As increased levels of dissolved phosphorus in farm fields are identified as a major factor in the number of algal blooms in Lake Erie, some are pointing to no-till planting as one of the primary causes of the phosphorus run-off.
But a watershed specialist working for the Natural Resources Conservation Service – citing a recently completed five-year study of the 4.9-million acre Western Lake Erie Basin watershed — refutes claims no-till is the main culprit.
No-till planting, also called zero tillage or direct planting, is planting through the stubble of the previous year’s crop. The technique is credited for increasing the amount of water and nutrients in the soil and decreasing erosion.
Some in the agricultural industry contend phosphorus applied to no-till fields stays in the top layers of the soil, which may easily run off.
Steve Davis, a NRCS watershed specialist contractor, says it’s wrong to blame no-till alone as the major cause of the increase in phosphorus reaching Lake Erie.
“There is a lot of no-till planting in the watershed,” he said. “But the percentage of long-term continuous no-till fields is still small.”
While phosphorus does run off from no-till fields, especially if it rains right after application, the same holds true if phosphorus is applied to the surface on conventionally tilled fields, according to Davis, who contends several factors working in concert are more likely to explain the increase in levels of dissolved phosphorus runoff.
• Changes such as the methods and timing of fertilizer applications
• More broadcast surface application versus row fertilizer
• Applying fertilizer in winter months or on frozen ground
• Increased soil compaction from larger equipment
• A trend toward applying two years worth of fertilizer on a corn crop
Conservation tillage, says Davis, is critical to controlling sedimentation of waterways and Lake Erie and going backwards on no-till isn’t the answer.
Instead, he is advocating for additional research to determine the causes of the changes in phosphorus levels.
According to water monitoring data, while dissolved phosphorus has increased in run-off, particulate phosphorus and sediment in run-off has declined as a result of the conservation practices applied in the lake’s watershed, Davis said.
“I agree we certainly need to drastically reduce dissolved phosphorus run-off in the watershed,” he said.
“But no-till is an important tool in a farmer’s conservation toolbox. In my crystal ball, I don’t see farmers going back to the days of fencerow-to-fencerow moldboard plowing and all the problems that caused. Fuel prices won’t allow that, costs of cleaning drainage ditches and dredging harbors won’t allow that, and certainly a public that values clean water won’t.”
The NRCS, through an incentive program, has allocated more than $4.9 million since 1996 for nutrient management systems that include practices such as cover crops, precision nutrient application, and no-till. About 462,262 acres have been involved in the program.
Results of the study can be seen at www.oh.nrcs.usda.gov/technical.