Abstract
The objective of this research was to calculate the energy return on investment (EROI) of the wheat and rice crops of Pakistan for the fiscal years 2000 to 2007. Energy inputs accounted for within the cropping systems included seed, fertilizer, pesticide, human labor, tractor diesel, irrigation pump electricity and diesel, the transport of fertilizer and pesticide, and the embodied energy of tractors and irrigation pumps. The major inputs to wheat were N fertilizer (57 percent), seed (17 percent), and tractor diesel (ten percent). The major inputs to rice were N fertilizer (40 percent), pesticide (30 percent), and labor (seven percent). The EROI of rice ranged between four and six, and averaged 4.9. The variation was smaller for wheat (3.0-3.8), and averaged 3.3. However, rice's EROI varied considerably over the study period while wheat's was relatively uniform. Wheat's input-output relationship was positive and linear, while rice's was negative and linear.