11 December 2009

4 minute read

North America

The researchers investigated how strip tillage and primed acclimation might improve the long-term conditioning, as well as short-term physiological endurance and recovery, of crops.

“Strip tilling is a well-established conservation technique which has been demonstrated to increase soil moisture and decrease soil erosion, but we’ve also found significant increases in root growth, plus changes in crop water-use patterns,” said Dr. Diane Rowland, an AgriLife Research crop physiologist at the Texas AgriLife Research and Extension Center in Uvalde. “Primed acclimation is exposing a crop to moderate drought stress during early development to help increase drought tolerance during later, more mature stages of development.”

Rowland said the researchers looked at how to improve crop physiology under typical field conditions in a way that’s analogous to the human physiology of a runner, particularly investigating aspects of conditioning, endurance and recovery.

"Like a marathon runner who must be conditioned for short-term stress and long-term endurance, crop plants must be conditioned for stress, be able to endure short-term challenges and have a fast recovery in order to produce good results," she said.

Collaborators in the research were Dr. Paxton Payton of Lubbock and Dr. Wilson Faircloth of Dawson, Ga., both with the U.S. Department of Agriculture’s Agricultural Research Service.

Rowland said improving the long-term or seasonal physiological conditioning of crops has translated into higher yields.

“But to get there, we also need to understand and address aspects of a crop’s daily or weekly physiological endurance, like how many days after irrigation a plant will ‘hit the wall,’ as well as its ability to recover or return to non-stressed levels,” she said.

The field research on these crop management techniques at the Uvalde center involved preparing a circular plot with quarter sections of cotton, corn and sunflower crops to be irrigated with a 50-acre center pivot. During the winter of 2008-2009 the plot was planted with ryegrass and grazed until one month prior to planting each crop. Then the quarter sections were tilled using both conventional and strip methods and prescribed three different irrigation treatments, one of them for primed acclimation.

A similar setup and system was established in Lubbock at the USDA-ARS Cropping Systems Research Laboratory to compare results.

The research showed using primed acclimation and strip tillage increased the overall performance or conditioning of the crops, and better conditioning produced better yields, Rowland said.

“Pound-per-acre cotton lint yields increased in both Uvalde and Lubbock as a result of employing these management techniques,” she said. “And data on the crops’ daily water use in terms of sap flow, which we measured using a stem flow gauge, indicate plant endurance increased as well."

Strip tilling improves crop endurance by lowering overall daily water use and increasing plant water-use efficiency, she added.

The data also indicate that primed acclimation may be "programming" the crop plants to better withstand water stress later in the season, possibly by triggering genetic defense mechanisms in the early season when moderate drought stress is applied, she said.

Rowland said the total irrigation water applied to the crops in primed acclimation was 1.2 inches to 1.5 inches less than the 100 percent irrigation standard used for comparison in the research.

“This means it could be possible to condition crops by irrigating less in the early season,” she said. “The results showed lower water-use rates or, to put it differently, lowered use of water resources. It may be possible to increase crop endurance by preserving the available water in the system.”

Rowland said to determine irrigation scheduling for primed acclimation they first needed to determine plant-stress-level as a cue for when to provide restorative irrigation.

“To do that, we used sensors we are currently testing in the Irrigation Decision Support Program at the Uvalde center," she said. “This system uses infrared thermometer sensors to directly monitor crop stress by detecting infrared canopy temperature.”

Rowland said plant recovery was determined by differences in a leaf fluorescence bioassay, which indicated restoration of the plant’s carbohydrate reserves.

“The results also showed that using the strip till technique improved plant recovery,” she said, adding that the method yielded superior recovery results in contrast to conventional tillage in each of the three irrigation scenarios.

“Lower water-use rates combined with greater yields, as were demonstrated in our research results, help validate the improved crop water-use efficiency of conservation tillage,” Rowland said.

She said the research shows the use of strip tillage and “developmentally timed water-deficit periods” to produce primed acclimation could help conserve water in South and West Texas cotton production. She noted that the techniques also held promise for other crops and for use in other regions.

“It appears the greatest benefit to crop producers would come from combining the two techniques,” she added. “Of course, a lot will depend on the crop and a number of climatic, environmental and geographic factors.”

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