Long-Term Cropping System Effects on Soil Nitrogen.
(S03-albrecht258786-poster)
Authors:
S.L. Albrecht* - USDA-ARS S. Machado - Oregon St. U.
Abstract:
Long-term research can guide agricultural development by identifying the effects of management practices on agronomic performance and soil quality. Long-term experiments on crop rotation, tillage, residue management and fertilization were initiated at the Pendleton Experiment Station in 1931. Wheat grown following summer fallow has responded to N fertilizer applications since the mid 1930’s. The amount of additional N required for optimum wheat yield has risen from about 17 kg N per ha in the 1940’s to more than 100 kg N per ha today. Nitrogen fertilization rate for optimum wheat yield is directly proportional to growing season precipitation and soil depth. Nitrogen mineralized during the year increased with increasing N fertilization and with reduction in tillage intensity and cropping
frequency; however, that amount of mineralization is small compared to the N requirements for greatest yields. Soil erosion has been low in our long-term studies, but over many years even minimal soil loss can have substantial impact on N levels. The major factors influencing changes in soil N, and organic C, were the frequency of summer fallow and the amount of crop residue left in the field.
Speaker Information: Steve Albrecht, USDA-ARS, USDA-ARS, CPCRC P.O. Box 370, Pendleton, OR 97801-0370; Phone: (541) 278-4392; E-mail: [email protected]
Session Information: Wednesday, November 5, 2003, 10:00 AM-12:00 PM Presentation Start: 10:00 AM (Poster Board Number: 1332)
Keywords: nitrogen; wheat; mineralization; soil organic matter
