Yield and Botanical Composition of an Irrigated Grass‐Legume Pasture as Influenced by Fertilization¹

Abstract

Irrigated pastures are becoming more important for animal production in several Great Plains and Western states. The majority of fertilization studies have been conducted at sites where surface irrigation practices were used on medium to fine textured soils. This study was designed to evaluate the effect of N, P, and K fertilization on forage production and grass‐legume composition of an irrigated pasture containing bromegrass (Bromus inermis Leys.), orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.) on sandy soils irrigated with automated sprinkler systems. Forage yields were recorded for 3 years at two sites and plant separations to determine the grass‐alfalfa composition were made at one of the two sites. The response to increasing levels of N was curvilinear at both sites throughout the 3‐year period. The application of 252 kg N/ha produced maximum yields at the Holt County site, whereas the use of 560 kg N/ha produced the maximum yields at the North Platte site. These N rates produced increases of 4.7 and 7.0 metric tons/ha, respectively. The response to applied P was linear at the Holt County site but had little influence on yields at the North Platte site. Applied K had no influence on forage yields at either site. Fertilization influenced the grass‐legume composition at the Holt County site to some extent, but trends were not consistent for the 2 years. The data show that N rates in excess of 252 kg/ha decreased the percentage of grass in the mixture while increasing the percentage of alfalfa. Since clipping frequency may have had some influence on grass‐legume composition, changes in the percentage of grass and alfalfa in the mixture cannot be entirely attributed to fertilization.

Row Spacing and Nitrogen: Effect on Alfalfa‐Bermudagrass Yield and Botanical Composition

“…Adding N helped to counteract yield loss from wider row spacing, but this did not occur via enhanced BG contribution, as percentage BG did not increase. Rehm et al (1975) reported that N fertilization beyond 250 kg ha -1 increased alfalfa yield at the expense of grass yield, but the alfalfa was not well nodulated.…”

Species and Stockpile Initiation Date Effects on Yield and Nutritive Value of Irrigated Cool‐season Grasses

“…Each year, a total of 224 kg ha −1 of N was topdressed as ammonium nitrate in split applications of 112 kg ha −1 late March, 56 kg ha −1 after harvest in late May, and 56 kg ha −1 after harvest for each of the 15 July or 15 August stockpile initiation dates. Total N applied and application timing followed recommendations for irrigated cool‐season grasses (Rehm et al, 1975; Moline et al, 1974). Irrigation water was applied via sprinklers to maintain root zone soil moisture at a minimum of 50% of available field capacity.…”

Importance and Effect of Nitrogen on Crop Quality and Health

“…The main beneficial effect of nitrogen fertilization of forages, on meat production per unit land, increases in yield resulting in increased carrying capacity (Wedin, 1974). In warm-season grasses, many studies found that increased nitrogen fertilization caused higher beef gains in kg/ha (Rhem et al, 1975;Perry and Baltensperger, 1979).…”