Legume establishment and persistence at sites varying in landscape position, grazing method, and soil characteristics

Iowa pastures are diverse in the landscapes and soil conditions present within small area units. Introducing legumes into these areas has the potential to improve seasonal distribution and quality of the pasture forage. This study was performed to quantify the spatial and temporal variation in legume contribution to the plant community when seeded into established cool-season grass pastures. Pastures were seeded with a mixture of eleven legumes and then divided into three grazing methods (non-grazed, continuous, and rotational), with each grazing method containing five landscape positions (upland, sideslope, bottomland, opposite sideslope, and opposite upland). Legume dry matter composition, legume species richness, legume diversity, and forage quality was determined during the grazing season and associated with site soil characteristics. Sideslope positions had greater legume dry matter composition (161 g kg-1) than either the upland (62 g kg-1) or bottomland landscape positions (7 g kg -1), and legume concentrations increased as the growing seasons progressed in the grazed treatments. Legume species richness also was greater for sideslope landscape positions. Legume dry matter composition showed a strong, positive linear relationship to species richness in continuous, rotational, and non-grazed treatments (r2 = 0.77, 0.84, and 0.74), and may potentially be utilized as a tool to estimate the need for re establishment in these pastures. Legume dry matter diversity using the Shannon-Wiener index was greatest for grazed pastures, but was positively linearly related to legume dry matter composition in only rotationally grazed paddocks (r2 = 0.88). Upland and bottomland sites with the greatest total available dry matter herbage production potential contained the lowest legume concentrations and legume herbage. Forage NDF was lowest and IVDMD was greatest on sideslopes (527 g kg-1, 630 g kg-1) compared to uplands (552 g kg-1, 608 g kg-1) and bottomlands (568 g kg-1, 560 g kg-1 ). Of all spatial and temporal variables, land slope best explained the variation in legume dry matter composition (r2 = 0.66) and species richness (r2 = 0.75). Competition resulting from the greater grass component at lesser slopes appeared to be a limiting factor for legume establishment. Land slope is easily quantified, and could serve as a basis for pasture division for differential fertilization, seeding, and grazing management

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country