Nutrient management is dynamic and challenging, so why write a nutrient management plan if it might change? What is the value of writing down what you might already be doing? All too often when we write a plan, we get to focused on the final product when the value is found in the journey.
For example, fertilizer rate recommendations are built around crop removal, which is yield multiplied by a crop removal value for the given crop. If the soil test values are below the target level, we apply crop removal plus some additional fertilizer to build the soil fertility. Likewise, if the soil test level is above a high target level, we apply less than crop removal to lower soil test levels. If this seems too simple to even write down, let alone put into a nutrient management plan, you need to take a closer look and think through the steps.
Yield goal is a simple concept, but specifically how do you determine a yield goal value to be used in the fertilizer rate calculations? Is that the running average of the past 3 years for the given crop? The last five years with the minimum and maximum yield removed? Is it the field’s APH? Is it the average for the field, the farm, the overall operation? Do you add 5 or 10% to the yield to reflect increased crop potential? Does the crop removal reflect what was removed last year, or what will be removed in the coming year? Is the crop yield averaged across the field or based on calibrated yield maps for last year or the last few years for the given crop? This is only one of many decisions that are being made when determining how much fertilizer to apply.
Writing a plan on how soil fertility is to be managed forces you to think through these fundamental details. While this may only seem to be practical for those producers writing their own plans, this is true for all nutrient management plans. If you are an independent consultant, have you documented how you manage soil fertility for your clients? If you are an ag retailer or cooperative, have you documented how you develop soil fertility recommendations for your customers?
Also keep in mind that this written plan is a living document, it can and will change. The second key value in a written plan is the evolution of the plan. As you implement the plan, situations and challenges will arise that will force you to question the plan. When this happens, document in the plan what occurred, and what the revised direction on the subject is. With this information you can revisit the topic and evaluate if the new direction accurately addressed the challenge or created others.
The ALGL agronomy staff is ready to discuss the various aspects of soil fertility to support you in your development of a nutrient management plan.