Sustainability of corn stover harvest strategies in Pennsylvania
Pennsylvania farmers have a long history of harvesting corn (Zea mays L.) stover after grain harvest for animal bedding and feed or as a component of mushroom compost, or as silage for dairy cattle feed. With the shallow soils and rolling topography, soil erosion and carbon losses have been minimized through extensive use of cover crops, no-till, and organic matter additions from animal manure. Our objective was to determine the effect of harvesting corn stover as a feedstock for bioenergy production in continuous corn or corn–soybean [Glycine max (L.) Merr.] rotations on corn grain and stover yields, soil carbon, nitrogen, phosphorus, potassium, and the potential for cover crops to mitigate negative impacts of stover harvest. Although there was not a significant effect of stover harvest on corn grain yields in continuous corn, stover harvest tended to increase yields in years with wet springs but decreased them in dry years. Under the corn soybean rotation, 100 % stover removal always resulted in lower grain yields. The harvest index (HI) varied from 0.45 to >0.6 over the 5-year period with the lowest HI values being in response to a late summer drought and highest values being associated with an early summer drought. In most cases, 60 % soil cover was maintained in fall and spring with 50 % harvest of corn stover. Without a rye (Secale cereale L.) cover crop, surface residue for 100 % stover harvest ranged from 20 to 30 %, whereas it was greater than 40 % when rye was established promptly in the fall. Soil carbon was similar across stover removal levels, crop rotations, and cover crops, as were soil nitrogen, phosphorus, and potassium concentrations, since nutrient removal by the grain and stover were replaced with fertilizer additions. Based on the crop yield, surface cover, and soil nutrient responses, partial stover removal could be sustainable under typical climate and management practices in Pennsylvania.