Little research has been done in the humid mid-Atlantic region to develop full-season N fertilizer recommendations for dryland no-tillage grain sorghum (Sorghum bicolor L. Moench) production. The objectives of this study were: (i) to determine the optimum rate of band-placed starter N fertilizer needed in combination with side-dress N applications to achieve economic grain yields, (ii) to investigate if pre-plant broadcast N applications are as efficient as band-placed plus side-dress N applications, (iii) to evaluate the response of grain sorghum yield to partitioned side-dress N applications, and (iv) to study the influence of residual soil profile mineral-N (nitrate and ammonium) on sorghum response to applied N fertilization. Multi-location field studies were conducted over three years. A range of N treatments of various starter-band and side-dress N rates were applied. The experimental data indicate that an optimum rate of N fertilization depends on residual soil mineral-N. Little or zero starter-band-N in conjunction with side-dress-N applications of 130 kg of N ha-1 for soils testing high in mineral-N ( 50 kg N ha-1 in the top 0.3m of surface soil) at planting, and a starter-band-N supplement of 40 kg N ha-1 in conjunction with 130 kg N ha-1 side-dress N for soils testing low in mineral-N at planting, optimized the grain sorghum yields in these experiments. Broadcast N applications were observed to be as efficient as band placed N applications when followed by rainfall soon after application. Grain sorghum yields did respond to the partitioned side-dress N applications. However, partitioning of side-dress N application again depends on the residual mineral-N level present in the soil. In order to consider residual soil mineral-N in making N fertilizer recommendations "Associated Nitrogen Fertilizer Equivalency" (ANFE) values were calculated. ANFE is the amount of applied N that has potential to produce the same yield as that produced by the residual soil mineral-N. The N fertilizer recommendations based on ANFE values were quite close for two out of four sites as compared to the N rates at which the maximum yields were obtained in this study. / Ph. D.
Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/29249 |
Date | 12 November 1998 |
Creators | Khosla, Rajiv |
Contributors | Crop and Soil Environmental Sciences, Alley, Marcus M., Brann, Daniel E., De Datta, Surajit K., Dillaha, Theo A. III, Martens, David C., Zelazny, Lucian W. |
Publisher | Virginia Tech |
Source Sets | Virginia Tech Theses and Dissertation |
Detected Language | English |
Type | Dissertation |
Format | application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf |
Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
Relation | ApendixC.pdf, ApendixD.pdf, ApendixE.pdf, vita.pdf, ApendixI.pdf, ApendixJ.pdf, ApendixG.pdf, ApendixH.pdf, ApendixF.pdf, ApendixB.pdf, ApendixA.pdf, chapter5.pdf, chapter4.pdf, chapter3.pdf, chapter2.pdf, chapter1.pdf, tables.pdf, figures.pdf, toc.pdf, ack.pdf, dedicate.pdf, Abstract.pdf, titlepge.pdf |
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