Farm Progress

Despite plentiful rainfall this season, central Alabama farmers are still showing a renewed interest in irrigation.Producers are warned against the danger of over-watering crops, especially with adequate rain.More specific, science-based scheduling will result in more efficient irrigation practices.

Paul L. Hollis

July 16, 2014

7 Min Read
<p>AUBURN UNIVERSITY REGIONAL Extension Agent Rudy Yates, left, discusses irrigation planning with Wesley Porter, Extension irrigation specialist for Alabama and Georgia, during a recent grower meeting at the Black Belt Research and Extension Center in Marion Junction, Ala.&nbsp;</p>

While irrigation or the lack thereof has not been much of an issue in Alabama so far this growing season, farmers in the state are still showing a renewed interest in insuring their crops against the risk of drought.

“There’s a lot of interest in irrigation in this region,” says Rudy Yates, regional Extension agent for 13 counties in west-central Alabama. “A lot more center pivots are going in – we’ve got first-time irrigators and others who are expanding existing irrigation.”

During a recent irrigation meeting with growers at the Black Belt Research and Extension Center in Marion Junction, Ala., Yates said crops were variable in the region this year.

“We’ve seen corn from tasseling to only chest-high. Soybeans are at various stages, and we’ve seen kudzu bugs in the field, though they haven’t reached economic thresholds yet. Spring rains have pushed everyone back, and some farmers are just now finishing their wheat harvest. Producers who are going behind wheat with soybeans are still planting,” he said in late June.

Wesley Porter, Extension irrigation specialist for both Alabama and Georgia, told growers attending the Marion Junction meeting that their voices needed to be heard as Alabama begins work on a comprehensive water plan.

“There are different issues that’ll be considered, such as water availability, and while it doesn’t seem relevant now, it will be in the very near future,” says Porter. “Surface water is plentiful, but it’s not always easy to access it. In the near future, Alabama will be putting together a comprehensive water plan, and as many producers as possible need to be involved in that plan.

Whatever direction Alabama takes as far as a statewide comprehensive water policy, it’s important, says Porter, that farmers stay involved in the process from the very beginning.

“Growers need to ensure that they voice their opinions and needs in the development of water plans. The trouble is that typically these plans and associated legislation and laws are developed by politicians with the average citizen and most populous regions in mind. 

“Typically, farmers get left out or are not properly considered in these cases. The wording of a particular bill or law could inadvertently hurt a farmer because there was no one there to voice the correct situations. Also, we usually do not see too many farmers involved in politics. However we need the representation of farmers, especially when a plan of this sort is being developed. A comprehensive water plan should consider both drinking water for large metropolitan areas and sufficient flows for downstream requirements. Growers need to be present and have a voice so that they are not left out of these plans.”

In Georgia, he says, the city of Atlanta has been influential in the water planning process because that’s where the population is centered.

“Farmers in the Flint River District in south Georgia have been willing to make investments and to show that they’re good stewards of their water resources. If they don’t have a plan to show that they’re managing water, they know it’ll be taken away from them,” says Porter.

Legislation passed in Georgia this year addresses irrigation efficiencies by requiring that all agricultural withdrawal permits in the Flint River Basin using overhead irrigation achieve irrigation application efficiencies of at least 80 percent by 2020. Mobile irrigation systems and solid-set irrigation sprinklers would be required to achieve 60 percent efficiency.

Currently, Alabama basically is operating under riparian water rights, but that will change quickly, says Porte

Don't irrigate too much

A few of the growers attending the central Alabama meeting were first-time irrigators, and Porter warned them against the danger of watering too much, especially in a year of plentiful rainfall.

It’s important, he says, to closely monitor crops and soil moisture.

“Make sure you don’t overwater, because overwatering can hurt yield and production just as much as under-watering can. Crop water-use changes throughout the season, and the peak demand on any crop is during fruit fill and development. Thus, this is the most critical time to keep an ample amount of water/soil moisture available to the plant.

