The behavior of water stressed cotton (Gossypium hirsutum L.) is well documented, but our knowledge of traits which can be genetically manipulated to improve drought tolerance is incomplete. This study was conducted to determine which morphological and physiological factors lessen the effects of water stress on the yield of two short-season cultivars [i.e., TAMCOT HQg5 CHQg5) and G&P 74 ÷ (GP74)] with a common parent in ancestry. Plants were grown in a rain shelterlysimeter facility containing a Pedernales fine sandy loam soil (fine, mixed, thermic Udic Paleustalf) in 1990 and 1991 at Temple, TX. Water stress was imposed by replenishing a fraction of the water lost to evapotranspiration, beginning about 78 d after emergence. HQ95 and GP74 did not differ in leaf area index (LA]) or in the rate of leaf area development before water stress was imposed. The rate of LAI decline and average LAI were similar between cultivars when water stress was imposed. HQg5 used more water and used it at a faster rate than GP74 when water stressed. HQg5 produced more bolls and had higher yield under both well-watered and water stressed conditions than GP74 in each of the 2 yr. The largest difference in boll load between cultivars occurred on sympodia branches in the lower canopy, where HQ95 had 37, 60, and 182% more bolls than GP74 when plants received 0, 50 or 75, and 100% of the depleted soil water. Whether well watered or water stressed, individual boll weight did not differ between the two cultivars. However, the harvest index and the production efficiency of bolls (i.e., bossl pr unit leaf area) of HQ95 was consistently higher than GP74 for all water regimes. On average, HQ95 allocated 21% more dry matter to yield and produced 32% more bolls per square meter than GP74. While differences in yield between the cultivars mirror harvest index, large differences in boll production efficiency suggested that the intrinsic photosynthetic capacity of HQ95 may be greater than GP74. C OTa~ON is grown under a wide range of climatesfrom the humid sub-tropics of South Carolina to the semi-arid desert of California. Yet, water supply remains a critical limitation of yield. Genetic variation in yield and water-use efficiency has been reported for cotton subjected to water deficits (Quisenberry and McMichael, 1991; Cook and EI-Zik, 1993). Also, the effects of water deficits and relationships between cotton growth and water requirements are well documented (Grimes and EI-Zik, 1982; Morrow and Krieg, 1990). However, a fundamental understanding of the intrinsic factors which could improve the ability of cotton to withstand water deficits remains to be developed. We know that cotton fruit production and retention

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Although Ethiopia has abundant land for irrigation, only a fraction of its potential land is being utilized. This study evaluates suitability of lands for irrigation using groundwater in Ethiopia using GIS-based Multi-Criteria Evaluation (MCE) techniques in order to enhance the country's agricultural industry. Key factors that significantly affect irrigation suitability evaluated in this study include physical land features (land use, soil, and slope), climate (rainfall and evapotranspiration), and market access (proximity to roads and access to market). These factors were weighted using a pair-wise comparison matrix, then reclassified and overlaid to identify suitable areas for groundwater irrigation using a 1-km grid. Groundwater data from the British Geological Survey were used to estimate the groundwater potential, which indicates the corresponding irrigation potential for major crops. Results indicated that more than 6 million ha of land are suitable for irrigation in Ethiopia. A large portion of the irrigable land is located in the Abbay, Rift Valley, Omo Ghibe, and Awash River basins. These basins have access to shallow groundwater (i.e., depth of groundwater less than 20 m from the surface) making it easier to extract. The comparison between available groundwater and total crop water requirements indicate that groundwater alone may not be sufficient to supply all suitable land. The study estimates that only 8% of the suitable land can be irrigated with the available shallow groundwater. However, groundwater is a viable option for supplementing surface water resources for irrigation in several basins in the country

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Grain sorghum [Sorghum bicolor (L.) Moench] and maize (Zea mays L.) in dryland conditions can experience environmental stress during grain filling, causing increased dependency on stored assimilate. Estimates of maintenance costs and efficiency of production of grain from stored assimilate are important for modeling yield production in such conditions. Our primary objectives in this study were to estimate the maintenance coefficient, the maximum decrease in leaf and stem dry matter, and the efficiency of production of grain from stored assimilate, all with severe stress during grain filling. We measured the loss of sorghum and maize stem dry weight and nonstructural carbohydrate (NCO) content and the increase in panicle and ear dry weight when severe shading stress occurred after anthesis. Extreme shading treatments were imposed from 7 to 8 d after anthesis until physiological maturity on three sorghum cultivars and a maize hybrid in the field at Temple, TX. Shading reduced the combined culm and leaf sheath weights of sorghum by 20 to 33% relative to the weights at anthesis. Measurements of NCO and dry matter of the maize hybrid indicated that 190 to 240 g kg−1 of the stem dry weight at anthesis represented assimilate available for respiration and growth. Mean maintenance coefficient values were 13 mg g−1 dry wt. d−1 for sorghum and 8 mg g−1 dry wt. d−1 for maize. Efficiencies of grain produced from stored assimilate were less than theoretical values. The importance of NCO stored prior to grain filling for maize and sorghum yield modeling appeared to be minimal.