Timing of Nitrogen Fertilizer Application for Annual Ryegrass Overseeded into Unimproved Perennial Warm‐season Pasture

Abstract

Successful production of herbage by cool‐season forage grasses in the southern Plains is heavily dependent on a sufficient supply of available nitrogen (N), and appropriate scheduling of N application is an important component of cost‐effective fertilizer use. The effects of different combinations of fall, early‐spring, and late‐spring increments of 22.3 lb N/acre on herbage dry matter (DM) and N yields of annual (Italian) ryegrass ( Lolium multiflorum Lam.) were tested over 3 yr. Fall N application had minimal effect on ryegrass establishment, measured in plant or tiller counts in the following spring. Application of N in fall did not produce harvestable herbage DM in fall and provided significant increase in DM yield in the following spring in only one year out of three. Early‐spring N application produced significant yield increase in two out of three years and provided a mean yield response of 17.2 lb DM/lb N applied. Application of N for regrowth after initial ryegrass harvest in early May produced a mean yield increment of 6.7 lb DM/lb N applied. There was no residual effect of fall or spring N application on warm‐season grass production. Limited N supply (<89 lb N/acre) is likely to be most efficiently used when applied at the beginning of the spring growing season.