asked my opinion of variable rate fertilizing this morning on Crop Talk.
We basically do not use it here technology wise. I know the technology is available and some swear by it but the few that use it often swear at it, especially when it doesn't work.
The appeal is great if you have variable soils across your field. I hear $50 per acre for grid sampling and the equipment or fees to use and apply variable rates. It sounds great to use less fertilizer, especially nitrate. The SAP test results at Farm to Plate made me think how we generally over apply nitrate fertilizer to our crops and under apply the other 16 nutrients. I am more concerned with nutrient balance to produce nutrient dense crops than I am to cut fertilizer rates using variable rate technology.
Years ago I saw how the Soil Doctor saved the Reed Farm in Washington Iowa tons of money by cutting nitrogen rates while increasing crop yields across the field. The nitrogen application varied from 0-100 lbs of side dressed nitrogen across their fields while the yield monitor stayed much more constant during harvest. I wish I had a rig with Greenseeker on it right now to touch up my wheat. I have a few yellow spots.
$50 per acre will buy a lot of lime and fertilizer year to year. I have had better results focusing on soil biology then cutting rates of fertilizer to save money while trying to produce the same or better yield. I don't see better yields with less fertilizer, just less cost.
The algorithm can be set up based on nutrient removal, past history and a host of variables. Which one do you choose? If we had really good field history records, I believe we could use variable rates as well as any other method. If the grid or harvest sample is flawed, then the algorithm is faulty. I see this too often.
The Adapt-N program is very interesting to focus on managing one of the most important yield driving nutrients and that is nitrogen. Dr. Michael McNeil showed us very interesting results of how the project is helping manage nitrogen usage by careful application of the nutrient when needed in Iowa and New York.
To the original poster, if you want to go this route, set your plan up carefully. Get the help of experienced minds who have worked with it the last 10 years. I work with professionals who can help you if need help. I can't find that at the co-op or any local location. It's going to take a lot of leg work and brain work but it can be done.
I am focusing more on the trinity of soil physics, chemistry and biology so one leg of the stool is not shorter than the other two. I am also focusing on the trinity of calcium, sulfur and nitrate as a yield and profit driving leader on my farm and the farms I work with.
How can you use variable rate fertilizer programs to increase profit on your farm?