Harvest timing and amount affect bioenergy crop water use on marginally-productive cropland

Authors: Jin, Virginia; Schmer, Marty; Wienhold, Brian; Mitchell, Robert - Rob

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/25/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Ligno-cellulosic feedstock production on marginally-productive croplands is expected to provide substantial ecosystem service benefits, including water conservation. Long-term field research directly comparing crop water use by annual vs. perennial bioenergy feedstock crops, however, is limited. Here, we evaluated seven years (2012-2018) of soil water availability to 120 cm depth under switchgrass (Panicum virgatum L., var. Cave-in-Rock) and no-till continuous corn (Zea mays L.). The effect of harvest timing on switchgrass (anthesis vs. post-killing frost) and harvested stover amount on corn (0% vs. 50% removal) on soil water availability over the growing season were assessed. Crop water use varied across years, depending on timing and amount of precipitation, but biomass harvest practices consistently affected patterns of water use each year. The percent of available soil water depleted by switchgrass over the growing season was generally higher for switchgrass harvested at anthesis compared to later post-killing frost harvest. Although total water use by post-frost harvested switchgrass were expected to be higher than anthesis-harvested grass because of total biomass differences, greater productivity of late-harvested switchgrass likely provided a thicker litter layer that protected soils against evaporative losses. For no-till continuous corn, removing 50% of stover resulted in greater depletion of available soil water compared to retaining stover, again likely due to the lack of a physical barrier protecting soils from evaporative losses. Patterns in soil water depletion were similar across all cropping systems early in the growing season, then tended to diverge by management system at crop canopy closure (mid-late July). Overall, our results supported expectations that perennial bioenergy grass production conserves more soil water compared to removing stover from no-till corn on marginally productive land, but the extent to which soil water is conserved will depend on biomass harvest timing and amount in both cropping systems.