Sampling irrigation water for routine lab analysis

Irrigation sampling is an important nutrient monitoring practice to determine water quality. Routine lab analysis is often performed to evaluate pH, electrical conductivity (EC), alkalinity, and available dissolved nutrients. Assessing irrigation water quality will help refine alkalinity neutralization and fertility programs and define limited or
excessive nutrients for the appropriate corrective procedure.

It's not uncommon to come across instances where crop maintenance and production takes precedence over nutritional monitoring such as irrigation water sampling. However, sampling and assessing irrigation water is an important nutrient monitoring practice to determine water
quality or chemical condition.

In general, a standard water quality analysis determines pH, soluble salts [referred to as electrical conductivity (EC)], and alkalinity or carbonates, bicarbonates, and hydroxides. In some instances, levels of dissolved nutrients such as N, P, K, Ca, Mg, S, Fe, Mn, B, Zn, Cu,
Mo, and Cl may be included or for an additional fee. Irrigation water should be assessed at least annually or more frequently depending on the crop, cropping cycle and system.

Evaluating irrigation water is important because water quality varies by geographic location, time, water source, well depth, and rainfall events. For example, in geographic regions of the United States where irrigation water is drawn from aquifers, alkalinity may be elevated due to the concentration of carbonate, bicarbonate, and hydroxide anions in the water. For this reason, growers located in these geographic regions are often challenged with substrate pH drift because alkalinity in irrigation water has the greatest effect on substrate pH rise than water pH. To mitigate the effect of alkalinity on
substrate pH, neutralization or acidification is needed. Therefore, water quality analysis will help determine the need to determine alkalinity levels and refine alkalinity neutralization and fertility programs. Water analysis will also define limited or excessive
nutrients dissolved in irrigation water that may manifest into nutritional deficiencies or toxicities (Fig. 1) and aid in the identification of the appropriate corrective procedure. 

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