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Development of field-specific spring N rate recommendations for winter wheat

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dc.contributor.authorScharf, Peter C.en
dc.contributor.committeechairAlley, Mark M.en
dc.contributor.committeememberBrann, Daniel E.en
dc.contributor.committeememberDillaha, Theo A. IIIen
dc.contributor.committeememberEvanylo, Gregory K.en
dc.contributor.committeememberMartens, David C.en
dc.contributor.committeememberReneau, Raymond B. Jr.en
dc.contributor.departmentCrop and Soil Environmental Sciencesen
dc.date.accessioned2014-03-14T21:21:56Zen
dc.date.adate2005-10-21en
dc.date.available2014-03-14T21:21:56Zen
dc.date.issued1993en
dc.date.rdate2005-10-21en
dc.date.sdate2005-10-21en
dc.description.abstractOptimum spring N fertilizer rates for winter wheat in Virginia vary widely from field to field, but traditionally spring N is applied at a uniform rate to all fields. A recently-developed tissue test procedure provides a field-specific evaluation of crop N status and predicts optimum N rate for the second spring N application in a split spring application management system. However, this procedure is based on a small number of researcher-planted experiments utilizing a single cultivar; it fails to provide field-specific rate recommendations for the first spring N application; and it is not accessible to farmers who are unwilling to split their spring N applications. Our objectives were: to evaluate the reliability of the tissue test procedure in a large number of farmer fields; to develop a method for making field-specific N rate recommendations for the first spring application in a split-application management system; and to develop a method for making field-specific N rate recommendations in a single-application management system. Forty-five spring N rate experiments were established in farmer fields over a five-year period. A range of N fertilizer rates was applied in early spring (Zadoks growth stage 25) and again in mid-spring (Zadoks growth stage 30) in all possible combinations. Yield data were used to calculate economic optimum N rates at growth stage (GS) 25 and GS 30 with split-application management, and at GS 25 with single-application management. These optima were regressed against a variety of predictor variables measured in the same fields. The reliability of the previously-developed tissue test procedure for making GS 30 N rate recommendations was confirmed. Tiller density was the best predictor of optimum GS 25 N rate with split-application management, while soil nitrate to 90 cm was the best predictor of optimum GS 25 N rate with single-application management. These three relationships fit together to form a flexible and powerful system for making spring N rate recommendations for winter wheat. This system increased estimated profit and apparent fertilizer efficiency in these experiments.en
dc.description.degreePh. D.en
dc.format.extentxii, 226 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-10212005-123017en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10212005-123017/en
dc.identifier.urihttp://hdl.handle.net/10919/40078en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1993.S337.pdfen
dc.relation.isformatofOCLC# 28529023en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1993.S337en
dc.subject.lcshNitrogen fertilizers -- Virginiaen
dc.subject.lcshWinter wheat -- Virginiaen
dc.titleDevelopment of field-specific spring N rate recommendations for winter wheaten
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineCrop and Soil Environmental Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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