Nutrients in irrigation water

Essential nutrients in plants

These are substances necessary for the metabolism and photosynthesis in plants including macronutrients (i.e. N, P, K, Ca, Mg and S) and micronutrients (i.e. Fe, Mn, B, Cu, Mo, Zn and Si).

Macronutrients normally represents a concentration of 1000ppm in plants while micronutrients are found in levels of 500ppm or less. High concentration of these micronutrients can be toxic for the plant.

Proper crop nutrient management often includes fertilization of some of these nutrients. Most producers do not consider irrigation water nutrient concentrations for fertilization program. This source of plant nutrients is important and can save producers money and prevent toxicity due to the application of high quantity these elements in fields. Therefore, the concentration of these nutrients in irrigation water should be tested and taken into account.

Except for nitrate-nitrogen (NO3-N), the concentration of most minerals/nutrients in groundwater does not change dramatically from year to year. Thus, for nutrients other than NO3-N, analysis of irrigation water approximately every 10 years is sufficient.

However, NO3-N concentration can vary from year to year in the same well and among wells in the same field. This variation will depend on many factors such as irrigation management practices, soil type (e.g. sandy soils, impermeable soils, etc.), depth of the water table and precipitation range. For example, the concentration of NO3-N in irrigation water can vary by 10 ppm or more within short distances. Therefore, testing irrigation water for NO3-N may need to be done yearly.