Landscape management and sustainable feedstock production: Enhancing net regional primary productivity while minimizing externalities

Authors: Lowrance, Robert; Anderson, William - Bill; MIGUEZ, FERNANDO - Iowa State University; Strickland, Timothy - Tim; Knoll, Joseph - Joe; Sauer, Thomas

Submitted to: Soil and Water Conservation Society
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2010
Publication Date: 9/27/2010
Citation: Lowrance, R.R., Anderson, W.F., Miguez, F., Strickland, T.C., Knoll, J.E., Sauer, T.J. 2010. Landscape management and sustainable feedstock production: Enhancing net regional primary productivity while minimizing externalities. In: R.Braun, D.L. Karlen, and D.Johnson (eds.) Sustainable Alternative Fuel Feedstock Opportunities, Challenges and Roadmaps for Six U.S. Regions. Proceedings of the Sustainable Feedstocks for Advanced Biofuel Workshop. Sept. 27-29, 2010, Atlanta, GA. Soil and Water Conservation Society, Ankeny, IA 50023 1-29.

Interpretive Summary: A landscape is an area of land, typically miles in extent where there is a regular and repeating pattern of ecosystems arranged based due to factors such as hydrology, elevation, and/or land use. People manage landscapes, notably to produce food feed, fiber, flowers, and fuel from agriculture. A wide variety of agricultural conservation practices are applied to manage agricultural landscapes typically to improve water quality and quantity, wildlife habitat, air quality. Net primary productivity (NPP) is a characteristic of the ecosystems that are part of an agricultural landscape. If we know the total amount of carbon assimilated by a plant and the total amount of respiration by the plant then NPP is just the difference in assimilation and respiration. Usually we do not know those values so generally NPP is estimated by direct measurements of aboveground net production (ANP) or is modeled. Nationally or globally, the NPP of crops does not always follow the pattern of “natural” NPP because of differences in the growth habit of crops. For instance a cotton plant produces lower NPP than a corn plant. Because of a variety of concerns about the effects of bioenergy production on the environment and land use change, there is a need to get high levels of NPP of bioenergy crops without impacting current crop and forest production. For this reason, production of bioenergy feedstocks may be largely done on what are considered marginal lands for modern agriculture. Studies have shown that globally, feedstocks produced on marginal lands may supply about 8% of total world energy demand. Some statewide estimates in the U.S. put the total higher. Marginal lands can be defined based on a number of properties. In the Little River Watershed (LRW) we defined marginal lands based both on how close land is to streams and waterways and on soil groupings. Where land near streams or non-prime soils were already in row crops or pasture, we assumed that they would be candidate areas for establishing perennial biofuel feedstock crops. Results of this analysis showed that there were adequate marginal lands in the watershed and in similar coastal plain landscapes to produce the feedstocks for a typical bioenergy plant without using any of the prime farmland. In areas like the LRW, about 38% of the feedstock could be grown by re-vegetating buffers and waterways and the remainder could be grown using about 17% of the marginal agricultural soils. Although farmers will make decisions based on numerous factors, the type of analysis described here will be useful in future decision making concerning the placement of biofuel conversion facilities and in guiding feedstock production to appropriate parts of the landscape.

Technical Abstract: An ecosystem is any area in nature where living organisms interact with the abiotic environment to produce an exchange of materials between the living and nonliving parts. A landscape is a heterogeneous land area comprised of a cluster of interacting ecosystems. Landscape ecology seeks to understand groups of ecosystems and the interactions among those ecosystems. Landscape management, especially for agricultural landscapes, involves directing the interactions of the ecosystems in the landscape to produced desired results – water quality and quantity, wildlife habitat, air quality. In agricultural landscapes the interactions are largely determined by technological factors (crops, domestic animals, fertilizer, tillage) interacting with weather, hydrology and edaphic conditions. Conservation practices are often focused at the landscape level, either by limiting and directing the outputs form agricultural ecosystems or by building sinks for water, sediment, nutrients, and pesticides into the landscape. Net primary productivity (NPP) is simply assimilation- respiration for a plant community. Generally NPP is estimated by direct measurements of aboveground net production (ANP) or is modeled. Nationally or globally, the NPP of crops does not always follow the pattern of “natural” NPP because of differences in the growth habit of crops. For instance a cotton plant produces lower NPP than a corn plant. Because of a variety of concerns about the sustainability and externalities of bioenergy crops, there is a need to achieve high levels of NPP without impacting current crop and forest production. For this reason, production of bioenergy feedstocks may be largely done on what are considered marginal lands for modern agriculture. Globally, feedstocks produced on marginal lands may supply about 8% of aggregate energy demand although some state wide estimates for the U.S. put the total higher. Marginal lands can be defined based on a number of properties. In the Little River Watershed (LRW) we defined marginal lands based on both proximity to streams and waterways and soil groupings. Where land near streams or non-prime soils were already in row crops or pasture, we assumed that they would be candidate areas for establishing perennial biofuel feedstock crops. Results of this analysis showed that there were adequate marginal lands in the watershed and in similar coastal plain landscapes to produce the feedstocks for a typical bioenergy plant without using any of the prime farmland. In areas like the LRW, about 38% of the feedstock could be grown by re-vegetating buffers and waterways and the remainder could be grown using about 17% of the marginal agricultural soils. Although farmers will make decisions based on numerous factors, the type of analysis described here will be useful in future decision making concerning the placement of biofuel conversion facilities and in guiding feedstock production to appropriate parts of the landscape.