Three Reasons to Broaden Your Fertigation Knowledge

While the benefits of fertigation are being recognized by more irrigation managers today than ever before, the staff of Irrigation Business & Technology thought perhaps that many farmers and managers of large urban landscapes aren't fully aware of the full variety of fertilizer products that can be applied through irrigation systems. Others may have tried fertigation without success. The following list of chemicals for fertigation and guidelines for their use were prepared by Dr. in San Luis Obispo and were presented by him during the Irrigation Association International Irrigation Show in San Diego, CA last November. Dr. Burt sees fertigation as a helpful tool to farmers as well as managers of large landscapes, such as golf courses, parks, and large commercial sites. Modern farmers and landscape managers often enlist the assistance of soil fertility specialists to assure maximum yield and quality. Fertigation enables irrigation systems to deliver the soil consultant's prescription with the greatest accuracy and least disruption. There are numerous considerations in deciding what chemicals to fertigate. They include cation‐anion balance, the form of fertilizer, solubility, compatibility and the pH of both the water and the soil. Because nitrogen fertilizer is injected more widely than any other nutrient, special attention is given to it here. However, fertigation is also practical for applying gypsum, phosphorus and potassium. Cation‐Anion Balance The total number of nutrient cations (positively charged ions) in a plant must equal the total number of nutrient anions (negatively charged ions) in a plant. The ammonium ion (NH 4 +) will be in competition with other cations for uptake. The nitrate ion (NO 3) will be in competition with other anions for uptake. A plant receiving nearly all of its nitrogen in the form of ammonium might become low to deficient in potassium (K +), calcium (Ca 2 +) and magnesium (Mg 2 +). The plant will compensate for the positive charge by absorbing more phosphate (H 2 PO 4) and sulfate (SO 4 ‐2) than normal. In addition, a plant that takes up primarily ammonium nitrogen will produce a more acidic root environment because the roots release H+ ions to balance the charge from taking up NH 4 + ions.