Soil School: How big crop yields impact soil nutrients

As combines roll across Ontario, growers are harvesting impressive crops that in many cases are producing record yields.

But with all that excitement, it’s important to remember the impact those huge yields will have on nutrient removal and what they take out of your soil bank account. On this episode of RealAgriculture’s Soil School, Brussels Agromart agronomist Steph Berlett shares what those splendid yields will be taking with them, including higher amounts of phosphorus and potassium.

She notes that increasing soybean yields from 55 to 75 bu/acre, for example, will remove remove an additional 15 lb of P and 25 lb of K. The story is similar for corn. When yield increases from 180 to 250 bu/ac the crop extracts an additional 24 lb of P and 18 lb of K. (Story continues after the video.)

Berlett says it’s important for growers to factor that extra removal into their nutrient plans for 2021. She also emphasizes the need to look for variability within fields — why do some areas of soybean fields hit 80 bushels on the yield monitor while other areas are under 40?

These lower yields are often observed on knolls and areas where typography varies within the field. Typically these areas are drier and lack the water-holding capacity to support high yields, says Berlett. She recommends growers consider organic amendments for these areas, including compost, manure, and biosolids to improve yield potential.

Berlett also reminds growers of the key role that overall soil health and organic matter plays in supporting yield. “Higher-yielding zones tend to correlate with our water-holding capacity, which goes back to our organic matter,” she notes. “When we run into drier scenarios, these higher organic matter fields can buffer and mitigate that stress longer and protect that yield potential.”

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