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 percent 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, but 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.
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
STARKVILLE, Miss. -- The Mississippi State University Extension Service will offer multiple opportunities March 3-5 for Delta row-crop producers to get help with an important irrigation planning tool.
STONEVILLE, Miss. -- Mississippi State University agricultural leaders looked far and wide to find a new specialist to guide farmers with irrigation concerns.
Drew Gholson started April 1 as an assistant professor and the irrigation specialist with the MSU Delta Research and Extension Center and the Mississippi River Valley Alluvial Aquifer Water Center. He replaces Jason Krutz, who was promoted to lead the Mississippi Water Resources Research Institute.
In this "What's New in Extension," Extension agents implement better safety standards, train to deliver Mental Health First Aid, and receive national recognition. Also, new irrigation and specialists join the Extension family.
On his Rolling Fork farm, Bill Rutherford is living the life he dreamed of as a child. (Photo by Kevin Hudson)
John Monroe has been familiar with the Mississippi State University Extension Service since he was a child.
“I grew up on a small farm in George County,” says Monroe. “My dad took gardening seriously, and we weren’t blessed with the best soil. So my dad worked very closely with the county agent. He’d come out to our place on a regular basis.”
Before adopting RISER techniques on his farm, irrigating was the part of the growing season Clark Carter always dreaded.
“We would string out plastic pipe, punch holes in it every couple of feet, and hook it up, only to see it blow out when we turned the water on,” says the Rolling Fork row-crop producer. “Very seldom did you get a run of pipe to fill up and water a field. It was unorganized chaos every year.