Figuring the real value of the residue on your fields is more important than ever now that stalks, stubble and cobs may be used to produce biofuel. What does that residue contribute to yield? How about water savings?
Simon van Donk is finding out. He's the water resources/irrigation specialist at University of Nebraska's West Central Research and Extension Center in North Platte.
His plots in tests for two years indicate corn may yield as much as 25 bu. per acre more with good residue in place compared with plots hand-cleaned of residue. He's working to determine why.
"We sparingly irrigated the crop, trying to simulate a deficit irrigation situation. The bare plots and residue plots got the same amount of water. On the bare plots, the corn was turning yellow and breaking off at the top of the stalk because it was dry. Corn on the bare plots was water-stressed more, which probably explains the 25 bu. per acre yield difference,” van Donk says.
In the first year of the test, water savings in the residue plots was minimal, he says, but, of course, producing an additional 25 bu. of corn requires some water, too.
"Looking at work by other researchers, my estimation is that it takes 2" to 4" of water to bump up the crop from 172 bu. per acre on bare soil to 197 bu. per acre on the residue plots. There is less evaporation in the residue plots, which could be what the yield increase can be attributed to,” van Donk says.
Corn planted into residue yielded 25 bu. per acre more than bare plots the first year, 17 bu. per acre more than the bare plots the second year.
"In the second year, the amount of water that stayed in the top 4' of soil in the residue plots was 1½" to 2" more than in the bare plots,” van Donk says.
"Most people know or believe that with more residue you can save water. The big question is about how much. In an average year, do you save 1", 5" or 7"? We're trying to get the quantification better than what we know now,” van Donk says.
After two years of looking at corn, van Donk's work will now focus on soybeans. He's curious to see if soybeans respond to residue as corn did.
"Soybeans may be different than corn because of the canopy cover.
Soybeans don't reach full cover as quickly as corn. We may get different results,” van Donk says.
Residue and Cows
Nebraska researcher Simon van Donk is also assessing residue value when cattle are part of the equation. He and a group of animal scientists are comparing plots irrigated by a center pivot where corn residue is kept in place, baled or grazed.
"We're measuring soil water and crop yields and also looking at nutritional value of the residue. What does it mean for cattle performance?” van Donk says.
"We're working with economists to get a bottom-line picture to help farmers get an idea whether it's better to graze or bale residue or do neither. How does it affect water usage? How does it impact cattle?” van Donk says.
"If you can sell the residue, that's appealing, but the residue itself has value in terms of water savings and nutrients. The nutrients from the residue go back into the soil. It is important to get the total picture,” van Donk says.
You can e-mail Charles Johnson at email@example.com.