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dc.creatorByrd, Robert Claudeen_US
dc.descriptionDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to, referencing the URI of the item.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.descriptionIssued also on microfiche from Lange Micrographics.en_US
dc.description.abstractThe Texas Agricultural Extension Service (TAEX) Soil Testing Laboratory currently utilizes a single phosphorus (P) extractant consisting of 1.43 M NH4OAc, 1. 0 M HCl, and 0.025 M EDTA-PH 4.2 to estimate plant available P for all soils in Texas. Research is needed to determine the suitability of this extractant for predicting crop P response for soils within the Blackland Prairie region of Texas. The objectives of this study were to determine the suitability of the TAEX P extractant for predicting crop P response, evaluate crop response to P fertilizer placement and rate, and compare extractable P levels from TAEX, Bray 1, Olsen, TAEX 1, TAEX 2, and TAEX 3 in selected Blackland Prairie soils. Five field locations were established with replicated P fertilizer treatments of 0, 20, 40, and 60 kg P ha-1 applied as both band and broadcast applications to each site for two years. Crop yields were evaluated to determine the effects of P fertilization. Representative soil samples (O to 10 cm) were obtained and extracted with the six P extractants. The current TAEX P extractant failed to predict three significant crop responses and all small responses to P addition. The Bray I and Olsen extractants recognized the need for P fertilizer, but recommended P fertilizer rates below the 40 to 60 kg P ha-' needed to obtain maximum yield. The TAEX 3 extractant appeared to be better suited for Blackland soils since it predicted the need for higher P rates. Band and broadcast P fertilizer applications were equally effective at all sites. TAEX and TAEX I extractants removed a larger proportion of total soil P than Bray 1, Olsen, TAEX 2, and TAEX 3 extractants. Olsen and Bray I extractable P were most significantly influenced by the addition of broadcast P fertilizer. Estimated critical P limits for the TAEX, TAEX 1, TAEX 2, TAEX 3, Bray 1, and Olsen extractants were approximately 152, 76, 26, 24, 27, and 14 mg P kg respectively. The TAEX 3 extractant better separated responding and nonresponding sites when compared to TAEX, Bray I, and Olsen extractants and may better crop P response on Blackland Prairie soils.en_US
dc.publisherTexas A&M Universityen_US
dc.rightsThis thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries in 2008. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use.en_US
dc.subjectMajor agronomy.en_US
dc.titleExtractable soil phosphorus in Blackland Prairie soilsen_US
dc.format.digitalOriginreformatted digitalen_US

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