WATER AND SOLUTE MOVEMENT UNDER CONVENTIONAL CORN IN CENTRAL SPAIN .2. SALT LEACHING

Leaching of salts under held conditions may be addressed through a com bination 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 m ays L.) to assess the leaching pattern of Ca2+, Mg2+, Na+, K+, Cl-, SO 42-, CO3H-, and NO3- under conventional cropping, River and well irrig ation water were used with salinities of 680 and 1580 mg L(-1), respec tively. Sampling of the soil water solution throughout the growing sea son was done for soil profile layers using a permanent ceramic-candle extraction system. Neutron probes and tensiometers allowed seasonal me asurements of soil water content and water movement in the profile. Le aching of salts was calculated as the product of deep drainage amounts times the salt concentrations at the 1.4-m soil depth. Total salt dra inage for river and well was 0.34 and 0.38 kg m(-2), respectively, Acc umulation of salts to a depth of 1.4 m in the soil profile showed valu es of 0.02 and 0.21 kg m(-2) in plots irrigated with river and well wa ter, respectively. Soil water balance and concentration of salts in th e soil solution indicated discharge of salts to the groundwater table with conventional cropping practices, Groundwater pollution was addres sed by matching irrigation to the evapotranspiration and by minimizing the concentration of sails in irrigation water.