46 Follow us on Twitter @BetterFarmingON Better Farming | November 2023 not a big issue. Our soils are well supplied with Ca. Plants contain twice as much Ca as Mg. Soils that are dominated by Ca have a better soil structure that supports greater amounts of plant-available water, better root expansion and nutrient uptake. Soils with a higher Mg content (>600 ppm) can exhibit a tight soil structure as soil particles tend to stick together and lose structure consolidating the soil, which contributes to poor internal drainage that can impair root function and limit nutrient uptake. My experience with higher Mg soils on mixed farms in the Guelph area supports my observations. When farms had livestock, forages in the rotation and manure, the soils remained well structured and productive, as the organic matter coated the clay particles to keep them from sticking together. As farms transitioned to row-crop production, livestock le these farms along with forages and manure applications. ese soils over time have become less productive as the structure and aggregate stability has decreased. Adding organic amendments and cover crops should help restore the soil structure. I’ve heard anecdotal reports of using gypsum to increase Ca levels and displace Mg to improve structure, but no signi cant increase in yields was reported. Some of these soils have Mg over 700 ppm and with Ca at 5,000 ppm, it was doubtful any additional Ca application would have helped. We have few serpentine soils where Mg is higher than Ca (2,500 ppm Mg and 2,000 ppm Ca). O en gypsum has been used to improve soil structure on this soil type. Mg is an essential nutrient for crop growth. It’s part of the chlorophyll content of plants so it’s involved in photosynthesis and sugar production but there is very little published research on Mg response on crops. Even though it is an essential nutrient, it is considered a secondary nutrient with lower use rates than the primary nutrients of N, P and K. Recommending Mg without de nitive response research carries a level of uncertainty. Every agronomist I speak with in the province sees the same issue with Mg. It is through a process of trying di erent things to improve crop yields, quality, stand longevity in forages and nutritional value that we arrive at a recommendation to use Mg in a cropping system. Working with a trusted adviser and evaluating crop progress would increase con dence in making Mg recommendations. Would it be better to have research on Mg? Yes, but I’m not very optimistic it will happen. Most likely it will be on farms working with clients, doing in- eld comparisons with and without Mg and measuring the performance di erences. e rst place to start in determining required nutrients is with a current soil test less than four years old. Using the 4R nutrient stewardship principles of source, rate, time and placement of nutrients helps to formulate an application strategy. Matching K application rates to crop removal is a place to start improving Mg uptake on livestock operations. Addressing the obvious, such as low pH with the appropriate limestone, improves the Mg supply. Supplemental applications of Mg containing fertilizers when the K:Mg ratio (in ppm) is one or greater will likely improve crop performance. BF crops: yield matter$ Time to grow? We like the sound of that. You’ve got a plan. The timing fits and the numbers work. All you need now is a financial partner who sees what youdo. Financial statements are important, but they only capture what happened in the past. That’s not the whole story. We look to the future too. Let’s go. WWW.GLENGARRYFARMFINANCE.COM Let's make it work. DALE COWAN Dale is agronomy strategy manager and senior agronomist for AGRIS Co-operative. He has been a regular contributor to Better Farming since its launch in 1999. CCA-ON, 4R NMS.
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