40 The Business of Ontario Agriculture Better Farming | February 2024 crops: yield matter$ growers who do not soil test. One thing that has changed in the past few years is a focus on variable rate fertilizer. There’s still a lot of discussion as to whether you should use grid sampling or a SWAT type of analysis that considers topography, yield potential and nutrient levels in the soil. A SWAT approach accounts for topsoil depth. If you have two soils in a field both testing 20 ppm for phosphorous, but one area has 10 inches of topsoil and the other only five inches, the 10 inches of topsoil can supply more phosphorous. We are also making strides with nitrogen on wheat, but not so much on corn. From all the research I’ve looked at it, it appears that the right rate of nitrogen is strongly correlated to the amount of seasonal rainfall. To get a better handle on nitrogen rate on corn, we need better rainfall predictions. I think we’ll get better rainfall predictions when you look at the strides made in weather predictions in the last three to five years. We do know that using some sort of nitrogen stabilizer increases the odds of keeping more nitrogen. But of all the products available, none stand out as “the silver bullet” to better nitrogen use. In the meantime, we have to keep trying. One of the things holding us back is a shortage of competent agronomists who can make good fertility recommendations over time. Unfortunately, we have a high turnover of fertility advisors. You probably need to be working with an advisor for more than five years before you can start making major improvement. We have made strides in some fertility areas. Applying sulphur to forages has taken off, as has applying sulphur to corn. Do we have good research from Ontario to back up rates of sulphur on corn? No. What we do have is experienced agronomists working with growers who want answers and successes. We’ve made good strides with manganese on winter wheat. Growers now realize that fields low in manganese when growing winter wheat must be treated in the fall as well as in the spring. One application is not enough. On their manganese deficient soils, Denmark applies manganese up to six times. Another area we are making strides in is with magnesium on corn, Applying magnesium to the soil is common in parts of Ontario that have low soil magnesium levels. In other areas of the province, more growers are using magnesium on corn. Boron is another nutrient that is increasing yield. We have known for years that boron is needed in alfalfa fields for highest yields, and now some growers are increasing corn yields by adding boron. Do we have Ontario research to document all these fertility recommendations? Not in the least, and we won’t get that research anytime soon. That means growers will have to work with retailers and agronomists to figure out what works on their fields. One of the biggest fertility changes is in the Tri-State change in fertilizer recommendations. First published in 1995, the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa (Extension Bulletin E-2567) has been a significant document for providing nutrient management information on field crops to farmers in Indiana, Michigan and Ohio. This team of agricultural professionals has decided to use the Mehlich 3 extraction as the official phosphorous extraction for field crops. Their recommendations also adjust phosphorous and potassium rates based on yields and cation exchange capacity of soil. It’s time that the soil fertility groups in Ontario start to collaborate with our American counterparts. We are doing this with diseases under the provincial guidance of OMAFRA’s field crop pathologist, Albert Tenuta, and with insects under the leadership of OMAFRA’s field crop entomologist, Tracey Baute. So, why do we need more secondary nutrients like sulphur and magnesium, and minor nutrients like zinc and manganese? The answers are simple. We’re getting higher yields and taking more out of the soil. We’re not using manure and forages on most corn, soybean and wheat acres. Yes, forages help make soil nutrients more available because of better soil structure, and some of the genetics may have more specific nutrient requirements than older genetics. Over the last two columns, I hope I’ve given you some things to think about and reasons to look at your own crop program to see how you’ve changed in recent years. BF PATRICK LYNCH Patrick writes a weekly crop production newsletter and is a popular speaker at farm meetings. Opinionated, controversial; formerly with OMAFRA and Cargill. CCA-ON. Magnesium deficiency between tile runs. Patrick Lynch photo
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