Much of Iowa's permanent pasture is declining in productivity because of overgrazing, inroads made by brush and other factors. An unimproved pasture like that at right provides poor growth of desirable grasses and legumes and permits weeds to grow instead.
Heady, Earl O. and Scholl, J. M.
"Pasture Improvement Costs and Returns,"
Iowa Farm Science: Vol. 8
, Article 4.
Available at: https://lib.dr.iastate.edu/farmscience/vol8/iss6/4