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Interpretive Summaries:
1998 - Establishing Updated Guidelines for Cotton Nutrition
1997 - Establishing updated guidelines for cotton nutrition
1996 - Establishing Updated Guidelines for Cotton Nutrition
Establishing Updated Guidelines for Cotton Nutrition, 1996
This project, which began in 1993, coordinates research activities on cotton nutrition from 2 field stations and 16 grower fields each year throughout the San Joaquin Valley. Project objectives include determining if yields can be maintained by supplying nitrogen (N) on an as needed basis, improving the predictive ability of current soil K test procedures and developing improved N and K recommendations. Paired comparisons conducted in the six San Joaquin Valley cotton-growing counties over three years indicated a significant cotton yield relationship to exchangeable soil K with the best fit for 5 to 15 inch soil samples. Soils that fix greater than 60% of applied K fertilizers all had significant lint responses to added K. New fertilizer guidelines (in press) developed form this research are: Soil K level, 80-110 ppm = apply 200 lb/A of K20, unless fixation is greater than 60%, then apply 400 lb; if soil K level is less than 80 ppm, = apply 400lb/A of K20. Cotton petiole concentrations at first bloom of less than 3.5% were indicative of lint responses to K fertilizer. The 1996 results substantiated that foliar K (9 lb of K2O) split in two applications one to three weeks after first bloom produced the greatest yield increases compared to that applied earlier or later in the season. Foliar applications of K should be recommended on potentially high yielding fields regardless of soil test or previous fertilizer applications. This project further documents the widespread K deficiency of cotton in the San Joaquin Valley and the substantial benefit of both soil and foliar K applications. CA-14F
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