Browsing by Subject "Winter wheat"
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Item Modeling Cotton and Winter Wheat Growth and Yield Responses to Irrigation Management in the Texas High Plains and Rolling Plains(2014-12-17) Attia Mohamed, AhmedA significant portion of the intensively cultivated agricultural areas in the U.S. is located in the Texas High Plains and Rolling Plains. In recent years, decreasing ground water supplies and precipitation variability are presenting challenges for profitable cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) production in these regions. A field study was conducted in 2012 and 2013 at Chillicothe, TX, to investigate the growth, yield, and water use efficiency (WUE) responses of cotton cultivars under different irrigation and tillage treatments. Results revealed that deficit irrigation of 45% of cotton evapotranspiration (ET) increased the dryland yield and WUE by 260% and 39%, respectively. The irrigation-by-variety interaction showed that the 90% ET replacement treatment involving PHY375 produced the greatest lint yield and WUE. Tillage did not significantly affect lint yield, WUE, and fiber quality. Increasing irrigation resulted in a linear increase in fiber length and strength, and a linear decrease in fiber micronaire. Two vegetation indices, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were calculated using spectral reflectance dat. During the peak growing season, NDWI performed better compared to NDVI as no saturation problems were observed. The Crop Water Stress Index (CWSI) calculated using canopy and air temperature measurements showed significant differences among irrigation treatments. It was also observed that the CWSI and NDWI were negatively correlated. A modeling study was performed using the cotton growth simulation model, Cotton2K, to investigate the lint yield, WUE, and economic return responses using 31 years weather records (1980 ? 2010) from the Texas Rolling Plains. Results revealed that replacing 112% ET maximized the yield while economic return was maximized at 108% ET. When water resources are limited, deficit irrigation at 80% ET replacement can be used to improve cotton WUE without significant yield and economic reductions in the semi-arid Texas Rolling Plains. A third study was performed on winter wheat using the DSSAT-CERES-Wheat model to investigate winter wheat growth and yield responses to irrigation management in the Texas High Plains using long-term weather datasets available for the Texas High Plains region (1980-2012). Results of winter wheat response to irrigation indicated that deficit irrigation between jointing and anthesis could significantly increase winter wheat grain yield and WUE. Application of 100 mm of irrigation at jointing and 120 mm at anthesis was found to produce a grain and biomass yields and WUE similar to full irrigation with significant amount of water saving.Item Potential economic benefits of adjusting dryland cropping practices based on seasonal rainfall expectations(Texas Tech University, 2003-12) Musunuru, Naveen KumarThe High Plains of Texas is classified as a semiarid area with an annual rainfall of 450 mm and an evapotranspiration ratio of less than 0.25. For the last decade, dryland yields for cotton, grain sorghum, and winter wheat production averaged approximately half of those for irrigated production systems. Conditions of high climatic variability coupled with frequent droughts account for the low crop yields obtained in this region. Cropping practices that might be used to take advantage of seasonal rainfall conditions would include crop choice, planting density, planting date and fertilization. At present very little or no information is available to encourage High Plains dryland farmers to modify the cropping practices based on seasonal rainfall expectations. CroPMan simulation model was used to evaluate the economic benefits of using alternative management practices for dryland cotton, grain sorghum and winter wheat production. The top three producing counties in the High Plains of Texas were selected for the analysis of below and above normal rainfall conditions/scenarios. Stochastic Dominance with respect to a function (SDRF) was used to introduce risk and take into account of inherent variability of dryland production systems. Expected net revenues above variable costs were compared for the selected crops across management practices. The results indicated that modifying cropping practices under below normal rainfall conditions would save a dryland cotton farmer in the range of $12 to $22/acre. Increased expected net revenues above variable costs for cotton production under above normal rainfall conditions were found to be in the range of $10 to $25/acre. The economic benefits resulting from adjusting grain sorghum production practices were found to be from $7 to $21/acre and from $3 to $5/acre under below and above normal rainfall conditions, respectively. The results for winter wheat showed that modification of cropping practices based on seasonal rainfall expectations would benefit a dryland winter wheat farmer in the range of $14 to $16/acre under below normal rainfall conditions. The expected profits for winter wheat production under above rainfall conditions were found to be from $11 to $20/acre. Results from this study reveal that dryland farmers would clearly benefit from modifying cropping practices based on seasonal rainfall expectations.