Impact of Soil Amino Acids on Crop Yield in Corn-Soybean Rotation. (S04-martens527335-oral)
Authors:
D.A. Martens* - Agricultural Research Service K.L. Loeffelmann - Agricultural Research Service
Abstract:
Research has failed to accurately determine plant available N released by soil N mineralization to reduce the need of fertilizer-N. The lack of success is due to the highly temporal and spatially variable mineral N that is the main form of N assimilated by plants, but compose only 2 to 5% of the total N content. Recent advances have identified from 80 to 90% of the total N fraction in soils (n = 22 soils) as amino acids (AA), amino sugars (AS) and NH4+ (collectively termed AA fraction). Application of this technology to 10 soils from a corn (Zea mays) and soybean (Glycine max) rotation sampled May and September (1997 - 1999) found that following corn (n = 6), net soil AA content decreased (315 kg N ha-1) and following soybean (n = 6), the net soil AA content increased (340 kg N ha-1). The
relationship between AA-N and corn yield for two climatically distinct years (1997 and 1999) showed a similar response and plateau function and suggest that many soils require smaller N rates than currently applied. The increased and decreased AA pattern was very similar for each soil, except for three soils that had frequent spring ponding, and suggested no preferential mineralization or immobilization of different fractions within the AA-N composition. Thus measuring a specific fraction such as the AS component, may provide essential information on the status of the entire AA-N fraction.
Speaker Information: Dean Martens, Agricultural Research Service, USDA-ARS Southwest Watershed Research Center 2000, Tucson, AZ 85719; Phone: 520 670-6380 ext. 156; E-mail:
Session Information: Tuesday, November 4, 2003, 8:40 AM-10:15 AM Presentation Start: 9:45 AM
Keywords: amino acids; total nitrogen; nitrogen cycling; corn soybean yields
