ENERGY IMPLICATIONS FROM EXTENDING WHEAT ROTATIONS IN THE BROWN SOIL ZONE OF WESTERN CANADA

Abstract

Energy inputs, energy output, and energy efficiency levels of six spring wheat (Triticum aestivum L.) rotations considered technically feasible for the Brown soil zone of western Canada were examined. Both direct and indirect energy input expenditures were considered. Energy output was measured as the metabolizable energy of the grain for human consumption. The results showed that total energy input per unit area was lowest for the traditional fallow-wheat rotation. The fallow-wheat-wheat and continuous wheat rotations receiving recommended rates of N and P fertilizers had non-renewable energy requirements that averaged 20 and 105% higher than for the comparable fallow-wheat rotation, respectively. Fuel use per unit area and energy investment in capital items were similar among the rotations, but they accounted for the greatest share of the total energy input of the fallow-wheat rotation. Energy expenditures on fertilizers and on herbicides increased as the proportion of summerfallow in the rotation decreased, and accounted for 5 to 45% of the total energy requirements of the rotations. Energy output and net energy produced (i.e., energy output minus energy input) generally increased with the more intensive crop rotations because of the greater quantity of annual grain production per unit area. The energy output/input ratios for the rotations were similar, except for the continuous wheat rotation receiving recommended rates of N and P fertilizers which was lower.