Producers reminded to consider the consequences of crop residue removal
by LuAnn Rolling,
District Conservationist
Removal of crop residue should be weighed against the potential impact on soil productivity. Crop residue removal affects soil nutrient availability, soil organic matter, erosion potential, soil water availability, yield and economics. While crop residue removal by grazing usually results in little nutrient or organic material removal, mechanical harvest removes nutrients and organic material critical to maintaining soil productivity.
How much corn residue can be safely removed from a field? This is not an easy question to answer. Sustainable crop residue removal rates depend on several factors such as soil erodibility, surface slope, cultural practices and climate conditions. Tillage, crop rotation and yield level are also important factors dictating how much crop residue can be harvested and still ensure sustainability of the system.
Recent studies suggest that only 20 to 30 percent of the total crop residue could be removed, based on ground cover requirements, to control soil erosion. However, other studies suggest that residue removal should be lower than 20 percent in order to maintain soil quality and nutrient cycling for long-term soil productivity.
The concentration of nutrients in crop residues varies with season, management practice, time of harvest and location. The typical nutrient contents are about 37 pounds/ton of N, 3.5 pounds/ton P2O5 and 33 pounds/ton of K2O. These nutrients will be permanently lost from the soil nutrient pool due to lack of replenishment from crop residue. Nutrient replacement cost, based on the Agricultural Research Service’s (ARS) National Soil Tilth Lab, would be about $33/ton. If you remove 3-4 tons per acre (5-6 round bales) the value of the nutrients removed would be $63 to $83 per acre. If you add the cost of harvest, based on 2017 “Crop Production Costs” from Iowa State University, at $20.84/ton the total cost would be $83 to $103 per acre.
Removing crop residue in excess of what the soil can tolerate will ultimately result in the deterioration of the soil resource and declining yield. Research by the ARS at the University of Nebraska Agricultural Research and Development Center found an average yield decrease of 6% over five years for continuous no-till corn when an average of 50% of the crop residue was removed each year.
While the nutrients removed can be replaced, the functions of soil organic matter are not so easily mitigated. Manure application after crop residue removal can be an important practice to mitigate negative effects of crop residue removal on soil fertility. Growing a cover crop would also minimize the negative impacts by protecting the soil surface, enhancing the soil biology and capturing remaining nutrients.
