Conservation Tillage Systems in the Southeast

Irrigation and Water Management

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No-till and reduced-tillage systems, with the inclusion of cover crops, increase infiltration. Additional causes of increased infiltration include increased porosity due to channels formed by rotting roots, earthworms, insects or tillage such as in-row subsoiling. In-row subsoiling breaks the hardpan while disturbing only a narrow strip of surface soil. Increased infiltration also increases subsurface water movement.

While cover crops and reduced tillage help with soil quality and infiltration, they do not affect the type of irrigation equipment used. In the Southeast, center pivot irrigation systems are typically used for large row-crop fields. These systems are compatible with conservation tillage systems. When cover crops are part of the rotation, soil organic matter may increase, increasing infiltration and the soil’s water-holding capacity. This could increase the time between irrigation events, which would reduce the number of irrigation events in a season as well as the total amount of water applied. An exception to this occurs when soil porosity is reduced through compaction. This reduction is field specific and is affected by the amount of organic matter in the soil profile, soil type, land slope and compaction levels. For two Group B soils in Georgia, runoff reduction due to the introduction of conservation tillage ranged from 29 to 46 percent [13]. This reduction is equivalent to 2.6–4.3 days of crop water use for these soils. The use of a conservation tillage system that includes cover crops and crop rotation can increase the time between irrigation events but does not require a change in irrigation equipment. The increased time between irrigation events is a direct result of the increased infiltration and deeper infiltration of rainwater and irrigation water.

Even though there is no need to change irrigation equipment when transitioning to a conservation tillage system, water management needs to be considered. Managing water on the farm not only saves water resources but can also save nutrients such as nitrate. If the proper amount of water is applied for plant use, the water and associated nutrients stay in the root zone and are available for plant use. If the water added exceeds field capacity, the extra water can move below the root zone or flow downslope away from the field, carrying valuable nutrients away from the plants. If cover crops are incorporated into a conservation tillage system, some of these nutrients may be recovered and recycled by the cover crop. Another direct effect of increasing infiltration and water-holding capacity is that more water is available for other uses on the farm.

Download the tables from Chapter 14.