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Ames Forester

Abstract

A cooperative study involving the City of Ames, Iowa State University, and the Iowa Department of Natural Resources has been initiated to utilize municipal sludge as “fertilizer” to increase the productivity of fast-growing trees and herbaceous crops. The tree and herbaceous crops are grown to produce renewable biomass useful as energy feedstock. The design of the planting and the growth characteristics of the tree and herbaceous biomass system are expected to effectively minimize the contamination potential of the sludge to surface and groundwater. Located at the new Ames Municipal Wastewater Treatment Plant, this system can be called an “agroforestry energy system." An arrangement using alternating strips of forage crops and trees is designed to produce greater yields of both crops than if each crop is grown individually. The tree crop benefits the agricultural crop by reducing wind and, therefore, water losses, whereas the herbaceous crop, next to the trees, increases the amount of sunlight able to reach the trees along the edges, therefore, increasing the woody biomass productivity. Approximately 40 acres of prime agricultural land will be devoted to the study. The tree species being used is a cottonwood hybrid (Populous x euramericana-clone NC-5326). The herbaceous crops consist of switch grass, forage sorghum and rye, and crambe (an industrial oil seed crop). The herbaceous crops are planted between the tree strips to provide the benefits mentioned above. The spacing arrangement is also designed to allow access for the sludge application truck (see figure 1). Three plantings will be made, one each in 1990, 1991, and 1992. Various agronomic rates of sludge will be applied starting the spring of 1991.

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