Question of the Week
Answer: With severe drought an all-too-common occurrence, some farmers turn to irrigation for a solution. Irrigation may not be feasible or even desirable. Fortunately, there are management options that can increase the soil's ability to store water for plant use. Soil can be managed in ways that reduce the need for supplemental watering and increase the sustainability of the farm.
There are several ways to enhance soil to increase water infiltration and storage of water in the soil. The amount of organic matter in the soil, soil aggregation characteristics, and the amount of ground cover all contribute to water content in soil.
Adding organic matter to soil will increase water retention and reduce irrigation needs. Organic matter in soil can increase water storage by 16,000 gallons per acre-foot for each 1% organic matter. Organic matter also increases the soil's ability to take in water during rainfall events, assuring that more water will be stored. Ground cover also increases the water infiltration rate while lowering soil water evaporation.
Soil aggregation refers to how the sand, silt, and clay come together to form larger granules. Good aggregation is apparent in a crumbly soil with water-stable granules that do not disintegrate easily. Well-aggregated soil has greater water entry at the surface, better aeration, and more water-holding capacity than poorly aggregated soil.
Some practices that destroy or degrade soil aggregates are:
• Excessive tillage
• Tilling when the soil is too wet or too dry
• Using anhydrous ammonia, which speeds the decomposition of organic matter
• Excessive nitrogen fertilization
• Excessive sodium buildup from salty irrigation water or sodium-containing fertilizers
Adding ground cover reduces soil erosion and helps increase water infiltration rates. Surface cover also reduces water evaporation from soil.
For more information, see ATTRA publication Drought Resistant Soil, at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=118. This publication details some of the strategies for drought-proofing soil and the concepts that support them.
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