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2022 Midwest Vegetable Guide

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Soil Fertility and Nutrient Management Midwest Veg Guide 2022 21 If you do not have or maintain proper check valves and interlocks, the injected chemicals could backflow into the water source. EPA and many state regulations specify that each system must contain a reduced pressure zone (RPZ) backflow prevention valve, or one or two independent check valves with low-pressure drains and vacuum relief valves, between the irrigation water source and the point of chemical injection. Also, most regulations require a power interlock between the irrigation pump and the chemical injector unit, a low pressure shut down switch and a check valve on the chemical injection hose. For specific requirements, check with the appropriate local or state agency. It is important to accurately calibrate the irrigation system and pesticide application rate. The chemigation operator must be aware of the irrigation system's application speed (acres per hour) for the chosen water application amount and the concentration of chemical solution to determine the rate of chemical injection. More information about the special equipment, operations, and calibration in overhead irrigation systems is available from the University of Minnesota Extension Service resources, Chemigation Safety Measures, and, Applying Nitrogen with Irrigation Water, available at . Organic Matter and Cover Crops Organic matter affects plant growth and frequently is referred to as the "glue" that holds soil particles together. It also promotes the development of soil aggregates, thus improving drainage, soil tilth, and soil structure. In sandy and sandy loam soils, organic matter improves water- holding capacity. You can add organic matter to the soil by various methods using green manure crops, cover crops, crop residues, animal manures, mulches, and composts. Green manure crops include sweet clover, alfalfa, thickly sown field corn, and summer seedings of soybean. These crops generally are plowed under before they are mature. At this stage, the plants usually contain the greatest amount of N and other nutrients, plus an adequate amount of moisture for rapid decay. However, green manure crops also can be plowed under in the mature dry stage. At that stage, they do not decompose as readily and additional N may be needed to aid decomposition. Typically, growers plant cover crops after harvest to protect the soil against erosion and terminate the cover crops the following spring. Depending on the cover crop, termination is accomplished through natural winter-kill, tillage, herbicide, roller-crimping, or tarping, Additional N may be needed to hasten the decomposition of the cover crop and avoid tie-up of soil nitrogen. This is especially important with winter rye, which should be terminated before it is 18 inches tall if it will be incorporated into the soil. The overwintering capacity of any cover crop is dependent on prevailing winter temperatures and conditions. Depending on winter weather, a cover crop may overwinter in one region and winterkill in another. Field peas and crimson clover generally winter kill, but sometimes they do not and must be terminated in the spring. Different cover crops frequently require different soil conditions for optimum growth. For example, alfalfa does best on well-drained soils, while Ladino clover grows on poorly drained soils. Some crops, such as cereal rye, have fibrous root systems, whereas others, such as sweet clover, have large. Whenever it is possible to use a mixture of these crops, the combination results in more organic matter to plow under. Cover Crops for Vegetable Farms This table describes some characteristics of cover crops that may be used for vegetable crops. For more information about cover crops, visit the Midwest Cover Crops Council website, , or refer to the SARE resource, Managing Cover Crops Profitably, at cover-crops-profitably-3rd-edition. Cover Crop Pounds/ Bushel Quantity of Seed per Acre (pounds) Desirable Seeding Dates Nonlegumes Rye 60 90-120 (alone) 90 (mixture) Sept. 1-Nov. 10 Perennial or common ryegrass 24 15-20 (alone) 5-8 (mixture) Aug. 1-Sept. 15 Sudangrass 40 20-30 May 15-July 1 Field corn 56 50-60 May 15-July 1 Winter barley 48 80-100 2-3 weeks before fly-safe date Wheat 60 90-120 Hessian fly-safe date Legumes Sweet clover 60 16-20 (alone) 10-12 (mixture) March 1-April 15 July 15-Aug. 20 Red clover 60 10-15 (alone) Feb. 1-April 1 Soybean 60 90-100 May 15-July 1 Alfalfa 60 12-18 March-April Hairy vetch 60 15-20 (mixture) Sept. 1-Nov. 1 Mixtures Rye/ hairy vetch 90/15-20 Sept. 1-Oct. 1 Ryegrass/ sweet clover 5-8 12-15 July 15-Aug. 20 Sweet clover/ orchardgrass 6-8 March 1-April 15

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