Shelter provided by a bioenergy crop (Miscanthus x giganteus) increases pasture production on dairy farms

Abstract

Growing bio-energy crops to reduce the use of fossil fuels is controversial if it is on land previously used for food production. In this research the ecosystem services value of re-instating shelter on irrigated dairy farms in New Zealand was assessed using the novel approach of planting a bio-energy crop as a shelterbelt. By planting a shelterbelt of Miscanthus x giganteus (Mxg), a tall Japanese grass that grows 4 m high, in the northerly corner of six fields, we measured the response of a ryegrass/white clover sward to shelter from drying northerly winds. Pasture height readings were collected using a C-Dax pasture meter from fields rotationally grazed every 20 -25 days. Differences in height between sheltered and open field were measured immediately pre-grazing over a two year period as the shelter developed. Mxg has rapid growth and shelter height in year two reached 2.8 m. Shading effect was minimal due to the shelter having a north-westerly and north-easterly aspect. In the second summer taller areas of pasture height were detected in sheltered areas. A likely mechanism for increased pasture production is higher rates of stomatal conductance in plants sheltered from drying northerly winds. We confirmed this as stomatal conductance of clover leaves was significantly higher in sheltered plants during periods when there was a persistent northerly wind blowing. By having bio-energy crops as a co-product of the existing farming system, in this case dairy production, the problem of replacing land used for food production with bio-energy cropping is overcome.