Fertilizer runoff could be reduced significantly if row crops such as corn and soybeans are replaced with perennial grasses harvested for biofuel production, say researchers from four Midwestern universities. Nitrogen runoff in the Mississippi River basin, blamed for creation of a “dead zone” each summer in the Gulf of Mexico, could drop 15-20 percent if switchgrass or miscanthus were planted on a quarter of the land now devoted to row crops, according to computer simulations.
“This study adds to the portfolio of evidence that perennials can be a major part of the solution to nutrient runoff,” said agronomist Andy VanLoocke of Iowa State University, co-author of the study published in the journal Global Change Biology Bioenergy. Perennial crops have longer growing seasons than corn or soybeans, the two most widely planted U.S crops, so they are available for longer periods to absorb nutrients that otherwise might wash away.
The study looked at perennial grasses commonly cited as potential feedstocks for cellulosic ethanol, made from woody shrubs, crop debris and grass. The cellulosic industry, slower to develop than projected, produces a trickle of fuel compared to corn ethanol. VanLoocke said the study shows “a perennial market would have a positive effect on water quality” and was an opening step in evaluating land-use practices.
So-called cover crops are another approach for control of nutrient runoff. The crops are planted after harvest to hold soil and nutrients in the field and yield way in the spring to a new planting of revenue crops. Three U-Illinois economists estimated the costs of $15-25 an acre to plant a low-cost cover crop. “The costs to the farmer of implementing cover crops are relatively straightforward to determine, but the benefits for the farmer are less apparent, especially in the short run,” say the economists at farmdoc daily. “Reducing nitrates in water bodies has public benefits that do not directly accrue to farmers.”