Leopold Center for Sustainable Agriculture
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Oak regeneration response to thinning from below
Most of the nation's productive forests are in nonindustrial, private ownership. To meet projected demands, timber harvests will need to increase on these lands. Iowa, which has 0.61 million hectares (ha) or approximately 1.5 million acres of commercial forestland, could benefit from capitalizing on this demand. However, the state's timber resource has been generally under-utilized. For example, Iowans have not harvested poletimber and low-grade sawlog materials from their woodlots because the market for such products has been lacking. Killing such trees to make room for better quality material involves costs that do not immediately increase net returns; thus, incentive to manage these woodlands has not been high.
Evaluation of interactions within a shelterbelt agroecosystem
A tree shelterbeit comprised of four rows of hybrid poplars was established near Ogden, Iowa in 1992 to evaluate shelterbeit characteristics and impacts on soil water content and crop growth andyieid. Major emphasis was on testing crops of corn and soybeans. The first three years saw little effects from the shelterbeit, and data from these years will be used to develop a baseline for future measurements. In the fourth and fifth years, corn yield patterns suggested that the shelterbeit increases yields in the zone leeward from the shelterbeit. Soybeans have not shown a response to the presence of the shelterbeit.
Native willow stream-bank plantings: a local resource to control erosion and provide an acceptable alternative riparian planting technique
Over three years, small willow cuttings ("posts") cut from local sites were planted into the stream bank on six sites along the Middle Raccoon River. These posts stabilize the bank, reducing erosion and protecting water quality. In addition, unlike most riparian buffer planting techniques, they do not take land out of agricultural row-crop production. They also provide shading and enhance wildlife habitat. Plantings are most successful if cut while dormant, planted on rivers or streams that have less than 50,000 acres drainage, and inspected regularly for insect and beaver damage (so that preventive measures may be taken where indicated). This technique was demonstrated to the public via field days and media coverage, and results of a survey assessing attitudes about adoption of the technique are being analyzed.
Sustainable tree-shrub-grass buffer strips along waterways
The midwestern landscape, which formerly consisted of prairies, wetlands, and forests, is now primarily devoted to agricultural purposes. Unfortunately, the resulting large-scale agricultural production has also produced nonpoint source (NPS) pollution of water, alteration of waterways, and disruption of wildlife habitat. NPS pollution, whether by sediment, fertilizers, or pesticides, is a problem nationwide. The agricultural community has addressed this problem by increasing soil conservation efforts and improving chemical application practices. One Best Management Practice (BMP) is the use of riparian (streamside) vegetative filter strips on watersheds prone to such pollution. Most such filter strips to date consist primarily of cool-season grasses.
Poplar tree buffer strips grown in riparian corridors for non-point source pollution control and biomass production
Throughout the Cornbelt eco-region, nitratenitrogen (NO3-N) is the most frequent pollutant exceeding the U.S. Environmental Protection Agency's maximum contaminant limits for municipal drinking water supplies. Agricultural fertilizers that leach or run off from row-cropped fields are the principal source of NO3-N. This potential contamination poses a health concern that is attracting increasing attention among the urban and rural populace alike.
Species and variety of conifers for Christmas tree production in Iowa
According to the National Christmas Tree Growers Association, Christmas tree production has expanded greatly in the last five years. More than 35.4 million trees were sold in the United States in 1987, a 25.5% increase over the previous year. Even so, nationwide the industry is beginning to suffer from overexpansion, especially in the retail lot markets. Small choose-and-cut operations are still doing well, however, and in most localities, there is a shortage of this type of tree-purchasing option.