K. A. Gravois

Optimizing selection for rough rice yield, head rice, and total milled rice

High rough rice yields are important for the profitable production of rice (Oryza sativa L.). The value of rough rice is determined primarily by head rice (whole milled grains) and broken rice, together referred to as total milled rice. The objective of this study was to optimize selection for rough rice yield, head rice, and total milled rice using path-coefficient analysis and selection indices. Thirty-seven long grain pure lines were grown in an experiment at three Arkansas locations during 1993 and 1994. In another test, twenty-eight F1 hybrids obtained from an eight-parent half diallel of long-grain rices were grown at two locations in Arkansas during 1991. For the pure lines, path analysis revealed that rough rice yield was approximately twice as important in determining total milled rice/ha than head rice. Path analysis for the hybrids revealed that rough rice yield was an even greater component in determining total milled rice/ha. Based on yield components for hybrid rice, panicle density had the largest direct effect determining total milled rice/ha. Filled grain/panicle, grain weight, and head rice, in that order, were secondary, but positive, factors determining total milled rice/ha. A selection index for pure lines based only on selection for head rice was 19.2 percent as effective as selection for total milled rice/ha directly. When selection for total milled rice/ha was based solely on rough rice yield, selection was 82.7 percent as effective as selecting for total milled rice/ha directly. Selection to improve total milled rice/ha should concentrate on increasing both rough rice yield and head rice. Rough rice yield should receive greater priority than head rice in selection strategies.

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.