Evaluation of Herbaceous Biomass Crops in the Northern Great Plains: Abstract
Evaluation of Herbaceous Biomass Crops in the Northern Great Plains: Abstract |
Herbaceous lignocellulose crops are a potential renewable feedstock for biochemical conversion systems second in size only to wood products. Several herbaceous crops are utilized as forage crops in the northern Great Plains, but forage quality considerations usually dictates a early harvest. Biomass cropping does not have this constraint; therefore, little information was available on herbaceous crops utilized as energy crops prior to this project. Our primary objectives were to evaluate the biomass yield and select chemical components of several herbaceous crops for energy crops in the northern Great Plains, compare the economic feasibility of energy crops with common competing crops, and evaluate biomass cropping on summer fallow lands.
Three good, two marginal, and one irrigated sites were used during 1988 to 1992 for the first component. At least six perennial and four annual biomass species were included at all sites. Three to four nitrogen (N) levels and a crop-recrop comparison (annuals only) were management intensities included. Biomass cropping on idled lands was performed on dryland at Carrington and evaluated the effects of removing leguminous biomass on fallowed lands. This report summarizes results from the 5-year project.
Forage sorghum produced the highest average biomass yield (16.9 Mg ha-1) when meaned across years at the Carrington irrigated site, the highest average biomass yield at 4 of 6 sites, and the highest biomass yield (23.3 Mg ha-1) in any one year and site. Sorghum X sudan and kochia were the highest yielding species each at one site, generally the droughty sites.
Perennial species generally did not have the biomass yield potential of the annuals. Switchgrass, where included, had the highest biomass yield (9.0 to 11.3 Mg ha-1 at two sites) of the perennials evaluated, intermediate wheatgrass and the CRP mixture generally were the highest yielding cool-season perennials.
Nitrogen fertilization levels above 50 kg ha-1 rarely increased biomass yields of annuals. Nitrogen fertilization was not needed for perennials the first two years, but was required the third and fourth years. Species by N level interaction was rarely significant. Growing biomass species on fallow probably does not pay even though slightly higher biomass yields occurred on fallow compared with recrop.
Although affected by species, the chemical composition of both annual and perennial species was affected more by the environment (site and year). Yield of chemical component was primarily affected by biomass yield and not chemical composition.
Herbaceous biomass cropping was an economically feasible alternative cropping enterprise in the three areas studied when biomass was valued at $39.2 Mg-1. Kochia as a biomass crop was the most profitable species in all areas. If excluded, forage sorghum or sorghum X sudan was selected. Switchgrass was more profitable where included than the common small grains grown in the area.
Kochia, a common annual weed, has potential as a biomass crop in the northern Great Plains, but additional research on production and physiology factors is needed. For example, we have shown that harvest after a killing frost dramatically reduces biomass yields and allelopathic effects prevents economic yields when kochia is grown on land previously cropped to kochia. Likewise, additional research on stand establishment of switchgrass seems warranted.
Biomass cropping on idled/fallowed land was basically a failure due to poor establishment of the leguminous crop. We believe that the concept has merit, but establishment problems must first be solved.
We conclude from this 5-year study that herbaceous biomass cropping is economically feasible in the northern Great Plains. If herbaceous biomass has a place in the energy picture of the United States, the northern Great Plains should be considered as a potential major contributor.