Miscanthus (Miscanthus x giganteus) and switchgrass (Panicum virgatum L.) are perennial grasses that can provide both renewable energy and ecosystem services, but the extent to which they do depends strongly on crop management. Nutrient use efficiency and wildlife habitat provision are influenced primarily by harvest management while soil stabilization and water protection are influencied primarily through field management at planting. Field trials were conducted in the Midwestern USA to evaluate the impact of 1) harvest time on nutrient cycling and yield; and 2) nurse crops on soil cover and plant productivity.
Results/Conclusions
Delaying harvest provides increased ecosystem services. Allowing a mature Miscanthus crop to stand in the field and complete its annual life-cycle through senescence reduced the amount of nitrogen (N) removed from the field by 10-fold compared to harvesting the crop while still green (from 400-40 kg N ha-1). Further, Miscanthus and some varieties of switchgrass can stand in the field without lodging over the winter, providing good cover for birds and small mammals. Unfortunately, harvestable biomass yield of both crops can drop by more than 50% with delayed harvest, especially in the winters of the Upper Midwest, so unless producers are compensated for ecosystem services, there is little direct incentive to manage for them. Methods to plant Miscanthus with nurse crops are promising. Further work is needed to refine nurse cropping so that soil and water quality are protected during the multi-year Miscanthus establishment phase while interspecific competition that will reduce Miscanthus yield is minimized.
