The kale crop was sown into a cultivated Pukematu silt loam soil, classified as a mottled Fragic Pallic soil (Carrick et al., 2000). Prior to the sowing of a new crop each year, the cultivated soil layer was replaced with topsoil (0–150 mm depth) taken from old (>15 years) pasture to ensure that each year of measurement reflected the effects of recent cultivation of old pasture.