Looking Back on Crop Removal

2021 has been another unique growing season to date. Some areas receiving more rain than needed, while other less than needed. This had led to either a highly variable crop or an outstanding crop, either way you can benefit from incorporating yield map crop removal into your fertility recommendations. 

Soil fertility recommendations have two key parts that are added together to arrive at a final nutrient application rate. Part one is crop removal. How much fertilizer do I need to apply to account for or replace the nutrients removed by harvesting a crop? The second part is how much fertilizer above crop removal do I need to apply to increase soil test levels from where they are to a target level over a given period of time. Most recommendation sets are built to move from the current soil test level to a target in 4 years, that time frame could also be extended to reduce application rates. Likewise, how much less than crop removal do I apply to reduce soil test levels to target levels over a given period of time.

Traditional soil fertility recommendations take the approach of predicting or forecasting crop yields for the coming year or two. That may be as accurate as forecasting the weather. When it comes to determining the amount of fertilizer needed to replace the nutrients removed by harvesting a crop, yield records are often more accurate than yield projections. 

Rather than forecasting yield using a 10-year average or a yield goal for future yield, and applying fertilizer in advance, shift your mindset to replace the nutrients that past crops have removed. For example, you may have forecasted a 200 bu/ac corn crop for 2021 sometime before planting the 2021 crop, spread fertilizer, and now due a good growing season the yields may look more like 220-225 bu/ac.  So effectively this leads to a 10-12% under application of fertilizer in 2021 by incorrect forecasting. The use of yield monitor data, storage structure estimates, and scale tickets of past yield values are significantly more accurate than forecasting future yields. 

When forecasting yields these overages are often not accounted for in the subsequent years. In years when yield is higher than expected we can actually short for the following crops. While routine soil sampling can catch these variances, there maybe an economic or agronomic impact until the next sampling cycle, or longer.

The main questions. So, what’s in it for the producer? And what’s in for the fertilizer retailer?  The producer’s key to future stability will be through better management. This process allows a producer to follow a low yielding year with an input reduction and hopefully be able to effectively maintain strong soil fertility after an exceptional yield year. The ag retailer that takes the effort to work through this transition building a stronger partnership with the producer in these tighter times will differentiate themselves in the marketplace. Better management is often the key to better profitability for both parties. Contact your ALGL agronomy representative with any questions you may have on this topic.