As world population grows and nations increase standards of living, demands for food, feed, fiber and fuel are increasing. The world's agricultural system is being increasingly challenged to meet these demands. Simultaneously, a changing climate signals new serious challenges that are reverberating across Iowa and other agricultural regions. These challenges are outlined in a new report to the governor and General Assembly, released Jan. 1 by a panel of research scientists from Iowa's three Regents institutions ("Climate Change Impacts on Iowa 2010," www.iowadnr.gov/iccac/).
Climate change is already affecting crop management in Iowa. Farmers are adapting to some of these changes, but can they adapt sufficiently to withstand new crop production challenges? The number of frost-free days has increased; farmers are planting earlier and using longer-season hybrids. The dew point temperature is rising, meaning dew comes earlier and stays later; farmers are buying wider combine heads and larger machines, allowing more acres to be harvested in less time. Longer periods of wet leaves increased risk of plant diseases; fungicides are being applied more than in the past. Frequency of very heavy rainfall events has increased in the upper Midwest more than 30 percent in the last three decades; tile drainage is increasingly important for crop production.
Are climate changes all bad for agriculture? Probably not. Longer growing seasons favor higher crop yields. Increased rainfall to some extent can reduce crop water stress and favorably affect yield, although the more frequent extreme events we are experiencing are associated with more crop damage from wind, hail, and flooding. Higher nighttime temperatures reduce grain-filling potential, negatively affecting yield. Disease pressure reduces crop yield potential and increases cost of production. Thinning top soil from elevated erosion rates reduces yield potential. Increased rainfall increases nitrate leaching and nutrient loss in runoff water.
A greater long-term climate change threat to Iowa may come from outside Iowa's borders. Climate events such as Russia's 2010 unprecedented heat and drought, substantially reduced world commodity supplies. This raised commodity prices, elevated Iowa land prices and has added pressure to bring increasingly marginal lands into row-crop production. Row crops, especially on marginal land, lead to increased soil erosion and nutrient loss. This is especially true when coupled with the heavy rainfall events that we are increasingly experiencing. In 2008, selected townships in Iowa had estimated soil erosion rates of greater than 50 tons peracre.
We must maintain vigilance, insuring that agricultural resources and production are not compromised. High agricultural production is critical for our best economic interest. Developing climate stresses will likely challenge our ability to maintain resources required for high and stable production levels. Our changing growing conditions dictate that now, even more so than in the past, we develop and adopt cropland management techniques that are resilient as well as productive. Iowa's rich top soil and water resources are treasures to be safeguarded; failure to adopt practices more resistant to stresses associated with climate change is not an option.
Richard M. Cruse is a professor at Iowa State University and director of the Iowa Water Center.