Agfax Buzz:
    July 11, 2014
    irrigation-pivot-small-cotton-06122014-featured

    Georgia Cotton: Irrigation Timing – Best Tool?

    AgFax.Com - Your Online Ag News Source

    By Clint Thompson, University of Georgia

    With rain being sparse in some areas of Georgia this summer, irrigation is a necessary expense all farmers have to consider. Whether it’s with the checkbook method, soil moisture sensors or software programs, cotton farmers have a plethora of options to choose from, says a University of Georgia Extension expert.

    Guy Collins, UGA Extension’s cotton agromomist, says during the three-week squaring period cotton crops need one inch of water per week depending on soil type and environmental conditions. The crop also needs this much water for the first week of bloom.

    A cotton crop’s water needs increase to one and a half inch during second week of bloom and top off at two inches for the third and fourth bloom weeks. For the fifth and sixth weeks of bloom, the crop’s water needs drop back to one and a half inches. That total drops further to one inch each week for the rest of the season until bolls begin to open in which irrigation ceases.




    For example, if a farmer’s cotton receives eight tenths of an inch of rain during the first part of the week of squaring, the crop only needs two tenths of an inch of irrigation later that week to reach the one-inch of water the crop needs for the week.

    Keeping up with the amount of water a cotton crop needs can be a confusing task and farmers also have to decide which irrigation method works best for their needs. “There’s not one method that’s superior to others. It just depends on the grower’s needs and what they can do,” Collins said.

    The checkbook method is an approach that’s suitable for growers that aren’t using sensors or any other way to calculate irrigation. It follows the growth curve of the plant. As cotton bolls develop and mature, the plant’s water requirements change. It’s important to consider how the amount of water needed by the plant changes throughout the season, regardless of the irrigation strategy used, Collins said.

    Unlike the checkbook method, sensor-based irrigation systems can more accurately account for other variables when determining the appropriate time to irrigate. Sensors measure the soil moisture and accurately determine how much moisture the cotton plants are receiving from the soil at a given point in time.

    According to Collins, a sensor can help the farmer account for differences in soil texture and rainfall and determine when to turn irrigation on and off. Without a sensor, the farmer’s just guessing, he said.

    Soil moisture sensors also help growers save money. Normally a 5-10 day dry period would be detrimental to a cotton crop. But that wasn’t the case during last year’s extremely wet summer.

    Without sensors, a farmer may have applied irrigation unnecessarily. Collins said sensors in the soil would have reported how much moisture still remained. Unlike other years, last year’s cotton crop would not have been harmed by going without water for 10 days because of frequent rains and surplus soil moisture.

    The 2014 season may be very different, as Georgia suffers through prolonged hot and dry spell in many areas.

    The downside to sensor-based irrigation, though, is the added expense and time they require. Collins said.

    An irrigation practice becoming more and more popular is subsurface drip irrigation — a way to water cotton beneath the soil. Collins said subsurface drip irrigation is ideal for smaller, odd-shaped fields not suitable for pivot irrigation.

    If a well is located nearby, subsurface drip irrigation may be an option. “All of a sudden, a field that would otherwise be a dry land field can now be irrigated, just through a different system,” Collins said.

    The benefit of this system is that it more accurately adjusts for rainfall. Because a farmer only irrigates a small portion at a time, the potential for water loss could be much less if it rains after an irrigation.

    “For example, in the pivot system, a farmer may apply an inch of water over a one or two-day period. But if a thunderstorm pops up later in the week and brings five-tenths of an inch of rain, there’s an excess of five-tenths of an inch of water. And, there’s five-tenths of an inch of irrigation that could have been saved,” Collins said.

    With the subsurface drip system, a farmer applies a couple of tenths of an inch of water per day. Since so little water is being distributed at one time, the farmer is less likely to lose valuable water if it rains later in the week.

    On the downside, drip systems require much higher maintenance than the pivot system, Collins said. This is why only a small percentage of farmers use the method, he said.

    In his UGA Extension work across the state, Collins meets growers that only irrigate when their cotton is wilting. He strongly advises against this.

    “Chances are, however, the farmer has already lost yields if the cotton is left without water for too long,” he said.


    Tags: , , , , ,

    Leave a Reply

    Name and Email Address are required fields. Your email will not be published or shared with third parties.

    Agfax Cotton News

    Cotton in Southwest: Resistant Pigweed Thrives: Aphids Won’t Quit – AgFax8-19

    Doane Cotton Close: Modest Deterioration in Crop Ratings8-19

    DTN Cotton Close: Meanders to Slight Gains8-19

    Tennessee: Dry Weather Persists in South, Stresses Crops – USDA8-19

    AgFax Cotton Review: World Consumption to Rise; Best Texas Yields in 3 Years8-19

    Farmland Prices Expected to Stabilize, Possibly Decline8-19

    Crop Insurance: Remember to Verify Acreage History at Local FSA Office8-19

    Georgia: Corn Harvest Underway, Cotton Loading Bolls – USDA8-19

    Alabama: Crop Conditions Decline Slightly with Dry Weather – USDA8-19

    South Carolina: Corn Harvest Underway, Most Crops Looking Good – USDA8-19

    Cotton Outlook: U.S. Production Increased 1M Bales8-19

    DTN Cotton Open: Bounces Inside Prior-Day Range8-19

    North Carolina Cotton: Brown Marmorated Stink Bug Reaches Piedmont8-19

    Alabama: Dry Weather Comes at Bad Time for Wiregrass Crops8-19

    Keith Good: Grain Transportation Network in U.S. Termed ‘Inadequate’8-19

    Oklahoma: Crops in Mostly Good Condition but Moisture Needed – USDA8-18

    Texas: Crop Harvests Underway or Expected to Start Soon – USDA8-18

    North Carolina: Cool, Wet Weather Keeps Crops in Good Condition – USDA8-18

    Mississippi: Rain Widespread Throughout State — USDA8-18

    Kansas: Dryland Crops Showing Drought Stress – USDA8-18

    Virginia: Light Soybean Insect Pressure, Poor Pasture Conditions – USDA8-18

    New Mexico: Scattered Showers Benefit Crops, Pastures, More Needed – USDA8-18

    California: Cotton Bolls Popping in Stressed Areas – USDA8-18

    Arizona: Cotton Boll Setting Complete with 40% Opening – USDA8-18

    Doane Cotton Close: Market Down Slightly8-18

    Missouri: Rice Headed at 79%, Cotton Setting Bolls at 87% – USDA8-18

    Virginia Cotton: Cut Out Showing Up a Little Early8-18

    Louisiana: Harvest Checklist for Yield Monitors, Yield Data8-18

    DTN Cotton Close: Settles at Four-Session Low8-18

    Florida: Dryland Crops Show Drought Stress with High Temps, Scattered Showers – USDA8-18

    Arkansas: Irrigation Termination in Some Areas, Continues in Others – USDA8-18

    Georgia: Cotton Opening in South8-18

    Flint on Crops: Nutrient Deficiencies at Root of Many Problems8-18

    DTN Cotton Open: Hovers Just Below Unchanged8-18

    Keith Good: Livestock Feed Can Carry Deadly PED Virus, Study Finds8-18

    California Cotton: More Bolls Opening And Early, Too – AgFax8-17

    California Cotton: Making Decisions With Good And Bad Retentions8-16

    Rose on Cotton: USDA Report Fed the Bears8-15

    Florida: Suppress Palmer Pigweed with a Ryegrass Cover Crop8-15

    AFB Cotton Close: Futures Slightly Lower8-15