Cook J.C.,Dep. of Crop and Soil science |
Gallagher R.S.,Dep. of Crop and Soil science |
Kaye J.P.,Dep. of Crop and Soil science |
Lynch J.,Pennsylvania State University |
Bradley B.,Dep. of Crop and Soil science
Agronomy Journal | Year: 2010
Legume cover crops can often meet much of the N demand of a crop. There may be, however, an asynchrony between N mineralization from the cover crop residues and crop N uptake, resulting in potentially substantial N loss. We hypothesized that manipulation of hairy vetch (Vicia villosa Roth.) termination and corn (Zea mays L.) planting dates would regulate the quantity of N available from the vetch, the mineralization rate from the vetch residues, and the relative rate of N uptake in the corn. Field experiments were implemented in 2007 and 2008 to study the integrative effects of delaying vetch termination/corn planting through the establishment of three termination/planting dates within the month of May (an early, middle, and late date). Greater vetch biomass was found as the termination date was delayed, with a 360 and 35% biomass gain in 2007 and 2008, respectively, over 4 wk. The soil N content, for all termination dates, followed a similar availability trend across the season in both years, but the quantity of inorganic N in the soil varied depending on termination date. The average corn grain yield in 2007 was 8.0 Mg ha -1 under vetch fertilization, with no difference among vetch biomass levels, and in 2008, ranged between 4.4 and 7.6 Mg ha -1, with significant differences depending on vetch biomass level. Our study concluded that although vetch N availability can be manipulated through termination date, the dependence on climate for vetch biomass levels and N release will complicate year-to-year predictability. © 2010 by the American Society of Agronomy.
Case A.J.,Dep. of Crop and Soil science |
Skinner D.Z.,U.S. Department of Agriculture |
Garland-Campbell K.A.,U.S. Department of Agriculture |
Carter A.H.,Dep. of Crop and Soil science
Crop Science | Year: 2014
Freezing tolerance is an essential trait for winter wheat cultivars. A genetic analysis of a Brund age × Coda winter wheat recombinant inbred line (RIL) mapping population was undertaken to identify quantitative trait loci (QTL) associated with freezing tolerance. Five-week to 6-wk old, cold-acclimated plants were frozen to -10.5, -11.5, or -12.5°C. The standardized mean per centage survival of all RILs within each tem perature was 61, 44, and 28%, respectively. A total of 2391 polymorphic DNA markers includ ing 1984 single nucleotide polymorphism (SNP), 232 Diversity Array Technology (DArT), and 175 simple sequence repeat (SSR) markers were used to create a genome-wide genetic linkage map. The QTL analysis identified six QTL that were associated with freezing tolerance at either a specific temperature or a combination of tem peratures. The QTL QFrbr.wak-5A was associ ated with freezing tolerance at all temperatures tested and was on chromosome 5AL. Further marker analysis indicates that this QTL is not an effect of known sequence polymorphisms at Vrn-A1. On the basis of map homology, QFrbr. wak-5A mapped at or near the CBF (cold bind ing factor) gene cluster at Fr-A2, but not an effect of TaCBF-A15, TaCBF-A14, or TaCBF-A12. Other QTL were located on chromosomes 2A, 3A, 5B, and 6D, and were significant at only specific temperatures. Identification of QTL associated with freezing tolerance may lead to useful genetic markers for marker-assisted selection, allowing for more efficient develop ment of freezing tolerant cultivars. Additional studies of this QTL will further enhance knowl edge of cold tolerance in wheat, as this QTL is not due to known sequence variation at Vrn-A1 or tested CBF genes. © Crop Science Society of America.