Tall Fescue and Smooth Bromegrass. II. Effects of Nitrogen Fertilization and Irrigation Regimes on Quality¹

Abstract

Both quantity and quality must be considered in selecting forages for livestock. This study was conducted to determine effects of N and irrigation treatments on the quality of tall fescue (Festuca arundinacea Schreb.) and smooth bromegrass (Bromus inermis Leyss.) forage in the Southern High Plains. ‘Fawn’ tall fescue and ‘Southland’ smooth bromegrass were grown on Pullman clay loam (fine, mixed thermic, Torrertic Paleustoll) under N rates of 0, 168, 336, 504, and 672 kg ha‐1 year‐1 on three water regimes: W‐l, a moderate (about 50‐cm) and W‐2, an adequate (about 100‐cm) irrigation water level, both distributed for season‐long production, and W‐3, a moderate (about 60‐cm) irrigation level distributed for cool‐season forage production. Forage was harvested and analyzed for N, P, K, Ca, Mg, NO3‐ and in vitro dry matter disappearance (IVDMD). Nitrogen fertilization increased N, K, and NO3‐‐N in both forages. The increased K levels increased the K/(Ca + Mg) ratios. Less marked effects of N included slight increases in IVDMD in both grasses, increases in Ca and Mg, and decreases in P in tall fescue but not in smooth bromegrass forage. The total N and NO3‐‐N were lower and the Ca and Mg were higher in forage from W‐2 than in that from W‐l and W‐3. With N rates through 336 kg/ha, NO3‐‐N remained below the 2,000‐ppm level considered harmful to livestock. Forage P and IVDMD were not affected by differences in irrigation. Although smooth bromegrass was superior to tall fescue in N, K, and Ca concentrations and in IVDMD, N fertilization at levels high enough to produce satisfactory yields increased the K/(Ca + Mg) ratios to levels considered critical for induction of grass tetany. With pure stands of smooth bromegrass, supplemental feeding of Mg would be necessary. Tall fescue contained more Mg than did smooth bromegrass, and its K/(Ca + Mg) ratios were favorable. Without P fertilization, feeding supplemental P would be necessary with both forages. Surface‐applied feedlot waste, at N rates equivalent to those applied as NH4NO3, was less than one‐half as efficient as NH4NO3 in increasing N to forage, but it increased P to levels satisfactory for nutrition of mature cows. Both irrigation adequacy and grass species must be considered in fertilizing for maximum production of high quality forage.

Nitrate and ammonium accumulation in bermudagrass in relation to nitrogen fertilization and season

“…Stems always had higher NO3--N concentrations than leaves. In the present experiment, nitrate concentrations in leaves and stems did not reach the potentially toxic levels of 0.34% NO~--N reported by Wright and Davison (1964) in other Gramineae and they were below 0.22% which is generally considered as a safe level (Eck et al, 1981). Nitrate-N concentrations obtained in bermudagrass were much lower than the ones we earlier found in perennial ryegrass growing in the same soil (Bergareche and Simon, 1988).…”

Large-scale manipulation of plant litter and fertilizer in a managed successional temperate grassland

“…The large majority of plant species lie along the unfertilized portion of the first axis, bolstering the assertion that fertilization decreases plant diversity (Grime 1979;Tilman et al 2002b). The distinct separation along the fertilization axis of F. arundinacea and B. inermis, the two most abundant grasses (see Table 2), indicates a stronger response to fertilization elicited by B. inermis, a species known to more efficiently utilize N when compared with F. arundinacea (Eck et al 1981 T describes the separation between groups (dissimilarity) and A is the chance-corrected within-group agreement. ''All'' indicates all four treatments included in the MRPP, and the remainders are MRPP pairwise comparisons of treatments to assess dissimilarity (lower T and higher A).…”

Concentrations of Mg, Ca, P, K, and Crude Protein in Fertilized Tall Fescue1

“…Gross and Jung (7) fertilized fescue in the greenhouse with MgS0 4 • 7H 2 0 (epsom salts) and found an increase in forage Mg at cool and intermediate temperatures but not at warm temperatures. Ec:K. et al (6) reported that N fertilization increased M;g in forage, but Hoijati et at. (10) showed an increase in forage Mg with increasing N rates in some growth periods but the reverse in another.…”