Cover Crops
Consider cover crops for land that is being fallowed due to drought.
When fall and winter precipitation have not replenished soil profile moisture for another growing season and below average moisture looms, growers are limited in what can protect fields from erosive winds. Additionally, many growers have leased or sold their water for 2003, but may have bare soil or minimal residue cover, and some vegetative cover is necessary. The question for many growers is what kind of crop will provide adequate cover at reasonable input costs.
A few items to consider are: soil condition, moisture availability, forage requirements, weed control/suppression, and future crop after cover crop. Soil conditions to consider include whether the field(s) in question have been tilled and are ready for a commodity crop, whether there is soil moisture to the three-foot depth, if any signs of soil compaction are present, and if the field(s) are highly erodible (HEL). Moisture remaining in the soil in late winter or early spring will assist the grower making the decision on quantity of seed to plant and how much of the remaining soil moisture will the cover crop need to adequately protect the soil. If the field has soil compaction at a shallow depth (<7 inches) the cover crop may be very sparse and not provide the needed protection. Fields with soils of HEL designation should have higher priority for cover crops and to remain in compliance with USDA. A wise move for all growers will be to probe the soils to the three-foot depth to determine the soil moisture status prior to putting in a cover crop this spring.
There are several types of cover crops that could be considered when planning for very limited or no irrigation water. First, small grains such as oats, wheat, triticale, and some millets at ¼ to ½ normal seeding rates will offer protection from erosion, especially wind, with little input costs. However, growers should not expect harvestable grain in this situation because it is our suggestion that at head eruption to just prior to flowering stage that the crop be swathed or mowed. The mowing/swathing device should be set to cut at the joint height or higher to eliminate seed production that could become weed problems from subsequent crops. A second group of crops includes legumes such as certain vetch species, medic, and red clover. These are valid choices when drilled at spacing narrower than 12 inches with a ¼ seeding rate of oats. Another possibility could be to drill long season soybeans (non-RoundUp Ready) in narrow spacing at 1/3 normal seeding rates. When they start to show flowers, use a broadleaf herbicide to stunt or kill and they will provide protection to the soil. For fields where pests such as nematodes are a problem, oil seed radishes are a great possibility for cover crop when drilled at close spacing. Turnips or even kale may offer other alternatives to the vegetable growers as cover crops at reduced seeding rates.
If the skies yield badly needed moisture, the above mentioned cover crops will have to be managed using contact herbicides or tillage to prevent them from going to seed, robbing soil moisture and becoming a weed pest for future crops.
