It’s a query Avat Shekoofa says she hears very often. “Why do the crops under my irrigation pivot not perform any better (or sometimes not as good) as my dryland crops?”
“That’s a hard question to answer because the situation is different for each farm, but it goes back to knowing the soil water holding capacity of your farm as well as the water needs of the crop you’re growing” stated Shekoofa, a crop physiologist with the College of Tennessee. “It’s very important to understand the growth stages where water is most critical and irrigate accordingly.”
Shekoofa has evaluated crop cultivars for drought tolerance in addition to the efficacy of irrigation construction and timing for the previous 5 years at the West Tennessee Analysis and Training Middle in Jackson. One factor she’s noticed in cotton manufacturing is that overwatering will be very detrimental to the crop and will clarify some producer disappointment of their irrigated cotton.
“In some situations, it could be that because of our soil types, we’re exposing those crops to long periods of saturation,” Shekoofa stated. “Ideally, our soils would allow an inch of water to be applied at one time, but we often see runoff at much lower rates in Tennessee soils, and subsequently, producers are forced to run the pivot several times to get the amount of water they need on the crop.”
She additionally stresses that turning the water on at the proper time is vital to maximizing yields. Cotton crops are notably prone to water deficit stress throughout the first 30 days of boll growth instantly following flowering.
“Within a silt loam soil, we have consistently seen what we call a semi-irrigation regime work best in cotton,” Shekoofa stated. “Semi-irrigation involves not irrigating until first bloom. At that point we advise applying 0.5 inch of water per week from first bloom to peak bloom, and then 1 inch per week from peak bloom to open boll.”
“This process gave us improved lint yield over rainfed cotton as well as cotton with irrigation protocol of 1 inch of water per week beginning at early square and increasing to 1.6 inches at first bloom.”
In 2020, the absolutely irrigated remedy in Shekoofa’s irrigation timing research was changed with sensor-based irrigation. The sensor-based irrigation remedy adopted the identical sample of semi-irrigation, however water was withheld till the sensors learn -70 to -80 kilopascals, a stress potential measurement of soil water.
“Based on averages from our research, that was a good time to initiate irrigation, but that’s not a blanket recommendation for everyone,” Shekoofa cautions. “Different soil types will respond differently and different crops will have different irrigation initiation levels.”
Soil moisture sensors are one software that may assist producers appropriately schedule irrigation by offering a measurement of water obtainable to the plant, however they are often expensive to put in. Shekoofa advises to not rely solely on anybody software.
“Remember the active root zone of the crop determines the depth at which to place the soil water sensors. Type of crop, soil depth and growth stage largely determine the active roote zone. The range to consider is 6 to 36 inches. In most cases two depths will be considered for soil water sensors installation.”
“Sensor knowledge is helping producers make adjustments, but we should still take into account documented rainfall and plant growth stages to make to optimize our irrigation decisions.”
“Agriculture irrigation accounts for nearly 80% of groundwater use in the United States. We are relying on water a lot, but learning that we can sometimes do more (or at least just as much) with less,” Shekoofa stated. “We have to at all times watch out of the quantity of water we’re utilizing. It’s vital to the planet.