The relationship between orchard crowding, light interception, and productivity in macadamia.
Orchard crowding in the macadamia industry is common and there has been concern that it reduces yield and quality. To investigate this, we monitored yield, nut quality, tree volume and light interception in macadamia (Macadamia integrifolia) cv. Kau (HAES 344) orchards in New South Wales and Queensland, Australia, that represented a range in crowding. The predicted rate of change in yield/ha with time remained positive, i.e. yield increased over time, for orchards with crowding levels up to a tree volume of 43 500 metre3/ha and light interception of 94%. There was a trend for the rate of yield change to decrease with increasing tree volume/ha. For orchards with tree volume >43 500 metre3/ha the rate was negative, indicating a slight decline in yield over time. There was no evidence of a detrimental effect of orchard crowding on percentage kernel recovery, unsound kernel, or grade 1 kernel. It appears that macadamia, unlike many other orchard crops, can maintain yield and quality up to a high level of orchard crowding. The implication of this is that timing of canopy management and optimum canopy dimensions will be dictated by management requirements for machinery access and effective spray coverage before yield decline becomes an issue.