Forage Production of Grass–Legume Binary Mixtures on Intermountain Western USA Irrigated Pastures

Abstract

Well‐managed irrigated pasture production can be optimized without nitrogen (N) fertilizer. The objective was to determine mixture and planting ratios of tall fescue (Schedonorus arundinacea Schreb.) (TF), meadow brome (Bromus riparius Rehm.) (MB), orchardgrass (Dactylis glomerata L.) (OG), timothy (Phleum pratense L.) (TIM), and perennial ryegrass (Lolium perenne L.) (PRG) with alfalfa (Medicago sativa L.) (ALF), birdsfoot trefoil (Lotus corniculatus L.) (BFTF), or cicer milkvetch (Astragalus cicer L.) (CMV) that maximize productivity. Planting ratios were 0:100 (grass:legume), 25:75, 50:50, 75:25, and three 100:0 grass monocultures fertilized at 0, 67, and 134 kg N ha−1. Seasonal production of TF–ALF was 12.69 Mg ha−1, equal to TF fertilized at 134 kg N ha−1. ALF mixtures with MB, OG, TIM, and PRG produced 12.57, 10.97, 11.77, and 10.74 Mg ha−1, respectively, and 8 to 40% more than grasses receiving 134 kg N ha−1. Production of BFTF mixtures with TF, MB, and OG were 11.69, 11.45, and 9.95 Mg ha−1, respectively, equal to their respective grass monoculture receiving 134 kg N ha−1. The BFTF–TIM and BFTF–PRG mixtures averaged 12% more forage than grass monocultures receiving 134 kg N ha−1. Production of CMV‐grass was similar to that of grasses receiving 67 kg N ha−1. Seasonal forage distribution was more uniform in ALF– and BFTF–grass mixtures, averaging 30% more at the second and third harvests than fertilized grasses. The TF and MB legume mixtures averaged 7% more production in the 50:50 planting ratios than the other two grass–legume mixtures, while the 50:50 and 25:75 ratios of OG and TIM–legume mixtures averaged 12% more than the 75:25 and the 25:75 PRG–legume planting ratio averaged 9% more than the 50:50 and 75:25. Forage production of grass–legume mixtures can equal or exceed fertilized grass monocultures and with more uniform distribution over the growing season.

Grass–Legume Forage Systems Effect on Phosphorus Removal from a Grassland Historically Irrigated with Reclaimed Wastewater

“…Overall, with just a few exceptions, herbage accumulation for the grass monocultures and grass-legume mixtures were mostly similar in this study. The fact that the grass monocultures were fertilized with N and did not differ from most of the grass-legume mixtures supports the use of grass-legume mixtures [51,52]. A similar observation was reported for alfalfa-tall fescue 50:50 seed rate mixture relative to the fully fertilized tall fescue treatment [52].…”

“…The fact that the grass monocultures were fertilized with N and did not differ from most of the grass-legume mixtures supports the use of grass-legume mixtures [51,52]. A similar observation was reported for alfalfa-tall fescue 50:50 seed rate mixture relative to the fully fertilized tall fescue treatment [52]. The benefits to be derived from the grass-legume mixtures are not only from an economic standpoint of the elimination of inorganic N input cost into the grass-legume mixtures but also from an environmental perspective of lowering N leaching into aquatic systems [51][52][53].…”

Binary mixtures of alfalfa and birdsfoot trefoil with tall fescue: Herbage traits associated with the improved growth performance of beef steers

“…Perennial forage legumes, when grown in mixtures with grass, can potentially supply some of the large N requirement needed in these productive pastures (Carlsson & Huss-Danell, 2003;Nyfeler, Huguenin-Elie, Matthias, Frossard, & Luscher, 2011). Legumes in a mixed grass-legume pasture may also increase forage mass per se, improve the seasonal distribution of forage mass, and improve forage nutritive value, thereby increasing the ability of a pasture to support livestock grazing throughout the summer (Cox et al, 2017;Guldan, Lauriault, & Martin, 2000;Sleugh, Moore, George, & Brummer, 2000;Zemenchik, Albrecht, & Shaver, 2002).…”

“…For instance, in New Mexico USA, an irrigated, non-grazed, binary mixture of tall fescue and alfalfa (Medicago sativa, L.) had greater clipped herbage mass in comparison with N-fertilized (168 kg N ha −1 year −1 ) tall fescue monocultures (Lauriault, Guldan, & Martin, 2003). In a similar irrigated, non-grazed environment, Cox et al (2017) also reported greater forage mass from tall fescue-alfalfa, and similar forage from tall fescue-birdsfoot trefoil (Lotus corniculatus L.) mixtures, in comparison with N-fertilized (67 kg N ha −1 year −1 ) and unfertilized tall fescue monocultures. Hoveland et al (1981) reported less forage mass, but greater average daily gains (ADG) with steers grazing tall fescue-birdsfoot trefoil mixtures compared to N-fertilized (168 kg N ha −1 year −1 ) tall fescue monocultures.…”

Management-intensive Grazing Affects Soil Health

“…Over the past decade, interest in MiG on irrigated pastures has increased steadily due to the prospects of reduced production costs, increased animal output, land use efficiency, and environmental benefits. This system is being considered as an option by many farmers and ranchers in the western US due to pressure to reduce public land grazing and the declining land available for pasture (Cox et al, 2017). Adoption of MiG has the potential to bring the benefits of intensively managed, improved pastures into the already established irrigated cropping infrastructure that exists on many ranches.…”