Saving fresh water by crop cultivation on salinizing soils, a survey

Global soil salinization covers large coastal and inland areas as a result of climate warming and poor irrigation practices. Water supply for the cultivation of vegetable and fodder crops covers a major part of fresh water sources at the expense of drinking water and water for industrial purposes. Salinity adapted crops are being cultivated in saline agriculture. Some high salt tolerant crops produce well under seawater (EC 40-50 dS/m) irrigation, other crops can be cultivated under brackish conditions. First we consider soil salinization viewed by soil scientists and crop physiologists. Second, we discuss the definition of salt tolerance of crops and measurement of salt tolerance in the field and other controlled indoor conditions. Growth response curves obtained under field or indoor conditions indicate how crop yield varies with increased salinity. Above a threshold salinity value in the curve, plant yield decreases with increased salinity (slope). Threshold salinity and slope values are generally applied to classify crops as salt tolerant, salt sensitive or intermediate. In saline agriculture crops are being cultivated as vegetable crops, fodder crops, ornamentals and as bio-energy crops. Use of large amounts of brackish water (salt concentrations ranging from 1 to 50% of that of seawater, EC values 0.125 dS/m), often regarded unsuitable for crop cultivation, can be successfully applied in saline agriculture, saving significant volumes or fresh water. There is an increasing need of salt tolerant crops for large scale saline agriculture at a global scale. Traditionally salt tolerance crops have been obtained by selection and breeding. Alternatively improved salt tolerance of crops can be obtained by genetic engineering. Genes involved in salt tolerance may be transferred and activated in salt sensitive crops.