Wheatgrass Response to Seasonal Applications of Two Nitrogen Sources

Abstract

Fall, winter, and spring applications of 20 lb. N/acre as urea or as ammonium nitrate were applied in each of 3 years to two introduced grasses, crested and Siberian wheatgrasses, on Oregon's high desert range. Mature herbage yield increased with fertilizers, but there were no significant interactions with application date. Urea increased mean yield 3% more than did ammonium nitrate, but the increase may not be of practical significance. Crude protein concentration of mature yields, evaluated in 1 year only, was not influenced by either fertilizer or application time. Fall- and winter-applied N fertilizer increased available soil nitrate concentration in mid-April, but differences due to date and source of N were nil.