Legume groundcovers have mixed effects on growth and yield of Macadamia integrifolia

The effects of Lotus pedunculatus (cv. Grasslands Maku) and Arachis pintoi (cv. Amarillo) groundcovers on growth and yield of 1-, 4- and 14-year-old macadamia orchards were investigated over 5 years near Lismore in northern New South Wales. Bare control plots were used at all sites, along with an unmown groundcover in the oldest orchard. Vegetative growth was assessed in terms of shoot extension, trunk diameter and canopy volume. The groundcovers had the greatest effect on vegetative growth of the trees when they were established into an existing sward, followed by the 4-year-old trees, and then the 14-year-old trees. Yields were collected from the 4- and 14-year-old trees and were generally similar under bare soil or groundcovers, with smaller or similar canopy volumes. Nut quality was not consistently affected by the groundcovers, whereas nut-drop was delayed. Acceptable yields can be obtained in macadamias with groundcovers, with potential benefits in terms of soil structure, fertility and stability. Mown and unmown plots have similar productivity.