Midwest Vegetable Guide - 2022 - 16

Soil Fertility and Nutrient Management
relevant field trials. Adjust these recommendations according
to experience, soil type, cropping history, additions of
organic matter, and crop culture system.
For example, suppose your vegetable crop is following
soybeans, alfalfa, or a grass-legume hay crop. If your soils
have more than 3 percent organic matter, you may not need to
add any sidedressed N. If your soils that have less than 3
percent organic matter, then half the total N can be applied
preplant and the other half sidedressed early in the crop
growth cycle.
Now suppose your vegetable crop is following corn, rye, oats,
wheat, or a previous vegetable crop. There may be no
residual soil N available, so the crop may benefit from
additional sidedress N. It may be useful to test the soil for
nitrate-N shortly before sidedressing to assess whether the
crop will benefit from the application.
Phosphorus (P)
P recommendations for vegetables are based on the soil test
value, the type of crop, and estimates of crop removal. On
mineral soils, most vegetables will benefit from P fertilization
if the soil test is less than 35-40 ppm P using the Bray-Kurtz
P1 extraction method.
If the soil test on a mineral soil is more than 80 ppm P, then
no additional P is recommended for most vegetables. P does
not move readily in the soil and applied P easily reacts with
soil minerals so that it is unavailable to the plant. That's why
P fertilizer is applied in bands near the crop when possible,
and starter solutions that are high in P are recommended for
transplants.
Potassium (K)
K recommendations for vegetables are based on the soil test
value, the soil CEC, the type of crop, and estimates of crop
removal.
Vegetables usually benefit from K fertilization if the soil test
is:
* Less than 85 ppm K in soil with low CEC (4 meq/100 g).
* Less than 115 ppm K in soil with medium CEC (16
meq/100 g).
The maximum annual K recommendation for most vegetables
is 300 pounds of K2O per acre. K fertilization is not usually
recommended if the soil test is more than 135 ppm K on a
soil with low CEC, or more than 165 ppm K on a soil with
medium CEC.
Calcium (Ca), Magnesium (Mg), Sulfur
(S)
Calcium (Ca), Magnesium (Mg) and Sulfur (S) are
considered secondary macronutrients because plants require
them in smaller amounts than N, P, and K. Ca and Mg
usually are deficient in acid soils. Adding the appropriate
16
form of lime solves most Ca and Mg deficiency problems
(see Soil pH and Adjustment). When Ca is deficient and there
is no need to increase soil pH, you may use gypsum (calcium
sulfate) as a source of Ca. Similarly, you can add Mg without
affecting pH by using Epsom salts (magnesium sulfate, 10
percent Mg), sul-po-mag (11 percent Mg), or finely ground
magnesium oxide (e.g., MAGOX, 58 percent Mg).
If a soil test shows low Mg (less than 50 ppm in Minnesota or
less than 40 ppm in other states), apply Mg at 100 pounds per
acre broadcast or 20 pounds per acre in the row.
If a soil test shows medium Mg (51-100 ppm in Minnesota or
40-69 ppm in other states) apply Mg at 50 pounds per acre
broadcast or 10 pounds per acre in the row.
If a soil test shows high Mg, no application is necessary.
You can make foliar sprays of Epsom salts at the rate of 10 to
15 pounds in a least 30 gallons per acre to temporarily solve
Mg deficiencies during the growing season.
If a soil test indicates a need for sulfur, materials such as
gypsum (calcium sulfate), Epsom salts (magnesium sulfate),
ammonium sulfate, potassium sulfate, or potassiummagnesium
sulfate can be used. Make sure to account for the
nutrients in addition to sulfur that these materials supply.
Micronutrients
Micronutrients include boron (B), chlorine (Cl), copper (Cu),
iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni),
and zinc (Zn). Of these nutrients, those most likely to be
lacking in Midwest soils used for vegetable production are B
and Mn. Zn may also be a concern in some areas.
Manganese (Mn)
Mn deficiency is common in some areas. Mn deficiency
occurs primarily on lakebed and fine-textured, dark- colored
soils with high pH. Cool, wet conditions tend to intensify Mn
deficiency. Beans, beets, onions, spinach, and tomatoes have
high requirements, but deficiencies also are reported for
cucumbers, peppers, and turnips.
Apply manganese sulfate at 2 to 4 pounds per 100 gallons per
acre to eliminate deficiency problems observed during the
growing season. Fungicides containing Mn can also help
correct deficiencies.
Boron (B)
B leaches readily, so responsive crops often need annual
applications on sandy loam, loamy sand, sandy, and muck
soils. Deficiency symptoms include browning on cauliflower
heads, cracked stems on celery, blackheart on beet, and
internal browning on turnip.
Midwest Veg Guide 2022
Midwest Vegetable Guide - 2022

Table of Contents for the Digital Edition of Midwest Vegetable Guide - 2022
