Energy and labour efficiency for three pairs of conventional and alternative mixed cropping (pasture-arable) farms in Canterbury, New Zealand

Abstract

The major energy inputs and outputs and labour inputs for each year of the rotation from three pairs of farms were measured. One of each pair was under conventional agriculture and the other under an alternative (organic or biodynamic) system. In the study locality, a mixed cropping system of farming is practised in which grazed grass/white clover pastures and/or grass and white clover seed crops are grown in rotation with arable crops. The energy input for sheep meat production was appreciably lower than that normally observed in intensive production in the Northern Hemisphere. This is principally because livestock graze outside throughout the year on forage that has been supplied with little energy-intensive fertiliser-N. Energy input was lower under alternative than conventional sheep meat production at two of the sites and similar at the third. For cereal crops (wheat and barley), energy inputs and grain yields were greater under conventional than alternative management owing mainly to fertiliser-N inputs under conventional management. These accounted for 23–63% of total energy inputs. Sown seeds and field operations contributed substantially to energy inputs under both farming systems. Fertiliser-N inputs under conventional management were low compared with those used in Europe and North America since cereal crops relied partially on N 2 fixed biologically during pasture and seed crop phases of the rotations. As a result, the energy efficiency ratio (energy output over input) was considerably higher than that commonly observed in intensive agriculture in the Northern Hemisphere. The energy efficiency ratio for cereal production was higher under alternative management at two sites but higher under conventional management at another. Over the entire rotation, the mean annual energy input was considerably lower under alternative than conventional management. Labour input was higher for production of individual cereal crops under alternative management but mean annual labour inputs over the whole rotations were slightly lower under alternative than conventional management.