THE CHEMICAL COMPOSITION OF RUSSIAN AND ALTAI WILD RYEGRASS AND CRESTED WHEATGRASS AS INFLUENCED BY N FERTILIZATION AND DATE OF HARVEST

Abstract

The effects of three rates of N fertilizer and nine fortnightly dates of initial harvest on the N, P, Ca, Mg and K concentrations and the K/(Ca + Mg) ratio of Russian wild ryegrass (Elymus junceus Fisch.), Altai wild ryegrass (Elymus angustus Trin.) and crested wheatgrass (Agropyron desertorum Fisch. Schult.) were studied on irrigated land for 2 yr. The N, P, K and K/(Ca + Mg) ratios declined with increasing maturity. The N, P, and K concentrations tended to increase with N fertilization, while N fertilization appeared to have little influence on percent Ca, percent Mg and the K/(Ca + Mg) ratio. Altai wild ryegrass had a higher N, P, Ca, Mg, K and K/(Ca + Mg) ratio than RWR which, in turn, was higher than CWG. Crested wheatgrass utilized prior to early June, RWR utilized prior to late June, and AWR utilized prior to early July had the suggested minimum level for lactating beef cows of 1.60% N. Only samples cut during May equalled the suggested minimum of 0.32% P. Supplementation with N and P may be required with rations or pastures using these grasses in June or later. The percent K was adequate on all sampling dates. The K/(Ca + Mg) ratio for CWG did not exceed the suggested maximum of 2.2, but the ratio for AWR and RWR was above this maximum for May, June and part of July, indicating there may be some danger of grass tetany with these grasses during the May-June period and supplementation with Mg and/or Ca may be required for good performance.