ABSTRACT
Summary Experiments were conducted on nitrogen (N) fertilization of long-term Russian wildrye (RWR) (Elymus junceus Fisch.) pasture and the effect of simulated spring grazing on quantity of forage available for fall use. A stand of RWR that had been fertilized with 45 kg N/ha and grazed annually for 10 years at Mandan, North Dakota, was divided into two experiments in 1978. The first evaluated effects from all combinations of 0, 45, 90, 135, 180, and 225 kg N/ha; 0, 45, and 90 kg phosphorus (P)/ha; and 0 and 135 kg potassium (K)/ha on dry-matter (DM) yields, whereas the second compared ten clipping treatments ranging from biweekly intervals to autumn (clipping after frost) harvests. Precipitation was above average in 1978, below average in 1979; in 1980 severe drought through June was followed by above-average precipitation during July and August. Yield increased with each increment of fertilizer N up to 180 kg/ha in 1978 and 1979. Yields ranged from 3,220 to 6,860 kg/ha in 1978 and 1,040 to 5,690 kg/ha in 1979. As yield on 17 July 1980 was only 110 kg/ha, treatment differences were of little practical significance. Yield of a harvest on 25 September 1980, after recovery from drought, ranged from 240 to 2,150 kg/ha for 0 through 225 kg N/ha, with each increment of N significantly increasing yield. Neither P nor K fertilization influenced yields. Biweekly clipping reduced yield each year and resulted in thin, weed-infested stands. Early July clipping led to maximum yields in 1978 and 1979 but not in 1980. Light spring grazing, simulated by a harvest at a 13-cm stubble height on 5 June 1978, led to 1,430 kg DM/ha at the autumn harvest compared with an autumn yield of 3,020 kg/ha where there was no spring grazing. A rate of 45 kg N/ha was insufficient to maintain optimum DM yield, especially during dry years. Limited spring utilization greatly reduced forage available for autumn grazing even though total production was increased. Biweekly harvests reduced overall yield and vigor.
