In the middle of a very hot and dry summer, such as occurred in many areas during 2013, no-tillers quickly recognize the residue covering the soil is normally cooler and wetter than with soils found in conventionally-tilled fields. They recognize that reducing stress on their no-tilled crops is a major benefit when summer weather turns hot and dry.
With all of the hoopla about hotter weather coming over the next 50 years, a recent study indicates no-till will help growers salvage some of the predicted yield losses, while being able to more efficiently deal with declining water supplies.
That’s one finding from an innovative Agricultural Research Service study that combined climate projections with 15 to 17 years of field crop data from the Central Great Plains Research Station in Akron, Colo.
Laj Ahuja and other U.S. Department of Agriculture researchers found no-till can help offset wheat, corn and millet yield losses due to hotter temperatures and higher levels of carbon dioxide that will likely occur over the next 36 years.
Global Warming Impact
Three crop rotations — wheat-fallow, wheat-corn-fallow, and wheat-corn-millet — were evaluated to see how yields might be affected. The scientists looked at rising carbon dioxide levels, increasing temperatures and a shift in precipitation from late spring and summer to fall and winter. The results indicate:
An increase in atmospheric carbon-dioxide levels from 380 parts per million by volume in 2005 to 550 parts per million in 2050.
An estimated 5-degree F increase in summer temperatures between 2005 and 2050, along with an 8-degree F increase by the year 2100.
But when researchers combined climate factors from 2005 to 2100, Ahuja says, the yield estimates for all three rotations dropped. However, the decline in corn and millet yields was more significant than with wheat.
In the no-till wheat-fallow rotation, wheat yields were higher than for conventional tillage through 2075. This indicates crop rotation and tillage practices have a greater impact on yields than any advantages offered by climate change, such as the growth-boosting and water-saving effects from carbon dioxide.
But when summer temperatures were projected to increase by 8 degrees F due to climate change by the year 2100, even the no-till yield advantage was lost.
“The negative effects of warmer temperatures would outweigh the benefits of higher atmospheric carbon dioxide on all the crops in these rotations,” Ahuja says. “High levels of carbon dioxide enhance photosynthesis in crops like wheat and help plants retain water by causing the stomatal pores on their leaves to partially close.”
Ahuja also analyzed 96 years of existing climate data at the Akron station. Atmospheric carbon dioxide levels increased from 300 ppm in 1912 to the current 380 ppm with the use of each of the three rotations.
“This study allowed us to double check the effects of high carbon dioxide over nearly a century of climate data, with actual rather than projected fluctuations in precipitation and weather,” he says. “The higher carbon dioxide levels increased yields of wheat and millet, but not corn.”
No-Till Helps — To A Point
Ahuja also looked at planting a month earlier and no-tilling to see if these two practices could help reduce future yield losses. Only the no-till option helped — by leaving a protective layer of residue that reduces evaporation and helps the soil retain water.
He says a major reason for lower yields is due to the crop maturing too early because of extreme heat, which doesn’t give the crop enough time to mature. As a result, corn hybrids, such as some of those being used by Southern growers, that require more heat units may yield better with future climate changes.
For now, no-till provides one answer to help growers harvest high yields with some crops, especially with drought conditions. But over the long run, breeders and geneticists will need to develop varieties that can tolerate higher temperatures.
Another option for no-tillers in drier areas of North America might be looking at replacing corn with grain sorghum to better handle dry and hot weather conditions.