in Trial 1. In Trial 2, yields increased 3,499 and 5,140 kg ha-1 with applications of 112 and 224 kg N ha-1, respectively. Responses to applied N were evident 4 years after application for some species, most likely due to the combination of improved grass vigor and recycling of fertilizer N immobilized in organic forms. Single applications of N were effective in improving dry matter production of some common grasses for multiple years, when water was suitable. The magnitude of response and potential economic return from fertilization were species dependent.