Warm-climate, legume-grass forage mixtures versus grass-only swards: An ecosystem services comparison

Abstract

Integrating warm-climate forage legumes into grass monocultures has received significant research attention during the past 70 years, but widespread adoption by end users has been elusive. The objectives of this review are to provide historical context regarding legume use in warm-climate grasslands; synthesize the current literature addressing contributions to grassland ecosystem services of warm-climate, grass-only vs. legume-grass mixed swards; and consider how to achieve more widespread adoption of legume technology in warm climates. For this review, warm-climate grasslands are considered those in areas between latitudes 30° N and 30° S, where C4 perennial grasses dominate. The literature suggests measurable advantages in animal performance, soil carbon accumulation, and nutrient cycling of legume-grass mixtures are most likely when grass-only swards receive little or no N fertilizer. Advantages are less or may disappear when mixtures are compared with grasses receiving high N fertilizer rates. In contrast, amelioration of greenhouse gas emissions is often most pronounced for mixtures when compared with grass-only swards receiving high rates of N, because of the magnitude of N fertilizer effects on emissions. Going forward, there is need to focus on selecting for, and thoroughly documenting legume persistence, achieving low-risk and affordable legume establishment methods, assessing compatibility of legumes in mixture with grasses prior to legume cultivar release, emphasizing adoption of both legume species and optimal management practices, and recognizing scientists must assume a larger and more intentional role in encouraging adoption by end-users of research innovations, in addition to our traditional role in technology and product development.

Species richness and functional diversity enhance winter annual forage productivity and nutritive value

“…Taken together, our results from Gainesville and Marianna agree with the assertion that the inclusion of certain functional groups can disproportionately affect forage nutritive value (Brink et al., 2015). The dominance of grasses in all treatments at Gainesville likely explains why we did not observe an effect of increasing functional diversity on forage shoot N concentration at this location (Figure S1a) since legumes are associated with greater N concentration and crude protein (Brown et al., 2018; Sollenberger & Dubeux, 2022). In Marianna, the influence of legumes, which accounted for approximately 25% or more of the proportion of harvested biomass (Figure S1b), increased forage shoot N concentrations.…”

“…T A B L E 5 Intercept and treatment coefficient estimates, standard errors, and 95% confidence intervals from the model for total average winter annual forage shoot nitrogen (N) concentration at two northern Florida locations. treatments at Gainesville likely explains why we did not observe an effect of increasing functional diversity on forage shoot N concentration at this location (Figure S1a) since legumes are associated with greater N concentration and crude protein (Brown et al, 2018;Sollenberger & Dubeux, 2022). In Marianna, the influence of legumes, which accounted for approximately 25% or more of the proportion of harvested biomass (Figure S1b), increased forage shoot N concentrations.…”

Agronomic responses and herbage nutritive value of elephant grass (Cenchrus purpureus) genotypes grown as monocrops and mixed with butterfly pea (Clitoria ternatea)

“…Considering this background, the present study was designed to evaluate agronomic responses and nutritive value of elephant grass genotypes grown as monocrops and mixed with butterfly pea. We hypothesised that (1) cultivating tall elephant grass genotypes with butterfly pea favours HA with greater nutritive value because legume inclusion can elevate the herbage protein concentration; and (2) grass–legume intercrops show greater yield stability than grass monocrops, considering the legume N contribution over the year compared with the use of inorganic fertilisers applied only in rainy seasons and subjected to leaching and volatilisation losses (Sollenberger and Dubeux Junior 2022). Thus, the objective of this study was to evaluate and explain variations in HA, yield stability, botanical composition, chemical/bromatological composition and DM digestibility in tall and dwarf elephant grass genotypes monocropped or mixed with butterfly pea.…”