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2022 Midwest Vegetable Guide

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Page 16 of 291

Soil Fertility and Nutrient Management Midwest Veg Guide 2022 17 Broccoli, cauliflower, celery, beet, turnip, and rutabaga are likely to respond to B applications of 3 to 4 pounds per acre when soil levels are low. Cabbage, carrot, lettuce, parsnip, radish, spinach, and tomato show a medium response and usually benefit from 1 to 2 pounds of B per acre. Bean, peas, and cucumber are sensitive to B, so do not apply it to these crops. You can add B to the soil with Borax (which contains 10.6 percent B) or Solubor (which contains 20.5 percent B). B applications are most effective if applied with the fertilizer at preplant or at the time of transplanting. Mid- or late season foliar applications are not as effective as early granular or foliar applications. It is important not to exceed recommended B rates to avoid toxicity in subsequent B-sensitive crops. Carryover is most likely after a dry fall and winter. Other micronutrient deficiencies are rare in field-grown vegetable crops in this region. Fertilizer and the Environment Nitrogen from both natural (manure, compost, green manure) and synthetic sources can be lost from fields, which can pollute water and increase greenhouse gasses that contribute to climate change. Similarly, natural and synthetic sources of P can move out of cropped areas and pollute waterways. With proper fertilizer management, vegetable producers can minimize environmental impacts and improve fertilizer use efficiency. Growers should know their crops, account for the nutrient values of all soil amendments, and test soils and plants to support their fertilizer decisions. Split N applications — applying some N before planting and sidedressing the rest during the season — are generally more efficient than complete preplant applications. However, split applications require growers to pay attention to crop growth and sidedress at the appropriate times: before crops are stressed, and early enough to allow crops to mature. Banding P at planting (with or without some P being broadcast/incorporated) is generally more efficient than broadcasting all P. Sidedressing P is not recommended because it is not mobile in soils. Generally, K and the minor elements do not contribute significantly to groundwater pollution, but growers should manage them properly to minimize costs and maximize efficiency. Minimizing soil erosion, timing irrigation properly, and avoiding excess irrigation will also improve fertilizer use efficiency and reduce losses from the field. Animal Manures and Composts as Fertilizers Animal manures and composts can provide significant nutrients to plants. The nutrient content of manures varies among animal species and within each species. Nutrients in composts can vary even more and depend on parent material and processing. Test manures and composts to determine the potential nutrient contributions and plan application rates based on their nutrient content. Avoid using composts of unknown origin or parent material. Improperly made composts, be they of rural or urban origin, can contain heavy metals, inorganic debris, diseases, and insects that are unwelcome on your fields. It is important to consider the timing of manure and compost applications. Fresh manure has potential to "burn" a crop because it often contains high levels of ammonia, and fresh or casually "aged" manure often contains human pathogens. For these reasons, it is rarely acceptable to apply fresh or "aged" manure to food crops while they are growing. Generally, a fall application is acceptable, ideally to a cover crop, and at least nine months before harvesting the next vegetable crop. Any use of manure or composts should follow current Good Agricultural Practices (GAPs), and mandates of the Food Safety Modernization Act (FSMA). The demands of a particular market may be more stringent. For guidance about GAPS and FSMA, see Produce Food Safety section. Fertilizer Application Methods Fertilizer application timing and methods vary from farm-to- farm depending on cultural practices and equipment. This section outlines common practices of efficient fertilizer placement and utilization. These practices can be modified to suit particular situations. Usually, growers can apply at preplant and disk into the soil 50-60 percent of the recommended N and all of the P and K fertilizer. This is especially true when the rates of a complete fertilizer will require more than 400 pounds per acre. We recommend band application for many direct-seeded vegetable crops. This technique applies a concentrated line of fertilizer 2 inches to the side and 2 inches below the seed furrow. This is an efficient way to apply fertilizer, and much of the P and K fertilizer can be applied this way. However, do not make banded fertilizer applications exceeding 80 pounds per acre of N plus K — this can injure seed. For crops grown on plastic mulch (with or without a raised bed) growers may apply fertilizer just to the bed area. As with broadcast applications, growers can apply a portion of the recommended N, and all of the P and K before planting. If N will be supplied through fertigation during the season, apply

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