Effects of sodic water on soil sodicity and nutrient leaching in poultry and sheep manure amended soils

The need to use saline and sodic waters for irrigating agricultural lands has increased due to a shortage of fresh water resources, especially in arid and semi-arid regions. One way to decrease undesirable effects of sodic waters on the physical and chemical properties of soils is to apply organic and chemical amendments. In this study, the effects of two organic fertilizers (poultry and sheep manure), and gypsum were evaluated in soil that received sodic water. These materials were added to a sandy loam soil at the rate of 5%, after which the treated soils and a control sample were incubated for one month at field capacity at 25–30 °C. Column leaching experiments using treated soils were then conducted under saturated conditions using two types of NaCl–CaCl2 solutions and three sodium adsorption ratios (SAR) (0, 10, 40) with a constant ionic strength (50 mmol l− 1). The results indicated that the application of sheep and poultry manure to soils caused an increase in cation exchange capacity (CEC) and greater adsorption of cations such as calcium, magnesium and potassium than sodium (Na+). Conversely, the addition of organic amendments led to increased Na+ leaching and a lower exchangeable sodium percentage (ESP). The ESP of the control soil after leaching with solutions with SAR of 10 and 40 increased significantly, but the level of sodification in treated soils was lower. The ESP of the poultry and sheep manures treated soils after leaching with solution with SAR 40 was significantly lower than control soil. Specifically, the rate of soil sodification in the treated soils declined in the following order: control soil > sheep manure treated soil > poultry manure treated soil > gypsum treated soil. Finally, the effects of gypsum on the sodification of soil by SAR 10 solution were the same as the effects of poultry manure, whereas the loss of cations and anions from poultry and sheep manure treated soils was greater than the loss from gypsum treated and control soils.