Continuous winter wheat cropping systems are used in some parts of the Pacific Northwest where high amounts of rainfall result in excessive residues that must be managed after grain harvest. Conventionally managed (CM) winter wheat crops typically require multiple tillage operations before this residue is adequately incorporated into the soil. Although CM techniques reduce residues and control weeds and diseases, repeated tillage also promotes higher levels of soil erosion.
The practice of burning fields and then conducting no-till or two-operation seeding--called burn/low-till, or BLT--provides an alternative to CM. After the postharvest residue is burned, only one or two tillage operations, including seeding, are needed in the next round of crop production. Burning the fields leaves the soil surface bare before new wheat seedlings begin to emerge, but undisturbed plant crowns that remain after burning help hold soil in place.
Agricultural engineer Don McCool and soil scientist Ann Kennedy work at the ARS Land Management and Water Conservation Research Unit in Pullman, Wash. They teamed with U.S. Forest Service scientist Pam Fletcher and Washington State University soil scientist Chris Pannkuk to conduct a three-year study that compared soil erosion rates and other factors affecting soil quality between BLT fields and CM fields.
The team found that BLT did not adversely affect soil loss or soil quality in fields used for continuous winter wheat production. Soil loss from BLT fields was as closely related to the number of tillage operations as to the amount of straw residue remaining on the soil surface. As in CM production, higher tillage rates in BLT fields generally resulted in increased soil loss.
This information can help producers evaluate the pros and cons of converting to BLT practices--which are subject to burning regulations that vary from state to state--for winter wheat production.