While there’s plenty of water in Texas this year, the recent drought in the state has many farmers looking for options more tolerant to drought. A U.S. Department of Agriculture (USDA) scientist is giving sorghum farmers some much needed guidance in how to save water by using less-than-optimal amounts of it.
Susan O’Shaughnessy, an agricultural engineer with the USDA’s Agricultural Research Service (ARS) in Bushland, TX, evaluated yields and water-use efficiency of early- and late-maturing sorghum varieties produced under four levels of deficit irrigation. She and her colleagues planted late-maturing and early-maturing varieties at optimal times and harvested both types at about the same time in the fall. They grew the crops for three seasons, tracked weather data and rainfall levels, and measured evapotranspiration rates—an indicator of the plant’s overall water needs. Above-average rainfall occurred in 2009 and 2010, and much lower-than-average rainfall occurred in 2011.
They found that on average, over the three growing seasons, crop water-use efficiency (the water used by the crop in relation to the crop yield) was typically greatest at the 55-percent replenishment level, but even a 30-percent replenishment at least doubled the yields when compared with no irrigation. At 80-percent replenishment, the late-maturing variety consistently produced higher yields than the early-maturing one, but the early-maturing variety produced sufficient yields to make it a viable alternative. Growers also risk severe or total losses if they practice even moderate deficit irrigation during droughts. In fact, total crop failures are likely without at least some irrigation in drought years like 2011.
More on this is available in the July 2015 issue of AgResearch magazine.