Herbage Production and Nitrogen Accumulation by Alfalfa and Cicer Milkvetch in the Southern Plains
Sixty to 100 yr of farming upland soils in the Southern Plains has depleted much of the N available to plants. This field study valuated alfalfa (Medicago sativa L.) and cicer milkvetch (Astragalus cicer L.) for persistence, herbage production, and N accumulation on two N-deficient soils (Woodward fine sandy loam, coarsesilly, mixed, thermic Typic Ustocrept; Pratt loamy sand, sandy, mixed, thermic Psammentic Haplustalf). A grass (Bothriockloa ischaemum L.) was grown as a control against which to measure N accumulation. After establishment in 1981 with sprinkle irrigation, the study was conducted under dryland conditions the following 5 yr when precipitation was near the long-term mean of 596 mm yr−1, Herbage was not harvested the year of establishment. On the Woodward sandy loam, average herbage yields were: alfalfa 4.5, cicer milkvetch 3.1, and grass 1.0 ha−1 yr−1; herbage N yields were 171. 124, and 9 kg N ha−1 yr−1, respectively. Residual N in stubble, crowns, litter, roots, and surface 10 cm of soil after six growing seasons was 1670, 1364, and 996 kg N ha−1 for alfalfa, cicer milkvetch, and grass, respectively. Cicer milkvetch on the Pratt loam} sand died during the dry summer of the second harvest season. Thus, cicer milkvetch appears marginally adapted to loamy upland soils and not adapted to deep sandy soils in the Southern Plains. Alfalfa persisted on the Pratt loamy sand with herbage yields about 87% of yields on the Woodward sandy loam. The performance of alfalfa, including apparent N2 fixation averaging 219 kg N ha−1 yr−1, is encouraging for use on marginal farmlands in the region.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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