Ontario Grain Farmer September 2022

more times the complex rotation is repeated, the better the long-term effects. Boosting soil organic matter — such as through the use of organic amendments and additional crops — also raises water holding capacity, providing more of a cushion in dry times. “Adding small grain cereals, forage legumes and other niche crops can add some costs and can complicate management practices,” reads the article. “The more complex the rotation and the more diverse the tillage practices, the higher the potential to reduce crop stresses. Add in the potential benefits for weed, pest and disease control, and the value may soon dramatically outweigh the cost for your farming operation.” 32 REDUCING NITROGEN IN DRY CONDITIONS Soil nitrogen supply and crop nitrogen demand are both influenced by the weather. This makes the maximum economic rate for nitrogen — that is, what’s required to achieve the highest yield — hard to predict. Further University of Guelph research conducted by Caleb Niemeyer, a former University of Guelph student and current agronomist and precision agriculture specialist with Woodrill Ltd., shows measuring moisture accumulation can help growers reduce their fertilizer bill. Optimal nitrogen rates vary between 140 and 260 kilograms of nitrogen per hectare, says Niemeyer. Rainfall has been shown to predict approximately 70 per cent of that variation, the amount of nitrogen required increasing with moisture level. “It means to look at rain this time of year, maybe back off some. Put 140 down at planting, then if it’s really dry, we don’t need to go back,” Niemeyer says, adding nitrogen losses are typically quite low in the midseason, but excessive loading can cause problems later in the year. “If we want to manage nitrogen to capture that huge variability in optimal rates, we have to adapt this split approach. When we’re putting on 190 kilograms of nitrogen and only need 140, that’s a huge loss to the environment.” l continued from page 31

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