June 08, 2000

LINCOLN, Neb. — Most of Nebraska's 6 to 8 million dryland row crop acres—mostly corn, soybeans and sorghum—are becoming stressed from nine months of the driest conditions in more than a century. Without additional moisture in the next couple of weeks, corn undergoing the most severe drought in southeast, south central and southwest parts of the state will die, University of Nebraska experts say.

Irrigation, traditionally important in the state, will sustain about 8 million acres of the state's row crops, but even that poses special challenges this year. The soil is so depleted of water that some irrigation pumps will be unable to keep up with water needs for growing crops. Pumps that can keep up likely will run continuously, which means the water table probably will drop much sooner than it traditionally does at the end of the growing season. High-priced diesel will double this year's irrigation fuel expenses. And, for irrigators relying on surface water, stream water rationing is likely.

Relief doesn't appear to be in view any time soon. NU State Climatologist Al Dutcher said central and eastern Nebraska are one step away from the "exceptional drought" category. This means yield losses are catastrophic, water shortages are severe (widespread mandatory water rationing, complete loss of surface water sources and livestock herd liquidations due to lack of water), and historically low river water flow rates.

Dry weather and higher temperatures are predicted through the end of the year, he added.

Some center pivots already have been running weeks ahead of schedule to help replenish the 6 to 8 inch subsoil moisture shortfall.

Wells pumping fewer than 600 gallons per minute will be unable to replenish soil moisture and keep up with crop water use as they grow and as temperatures get hotter, said Bill Kranz, NU irrigation specialist. Corn's first critical stage will be mid-June when plant leaves and roots enter a growth spurt. By July 4, corn water uptake will be about 0.35 inch of water per day, compared to about 0.10 per day now.

Before watering and throughout the season, Kranz advises deep soil probing to detect the amount of available soil moisture. Knowing what is available helps producers better plan their irrigations, he said. By mid-June, corn roots will reach 2 to 3 feet deep, which means water must be available for nutrient uptake and plant cooling.

NU Irrigation Engineer Dean Eisenhauer recommends irrigators apply 0.75 to 1.5 inches of water per irrigation. Small applications of less than 0.75 inch encourages excess evaporation from the soil, he said. Amounts over 1.5 inch likely will cause some runoff. Eisenhauer said it would take three days to put an inch of water on 125 acres from a well pumping 800 gallons per minute. Each inch would cost more than $200 to apply in fuel costs alone. However, each inch of water effectively stored in the soil likely returns more than 5 bushel of corn yield per acre, he noted.

Furrow irrigation, on the other hand, is more complex. Furrow irrigators have much more field preparation—cultivating, ditching and laying out pipe—to do before the well is ever turned on. This year, these tasks need to be done in quick succession to keep soil from drying out more and cracking, which would only increase infiltration and make it difficult to get the water to the end of the row, Eisenhauer said.

However, as of early June corn is too small to ditch; it needs to be at least a foot high, or it will get buried. Cultivating destroys weeds and breaks up residue and dirt clods. Ditching prepares a nice waterway so the water can flow down the row smoothly. When infiltration is too high, Eisenhauer recommends packing the furrows after ditching by driving a small tractor up and down the rows. This will help get water down the row, instead of infiltrating deeper.

In addition, NU cropping system specialist Bob Klein encourages the common practice of irrigating every other row. That way more area is covered at one time, and more water can run down the row to help get it to the end. However, if fields haven't gotten any rain, Klein also recommends alternating rows that receive water so nitrogen fertilizer can move easily into the plant. Without water, the nitrogen will just sit there and be of no use to the plant.

Where well capacity is limited, Klein also suggests filling as much of the soil profile as possible, while leaving some space for rainfall.

The drought already has taken its toll on southeast Nebraska wheat. By June 1, about half the wheat in Gage and Saline counties had been cut for hay. Its yield potential was destroyed by lack of moisture since fall and more recently, high temperatures. For many other parts of the state, wheat is expected to yield half of normal.

First-cutting hay, too, has yielded just a fraction of normal, sending hay prices up. Nebraska Department of Agriculture has instituted an emergency hotline number, (800)422-6692.

This doesn't even take into account grain sorghum, the state's third largest row crop. Many producers held off their normal planting at the end of May, knowing that if they planted, without substantial additional moisture, even this drought-tolerant crop won't make a yield.

The drought's effects go beyond agriculture. Water rationing already has been implemented in five Nebraska communities, and 80 more are reported to be at risk.

The drought affecting Nebraska also encompasses parts of Iowa, Illinois, Missouri, Texas, New Mexico, Louisiana, Arkansas, Alabama, Georgia and Florida. At least half a dozen additional states are extremely dry or in early drought stages.

06/08/00-CA

Allen Dutcher - Ph.D
School of Natural Resources
State Climatologist
(402) 472-5206

Bill Kranz - Ph.D.
Biological Systems Engineering
Associate Professor
(402) 370-4012

Bob Klein
Agronomy
Professor
(308) 696-6705

Dean Eisenhauer - Ph.D.
Biological Systems Engineering
Professor
(402) 472-1637

Cheryl Alberts
IANR News and Publications
(402) 472-3030

Department: Agronomy|Biological Systems Engineering|School of Natural Resource Sciences