Pulse Crops Improve Energy Intensity and Productivity of Cereal Production in Montana, USA

Energy consumption, intensity, and productivity are indicators of agricultural sustainability in the face of fossil energy scarcity and price volatility. In this study, budgets of energy embodied in crop production inputs were compiled for 14 paired pulse (annual grain legume)-wheat and wheat-wheat crop sequences using data collected from Montana farmers. We report two energy performance metrics: net energy yield (NEY), the energy content of harvested crop minus energy required to produce it, and energy intensity (EI), the ratio of input energy to mass of crop harvested. Nitrogen fertilizer accounted for 58% of the energy used in wheat production, and its absence largely accounted for the 53% reduction in energy inputs to pulses relative to wheat. EI of pulses was lower than for wheat, and pulse crops also resulted in reduced EI and increased NEY for the subsequent wheat crop compared to wheat grown following wheat. The largest component of the improved energy performance of wheat following pulses was increased yield rather than decreased inputs.