Evaluation of Herbaceous Biomass Crops in the Northern Great Plains: Summary, Conclusions, and Recommendations
Evaluation of Herbaceous Biomass Crops in the Northern Great Plains: Summary, Conclusions, and Recommendations |
Biomass cropping in the northern Great Plains has real potential! Environments sampled ranged from the relatively cool, wet year in 1992 to the very dry years of 1988 and 1989. They also included the exceptional yielding year of 1990 at Prosper and Leonard, and 1991 at Glenfield and Leonard. Therefore, reported biomass yields should be indicative of the variation expected if biomass cropping occurred in the northern Great Plains.
Greatest biomass yields were obtained from forage sorghum at Prosper and Carrington irrigated when meaned across years. Sorghum X sudan frequently yielded greater than forage sorghum in drier environments. Annually seeded kochia frequently was competitive in biomass yield to the sorghums, and occasionally was the highest yielding species, especially under drought stress. Foxtail millet generally was lower yielding than other annuals.
Perennial species generally did not have the biomass yield potential of the annuals. However, the 1.2 million hectares of CRP land primarily established with the CRP mixture is a potential vast resource for biomass production. Intermediate wheatgrass, the CRP mixture (dominated by intermediate), and reed canarygrass (limited observations) generally were the highest yielding cool-season species/mixtures.
We obtained only limited data on switchgrass due to its very poor establishment. But, where adequate stands were obtained (Leonard and Prosper), switchgrass showed its potential as a promising biomass species in the northern Great Plains. We conclude that additional research on switchgrass, especially on stand establishment, should be funded in the northern Great Plains to more fully evaluate its potential as a biomass species.
Biomass yields of perennials were unaffected by N level during the first two years of production, but were increased by N fertilization during the third and fourth years of production (switchgrass was an exception). Biomass yields of annuals rarely were increased by an additional unit of N above 50 kg ha-1. Crop-recrop comparison generally was nonsignificant; therefore, growing biomass on recrop land is the best option even though biomass yields might be slightly lower in some years.
The environment (site and year) had a strong influence on the chemical composition of both annual and perennial species, and tended to be a more important factor than N level, cropping system, or species. The one exception to this comment was the differences in chemical composition of warm- vs. cool-season perennials.
Biomass cropping was economically feasible in the three study areas evaluated when biomass was valued at $39.2 Mg-1 and marketing-year average price for competing crops was used. One or more biomass crops had a higher net return than the area's best conventional crop. Kochia and forage sorghum were generally the most profitable biomass species. Switchgrass, included only in the Red River Valley comparisons, was more profitable than the common small grains grown in the area. We conclude that biomass cropping is an economically viable alternative crop, especially in the Hettinger and Glenfield areas (the lowest yielding), since few cropping alternatives exist.
Kochia was the most profitable biomass species primarily due to very low input cost. No herbicide was needed for weed control and only limited N fertilization was used. No special equipment would be needed for production. Kochia was the highest yielding species in the most arid region and could be produced on some of the cheapest land. However, there is much we do not know about kochia production like optimum fertilization, consistent seed germination (1991), seed production, allelopathic effects, volunteer plants, etc. The only apparent disadvantages of kochia as a biomass species seems to be the relative high ash and N concentrations, and its weedy nature. We conclude that additional research should be funded to further evaluate kochia as a biomass crop for the northern Great Plains.
Biomass cropping on fallowed land utilizing a leguminous biomass species was successfully evaluated in 1990-91 only due to stand failures in two other years. We still believe the concept has merit, but more effective establishment techniques like no-till would need to be incorporated into the system.
Biomass yields of kochia dropped precipitously by delaying harvest until after a killing frost from loss of seed and leaf. Therefore, kochia must be harvested prior to frost to prevent yield loss. It may also be necessary to harvest earlier to reduce seed loss to prevent it from becoming a weed problem in subsequent crops.
Stand maintenance at high N fertilization levels should not be a problem in the northern Great Plains. Nitrogen fertilization of bromegrass at 294 kg ha-1 for 38 years at Fargo has resulted in only slight stand deterioration compared with an unfertilized treatment. Little deterioration of perennial stands occurred in these experiments.
Herbaceous biomass can be economically produced in the northern Great Plains. If herbaceous biomass has a future in the energy picture of the United States, the northern Great Plains should be considered as a low- cost producer.