Leaching effect of rainfall on soil under four-year saline water irrigation

In the context of the overall competition for water resources it is important to understand the complex dynamics of crop water management including evapotranspiration, water quality, and leaching requirement, each of them depending on the site-specific conditions. The research started with grain maize and continued with sunflower, grain maize, and wheat, at the experimental field. On both grain maize and sunflower, 10 irrigation treatments were compared that resulted from the factorial combination of two types of water (fresh and brackish water) with five irrigation regimes; the scheduled treatments were applied by furrow irrigation. The amount of salts brought into the soil with the irrigation water during the three irrigation seasons of our trial increased shifting from the lowest to the highest irrigation regime and with the increase of salinity in the irrigation water. From the study of salt distribution in the soil it follows that at the end of the irrigation season the salt concentration increased by passing from the middle of the furrow, a zone more subject to leaching during irrigation, to the intermediate zone between the furrow and the ridge, and in the middle of the ridge between two contiguous furrows, an area of confluence of the wetting and salt accumulation fronts. The leaching water supplied during the irrigation season was poorly efficient in leaching the salts brought in through irrigation, whereas the rainfall water of the autumn-winter period after the irrigation season ensured a good control of soil salinity