ENERGY OUTPUT-INPUT RATIO OF MAIZE AND SORGHUM MANAGEMENT-SYSTEMS IN EASTERN NEBRASKA

Crop management systems need to be designed to help farmers maintain e conomic profitability, while conserving external energy resources and farming in an environmentally responsible manner, The objective of thi s study was to determine the energy output:input ratio of several maiz e (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench.) management systems that are typical of eastern Nebraska, USA. Management variable s were, (1) nitrogen (N) fertilization, (2) previous crop (cereal or l egume), (3) tillage (none or traditional), (4) herbicide (none, banded , or broadcast), and (5) water (dryland, limited irrigation, or full i rrigation). Eleven management systems were delineated from different c ombinations of the last four variables and compared at different level s of N fertilization, The energy output:input ratio ranged from 4.1 +/ - 0.5 in fully irrigated, broadcast herbicide, traditional tillage sys tems with cereal as previous crop and no N fertilizer to 11.6 +/- 2.5 in dryland, broadcast herbicide, traditional tillage systems with legu me as previous crop and no N fertilizer. The energy output:input ratio decreased with the addition of N fertilizer in all management systems , except in fully irrigated, continuous cereal systems. Management sys tems with legume as previous crop had a greater energy output:input ra tio than those with cereal as previous crop. Under dryland conditions with traditional tillage, the energy output:input ratio was greater wi th herbicide usage than without, Dryland management systems had greate r energy output:input ratios than systems with irrigation. The obvious short-term advantage of greater food production from irrigated agricu lture using high levels of fossil fuel derived inputs must be balanced against the long-term costs to society of depleting a scarce and non- renewable energy resource. Rotation of cereals and legumes under dryla nd conditions in the western Corn Belt may be more sustainable for the future based on energy use efficiency because of lower fossil fuel re quirements from N fertilizer and irrigation.