Midwest Vegetable Guide - 2022 - 21

Soil Fertility and Nutrient Management
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
extension.umn.edu.
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,
Midwest Veg Guide 2022
21
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,
mccc.msu.edu, or refer to the SARE resource, Managing
Cover Crops Profitably, at sare.org/resources/managingcover-crops-profitably-3rd-edition.
Cover
Crop
Nonlegumes
Rye
Perennial or
common
ryegrass
Sudangrass
Field corn
Pounds/
Bushel
60
24
40
56
Winter barley 48
Wheat
60
Legumes
Sweet clover
Red clover
Soybean
Alfalfa
Hairy vetch
Mixtures
Rye/
hairy vetch
Ryegrass/
sweet clover
Sweet clover/
orchardgrass
60
60
60
60
60
Quantity of Seed
per Acre (pounds)
90-120 (alone)
90 (mixture)
15-20 (alone)
5-8 (mixture)
20-30
50-60
80-100
90-120
16-20 (alone)
10-12 (mixture)
10-15 (alone)
90-100
12-18
15-20 (mixture)
90/15-20
5-8
12-15
6-8
Desirable
Seeding Dates
Sept. 1-Nov. 10
Aug. 1-Sept. 15
May 15-July 1
May 15-July 1
2-3 weeks before
fly-safe date
Hessian fly-safe
date
March 1-April 15
July 15-Aug. 20
Feb. 1-April 1
May 15-July 1
March-April
Sept. 1-Nov. 1
Sept. 1-Oct. 1
July 15-Aug. 20
March 1-April 15
http://extension.umn.edu http://mccc.msu.edu https://www.sare.org/resources/managing-cover-crops-profitably-3rd-edition/ https://www.sare.org/resources/managing-cover-crops-profitably-3rd-edition/
Midwest Vegetable Guide - 2022

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