Browsing by Subject "irrigation"
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Item Deficit Irrigation Programs for Water Conservation in the Management of Bermudagrass Fairways in Texas(2014-04-29) Hejl, Reagan WesleyGolf course water use in Texas has become increasingly regulated in the past decade due to persistent drought conditions, diminishing water supplies, and rapidly a growing population. Many golf courses have been faced with considerable cutbacks in irrigation allocations, but information is limited regarding critical levels needed for maintaining adequate turf quality, persistence, and recovery from divots and traffic. Furthermore, the effects of irrigation water quality on minimal irrigation requirements has not been fully resolved. A series of field and greenhouse studies were conducted over the course of two years in College Station, TX, to determine the effects of continuous reference evapotranspiration (ET_(o))- based deficit irrigation levels on quality of bermudagrass fairway turf. Turf quality evaluations from both seasons showed that in the absence of traffic, irrigation levels of 0.3 x ET_(o) were sufficient to maintain acceptable turfgrass quality during summer months (at a 3-day per week irrigation frequency). Canopy temperatures increased considerably as irrigation was reduced; with up to a 20? increase detected between irrigated and unirrigated plots. Upon resumption of full irrigation levels in September, unirrigated and deficit-irrigated plots quickly recovered to ~90% green cover within 8 weeks in year 1. However, unirrigated plots were much slower to recover in the second season, only reaching ~30% green cover by 8 weeks. The delayed ability of unirrigated plots to rebound following successive years without irrigation suggests a cumulative effect of drought stress on bermudagrass health and vigor. Traffic treatments delayed recovery across all irrigation levels. Greenhouse investigations into irrigation water quality (reverse osmosis (RO), saline, and sodic) and plant growth regulator trinexapac-ethyl (TE) effects on bermudagrass evapotranspiraton and tolerance to deficit irrigation were also undertaken. Irrigation water quality failed to significantly influence minimal irrigation requirements, but turf irrigated with sodic irrigation did exhibit considerably higher evapotranspiration (ET) rates relative to those receiving saline or RO irrigation. TE improved bermudagrass quality and delayed leaf firing under the soil moisture stress from deficit irrigation. The findings from this research provide timely and practical information for turf managers who must increasingly utilize ET-based irrigation scheduling and/or low-quality water sources in the management of golf course turfgrass systems.Item Influence of planting depth on landscape establishment of container-grown trees(2009-05-15) Bryan, Donita LynnTree transplanting practices influence plant survival, establishment, and subsequent landscape value. The inability to adequately quantify effects of inappropriate tree planting and transplanting practices threatens long-term viability and productivity (sustainability) of trees within terrestrial ecosystems. Tree planting depth, i.e. location of the root collar relative to soil grade, is of particular concern for tree growth, development, and performance in the landscape. A series of model studies was conducted to investigate effects of planting depth, container production methods, and transplanting practices on landscape establishment of container-grown trees. Studies included determining the effect of planting depth and soil amendments on live oak (Quercus virginiana Mill.) and baldcypress (Taxodium distichum (L.) L. Rich.), the effect of planting depth during container production and subsequent landscape establishment of lacebark elm (Ulmus parvifolia Jacq.), the effect of planting depth and irrigation practices on landscape establishment of sycamore (Platanus occidentalis L.), and the effect of planting depth and transplant season on landscape establishment of baldcypress. Optimum planting depth varied among species and was dependent on cultural practices and/or environmental conditions. Overall, live oak and baldcypress growth was better when planted with root collars at grade in sand in raised beds compared to planting below grade in control soils. Lacebark elm growth was greater when planted at grade during the initial container production phase and below grade in the second container production phase. Subsequent landscape establishment was variable, but planting at grade to 5 cm above grade produced greater growth. Sycamore trees planted below grade had increased mortality and decreased growth compared to trees planted at grade or above grade, while irrigation had no effect. Baldcypress planted above grade had reduced growth compared to those planted at or below grade, while transplant season had no effect. Species and cultivars within species may differ markedly in their response to environmental/cultural stresses, including planting depth. Each tree species originating from a specific environment may represent an ecotype adapted to that particular environment. Therefore, tree survival and performance may depend on the difference between the environment from which the tree was grown and the experimental system into which it is introduced.Item