Effects of crop rotation on energy use efficiency of irrigated potato with cereals, canola, and alfalfa over a 14-year period in Manitoba, Canada

Crop rotations can be used to optimize energy use efficiency (EUE) by preserving or enhancing optimal fertility and chemical use and reducing greenhouse gas (GHG) emissions. A field experiment consisting of six rotations of potato (Solanum tuberosum L.) with canola (Brassica napus L.) (P-C), wheat (Triticum aestivum L.) (P-W), canola-wheat (P-C-W), oat (Avena sativa L.)-wheat (P-O-W), wheat-canola-wheat (P-W -C-W), and canola underseeded to alfalfa (Medicago sativa L.)-alfalfa-alfalfa (P-C(A)-A-A) was conducted on a clay loam soil in Manitoba, Canada for 14 years to assess the relative energy use performance of potato and all crops in each rotation. The potato phase in the P-C(A)-A-A rotation had the largest average annual net energy (93.5 GJ ha−1), the largest output/input energy ratio (3.65), the highest potato yields harvested per GJ input (1013 kg GJ−1) and the lowest cost per tonne of carbon retained ($912 t−1) in comparison with potato in the other rotations. The net energy, energy ratio, and potato yield harvested per GJ input used for potato in P-C(A)-A-A was, respectively, 11%, 10%, and 9.5% higher than 2-yr P-W or P-C rotations. Similarly, cost per tonne of carbon retained for potato in the 2-yr rotations was 8% higher than for potato in the P-C(A)-A-A rotation. The 2-yr rotations performed well in terms of EUE and economics in early cycles of the study but became less efficient as the study progressed due to buildup of plant diseases and decreased yields. The EUE indicators of entire rotations were different; however, the overall results suggested that the longer P-C-W or P-C(A)-A-A rotations are beneficial in that P-C-W provided better economic and EUE outcomes overall while P-C(A)-A-A provided the best potato yield and environmental indicators. These findings suggest that potato growers should include a legume in their crop rotation systems to enhance energy use efficiency while maintaining crop productivity.