ProCrop 1999

DEEP ROOTED CROPS FOR SALINE SOIL MANAGEMENT

Several studies have shown the value of alfalfa as an excellent choice to help lower the water table. Alfalfa should be used as a part of a rotation or as a permanent water barrier when it is necessary to control the flow of salt water from one soil to another. Along ditches, potholes and intermittent streams, a 30-foot strip of alfalfa will use enough water that salts are kept from nearing the surface. In situations where the water table is too high, alfalfa will lower it better than any other crop. In recharge areas, alfalfa can use a large amount of water before it has a chance to discharge farther down slope.

Other possible rotational crops are sunflower and safflower. However, they are not as good as alfalfa in using water because of their relatively short growing seasons.

Sweet clover would be an excellent green manure crop which would help on fallow by lowering the water table and supplying nitrogen for the next crop. Water use by sweet clover is often great enough to reduce yields the following season. Proper management will reduce this risk. If a green manure was used, a shallow tillage instead of plowing would be recommended, so that salts are not returned to the surface.

There may be years when, despite the best water table management, excessive rainfall could again raise the water table close to the surface. However, the chances of this event would be greatly reduced if the water table was lower initially. Lowering the water table should be viewed as a long term management tool, and neither a quick nor permanent renovation technique.

Late-maturing crops with deep rooting properties are important for saline soil management for the following reasons:

1.Late-maturing crops provide a mulching soil cover until frost, reducing the potential for late summer and early fall surface evaporation.

2.Deep-rooted crops leave the soil drier at deeper depths going into the winter, increasing the potential for salts to leach away from the soil surface.

3.Deep-rooted crops can use more water at the capillary water boundary, preventing further upward movement.

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