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Professor warns fertilizer recommendations could be costly
By NANCY L. SMITH
OCEAN CITY, Md. (Dec. 2, 2014) — “The wide range of fertilizer recommendations for the same crop, yield goal and soil test values from one state to another is almost frightening,” said Dr. Brad Joern of Purdue University at the 20th annual Mid-Atlantic Crop Management School on Nov. 19.
Joern, an agronomy professor, noted that differing fertilizer recommendations from land grant universities in adjoining states can result in more than double in fertilizer costs for farmers on the wrong side of a state line.
“We have 50 fertility czars,” complained Joern.
Few states provide recommendations that distinguish between owned and leased land, he said.
A nutrient build-up/maintenance approach is best for owned land, but a waste of money for leased land, which would be better served with a sufficiency approach.
He said the nutrient build-up/maintenance approach involves building nutrient levels to a critical level over several years and maintaining that level with regular fertilizer additions.
It is best for land a farmer owns and will farm for years and wants to increase fertility and protect against future fertilizer price increases.
The sufficiency approach, Joern explained, is not designed to build soil fertility to a critical level and is a better choice for leased land where there is no need to fertilize beyond the level needed for maximum growth in a single year.
It would apply to the one-half of U.S. farmland that is rented, he said.
Joern judged current fertilizer recommendations as “too prescriptive” and called for more regional and flexible approaches.
“We need to eliminate state border magic,” he said.
He predicted these next-generation risk-assessment tools will be more regional, quantitative and process-based.
He proposed more flexible, risk-based approaches to take advantage of emerging technologies.
He proposed using software that considers a farmer’s fertilizer budget to tell how to maximize the return on the farm.
For nitrogen fertilizer, he suggested models and tools that are process-based, using on-farm research tools so farmers could conduct research on their own farms using their own systems. He predicted this approach would reduce net application rates and losses while increasing nitrogen utilization efficiency yield and profitability.
Land-Grant universities should encourage phosphorus fertilizer incorporation with minimal disturbance, Joern said. Hydrology must be considered, he said, when making phosphorus recommendations.
Joern also proposed outright bans on the application of nitrogen and phosphorus fertilizers on frozen or snow-covered ground.
He encouraged pressure on the fertilizer industry to bring back triple super phosphate.
An overarching conservation issue, he stressed, is optimizing no-till and never-till cropping systems.
He proposed that riparian zones and harvested perennial vegetation be standard operating procedure near ditches, water bodies and be primary cost-share targets.
The bottom line, he said, is that similar soils and similar climates should be the basis for fertilizer recommendations without regard to state boundaries.