Project Summaries

10-749  Project Manager: P. F. O'Leary


Leo Espinoza, University of Arkansas

The ability of a cotton plant to recover from sub-optimum levels of nitrogen (N) and potassium (K) is critical for sustainable cotton production. Knowing when granular fertilizers are no longer an option in alleviating a nutrient deficiency will allow for the implementation of more effective corrective measures. The objective of these experiments was to assess the yield response of cotton to nitrogen (N) and potassium (K) fertilizer applied at different growth stages, under deficient soil nutrient levels. Identifying the growth stage at which soil applied N and K fertilizer are not an effective option to correct deficiencies of each nutrient, when grown under suboptimum soil nutrient levels, was an additional objective of these studies.  Results of these studies show that soil applied N and K fertilizer can effectively reduce the loss of yield potential, if applied no later than 300 and 400 heat units after first bloom. Delaying the application of the needed nutrient beyond 400 heat units, under deficient potassium and nitrogen conditions, resulted in significant yield loss potential.
The accelerated progression towards physiological cutout during the 2010 season, evident in COTMAN, required that all the nitrogen be supplied early in the season. During 2010, 40 lb N/acre were applied by emergence, but under the conditions of the studies, it appeared like 40 lb N/acre was not enough for cotton plants to build a plant structure to optimize yields. When the sidedress nitrogen application was delayed by first bloom, more than 300 lb of seed cotton were not materialized, compared to yields observed when the fertilizer was applied by first square. During the 2011 and 2012 seasons, 60 lb N/acre were applied by emergence. This amount appeared to be sufficient for cotton plants to build enough structures and maximize yield potential if the rest of the nitrogen needed was applied no later than 400 heat units after bloom. Results from these studies underscore how important the timely application of N and K fertilizers are in current cotton production.

Yield partition of plants under both K-deficient and K-sufficient conditions showed similar plant development by first bloom. The detrimental effects of a K deficiency in cotton are not typically obvious by the 1st or 2nd week of bloom. In this study, plants growing under K-deficient conditions had similar numbers of first position bolls, when compared to plants growing with sufficient K. When yields were separated by boll position, based on sympodial node,  it was clear that a significant portion of the yield differences among plants growing under deficient and sufficient K, could be attributed to reduced 2nd and 3rd positions bolls. 


Project Year: 2012

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