Plant nutrition as a function of irrigation water quality Prof. Uri Yermiyahu Agricultural Research Center (ARO), Volcani Center,  Israel

Water scarcity is ever increasing the need and desire to utilize non-conventional sources of water for irrigation. Water for irrigation today includes brackish groundwater, recycled wastewater and desalinated water. Each type of water has a unique chemical composition, requiring independent consideration regarding management of crop nutrition. Water quality/composition has influence and repercussions on interactions with fertilizers, soil chemistry and nutrition, and of course, on plants. 

In order to adapt the fertilization regime to irrigation water quality the contents of inorganic macro and micro essential nutrients have to be taken into account. The most conventional sources of irrigation water are groundwater, lakes and rivers. In many regions, this type of water contains calcium, magnesium, sulphur and boron. However, in other regions such water sources can be poor in these nutrients. In brackish groundwater one may find also potassium and chloride whereas in recycled wastewater, nitrogen, phosphorus and micronutrients are found. Contrastingly, desalinated water contains only calcium and boron.

High concentrations of essential elements and other ions affect the uptake of nutrients by plants. For example, brackish water and recycled wastewater contain high concentrations of sodium, which might inhibit potassium and calcium uptake and high concentrations of chloride and sulphate which might inhibit nitrate uptake by plants. In addition, Irrigation with water containing high mineral concentrations requires a leaching fraction which, consequently, increases amount of applied fertilizer and may create environmental hazards.

The soluble organic matter found in recycled wastewater can contribute nitrogen and phosphorus but the mineralization rates of these nutrients are complex and it is difficult to assess their contribution to plant nutrition.

The talk will address these issues and bring examples and case studies from horticultural crops including fruit trees, fresh herbs and vegetables.