There is growing interest in the potential for improving nonrenewable energy use efficiency of traditional agricultural production activities in the Canadian prairies. This study, which was conducted on three soil textures in the Brown soil zone of southwestern Saskatchewan, examined the energy performance of conventional tillage (CT), minimum tillage (MT), and no-tillage (NT) management practices for spring wheat grown in fallow-wheat (F–W) and continuous wheat (Cont W) rotations over a 12-yr period (1982–1993). Metabolizable energy output increased with cropping intensity on a silt loam at Swift Current and on a clay at Stewart Valley (average of 16 751 MJ ha–1 for F–W and 24 110 MJ ha−1 for Cont W), but not on a sandy loam at Cantuar (average 14 828 MJ ha−1) where soil water-holding capacity was limited. Further, because grain yield was rarely significantly influenced by tillage method, the latter had little influence on the overall output of metabolizable energy. Total input of nonrenewable energy per unit of rotation also increased with cropping intensity (average 2585 MJ ha−1 for F–W and 5274 MJ ha−1 for Cont W). This was primarily because of the higher rates of N fertilizer that were required with stubble cropping. We found little or no net energy savings with NT management; the F–W (MT) system tended to have the lowest overall nonrenewable energy requirement at all test sites. Although the use of conservation tillage practices provided significant energy savings in fuel and machinery, particularly for F–W systems, these were largely offset by increases in the energy input for herbicides, and higher rates of N fertilizer that were required for NT managed areas. Consequently, net energy produced (energy output minus energy input) had similar patterns as metabolizable energy output. In contrast, when efficiency was expressed as ratios of energy output to energy input, or quantity of wheat produced per unit of energy input, the values were higher for F–W (average 6.2 and 456 kg GJ−1, respectively) than for Cont W systems (average 3.8 and 278 kg GJ−1, respectively). These measures of energy efficiency also tended to be higher for CT and MT than for NT management on the medium- and fine-textured soils, but on the coarse-textured soil, tillage had no influence on the energy efficiency of the cropping systems. We concluded that the potential for achieving energy savings by adopting conservation tillage management for monoculture wheat rotations is low in this semiarid region. This was because of the lack of consistent yield advantages with MT and NT, and due to the few tillage operations that are traditionally used to control weeds on summerfllow areas and to prepare the seedbed with CT management. Key words: Wheat, minimum tillage, no-tillage, nonrenewable energy, energy output/input, energy efficiency
Minimal Monitoring of Improvements in Energy Performance after Envelope Renovation in Subsidized Single Family Housing in Madrid
