Managing Marginal Water Quality in Sustainable Agriculture
Darren Jones, PCA – While drought conditions continue to worsen in the states west of the Rockies, water quality is of increasing concern for farms. With record low water allocations from Water Districts this year, more stress will be placed on our wells to make up the difference for trees to survive and bear fruit. Agricultural wells are already facing problems with diminished water quality. With low reservoir levels and a lack of surface water applied to help replenish aquifers, water tables are continuing to lose quantity and quality of water. Bicarbonates and sodium are the primary contaminates that must be addressed if we have a hope of delivering quality fruit to the shed.
Bicarbonates work against crop performance by slowly sealing off the surface of the soil. Water has a harder time against salt build up to penetrate the soil surface and work to the rootzone. As soils dry, by either the use of water by evapotranspiration in trees and vines or by excess evaporation, bicarbonates work to precipitate calcium from clay soil particles leaving a sodium ion in place of desirable calcium ions. Over time, a calcium rich soil will become a sodium rich (sodic) soil. For this reason, growers must keep these bicarbonates moving through the soil profile by adding weak acids to irrigation water.
Sodium is one of the most soluble cations that are found in water. As such, you can find sodium in varying quantities in almost all water used for irrigation. Sodium causes poor conditions for growth, especially in the early stages of plant life, due to the binding clay particles in the soil. The soil then becomes sealed off, reducing water infiltration and, thereby, the amount of water available to the plants. When soils dry, sodium causes clumping of the soil making for a profile that is more difficult to cultivate. Since sodium is highly soluble, it is readily taken up by the plant. Sodium toxicity is most often observed as scorching or necrosis in the margin of leaves. Soil applied calcium helps to displace the sodium ions in the soil profile, allowing for rainfall and other clean water to flush it out of the root zone.
Good news: there is a solution to these irrigation water issues with improving overall soil health. Soils that are well flocculated and maintain healthy levels of microbiological activity better resist contaminates in marginal water. Maintaining appropriate levels of available calcium, magnesium, and potassium is key to healthy soil. These elements keep soils flocculated, allowing for better water infiltration.
The severity and multiplication of disease are enhanced when calcium and potassium levels are deficient. (Kiraly, 1976)
Most US soils are deficient in at least one of these three elements, and it is more common for soil to be deficient in both calcium and potassium. These elements should be added to the soil as often as needed to maintain appropriate levels.
Available soil carbon is often an overlooked element that is imperative to the health of the soil. Free carbon feeds the microbiology, making it important to keep the biology in soils well fed. Active soil biology influences nutrient uptake for plant. Healthy, well-nourished plants resist both biotic and abiotic stress more efficiently.
Agriculture is facing many threats including, but not just limited to increased input pricing and a decrease in water quality available to farms. A solid nutritional program should focus on soil health first to help alleviate these problems. Soil is, after all, the basis of everything we do in agriculture.
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By utilizing a low rate, organic liquid calcium like Calcium 880Plus™ or dry powder calcium with ProCal™, growers water management program with a weak acid like Absolute Acid™, Ferticell™ delivers a multi-faceted approach to managing poor quality water and preparing soils for it. When growers focus on soil health, they prepare in advance for poor water quality in sustainable agriculture, and how to work with what they are given, letting the soil work for them.