Residue and nutrient cycling

Leaving crop residue on the soil surface after harvest will improve nutrient cycling, and ultimately, soil quality and productivity. It also prevents erosion from wind and water.

Mahdi Al-Kaisi is a soil management professor at Iowa State University. He says studies prove that crop residue saves farmers about $22 per-acre in nutrients that they don’t have to apply.

"It was estimated residue could contribute about 37 lbs. of organic nitrogen to the soil per-acre. About 3.5 lbs. of phosphorous per-acre, and approximately 33 lbs. of potassium. Calcium about 21 lbs., and magnesium about 17 lbs.," says Al-Kaisi.

Al-Kaisi says over the long-term, soil fertility losses from residue removal are slow, but permanent. Short-term, the impact is an acceleration of soil loss, which affects more than just the field. 

"Especially in the spring when you have high-intensity rain, we have a lot of sediment and nutrients in the lakes, the rivers and ditches, and that’s going to add to the cleanup costs for the counties," he says. "When these sediments leave the field, it’s going to carry with it a significant amount of organic matter."

Al-Kaisi says leaving crop residue can create management problems in some fields. However, there are alternatives such as planting a cover crop, or strip tilling where only about 25% of the field is tilled.

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