Project Summaries

03-345TX  Project Manager: J. M. Reeves


Gaylon D. Morgan, D.L. Coker, M.L. McFarland, D.A. Mott, and Z.P. Eder, Texas AgriLife Extension Service

Yield-limiting problems reduce profitability and need to be solved by agronomic management. Studies under field-scale conditions are needed to ensure applicability of the results. The Texas Extension Agronomy program has the responsibility to bring solutions to producers statewide. A wide variety of educational materials needs to be available for greatest effectiveness of communication. Specific objectives of this project are to: 1) Identify and evaluate new production technologies; 2) Farm level evaluation of agronomic management strategies that address farmers' current production problems; and 3) Develop and deliver educational materials and programs to producers. In 2012, several studies were conducted, but this summary will focus on two studies - a yield response study of soil applied potassium, and measuring boll maturity.

The frequency and severity of potassium (K) deficiency symptoms in the Central Blacklands and Upper Gulf Coast regions of Texas have increased in recent years. While very dry conditions have contributed to this response, the clay-dominated soils in these areas have traditionally provided adequate K for optimum production. Studies were initiated at two field sites, Williamson county in the Central Blacklands and Wharton county in the Upper Gulf Coast where mid-season K deficiencies had been observed to investigate cotton yield response to soil-applied K fertilizer. In mid April, cotton cv. Phytogen 499 was planted into a Lake Charles clay loam at the Wharton site and cv. DP 0935 into a Burleson clay at the Williamson site. Based on soil test results, 60 and 35 pounds K2O per acre were recommended for the Williamson and Wharton sites, respectively. Treatments were 0, 25, 50, 75 and 100 pounds of K2O per acre applied shortly after planting using liquid 2-6-12 at the Wharton site, and 0, 40, 80 and 120 pounds of K2O per acre applied both as liquid 2-6-12 and as granular 0-0-62 before planting at the Williamson site. Monthly rainfall during the season was below normal at both study sites. Lint yield responded to rates of applied K equal to and greater than that recommended at both sites. Liquid K applied in a subsurface band had a greater, positive effect on lint yield compared to granular K surface band applied and incorporated. Applied K improved length, strength and uniformity at the Williamson site. These studies will be repeated to better assess the influence of seasonal differences in rainfall, crop rotation and soil properties on the results. Results will soon be available demonstrating the impact of the potassium application on cotton lint yields, quality, and net returns.

Another study conducted as part of this project is measuring cotton boll maturity. Cotton (Gossypium hirsutum) typically requires termination due to its perennial growth habit. Evaluating end-of-season plant maturity is an important management tool that helps producers make time-sensitive decisions regarding irrigation termination and harvest aid application timing. Plant maturity is generally determined in-field based on the farmer's guesswork and experience, utilizing traditional techniques such as cutting bolls open to determine the last harvestable boll, or estimating heat unit accumulation based upon the number of nodes above the uppermost white bloom. However, each of these methods is subjective and has its own limitations. The physiological principal behind this project is to quantify the reduction in boll moisture content as the boll matures and correlate the moisture content to cotton boll age, as quantified by heat unit accumulation.

The study was designed to provide two boll moisture sampling methods (in-suture and in-lock) for 10 bolls per timing treatment in irrigated and dryland cotton, with three replications. Twenty total cotton blooms per replication were tagged within a row plot at white flower on three-day intervals for 21 days in adjacent irrigated and dryland cotton fields. When sampling boll moisture, the more mature bolls were prone to splitting during probing, resulting in inconsistent moisture readings. Taking moisture measurements from in-lock rather than in-suture reduced the incidence of boll splitting. The bolls in the dryland field split open more easily than those in the irrigated plot, which in addition to lower overall moisture content and increased maturity due to drought stress, could help explain the lower moisture readings from the dryland plot. Taking two in-lock measurements from each boll tested appeared to be the best method for determining boll moisture content. The moisture probe design could be significantly improved with shorter, thinner prongs. This would reduce the chance of the boll splitting open, thereby improving the accuracy of each measurement while ensuring uniform probe depth for each boll sampled. Additionally, prongs that were more narrowly spaced would likely increase the consistency of the measurements. Overall, this preliminary research determined that determining boll maturity by analyzing moisture content can be achieved both accurately and practically. Additional work needs to be done to further evaluate the robustness of the boll maturity quantification method.


Project Year: 2012

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