Lime: Not all it’s cracked up to be
FIELD EVALUATIONS NEEDED
One of the things likely to change even before completing new research is how lime is applied. Hoiberg pointed to the potential with precision ag technology. Grid soil sampling has long shown the tremendous variability of pH and other soil characteristics within a field. He suggested that the tried and true method of broadcasting a fl at rate of lime across a field once every three to five years might not provide optimal results.
He advised retailers, crop consultants and growers to begin field evaluations with enhanced awareness of source and fineness, while doing strip trials, annual soil testing and variable rate applications. “The more people get involved and the more data we can collect from on-farm trials on different rates and liming materials over different soil conditions, the better,” he said.
Even if crop yields seem unaffected, things like nutrient availability may be impacted in ways not yet understood. Hoiberg pointed out that while crops seem fairly adaptable to a range of pH, the range for yield may not fully encompass the right pH for full nutrient uptake and availability to plants.
“Without testing pH on a yearly basis, it is hard to determine exactly how fast and completely the liming material is changing pH, and how long the reaction is lasting” said Hoiberg. “There may be a lot of soils that are under limed. Given that everything from biological activity to nutrient availability is governed by pH, the implications are big for overall soil health, which governs how well crops perform, and even bigger for nutrient management strategies.”
Jerry Hatfield, Ph.D., Agricultural Research Service, discussed the importance improved measurements of limestone has for agriculture.
5 R’S FOR LIME
Mahrt suggested that the 4Rs of right source, right rate, right time and right placement be applied to lime as it has been to fertilizer. Hoiberg suggested that the right pH should be the fifth R when it comes to responsible fertilizer use. Lime needs and deserves more attention in the research lab, in the field and in the regulatory area.
“Our ultimate goals from this meeting are to better understand reactivity of liming materials in a wide range of soils, and how source, purity and fineness affect this reactivity. To achieve this, much research is needed evaluating the different reactivity tests, followed by soil incubations in a lab setting, and finally attempting to correlate in the field, where it really matters,” said Hoiberg.
“We need to gain industry support for this research that will make necessary changes to the scoring system to fully inform growers about the product they’re buying. Ultimately, we want to elevate liming materials to equal footing with other farming inputs and establish a nationwide standardization system.”
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