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submitted by Eric Novey, Soil Conservationist, NRCS
Do you ever sit and wonder if the expense that goes into cover crops is worth it? You already know what they are costing you, but do you know what cover crops are giving back to you? With the cost of production continually increasing, thoughts on how to trim expenses take over.
Currently in Iowa, fertilizer prices are between .50 and .75 cents per unit for nitrogen (depending on the form), phosphorus around .80 cents per unit and potassium roughly .50 cents per unit. Those prices are a welcome sight to farmers as they are down from fall of 2022 but are still quite high compared to recent years. According to the University of Illinois Department of Agricultural and Consumer Economics, nitrogen fertilizer costs per acre will be near record levels for 2023 on many farms.
In addition to extreme fluctuations in input costs, farmers must also grapple with everchanging weather pattern extremes. The latest assessment report by the Intergovernmental Panel on Climate Change concluded that it is an “established fact” that human-caused emissions are causing temperature increases, in turn leading to more extreme weather. From record flooding to crippling drought it seems there is no relief in sight for farmers. According to the Environmental Protection Agency, nationwide nine of the top 10 years for extreme one-day precipitation events have occurred since 1996. How do farmers protect themselves from these uncontrollable variables? Cover crops might be the answer.
Rick Clark, a Williamsport, Indiana, farmer was recently featured in No-Till Farmer magazine for performing an experiment on his cover crop where he measured the nutrient content in plant tissue at different growth stages of his cereal rye. His results showed 82 lbs./ac. of nitrogen, 32 lbs./ac. of phosphorus, and 133 lbs./ac. of potassium were captured inside of his 12-inch-tall cereal rye. The following year he performed the same experiment but allowed the rye to reach a height of 18 inches. Lab results showed 120lbs./ac. of nitrogen and 213 lbs./ac of potassium were captured.
Using Clark’s experiments as an example, at the 12-inch height, the cereal rye would protect between $41 and $61.50/ac. of nitrogen and $66.50/ac. of potassium from leaching out of the soil profile. At the 18-inch height the cover crop would protect between $60 and $90 per acre of nitrogen and $106.50 per acre of potassium. The more biomass (or growth) the cover crops were able to achieve, the more nutrients they were able to capture. Practicing delayed termination of covers capitalizes on this allowing for the maximum nutrient capture.
As cover crops decompose, they provide crops a form of slow-release fertilizer. However, it is important to note when practicing delayed termination, captured nutrients may not be readily available to newly planted cash crops. “The N accumulated in the cover crop biomass will be available to crop absorption after mineralization, which depends on soil moisture and temperature, soil type, and the carbon to nitrogen ratio (C:N ratio) of the biomass” (Gil and Fick, 2001).
According to the Midwest Cover Crop Council, “Cereal rye residues often have high C:N ratios and may immobilize soil N. Because of that starter fertilizer is typically recommended to overcome immobilization, with a rate between 30–50 pounds of actual N per acre.” In addition to capturing nutrients, cover crops also attract soil microbes which play a vital role in making nutrients available for plant uptake. According to Dave Stark, a molecular biologist, and biochemist who serves as the president of Holganix, “A plant will spend 30% of its energy to secrete food in the root zone just to attract microbes.” Additionally, if soil microbes become too far out of balance it can cause plants to show nutrient deficiencies even when nutrients are indeed present in the soil. “For example, yellow corn can be caused by too much bacteria in the microbiome. Developing diverse crop rotations and using cover crops promotes the growth and balancing of soil microbes,” Stark says.
Costs of implementing cover crops are readily apparent to producers however the benefits can be much harder to realize, especially in the short term. Continual increases in farm input expenses paired with increasing weather extremes leads to difficult decisions for producers. Please consider what cover crops can give back the next time you look to trim expenses.
