Title page for ETD etd-101198-103006


Type of Document Dissertation
Author Khosla, Rajiv
Author's Email Address Rkhosla@lamar.colostate.edu
URN etd-101198-103006
Title Development of Nitrogen rate Recommendations for No-till Dryland Grain Sorghum in Virginia
Degree PhD
Department Crop and Soil Environmental Sciences
Advisory Committee
Advisor Name Title
Alley, Marcus M. Committee Chair
Brann, Daniel E. Committee Member
De Datta, Surajit K. Committee Member
Dillaha, Theo A. III Committee Member
Martens, David C. Committee Member
Zelazny, L. W. Committee Member
Keywords
  • Side-dress
  • Soil mineral-N
  • Sorghum
  • Nitrogen
  • Broadcast
  • Starter-band.
Date of Defense 1998-10-26
Availability unrestricted
Abstract
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.

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