38 Ate Today? Thank a Farmer. Better Farming | December 2024 crops: the lynch fileS INSIGHT FROM AGRONOMISTS Adapting to changing conditions for optimal yields. By Patrick Lynch I work with a group of agronomists who I once helped to train. I was the teacher and they were the students. Now they are the teachers and I am the student. I recently asked them about some of the interesting things they did this year. The first was Jonathan Zettler CCAON, who works in the Harriston area and operates Fieldwalker Agronomy. He spends a lot of time working with soil, water, and topography maps (SWAT MAPS). SWAT MAPS is a systems approach to managing field variability by using soil tests, plant stand counts, and prescriptions within each of the 10 predefined SWAT MAPS zones. A SWAT MAP encompasses multiple soil and water attributes that can affect crop variability in a field. These include texture, dissolved salts, organic matter, topography, elevation, water flow paths, and relative water potential. Jonathan says his biggest successes have been varying populations and nitrogen rates. He says he hasn’t dramatically reduced inputs but redistributes inputs where they obtain better response. He varies corn populations from 28,000 plants to 36,000-38,000 in some fields. The beauty of his system is that he scouts the fields to see if the population that was supposed to be dropped ends up having the correct population. He spends a lot of time checking this and believes that the final stand is typically about 95 per cent of what was prescribed to be dropped. Jonathan says that to be successful at variable population, you must have a good planter and it must be maintained. When he uses variable rate nitrogen, he tries to apply nitrogen to those areas of the field that will respond. He believes that over-applying nitrogen can reduce yields. There is research to support this thought. I was always intrigued by some older research on corn that showed the usual nitrogen response of the first units of nitrogen giving good Jonathan Zettler Plant ‘as early as possible’ when the soil is fit. Emily McKinlay photo
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