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2022 Midwest Vegetable Guide

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Soil Fertility and Nutrient Management Midwest Veg Guide 2022 15 Here are the typical CEC ranges of various soil types: Soil Texture CEC Range Sands 5-15 Silts 8-30 Clays 25-50 Organic soils 50+ Base saturation is the percentage of the total CEC occupied by basic cations such as Ca, Mg, and K. Base saturation is related to soil pH and soil fertility. On acid soils, the percent base saturation of Ca and Mg is low. The saturation of the different cations is important because plants take up some cations more easily than others. The base saturation for Ca should be 60 percent or more; Mg should range between 10 and 15 percent; K should range from 1 to 5 percent. Excess levels of one cation can reduce the uptake of another. Some soil scientists believe that there should be specific Ca:Mg ratios and Mg:K ratios (2:1). Most horticulturists believe that if base saturation levels are at the minimum levels suggested here, then it is not important to maintain specific proportions or ratios. Crop Nutrient Requirements Vegetable crops require 17 essential elements (nutrients) for development and reproduction. In addition to carbon (C), hydrogen (H), and oxygen (O), plants need macronutrients in large concentrations and micronutrients in relatively small concentrations. Each crop has a crop nutrient requirement (CNR) for particular nutrients. The CNR is defined as the total amount of the nutrient (in pounds per acre) the crop requires to produce optimum economic yield. The concept of optimum economic yield is important in vegetable production, because applying a certain amount of a nutrient might produce a lot of biomass, but may produce negligible marketable product due to small fruit size, small number of fruits, or large number of culls and small number of marketable fruits. Always consider fruit number, size, and quality in the CNR concept for vegetable production. The best way to achieve the CNR is to begin with a soil test. The results from a soil lab analysis include recommendations for the amount of lime or sulfur needed to balance the soil pH, and indicate the amount of fertilizer needed to deliver the CNR. Macronutrients Nitrogen (N), phosphorus (P), and potassium (K) are the primary macronutrients, and they are commonly applied in fertilizers for field vegetable production. Plant nutrient recommendations are often given as pounds of N, pounds of phosphate (P 2 O 5 ) and pounds of potash (K 2 O) per acre. It is up to growers to figure how much fertilizer or product they must apply to meet the suggested recommendations. This can be tricky, because growers may need more than one kind of fertilizer product to meet the recommendations. Fertilizer products are required to list the percent N, P 2 O 5 , and K 2 O equivalent they contain — and the products are listed in the order: N-P-K. For example, a fertilizer labeled 10-10-10 contains the equivalent of 10 percent N, 10 percent P 2 O 5 , and 10 percent K 2 O. So a pound of this fertilizer would contain 0.1 pound each of N, P 2 O 5 , and K 2 O. Urea labeled 46-0-0 contains 46 percent N, 0 percent P 2 O 5 , and 0 percent K 2 O. Potassium chloride (muriate of potash) labeled 0-0-60 contains 0 percent N, 0 percent P 2 O 5 , and 60 percent K 2 O. Organic fertilizers are also labeled this way — a 3-2-2 product contains 3 percent N, 2 percent P 2 O 5 , and 2 percent K 2 O. It is important to note that some of the N and P in organic fertilizers require warm, moist soil and microbial activity before it is available to plants. Let's say a nutrient recommendation calls for 100 pounds of N and 100 pounds of K 2 O per acre. A grower could meet that recommendation by using 217 pounds of urea (217 pounds of urea X 0.46 N = 100 pounds of N) and 167 pounds of potassium chloride (167 pounds of potassium chloride X 0.60 K 2 O = 100 pounds of K 2 O). A grower could also meet that recommendation by using 1,000 pounds of premixed 10-10-10 fertilizer (1,000 pounds of fertilizer X 0.10 N = 100 pounds of N; 1,000 pounds of fertilizer X 0.10 K 2 O = 100 pounds of K 2 O). But that same fertilizer would also supply 100 pounds of P 2 O 5 that is not needed. So, using such a fertilizer could be a waste of money and could pollute surface or ground water. If you choose a premixed fertilizer, select the ratio of nutrients that comes closest to the amount of recommended nutrients. It is not necessary to be exact as long as any differences are reasonable. If you can't get to the recommended nutrient application using premixed fertilizers, it is fine to first make a base application using a standard fertilizer ratio, and then apply individual elements to reach the recommended nutrient levels. For example, you can supply extra N with urea or urea ammonium nitrate (UAN) solution; you can supply extra K with muriate of potash. Custom-blended fertilizers can be made to almost any desired ratio. Nitrogen (N) Standard soil tests aren't very useful for predicting how much N fertilizer you need to apply to optimize yield and qualilty. N fertilizer recommendations account for the soil type, amount of organic matter in the soil, field history, and crop. The recommendations in this guide are based on data from

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