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Field Production Information 28 Midwest Veg Guide 2022 With plastic mulch, yields of pepper, eggplant, and summer squash are higher most years, and harvest can be up to seven days earlier than unmulched plantings. Clear plastic mulch is common in early sweet corn production. Growers can plant sweet corn in hills, single rows, or double rows, and apply herbicides before laying the plastic. Clear plastic mulch warms the soil and contributes to early harvest and quality produce. Herbicides that were applied before the mulch was laid may break down before the crop matures. Unless otherwise advised, never apply herbicides over the top of plastic mulch. An alternative to the clear mulch/herbicide system is the Infra-red transmitting (IRT) or wavelength selective mulch system. IRT mulches provide similar soil warming to clear film while controlling most weeds like black plastic. Apply all fertilizer before laying the plastic, but reduce the total amount applied by 10-15 percent, or apply some of the required fertilizer and plan to provide the rest through fertigation. Mulch layers are available in various widths. They also can be adapted for raised beds and for the laying of trickle irrigation tubes all in one operation. Trickle irrigation combined with plastic mulch offers several advantages: it uses water economically, requires less energy for pumping, wets leaf surface less, allows for easy fertilizer application, provides a uniform moisture supply, and allows the application of certain insecticides and fungicides. Irrigation and Water Management Vegetables require an adequate supply of moisture throughout their entire growth. While the frequency and amount of water varies according to individual vegetable crop, its age, current soil moisture, soil type, and weather conditions, generally 1 to 1.5 acre inches of water are required each week. One acre-inch is 27,154 gallons of water. Effective Rooting Depth of Selected Vegetables Shallow (6-12 inches) Moderate (18-24 inches) Deep (> 36 inches) Beet Cabbage, Brussels sprouts Asparagus Broccoli Cantaloupe Lima bean Carrot Cucumber Pumpkin Cauliflower Eggplant Sweet potato Celery Pea Watermelon Greens & herbs Potato Squash, winter Onion Snap bean Pepper Squash, summer Radish Sweet corn Spinach Tomato Vegetable Crops and Growth Period Most Critical for Irrigation Requirements Crop 1 Most Critical Periods broccoli, cabbage, cauliflower, lettuce head development carrot, radish, beet, turnip root enlargement sweet corn silking, tasseling, and ear development cucumber, eggplant, pepper, melon, tomato flowering, fruit set, and maturation bean, pea flowering, fruit set, and development onion bulb development potato tuber set and enlargement 1 For transplants, transplanting and stand establishment represent a most critical period for adequate water. The total available water holding capacity (AWHC) for a given location depends on soil texture, organic matter, and rooting depth. AWHC estimates are best obtained from the county soil survey or the local Soil and Water Conservation District office. The table 'Available Water Holding Capacities for Several Soil Types' shows AWHC estimates for some typical soil textures in the upper Midwest. Irrigation should be initiated for most crops before 50 percent of the available water is removed by the plants in the active root zone. In most vegetable crops, the majority of the roots are usually within the top 6 to 18 inches of soil. When using a trickle irrigation system on shallow-rooted, water sensitive crops (lettuce, peppers, etc.), the allowable depletion is generally 20 to 25 percent of AWHC and the system is run more frequently. With deeper rooted, more drought-tolerant crops (pumpkin, watermelon), a higher depletion allowance can be used without loss of yield or quality. Available Water Holding Capacities for Several Soil Types Soil Texture Available Water Holding Capacity In Inches per Inch of Soil In Inches per Foot of Soil Loamy fine sand 0.08-0.12 0.96-1.44 Sandy loam 0.10-0.18 1.20-2.16 Loam 0.14-0.22 1.68-2.64 Silt loam 0.18-0.23 2.16-2.76 Clay loam 0.16-0.18 1.92-2.16 Soil Water Monitoring Two common ways of estimating soil water deficit to assist irrigation scheduling are: 1. Measuring soil water tension with soil moisture sensors. 2. Observing the feel and appearance of soil samples collected using a soil probe or shovel. Soil water tension can be monitored at a given point in the active root zone by electrical resistance moisture blocks or