Salts In Irrigation Water Research Articles

Water and Solute Movement under Conventional Corn in Central Spain. II. Salt Leaching

AbstractLeaching of salts under field conditions may be addressed through a combination of the soil water balance and the drainage and concentration of salts in the soil profile. A field experiment was conducted in the 1991 growing season on a Typic Xerofluvent soil planted to corn (Zea mays L.) to assess the leaching pattern of Ca2+, Mg2+, Na+, K+, Cl+, SO2−4, CO3H−, and NO−3 under conventional cropping. River and well irrigation water were used with salinities of 680 and 1580 mg L−1, respectively. Sampling of the soil water solution throughout the growing season was done for soil profile layers using a permanent ceramic‐candle extraction system. Neutron probes and tensiometers allowed seasonal measurements of soil water content and water movement in the profile. Leaching of salts was calculated as the product of deep drainage amounts times the salt concentrations at the 1.4‐m soil depth. Total salt drainage for river and well was 0.34 and 0.38 kg m−2, respectively. Accumulation of salts to a depth of 1.4 m in the soil profile showed values of 0.02 and 0.21 kg m−2 in plots irrigated with river and well water, respectively. Soil water balance and concentration of salts in the soil solution indicated discharge of salts to the groundwater table with conventional cropping practices. Groundwater pollution was addressed by matching irrigation to the evapotranspiration and by minimizing the concentration of salts in irrigation water.

Functional Form Selection for Regional Crop Response to Salinity, Water Application, and Climate

Salts in irrigation water impair plant use of water, reduce plant growth, and lower farm productivity. United States agricultural productivity suffers millions of dollars in losses each year due to salinity. Because of the extent of the problem, salinity has become one of the dominant issues in national water quality policy. Generally, water quality policy decisions are based on regional effects, yet all existing estimates of yield response to salinity are from field trials. Regional policy forecasts based on the results from field trials can be misleading. Field trial results may be very precise for a set of controlled conditions but may fail to capture the actual heterogenous nature of farm productivity and farmer response to deteriorating water quality. Regional production forecasts may be more precise if they are based on regional production models parameterized with regional observations. This research estimates regional crop production models. Regional field crop yields are modeled as a function of water salinity, water application rate, and climate. With salinity included as an explanatory variable, the model measures the influence of changes in water quality on agricultural production. Water application rate as an explanatory variable in the model captures managerial responses to rising water costs and increasing salinity levels. With climate included as an explanatory variable, the model accounts for regional differences in growing conditions. Three functional forms are examined: the quadratic, the log-log, and the linear threshold. The models were applied to the following western irrigated field crops: corn (Zeu mays), sorghum (Sorghum bicolor), barley (Hordeum vulgare), winter wheat (Triticum aestivum), durum wheat (T. turgidum), and other spring wheat. Empirical results indicated that the quadratic specification best captures regional yield response to irrigation water salinity.

Soluble Salt Concentrations in Runoff Waters from Soils Previously Cropped to Rice

AbstractSoluble salt damage to rice in Arkansas has been evident in recent years. In order to adequately model salt balances for Crowley silt loam soil (Typic Aibaqualfs) cropped to rice (Oryza sativa L.) and soybean (Glycine max L. Merr.) in the Grand Prairie region of Arkansas, a description of soluble constituents in runoff water was needed. Three fields were monitored for soluble salts in runoff and irrigation water as well as runoff volume. As cumulative runoff increased, a logarithmic decline in the concentration ratio of runoff water salt concentration to irrigation water salt concentration was found for electrical conductivity (EC), Ca, Mg, Na, SO4, and Cl for the first 10 cm of runoff after removal of the rice floodwater. The equation in which the logarithm of the concentration ratio was the dependent variable and cumulative runoff was the independent variable had a common slope among fields for the solution variables studied. A common intercept was found for Ca and Na but not for EC, Mg, SO4, and Cl. A second linear relationship was developed where the intercept in the above for SO4 and Cl was found to be a function of irrigation water concentration. At one field where sufficient data were available the concentration ratio stabilized after 10 cm of runoff and could be predicted using the concentration ratio equation where cumulative runoff was set at 10 cm.

Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds

AbstractIrrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes.

Salt Water Irrigation in Sand Area in Dry Region

Salt Water Irrigation in Sand Area in Dry Region

Salts in Irrigation Water

Salts in Irrigation Water