USDA Central Great Plains Research Station, Akron, Colorado, USA

"It all starts with good wheat stubble."

That’s the conclusion of Merle Vigil, director of the USDA-ARS Central Great Plains Research Station located in Akron, Colo. For 15 years, Vigil has studied cropping systems, tillage methods and crop rotations at the research station. The Akron station serves an area which includes the extreme southeastern corner of Wyoming, eastern Colorado, the western third of Kansas and the Nebraska panhandle.

undefinedOne of Vigil’s research interests is the effect of crop residue on moisture utilization and production capacity in this low precipitation area. While farmers often have anecdotal evidence of the benefits of higher profile stubble on moisture retention, Vigil has documented and scientifically measured, controlled and replicable experiments that have made him an advocate of tillage and harvesting systems which leave residue on the soil. And, he is convinced the pivotal point on which the whole system hinges is wheat stubble, as wheat typically is the heart of any crop rotation grown in the region.

Vigil oversees the station’s test plots on which a variety of crops is grown, including the basic three produced in eastern Colorado, wheat, proso millet and dryland corn, as well as soybeans, grain sorghum, sunflowers and more exotic crops such as mung beans and cowpeas. But, the base crop in nearly all the rotations is wheat because the silhouette factor of its stubble provides the most benefit for crops grown after it. Vigil believes that farmers in low-moisture areas, such as eastern Colorado and western Kansas, should be stripping their wheat for the most benefit.

According to Vigil, stripper header harvested stubble provided more moisture conserving benefits than conventionally harvested stubble. His research has found that the stripped wheat stubble reflects heat, reducing evaporation; increases water infiltration; slows down the wind, furthering reducing evaporation; traps snow and, ultimately, increases soil water storage

For a region where rainfall averages from 9 to 18 inches a year, with most areas averaging closer to 12 inches, that increased soil water storage can be critical for plant development. Some of the research is indicating that the value of one inch of stored water can equal an average of 25 additional dollars per acre, depending on the crop.

 

The research station’s stubble height studies have shown definite advantages for taller stubble in moisture catch (particularly snow) and retention. A recent three-year study completed in fall of 2006 (results are currently available from the first two years) sought to measure the impact stubble height had on stored soil water and subsequent dryland corn yield. The study involved installing tubes which measured soil water in stripped wheat stubble and conventionally harvested stubble.

 

Vigil was not surprised to find that the stripped stubble caught more snow (the lone blizzard in 2003 found the stripped stubble catching a snow depth of 11 inches compared to 2 inches in the conventionally harvested stubble) and stored 1.3 inches more water in the soil during the fall, winter and spring. The second year of the study found 1.32 inches more water was stored in the stripper-header residue, with precipitation storage efficiency 26 percent higher than in the conventional straw. The research station published the first two years of study results in each respective year’s annual report. A full analysis of the three-year study will be made available to the public in the future, but Vigil is excited about the results and what it can mean for farmers in the region. However, he is quick to caution that there is more to yield results than how much moisture is stored in the soil during the fall, winter and spring.

“This is nice, but it’s not the whole story,” Vigil said. “(Yield) also depends on what happens at flowering. If there is rainfall at flowering, then the stripper header can make a huge difference on yields.”

Vigil and his fellow researchers at the station are currently working with skip row plantings using primarily corn and grain sorghum. Stripped straw plays a critical role in capturing and maintaining moisture for the skip row system, which stores moisture in the unplanted strips (or skips) between the planted rows. They are seeing some very promising early results from their test plots.

“Plants don’t plan well for their future. If there is available moisture, they use it up,” Vigil said in explaining the concept behind the planting system. “By skipping rows we are storing moisture which won’t be used until a plant’s roots grow into the unplanted areas. They use the water as they grow into it where in a conventionally planted field, the plants use the water equally across the field and when it’s gone, it’s gone. The plants have to wait for additional rain, or irrigation, for needed moisture, which may not come when needed. With skip row, the stored water is accessed over a longer time period.”

Vigil and his fellow researchers believe so strongly in the benefits of stripping wheat over conventional harvesting in low precipitation areas that they have tested their stripper header, a Shelbourne 18-foot model, on a variety of crops. They have successfully stripped millet (traditionally swathed and then harvested), soybeans, peas, garbanzo beans, rice, triticale and barley – even though stripper header manufacturers do not recommend using a stripper header on anything other than small grains, such as wheat, triticale, barley and rice. Researchers have also tried the stripper header on grain sorghum with mixed results.

“We found that with most of these crops, the stripper header did leave a nice high profile stover,” Vigil said, adding that each additional inch of profile helps capture more moisture.

He added that while the research is still out on the benefits of stripping row crops in low-moisture systems, there is no question in his mind about the benefits of stripping wheat in the High Plains area. Even factoring in the costs of purchasing a stripper header which might only be used for wheat harvest, the economic benefits are worth it. The snow catch study of the 2004 corn harvest found a 20 bushel advantage in the stripped stubble. Assuming a $2.39/bushel corn price, the value of the stripper header stubble was $47.80 per acre. While the yield results were not as dramatic in 2005, the stripper stubble still provided an additional $16.49 per acre over the conventionally harvested stubble.

“We strip everything (at the research station),” Vigil said. “We don’t think there’s any other way for no-till cropping systems in low moisture areas. The benefits of the moisture catch and retention for our area of the country are supported by our research.”

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