Interseeding annual warm‐season grasses into pastures: Forage nutritive value and yields

Abstract

Interseeding annual warm-season grasses into pastures often increases forage accumulation. Yet, impacts on nutritive value and yields remain unreported. We analyzed forage collected from five Nebraska and Kansas experiments in 2015-2016 (eight environments) for crude protein (CP), neutral detergent fiber (NDF), and in vitro organic matter digestibility (IVOMD) concentrations and yields. Each experiment subjected perennial cool-season grasses to two harvest frequencies (once at 90 d and twice at 45 and 90 d after interseeding) and four interseeded annual warm-season grass types-pearl millet [Pennisetum glaucum (L.) R. Br.], sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud) de Wet & Harlan], a sorghumsudangrass hybrid (S. bicolor × S. bicolor var. sudanense), and an unseeded control. Across environments, 90-d CP and IVOMD concentrations increased while CP and IVOMD yields decreased in interseeded pastures when harvested twice, indicating presence of nutritive value-yield tradeoffs. Pastures interseeded with sorghumsudangrass had greater 90-d IVOMD concentrations and CP and IVOMD yields when harvested once but only greater 90-d IVOMD concentrations when harvested twice compared to unseeded pastures. Interseeding sorghum-sudangrass provided an effective strategy to increase CP and IVOMD yields in late summer in humid environments with tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.] and in mid-and late summer in humid environments with smooth bromegrass (Bromus inermis Leyss.) and semiarid environments with western wheatgrass [Pascopyrum smithii (Rydb.) Á. Löve]. Interseeding annual warm-season grasses did not consistently increase CP and IVOMD yields in semiarid environments with smooth bromegrass and crested wheatgrass [Agropyrum cristatum (L.

Nitrogen fertilizer rate and timing effects on smooth bromegrass interseeded with sorghum‐sudangrass

“…The lack of better establishment probably contributed to the absence of interseeding effects on summer and total forage mass in this experiment (Table 2), in contrast to success of earlier experiments described by Guretzky et al (2020Guretzky et al ( , 2021. Factors that may have limited the effectiveness of interseeding included the dry soil conditions in 2018 caused by a particularly warm May and late seeding in 2019 caused by wetter, colder months in May and June (Figure 1).…”

“…izer rates and timing affect the establishment and productivity of annual warm-season grasses (Mercier et al, 2021). In the research completed by Guretzky et al (2020Guretzky et al ( , 2021, N application occurred after annual warm-season grass emergence in early summer to minimize competition from existing perennial cool-season grasses. The timing, however, contrasted with conventional N fertilizer application to perennial cool-season grass pastures in early spring, leading to questions about the rate and time N fertilizer should be applied at in pastures interseeded with annual warm-season grasses.…”

“…In recent research, cool‐season grass pastures interseeded with sudangrass and sorghum‐sudangrass ( Sorghum bicolor × S. bicolor var. sudanense ) have been shown to have 100 to 214% greater forage accumulation than unseeded pastures (Guretzky et al., 2020) and greater mid‐ and late summer yields of crude protein and digestible organic matter (Guretzky et al., 2021). Critical to the success of interseeding pastures is an understanding of how N fertilizer rates and timing affect the establishment and productivity of annual warm‐season grasses (Mercier et al., 2021).…”

Seeding Rate Effects on Forage Mass and Vegetation Dynamics of Cool-Season Grass Sod Interseeded with Sorghum-Sudangrass

“…Indeed, harvesting only once at 90 d increased forage accumulation by 69% [8], crude protein yields by 126% [9], and in vitro organic matter digestibility yields by 202% [9] relative to harvesting twice at 45 and 90 d after interseeding sorghum-sudangrass. However, harvesting twice versus once increased 90 d crude protein concentrations by 30% [9] and might fit better in grazing systems that need forage in mid-summer or cannot stockpile the forage for utilization later in summer.…”

“…Trotter], whether by broadcast or no-till drill seeding, into tall fescue managed just with haying could increase DM yields relative to unseeded tall fescue [7]. Across a multi-environment study in Kansas and Nebraska, cool-season grass pastures harvested in late spring and interseeded with sudangrass and sorghum-sudangrass without any herbicide suppression had 100-214% greater forage accumulation across summer than unseeded pastures [8] and greater mid-and late-summer yields of crude protein and digestible organic matter [9].…”