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RESEARCH ARTICLE
Contents Vol 45(11)

The economics of managing tree–crop competition in windbreak and alley systems

R. Sudmeyer A C and F. Flugge B
+ Author Affiliations
- Author Affiliations

A Department of Agriculture Western Australia, PMB 50, Esperance, WA 6450, Australia.

B CRC for Plant-based Management of Dryland Salinity, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.

C Corresponding author. Email: rsudmeyer@agric.wa.gov.au

Australian Journal of Experimental Agriculture 45(11) 1403-1414 https://doi.org/10.1071/EA04155
Submitted: 30 July 2004  Accepted: 3 December 2004   Published: 16 December 2005

Abstract

Re-introducing trees and shrubs into agricultural landscapes as agroforestry systems establishes a tension between long-term objectives, such as increasing shelter, water use, nature conservation and harvesting tree products, and the short-term objective of maximising crop and pasture profitability. This paper describes the growth of crops, pastures and trees at the tree–crop interface in agroforestry systems and the economic returns from alley farming and windbreak systems using various tree–crop competition management strategies in the Esperance region of Western Australia.

Severing lateral tree roots (root-pruning), harvesting mallees and allowing them to coppice, or thinning trees for sawlog regimes increased the yield of crops and pastures in the competition zone. In some instances, these increases were significant: root-pruning increased the annual return from crops grown in the competition zone of Pinus radiata by up to $548/km of the tree line at 1 site. Conversely, root-pruning reduced tree growth by 14–43% across all sites. Therefore, where trees provide benefits, such as shelter from damaging winds, the benefits of reduced tree–crop competition may not offset the consequent reduction in rate of tree growth. For mallee–crop alley systems on agriculturally productive soils, mallee growth rates must be high enough to compensate for crop losses in the competition zone. On less agriculturally productive soils, block-planting mallees may be more profitable than alley systems or crops without competition (sole-crops).

This research has shown that competition management strategies can be used to manipulate the relative productivity of trees, crops and pasture at the tree–agriculture interface. The use of these strategies will depend on the relative economic value of tree and crop products and the value placed on other tree benefits, such as shelter and reduced groundwater recharge.

Additional keywords: coppicing, oil mallees, root-pruning, tree–crop interactions.


Acknowledgments

The authors would like to thank the Grains Research and Development Corporation for funding this research, Rob Johnstone, Ken deGrussa, the Lewis family, Ewin Stewart and Brendan Freeman for making trial sites available on their farms. Micheal O’Connell is thanked for his excellent advice and assistance with the economic analysis. We also thank Shirley Milne and Dimphia McGuigan, for their technical assistance, the staff of EDRS; particularly Colin Boyd and Noel Rennie for sowing and harvesting trial crops and David Hall, Don Cooper and Alan Herbert for their comments on the manuscript.


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