Mitigating cotton revenue risk through irrigation, insurance, and/or hedging(2009-05-15) Bise, Elizabeth HartTexas is the leading U.S. producer of cotton, and the U.S. is the largest international market supplier of cotton. Risks and uncertainties plague Texas cotton producers with unpredictable weather, insects, diseases, and price variability. Risk management studies have examined the risk reducing capabilities of alternative management strategies, but few have looked at the interaction of using several strategies in different combinations. The research in this study focuses on managing risk faced by cotton farmers in Texas using irrigation, put options, and yield insurance. The primary objective was to analyze the interactions of irrigation, put options, and yield insurance as risk management strategies on the economic viability of a 1,000 acre cotton farm in the Lower Rio Grande Valley (LRGV) of Texas. The secondary objective was to determine the best combination of these strategies for decision makers with alternative preferences for risk aversion. Stochastic values for yields and prices were used in simulating a whole-farm financial statement for a 1000 acre furrow irrigated cotton farm in the LRGV with three types of risk management strategies. Net returns were simulated using a multivariate empirical distribution for 16 risk management scenarios. The scenarios were ranked across a range of risk aversion levels using stochastic efficiency with respect to a function. Analyses for risk averse decision makers showed that multiple irrigations are preferred, and that yield insurance is strongly preferred at lower irrigation levels. The benefits to purchasing put options increase with yields, so they are more beneficial when higher yields are expected from applying more irrigation applications.Item Responses of Grain Sorghum to Profile and Temporal Dynamics of Soil Water in a Semi-arid Environment(2014-02-24) Bell, Jourdan MDevelopment of efficient irrigation strategies is a priority for producers faced with water shortages. Managed deficit irrigation attempts to optimize water use efficiency (WUE) by synchronizing crop water use with reproductive stages. Soil water use and yield of grain sorghum [Sorghum bicolor (L.) Moench], on a Torrertic Paleustoll in the Texas High Plains, USA, were evaluated during the 2010 to 2012 growing seasons under three sprinkler irrigation strategies: full (FI), deficit (DI), and managed deficit irrigation (MDI). Soil water contents were measured weekly at 0.20-m intervals from 0.10 to 2.30 m depth using a neutron moisture gage. Irrigation for the FI treatment was scheduled when root zone water (0 to 1.6 m) was depleted to 50% of the potential plant available water (PPAW). The DI treatment was irrigated at 50% of FI. The MDI treatment was irrigated at 75% of FI between growing point differentiation and half-bloom, 50% of FI after half-bloom, and less than DI prior to growing point differentiation. Fully irrigated sorghum grain yields averaged 3.7 Mg ha^(-1) greater (p < 0.001) than deficit irrigated sorghum in all years. Seasonal crop water use under MDI averaged 29 mm greater than DI. Concomitant with increased water use principally during the reproductive period, MDI yields averaged 1.6 Mg ha^(-1) greater than DI, which was significant in 2010 and 2012 (p ? 0.006). The WUE of FI sorghum was significantly greater than MDI in 2012 (p = 0.003) and DI in 2010 and 2012 (p ? 0.001). In 2011, crop water uptake was restricted to above 0.6 m when water contents deeper in the profile were less than 42% PPAW. In 2010 and 2012, seasonal crop water uptake in the profile below 1.0 m was small (<14 mm) and did not appreciably increase in response to imposed soil water deficits. The rooting zone for evaluating plant water status and hence irrigation scheduling depended on initial profile water contents and possibly root density deeper in the profile. Results suggest that WUE?s of grain sorghum are not compromised under MDI compared with FI in most cropping seasons.Item Urban Sodicity in a Humid Subtropical Climate: Impact on Biogeochemical Cycling(2012-10-19) Steele, Meredith KateUnderstanding the mechanisms of non-point source carbon and nutrients in urban watersheds will help to develop policies to maintain surface water quality and prevention of eutrophication. The purpose of this dissertation is to investigate the impact of sodium on carbon and nutrient leaching from the two main contributors; soil and leaf litter, and calculate the sodium exports in a humid subtropical urban river basin. The first chapter reviews the current literature on urbanization in watersheds. Chapter II quantifies the carbon and nutrient in intact soil core leachates and in water extractable solution from urban soils collected from 33 towns and cities across the state of Texas. Chapter III investigates the impact of sodicity and salinity on water extractable organic carbon and nitrogen from vegetation. Chapter IV investigates the export of sodium and chloride from the upper Trinity River basin. The results derived from this study indicate that sodium exports are elevated in urban watersheds and further that sodium in irrigation water elevates the loss of carbon and nutrients from both watershed soil and senesced vegetation and that this may contribute to high concentrations in urban freshwaters.