On Tuesday, October 16, the Iowa Corn Growers Association joined other agriculture organizations in a letter to the Iowa Environmental Protection Commission, or EPC, opposing a ban on the practice of applying liquid manure to fields where soybeans are to be planted as the next crop. The EPC met on October 16 and decided to reject the manure application ban proposal, thus upholding the current application standards.
“ICGA supports the commission's decision which allows farmers to make crop management decisions appropriate for their farms," says Mindy Larsen Poldberg, director of government relations. Other groups signing on to the letter included the Iowa Soybean Association, Iowa Pork Producers Association and Iowa Farm Bureau.
Commissioners let stand a five-year-old rule that allows up to 100 pounds of nitrogen per acre from manure applied to soybean fields. Iowa State University researchers presented studies that showed the practice would have little effect on nitrate pollution of groundwater or surface water. Environmental activist groups had asked the Iowa EPC to enact this proposed ban. However, the ISU researchers did say that applications of larger amounts of manure (over 100 pounds per acre) would lead to larger increases in nitrate pollution, based on their studies.
Applying up to 100 pounds of manure per acre is still allowed for bean ground
The application of manure under 100 pounds leads to a small boost in yield, even though soybeans take nitrogen from the atmosphere and add it to the soil, and can be grown without adding fertilizer if soil tests high enough in phosphorus and potassium.
Dave Petty, a Hardin County farmer and cattleman who is chairman of the EPC, notes that USDA surveys show only 7% of the U.S. soybean crop acres are fertilized with manure. He said the commission should let farmers apply the manure at the low rate in an emergency. Five years ago, the members of the panel at that time voted to consider banning the practice if studies showed that a ban was necessary and would be effective in reducing nitrate pollution of water supplies. The EPC five years ago gave the Iowa agriculture organizations and Iowa State University researchers five years to do studies and gather evidence.
ISA supports EPC's decision on manure application on soybean fields
“The Iowa Soybean Association strongly supports the Iowa EPC's decision to maintain the ability of Iowa farmers to effectively manage livestock nutrients for use on ground to be planted to soybeans," says ISA spokesman Aaron Putze. “That has been the interim policy for the state of Iowa for the last five years."
As the state assesses the many issues related to nutrient management and water quality, the issue of applying manure to soybeans is limited in terms of land and water area affected, he adds. It's not a widespread practice. But a ban would have unintended consequences for farmers. By maintaining current policy, farmers retain the flexibility to apply manure to acres that may grow soybeans at the precautionary rate of 100 pound N, as illustrated and recommended by ISU scientists.
Data is inconclusive that application of manure on the few acres that receive it (an average of 7% of soybean acres over the past 40 years) affects water quality, says Putze. When trying to determine whether there might be certain outcomes from nutrient management for a specific field, many variables must be considered. They include weather conditions, crop uptake rates, existing nutrient content of soil, drainage system configuration (or lack of drainage), topography, conservation practices, timing of application and placement and method of application.
“To achieve water quality improvements, we must approach the issue from a watershed perspective, understanding how management systems function and address the fact that problems and solutions will be uniquely suited for the landscape we are dealing with," he adds. “Therefore, we applaud the EPC's big picture view of this issue and look forward to the unveiling of the state's new nutrient strategy that is being designed to create a larger plan for water quality improvements."