Despite grain yields remaining at or near record levels, low crop prices are prompting many producers to reduce P & K fertilizer application rates and skipping soil testing as a cost-saving measure. While the decision to apply a fraction of the estimated removal-based rate might be justified in high-testing soils and may increase profits in the short-term, higher nutrient rates will be necessary in the future because soil-test values will decline. The risk of yield loss in areas below the optimum soil test levels due to under-fertilization exists, and the results of this recent study show that the amount of areas that fall below state optimum levels for P & K may be more widespread than producers estimate when deciding to reduce their input costs. This points to a simple conclusion: Soil sampling and testing is even more relevant with unfavorable crop prices.
In an article written by Dr. Antonio Mallarino for Integrated Crop Management News and Iowa State University Extension and Outreach, he highlights a few important points that support this. (Read the entire article here.)
- Use soil sampling and testing to make rational decisions. Producers should not reduce P or K application in soils testing Very Low, and in the short-term may consider slightly reducing the rate in soils testing low and optimum. A low starter rate only may be justified in high-testing soils.
- Watch yield level and P & K removal to maintain Optimum values. There is a good long-term relationship between P & K removal with harvest and soil-test values. Producers looking to save money by withholding or reducing application rates should only do so in high testing areas and only until levels decrease to the optimum category.
- Use a good soil sampling method and variable-rate technology application. This technology can be used to target application to the most deficient field areas to get the highest possible return when price ratios are unfavorable.
- Do not reduce the recommended P & K rate for low-testing soils by banding. Research over several decades has shown banding P & K is seldom more efficient than broadcasting, and reducing the rate in low-testing soils increases the risk of yield loss, may reduce profits from production, and increase the fertilization rates in the future.
While producers may be in a mode to cut input costs, soil testing and maintaining good fertility should not be skipped.