Recommendations (Agronomic Crops)

The RECOMMENDATIONS section gives you the bottom line: how much fertilizer or lime should you apply for optimum production of your crop. For some people, this may be the only part of the Soil Test Report that they are concerned about.

The first line of the RECOMMENDATIONS section gives the cropping history. In the Example Report it tells you Crop Before Last: Corn, Grain and Last Crop: Soybeans. Cropping history is important in determining nitrogen recommendations when a legume is included in the rotation. In this case for corn following soybeans, the nitrogen recommendation will be 30-35 lb/A (pounds per acre) less than it would be for corn following corn or most other non-legume crops. See Fertilizer Recommendations for Agronomic Crops in Minnesota for more information on nitrogen credits for previous crops

The first box on the left side of the RECOMMENDATIONS section gives the “Crop and Yield Goal”, in this case Corn, Grain and 120 bu./acre. Yield goal is no longer used in determining nitrogen recommendations for corn, but it is still used for phosphorus and potassium recommendations and is a factor in determining nitrogen recommendations for other crops. This box also gives a list of pertinent Comments. In this case, numbers 3, 5, 11, 18, and 24 are specified. We will discuss these Comments in the next section after we go through the lime and fertilizer recommendations.

The next column to the right of “Crop and Yield Goal” is labeled “Method” and gives two application options for the recommendations that follow: “Broadcast” and “Row/Drill”. Broadcast refers to spreading fertilizer or lime on the surface of the soil before planting and incorporating it with subsequent tillage. Row/Drill refers to methods of placing fertilizer close to the seed at planting. The term Row means that fertilizer is placed in a “starter” band that is traditionally two inches to the side and two inches below the seed. The term Drill means that fertilizer is applied along with small grain seed as it is planted with a grain drill. For more information on applying fertilizer close to the seed, see the University of Minnesota Extension publication Use of Banded Fertilizer for Corn Production.

The next column is labeled “Lime #ENP/A” and the recommended rate is 2000 pounds of ENP per acre using a broadcast application. ENP stands for Effective Neutralizing Power. Giving the lime recommendation in ENP units provides a uniform way of expressing the lime requirement, because there are a variety of liming materials on the market that differ in their purity, their particle size distribution, and their neutralizing capacity in the soil. The analysis on the label of a liming material will tell you the pounds of ENP per ton of the product. Crops differ in their optimum pH and liming rates differ accordingly. For corn, the lime requirement is designed to raise soil pH to 6.0. For more information on liming and liming materials, see the University of Minnesota Extension publications Lime Needs in Minnesota and Liming Materials for Minnesota Soils.

After lime is the “N lb/A” column label and for corn the recommendation box below it is left blank. This is because the recently updated nitrogen recommendations for corn require some inputs by the corn producer to tailor them to the unique situation of their field and farming operation. Nitrogen recommendations for corn are now based on the productivity potential of the soil, the ratio of the price of N fertilizer to the value of the crop, the producer’s risk tolerance, the previous crop, the nitrate-N soil test if it is recommended for your location or conditions, and manure applications. As mentioned above, if you are growing corn an information sheet New Nitrogen Guidelines for Corn Production in Minnesota (Microsoft Office document icon new_nitrogen_guidelines.doc) was included with your Soil Test Report. Work through that sheet to determine the N fertilizer rate that best fits your field and situation. For additional information on the new N guidelines, see the University of Minnesota Extension publicationFertilizing Corn in Minnesota. For information on nitrogen fertilization of crops besides corn, see the sections on various other crops in Fertilizer Recommendations for Agronomic Crops in Minnesota.

The next two columns in the RECOMMENDATIONS section are labeled “P2O5 lb/A” and “K2O lb/A”. Phosphate (P2O5) and potash (K2O) are the terms and chemical formulas used to express the amounts of phosphorus and potassium in a fertilizer recommendation. The fertilizer recommendation for phosphate is 50 lb/acre broadcast or 25 lb/acre row/drill. The fertilizer recommendation for potash is 50 lb/acre broadcast or 30 lb/acre row/drill. Row (or band) application of phosphate and potash close to the seed permits the use of lower rates of fertilizer for some crops (corn, wheat, and barley) that result in equivalent yields compared to higher rates of broadcast fertilizer. Band application of phosphate and potash is especially effective when soil conditions are cold and wet at planting. For more information on phosphate and potash fertilization of corn, see the previously cited University of Minnesota Extension publications Fertilizing Corn in Minnesota and Use of Banded Fertilizer for Corn Production. For information on phosphate and potash fertilization of crops besides corn, see the sections on various other crops in the previously cited bulletin Fertilizer Recommendations for Agronomic Crops in Minnesota.