P, K Soil Tests Could Cut Costs

With fertilizer prices the highest they’ve ever been, the most important thing your row crop grower-customers can do is take a soil sample and have it analyzed, say Purdue University agronomists.

"A soil test is critical to making sure soil pH is good for crop production and managing fertilizer nutrients like potassium and phosphorus," says Jim Camberato, Purdue Extension soil fertility and plant nutrition specialist. "This soil test should analyze potassium and phosphorus levels, which will help a grower determine whether or not those nutrients need to be added."

Purdue agricultural economists expect to see prices for potash at or more than $900 per ton, anhydrous ammonia around $1,000 per ton, and monoamonnium phosphate and diamonnium phosphate at $1,100 or more.

"Because of these prices, soil testing is critical," Camberato says. "You can’t just look at your soils and know the nutrient level. The only way to know what your nutrient levels are is to take a soil sample and have it analyzed by a laboratory."

If the results show high levels of potassium and phosphorus, your grower then has the opportunity to withdraw those nutrients this year and delay the purchase and application of fertilizer to another year, Camberato says.

"By knowing a field’s nutrient levels, you can calculate how long those nutrients can be taken from the soil," he says. "It’s kind of like banking, you put nutrients in and after a while you have enough built up that you can take some out.”

If a particular field is at or below the critical level, or the level when there is still a good chance of getting a yield response to nutrient additions, your producer should not skip fertilizer application, Camberato says. But if a field is above the maintenance limit or the level where there is very little chance of getting a yield response from additional potassium and phosphorus, your grower-customer may be able to avoid paying high prices for fertilizer by using the nutrients already in the soil, he adds.

Learn more about banking potassium and phosphorus.

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