Dwayne R. Buxton

Comparative economic analysis of perennial, annual, and intercrops for biomass production ☆

Herbaceous crops may be an important source of renewable energy. Production costs can be more competitive by increasing yields so that overhead costs are applied to more biomass. Most previous economic studies of energy crops have concentrated on the production of switchgrass (Panicum virgatum L.). This study analyzes the biomass yield and economic potential of several high-yielding annual and perennial crops on prime and marginal, sloping land. Crops evaluated were reed canarygrass (Phalaris arundinacea L.) harvested twice per year; switchgrass and big bluestem (Andropogon gerardii Vitman var. gerardii); alfalfa (Medicago sativa L.); and sweet sorghum, forage sorghum [both Sorghum bicolor (L.) Moench], and maize (Zea mays L.). The intercropping of the two sorghum species into reed canarygrass and alfalfa was also analyzed. All crops but alfalfa were fertilized with 0, 70, 140, or , with economic analysis performed assuming . Sorghums were most productive, with more than of dry matter ha−1. Switchgrass was the highest-yielding perennial crop. Costs per ton of biomass produced were lowest for sorghum, somewhat higher for switchgrass, higher still for big bluestem, and highest for alfalfa and reed canarygrass. Yields per ton for intercropped species were higher than for perennial species but lower than for monocrop sorghum. Costs per ton for intercropped species were less than for either alfalfa or reed canarygrass, but were higher than costs per ton of monocrop sorghum. Although the sorghums had the highest yields, high potential for erosion on sloping soils may preclude their use on these soils.

Genetic modification of lignin concentration affects fitness of perennial herbaceous plants

Abstract Populations of four perennial herbaceous species that were genetically modified for altered lignin content (or associated forage digestibility) by conventional plant breeding were evaluated for two agricultural fitness traits, plant survival and plant biomass, in three Northcentral USA environments for more than 4 years. Reduced lignin concentration or increased digestibility resulted in increased winter mortality in two of four species and reduced biomass in one species. Results from other experiment indicate that these apparent genetic correlations may be ephemeral, suggesting that selection for fitness can be successful within high-digestibility or low-lignin germplasm. Results indicate that perennial plants genetically engineered with altered lignin concentration or composition for use in livestock, pulp and paper, or bioenergy production should be evaluated for fitness in field environments prior to use in agriculture.

Forage Quality for Ruminants: Plant and Animal Considerations1

Abstract Forage quality is a function of nutrient concentration, intake, nutrient availability, and partitioning of metabolized products within animals. Of these factors, intake potential is the major determinant of production by animals fed forage-based diets; however, it is one of the most difficult aspects of forage quality to determine or predict because variation among animals has a large influence on intake. Physical fill limits intake of forages with high cell wall concentrations when fed to animals with high energy demand. Hence, grasses, with their higher cell wall concentration, typically have lower intake than legumes. Energy availability of forage is also limited by cell wall concentration because cell contents are almost completely digested, whereas forage cell walls are slowly digested. Thus, the proportion of cell walls to cell contents is a major determinant of energy availability in feeds. Protein digestion by ruminants is complex. When crude protein concentration in herbage drops below 7% of dry matter, ruminal fermentation of forages may be limited and protein requirements of animals may not be met. Additionally, inefficient use of protein in high quality forages may limit performance of high producing animals. Usually, only about 25% of the forage protein escapes degradation from the rumen. Efficiency would be improved if a larger portion of forage protein passed from the rumen undegraded so that it can be degraded in the intestines where absorption is more efficient. Another important plant factor influencing forage quality is herbage maturity. Systems are now available for determining maturity of both legumes and grasses that will become more important as aids for predicting forage quality before forages are harvested or grazed. Forage quality is also influenced by the environment in which forages are grown and by soil fertility and these cause year-to-year, seasonal, and geographical variation in forage quality even when herbage is harvested at the same stage of maturity.

Cellulase and Bacterial Inoculant Effects on Cocksfoot and Lucerne Ensiled at High Dry Matter Levels

Limited information exists on the response of grass and legume silage to enzyme and bacterial inoculant treatments when wilted to drier than desired conditions. This study was undertaken to evaluate the impact of cellulase (from T richoderma longibrachiatum) application rate, when combined with a bacterial inoculant (L actobacillus plantarum and Pediococcus cerevisiae), on the fermenta- tion characteristics of cocksfoot (Dactylis glomerata L) and lucerne (Medicago sativa L) ensiled at high dry-matter concentrations. Forages were wilted to near 600 g dry matter kg~1 and cellulase, combined with inoculant, was applied at 0E30 ml kg~1 herbage and at two, four and eight times this concentration (at least 2500 IU ml~1). Cellulase was also applied alone at 0E60 ml kg~1. Wilted forages were ensiled in laboratory silos for 60 days. E†ect of cellulase application rate on neutral detergent Ðbre concentrations of the silages was small and incon- sistent. Averaged across species, only the intermediate cellulase concentrations decreased neutral detergent Ðbre concentration (P \ 0E082). The limited cell-wall degradation was probably related to the high silage dry-matter and lignin con- centrations. Cellulase combined with inoculant increased total fermentation, when averaged across species. In cocksfoot, cellulase combined with inoculant decreased pH and concentration but increased the lactic : acetic acid NH 3 -N ratio of control silage, with most of the e†ect caused by the inoculant. Cellulase applied alone to lucerne caused a higher lactic : acetic acid ratio than the control or when combined with the inoculant at the same cellulase rate. Thus, the e†ect of cellulaseEinoculant mixtures on silage quality varied among plant species, with cocksfoot generally more responsive than lucerne.