Smart orchard design improves crop pollination

1. More sustainable and environmentally-friendly agricultural practices, including ecological intensification, are needed to reduce biodiversity loss and environmental degradation.

2. We evaluated the potential of ecological intensification through the enhancement of pollination services in an intensively managed and insect-pollinated crop, Macadamia integrifolia. We compared the effects and importance of agronomic practices that include agronomic input (i.e. irrigation and managed honeybees), orchard design requiring no external inputs (i.e. spatial orchard structure) and landscape factors in ten South African macadamia orchards.

3. In comparison to experimental pollinator exclusion, insect pollination increased the initial and final nut set by 304% and 23%, respectively. However, nut set was pollination limited as hand pollination further improved nut set.

4. Flower visitation rates increased with the cover of semi-natural habitats in the surrounding landscape (1km radius). This effect was outperforming the effect of the number of managed honeybee colonies, as agronomic practice.

5. Initial nut set increased with orchard design and flower visitation rates. Perpendicular orientation of the planted macadamia rows towards the semi-natural habitats increased initial nut set more than threefold compared to parallel row orientation. The initial nut set was 80% higher at the edge to semi-natural habitats than in the orchard centre. In contrast, agronomic practices, such as irrigation, did not increase initial nut set.

6. Final nut set depended on the preconditions of the initial nut set, additionally, high altitudes and the position in the centre of the orchard had positive effects.

7. Synthesis and applications. Pollination services were prerequisites for high yields in macadamia and could be improved without further agronomic input. Especially, the orchard design, i.e. spatial arrangement of tree rows and semi-natural habitats at local and landscape scales, was more important to boost insect pollination and the initial development of macadamia nuts than agronomic practices, such as high levels of irrigation. Considering the urgency to reduce the environmental impacts of agricultural production, we highlight the high potential of ecological intensification by a smart orchard design and the restoration and conservation of semi-natural habitats in the orchards and their surrounding landscape.