Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 2002-2004
increases in yield and NUE while improving soil quality and achieving a net reduction in greenhouse gas emissions. Likewise, simulation modeling studies based on this work indicate tremendous untapped potential to increase carbon inputs to soil through return of stover in irrigated continuous corn systems that consistently achieve yield levels near the yield potential ceiling of current hybrids (Figure 2). Renewable energy. Substitution of renewable energy for imported oil is a goal that resonates strongly with both the general public and the environmental movement. Ethanol production from corn grain, and eventually from crop biomass, is one option to produce renewable energy and decrease net emissions of greenhouse gases by burning renewable fuel rather than fossil fuels. The big issue is whether ethanol can be produced from corn in a manner that is energy efficient and without negative effects on the environment. It turns out that NUE has a major impact on both energy and environmental aspects of ethanol from corn because N fertilizer represents about 50 percent of the total energy used in corn production systems, and losses of N have a major influence on ground and surface water quality. I would argue that the most relevant analysis of energy efficiency in corn-to- ethanol systems should be based on progressive crop and soil management technologies used by the top 5 to 10 percent of corn growers using farming methods that are likely to be widely adopted within 10 to 15 years (or more quickly with appropriate policies and investment in extension). The trajectories in both yields and NUE of the past 25 years suggest that such progress will continue into the foreseeable future (Figure 1). Fall 2004 Fluid Journal 3 Using data from the University of Nebraska Carbon Sequestration Program as reported in Table 2, which includes the actual energy values for all inputs used in producing the corn as well as the energy costs of transportation to the ethanol plant and in conversion to ethanol, we found a large net energy surplus equivalent to 215 gallons of diesel fuel equivalent per acre for irrigated corn, and 166 gallons for rain-fed corn. If we assumed yield levels obtained in this study on 25 percent of the irrigated corn area in Nebraska could produce about 1.7 billion gallons of diesel equivalent, that would be enough to meet the annual fuel requirements for all the cars and trucks in Nebraska, Iowa, and Kansas combined. Moreover, the high NUE achieved in the study would reduce losses of N to the environment by a substantial margin compared to today's average farmer. Advantages of fluids Fluid fertilizers have a number of advantages in seeking to achieve higher yields and nutrient efficiency while reducing greenhouse gas emissions. They allow more precise nutrient balance and placement to meet crop demand and to maximize root contact--especially during the critical early crop establishment phase. Fluid N formulations reduce reliance on anhydrous ammonia, which has the greatest potential for losses via denitrification to nitrous oxide---the most potent of all greenhouse gases. When used for fertigation, fluids typically increase NUE substantially by achieving greater synchrony between crop N demand and the N supply, thus avoiding excess available N vulnerable to loss. Dr. Cassman is professor in the Department of Agronomy and Horticulture at the University of Nebraska. Figure 2. Annual C sequestration over 20 years as infl uenced by corn productivity and tillage method. Absolute annual rates are shown (left). Values (right) are absolute annual rates (lb C/A/yr) while percent increases are shown for effects of tillage and yield. Ya = actual yield; Yp = yield potential; NT = no- till, CT = conventional-till.
Fluid Journal 1999-2001
Fluid Journal 2005-2007