Midwest Vegetable Guide - 2022 - 28

Field Production Information
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)
Beet
Broccoli
Carrot
Cauliflower
Celery
Pepper
Radish
Spinach
28
Moderate
(18-24 inches)
Cucumber
Eggplant
Pea
Greens & herbs Potato
Onion
Snap bean
Squash, summer
Sweet corn
Tomato
Deep
(> 36 inches)
Cabbage, Brussels sprouts Asparagus
Cantaloupe
Lima bean
Pumpkin
Sweet potato
Watermelon
Squash, winter
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
Midwest Veg Guide 2022
Vegetable Crops and Growth Period
Most Critical for Irrigation
Requirements
Crop1
broccoli, cabbage,
cauliflower, lettuce
cucumber, eggplant, pepper,
melon, tomato
bean, pea
onion
potato
Most Critical Periods
head development
carrot, radish, beet, turnip root enlargement
sweet corn
silking, tasseling, and ear development
flowering, fruit set, and maturation
flowering, fruit set, and development
bulb development
tuber set and enlargement
1For 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
Loamy fine sand
Sandy loam
Loam
Silt loam
Clay loam
Available Water Holding Capacity
In Inches per
Inch of Soil
0.08-0.12
0.10-0.18
0.14-0.22
0.18-0.23
0.16-0.18
In Inches per
Foot of Soil
0.96-1.44
1.20-2.16
1.68-2.64
2.16-2.76
1.92-2.16
Midwest Vegetable Guide - 2022

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