Nitrogen Fertilizer Management Strategies for Upland and Pima Cotton

J.C. Silvertooth, J.E. Malcuit, and T.A. Doerge


 
ABSTRACT

A project was initiated in Arizona in 1990 consisting of two field experiments at two locations, maricopa (Casa Grande st, 1,175 ft. elev.) and Safford (grade cl, 2,800 ft. elev.). The objectives of this project were: a) to validate and refine nitrogen (N) fertilization recommendations for both Upland (Gossypium hirstum L.) and Pima (G. barbadense L.) cotton; and b) compare the relative effectiveness of several N management strategies on efficiency and yield of cotton. The experiments each utilized n management tools such as pre-season soil tests for NO3-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring (such as plant mapping) to ascertain crop fruiting patterns and crop N needs. Results ar both locations revealed a strong relationship between the crop. This pattern was further reflected in final yield analysis in response to the N fertilization regimes used. At maricopa, fruit retention levels were low, petiole NO3-N concentrations relatively high,a nd yield responses to higher and later application of fertilizer n were negative (P<0.05). At Safford, fruit retention levels were higher, petiole concentrations of NO3-N reflected strong crop demand of N, and a positive response (P<0.05) to rates of fertilizer N up to 190 kg N ha-1 was measured. Results from these studies exemplify quite well the complimentary nature of petiole testing for actual N fertility status and plant mapping information, which provides some estimate of the developing and existing fruit load. Used in combination these N and crop management tools offer a relatively simple approach to the decision making process associated with the N fertilization of a dynamic cropping system such as cotton. These experiments provide information needed for validation and refinement of N management recommendations in cotton production systems, which integrate tissue testing with crop measurement techniques in an effort to optimize agronomic efficiencies and minimize negative environmental impacts from fertilizer N inputs. These experiments are part of a long-term project and will be continued over the course of the next three crop seasons.



Reprinted from 1992 Proceedings Beltwide Cotton Conferences pg. 1182
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998