Irrigation, Soil and Water
Most crops can utilize about 2.5 - 3 feet of soil profile to extract moisture. This gives a growing plant about 2.5 - 3.5 inches of available water to carry it without additional rainfall. Emerging crops use very little moisture early in the season and a good profile of moisture will carry these plants for about a month without supplemental moisture.
As the crops get larger and begin to canopy, a full profile will only last about 8 - 14 days. This typically begins to occur in early June through August. Rainfall is the best hope for supplemental moisture since it is free, but it is not 100% effective. As soils seal over from rain or irrigation they take water slower, thus making rainfall less effective. Determining how effective a rainfall is should be done with a soil probe, shovel, or some type of device to determine how deep the moisture soaked. Hard fast rains can run-off as much as 75 percent of the water where a slow steady rain can soak as much as 90 percent. The type of rainfall event will determine its effectiveness as well as the amount of moisture already in the soil.
Tillage will often dry out the soil surface as deep as 2 - 3 inches, but doesn't really effect the deeper moisture. Rainfall is the best choice for replenishing the shallow moisture early in the year, irrigation may be required during the summer months. Supplemental irrigation is not typically needed until mid to late June on most crops under normal rainfall conditions. However, it is never too early to get prepared for irrigation even if it is early because it will certainly be needed in July and August to meet crop demand.
Frequently Asked Questions
How
much yield benefit do we get from irrigation in Mississippi?
How
much water does it take for different irrigation systems?
How
many acres of the different crops are irrigated?
When
do you start to irrigate different crops?
Publications
MSUcares
Environmental Quality publications
Irrigation
Facts
Rice
Flood Guide
Greenhouse
Plans
Fruit
and Nut Review
Irrigation
Water Quality Guidelines for Mississippi
Irrigation
System Selection
Fertigation-The
Basics of Injecting Fertilizer for Field Grown Tomatoes
Border
Irrigation System
Soybean
Irrigation
Common Conversions:
450 GPM = 1 acre inch
per hour or 1 cubic foot per second (cfs)
1 gallon = 8.33 pounds
1 cubic foot = 7.48 gallons = 62.4 pounds
1 acre-inch = 27,000 gallons = 1 acre flooded one inch deep
1 acre-foot = 12 acre-inches = 43,560 cubic feet = 325,900 gallons
1 gallon = 3.785 liters = 0.003785 cubic meters
1 cubic meter = 1000 liters = 264.2 gallons
A column of water 2.31 feet high exerts a pressure at the base of one psi
1 psi = 2.31 feet of vertical elevation change for water.
1 atmosphere = 14.7 psi = 33.95 feet of water
1 inch of mercury = 1.13 feet of water
