Cotton maturity and the irrigation timing paradigm
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Because cotton (Gossypium hirsutum L.) is generally recognized as being biologically drought tolerant, it has been commonly adapted to semi-arid regions throughout the world. In many of these regions, cotton is grown under non-irrigated conditions with marginal rainfall, such as the Texas High Plains, where water is the major limiting factor. Declining water tables in underground aquifers of irrigated areas, greater demand for irrigation of various agricultural crops to increase production, and increased pumping costs all focus attention to the overall water problem. Multiple research trials were conducted to investigate the intricate relationship between the timing of cotton crop maturity and irrigation in order to improve crop selection and irrigation management. A multi-state study used vertical mapping to quantify cotton maturity and determine how well in-season measurements correlate with cultivar maturity as measured by boll distribution, as well as tested the effects of multiple yield environments on cotton maturity. Another study aimed to discern and quantify the effects of a vast range of irrigation rates and timings on one mid-season cotton cultivar; specifically examining the relationship between three rates and three periods of irrigation treatments on end-of-season boll distribution and fiber quality, and the effect irrigation timings have on each other. Furthermore, in order to further investigate ultra-drought sensitive phases of growth and development, various maturing cotton cultivars were subjected to different timings of episodic drought to determine the effects on boll distribution, yield, and fiber quality. Results indicated that boll distribution is another facet of maturity different from flowering progression, and that boll accumulation proves additional information that extends beyond node-by-node boll distribution estimates. A single index for a cultivar necessitates several locations and a standard cultivar for comparison. Additionally, low irrigation levels prior to flowering had a minimal effect on upper plant boll production, supporting the notion that early season irrigation may be stored for use later in the season to achieve high boll production and retention. Cotton that is stressed prior to flowering may develop larger root systems that become advantageous in later phases of the plant’s growth. Cotton that was stressed during early flowering periods had the lowest results in terms of boll distribution and yield. However, many of these treatments still produced lint with sufficient fiber quality characteristics. In general, early cultivars were able to bounce back from episodes of episodic drought, setting bolls with superior distribution and producing higher yields. This information may be vital for producers whose irrigation capacity has been declining, or who want to maximize profits by fine tuning their irrigation to more precisely match the varieties they may be growing.