A good understanding of the amount of plant nutrients removed from the soil in the harvested portion of a crop is an important aspect of nutrient management. While a number of sources provide estimates of the amount of plant nutrients removed with a harvested crop, more precise nutrient removal values can be obtained by analyzing the concentration of nutrients in the crop. This can be done by submitting grain samples for a Crop Nutrient Removal Analysis.
There are several factors that can cause the actual concentration of nutrients in a given crop to vary from the average, including weather conditions, plant genetics, management practices, and soil properties
Nutrient removal analysis is similar to other plant tissue analyses in which the material is dried, ground and digested so that the concentration of various nutrients such as nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, and various micronutrients can be determined for the sample. For grain samples, the results are then calculated and expressed as pounds per bushel based on a standard test weight and moisture content for a given crop. As with any other analysis, proper sample collection is crucial. For grain crops, collect a sample of grain that best represents the entire area, and submit 1 to 2 cups to the lab for analysis. Results will be presented on a pound per bushel and pounds per acre basis. The crop removal data can be reported based on the actual crop yield for the sampled area if the yield is provided for the submitted sample.
The utility of this type of analysis is not limited to grain samples. This data can be very useful for determining nutrient removal for other commodities such as fruits, vegetables, hay, straw, and silage. Since harvesting these crops often removes greater amounts of vegetative material and the concentration of nutrients in vegetative parts of a plant can be quite variable, nutrient removal values can differ considerably. To analyze for nutrient removal in these crops, submit 1 to 2 pounds of material for analysis.
Although considerable differences may exist between the results of a specific analysis and the reference values, this data is not intended to assess the fertility status of a crop or diagnose nutrient deficiencies. While nutrient removal data can be a valuable tool for managing soil fertility, it is only one piece of the puzzle. A good routine soil sampling plan remains the basis for a sound soil fertility program.