Studies also have shown yield advantages for corn when excess stover is removed. The remaining residue in a sustainable stover harvest program ensures soil erosion prevention, soil organic carbon maintenance and soil fertility management.

“Concern with removal of organic matter and nutrients with the stover harvest tends to be the primary limiting factor on the minds of growers,” says Heggenstaller.

As fields are evaluated for stover harvest, the estimated productivity level guides the amount of residue left on the field. Typically, corn grain and stover are produced in a roughly 1:1 ratio. If a field yields 150 bu./acre, which equals 3.6 tons of grain at 0% moisture, it should produce approximately 3.6 tons of stover. In general, every field under continuous corn with no-till or conservation tillage needs about 2.3 tons of residue/acre to keep organic matter constant. As corn yields grow, stover increases, resulting in greater potential for stover removal in highly productive fields. 

Soil erosion is another major consideration. A sustainable stover harvest program must leave enough residue on the soil to mitigate water and wind erosion. The amount of residue needed to manage erosion varies greatly depending on field characteristics and management practices, but it is often significantly less than the total produced. Tools such as RUSLE2 (Revised Universal Soil Loss Equation, version 2) and WEPS (Wind Erosion Prediction System) are available to develop a soil conservation plan.

From a soil fertility standpoint, the impact of a stover harvest is complex. A partial stover harvest will increase the removal of plant nutrients; however, short- and long-term effects will vary for different nutrients. Nutrient removal tables provide estimates of pounds of nutrients per ton of dry stover. The tables are useful as a general guide, but they tend to overestimate the amount of nutrients actually removed by a stover harvest. In general, growers should monitor fertility and account for nutrient removal in fertility programs, particularly with phosphorus and potassium.

 “When considering stover harvest, growers should be thinking where they want to go with crop production, not where they are today,” says Heggenstaller. “As grain yields and residue levels increase, it becomes more sustainable and economical to harvest a portion of stover and use it to produce other products than to till it into the soil.”