“Look at Extension water-use budgets and subtract any rainfall from those, and keep in mind that 60 to 100 days is your highest water use for corn. In some of these Black Belt soils, I’ve seen that the top 6 inches are drying out, but below 6 inches is saturated. When soils have a high water-holding capacity, there’s a danger of watering too much. Roots need oxygen, so you don’t need flooded or saturated conditions.

“After about two days of a flooding condition, you start hurting yield. There’s a fine line between too much and too little. If your roots have ample water, then you need to be patient. If you’re staying saturated, you’re doing more harm than good.”

Corn ideally needs about 30 inches of water each year, including rainfall and irrigation, he says. You want to push your irrigated fields because you have a higher yield capacity there, but you can be a little more conservative at times. A good rule-of-thumb may be that for every two irrigation applications on sandier soils, make one on darker, heavier soils.”

Porter urged growers to investigate the availability of cost-share funds for making existing irrigation systems more efficient.

“The NRCS has the Environmental Quality Incentives Program (EQIP) that will cost-share with low-pressure drop nozzles. High-pressure nozzles are highly inefficient, and you want to get the water down closer to the crop. You can go low-pressure, variable rate and get soil-moisture sensors with help from this program. It has changed some since the latest Farm Bill was passed, and there are new numbers, so check it out. It used to be about a 75-percent cost-share.”

More specific scheduling needed

While there are various methods for scheduling irrigation, Porter says he would like for growers to do less “drive-by” scheduling and more specific, science-based scheduling

“If you’re seeing visual cues of water stress, then you have already lost biomass production and yield. I would stay away from visual evaluations of a crop. Crops respond differently. There are documented cases where if it’s very hot, corn will twist regardless of the amount of water present. If you have soil moisture sensors, look at them. I would stick a soil sample probe in the ground if I was unsure to see for myself.

There are published checkbook irrigation methods out there that work well for crops in the Southeast region. These are free, and they require growers to only monitor the rainfall they receive and apply irrigation based on the crop water requirement minus the rainfall. There are also online scheduling tools and apps available for producers to use too, of which many are free.”

For growers who like to use technology and want to make more of an investment, there is an entire array of soil moisture sensors on the market, he adds.

“There are also many consultants who will help growers with their irrigation scheduling. As always, it is up to the individual farmer to decide which method is best for him, but it definitely needs to be better than just looking at the crop for signs of stress. We need to do all we can to maintain high yield levels and protect our investment.”

A new smartphone app developed by University of Georgia and University of Florida researchers was released this year that will help cotton farmers in those states irrigate more efficiently. The app is programmed to use data from UGA’s Georgia Automated Environmental Monitoring Network (GAEMN) and the Florida Automated Weather Network (FAWN) to assess weather conditions that factor into irrigation needs. So, currently, it obviously works best in Georgia and Florida.

“Alabama growers need good access to weather stations, as they have in Florida and Georgia. The checkbook method, even with all of the rainfall last year, recommended 13 inches of water in a field trial while the cotton app recommended 3 inches of water, taking into account temperature and other factors. In this trial, dryland cotton produced 1,450 pounds per acre. But if you over-irrigated, you lost 100 pounds per acre. Over-irrigation definitely can hurt you in wet years.”

Also, growers shouldn’t assume 100-percent efficiency when they irrigate, says Porter. “I would assume 75 to 80-percent efficiency, so if you think you’re putting on 1 inch, I would say you’re probably getting .8 inch down to the crop. If you want to put out ½ inch, bump it up to .6 or .65 inch. And if you get 1 inch of rain in 30 minutes, you know that’s not all going to the crop. At least 50 percent will run off your field. The first ½ inch will saturate, and the rest will run off. If you get 1 inch in a full day, you can assume that about 90 percent reaches the crop. Try to be as smart and diligent as possible during your water monitoring.”

About the Author(s)

Paul L. Hollis

Auburn University College of Agriculture

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