15 Follow us on Twitter: @PrairieFarming Better Farming | April 2024 Drought & soil nutrients rains, followed by good growing conditions, could result in volunteer crops and weeds germinating and growing. “If these plants are not controlled, but are allowed to grow quite large, there will be a considerable amount of nutrient taken up into the plants, and there will be reduced nutrients available to the following crop,” he says. Hammermeister notes that following the 2021 drought, swathed or harvested fields of canola started to regrow, even to the point of flowering and podding, and some farmers experienced similar phenomena in 2023. He found a strong correlation between nitrogen supply potential and stubble type. “Cereal stubbles tended to have higher N supply power because they completed their life cycle and, with the use of pre-harvest glyphosate, less weed growth occurred after harvest. The canola fields started to regrow and N supply rates were depressed,” Hammermeister says. He says that, in theory, farmers should be able to use less nitrogen fertilizer in 2024 due to last season’s growing season and fall weather conditions, but notes there can be a high degree of variability between fields. “As an example, for one of my customers having sampled 35 fields, there was a range of N supply potential from 35 lb to 200 lb/ac. It will pay big dividends to tailor fertilizer application rates field by field.” Nutrient variability can be affected by soil texture and soil moisture-holding capacity. Crops succumb to stress earlier on lighter textured or sandy soils, which hold less moisture, than on loam and clay soils. “Depending on the degree of crop growth, there will be an influence on residual nutrients,” Hammermeister says. “The impact of the variability on fertility planning is determined by how much of the field has which type of soil texture.” Dry winter A dry winter in a thirsty Prairie region complicates matters. “Below-normal winter precipitation may be more of a problem given that it is the main source of water for soil recharge in the spring and supports seed germination and nutrient availability until the summer rain comes,” says Derek MacKenzie, an associate professor at the University of Alberta’s Soil-Plant Relations Lab. Geisel adds that early and timely rains can offset that dryness, providing “tremendous results when it comes to our crops.” Farmers and agronomists should discuss their expectations and develop a solid plan for their crops, he says. “Contingency plans in case of those timely precipitation events could include tissue testing and top dressing to provide extra crop nutrition if yield potential increases from that of the spring plan,” Geisel says. “Using proven products that provide the nutrients the crops need and reduce losses is key to making the most of these applications.” Schoenau sees significant value in checking the depth of soil moisture in the spring within the rooting zone. “The presence or absence of stored soil moisture, especially in the subsoil, is good to know as it is an important contributor to the total available water, yield potential, and nutrient demand of crops here on the Prairies,” says Schoenau. Mario Tenuta, a University of Manitoba professor of applied soil ecology, says that without replenished soil moisture from snowpack and spring rains, farmers ought to adjust their yield expectations and N requirements. “If a field is going into 2024 planting with lower moisture than usual, consider also adjusting yield goals and N addition.” He adds that if normal precipitation moistens soils this year, mineralization during the growing season will inFall soil testing gives an indication of the nutrition in the soil after harvest, and can be used by agronomists to develop with fertilizer recommendations for the next year. Edgar Hammermeister photo
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