1365-2664/asset/olbannerleft.gif?v=1&s=8b608cc23970983efcf0bf9354181123ee4feba9)
1365-2664/asset/olbannerright.gif?v=1&s=01405a21098d64198820bdbe2e30807b513e69f2)
You have full text access to this OnlineOpen article
Comparing biological productivity in cropping systems: a competition approach
Article first published online: 13 JUN 2002
DOI: 10.1046/j.1365-2664.2002.00732.x
1365-2664/asset/cover.gif?v=1&s=4510998017eb804e0bc24f63389b75ebb87101b7 "Journal of Applied Ecology")
Additional Information
How to Cite
Park, S. E., Benjamin, L. R. and Watkinson, A. R. (2002), Comparing biological productivity in cropping systems: a competition approach. Journal of Applied Ecology, 39: 416–426. doi: 10.1046/j.1365-2664.2002.00732.x
Publication History
- Issue published online: 13 JUN 2002
- Article first published online: 13 JUN 2002
- Received 5 February 2001; final copy received 14 March 2002
- Abstract
- Article
- References
- Cited By
Keywords:
- additive series;
- competition indices;
- intercropping;
- LER;
- methodology;
- regression model;
- response surface
Summary
- 1Intercropping, the practice of growing two or more crops in close association, is attracting increasing interest in developed countries, primarily due to claims that it can provide increased yields in an environmentally sustainable manner.
- 2The land equivalent ratio (LER) is frequently used to attest the claim that intercropping produces a greater total biological productivity per unit area of land than monocropping. However, similar to other indices, the value of the LER is dependent on the relative densities of the two crops and fails to provide an indication of the optimal crop density combination required to produce maximum biological productivity. We used an alternative methodology to predict the optimum density for planting two crops in a mixed stand.
- 3Maize and beans were grown both in monoculture and in intercropped stands at a range of densities. Monocrop stands of both maize and bean displayed an asymptotic yield–density relationship. When a second crop was introduced into the stand there was no effect on the yield of maize, but there was a large reduction in the yield of bean.
- 4The LER did not demonstrate an unequivocal advantage to intercropping. Less than a third of the LER values, over the range of densities considered, were greater than one, although none was significantly different to unity. The highest values were obtained from those plots sown with a high density of maize.
- 5An alternative method of analysing the biological productivity of an intercrop system is proposed. This approach requires a combination of (i) an additive experimental design, (ii) the use of a regression model to measure the competitive effect of two species, and (iii) the presentation of the net competitive effect on individual and total yields using a response surface. The reciprocal model was used to dissociate and quantify intra- and interspecific competition, estimate a competitive equivalence coefficient and predict the individual yields of the full complement of density combinations included in the maize and bean experiment.
- 6The model explained up to 90% of the variation in the observed yields of maize and bean in an intercrop. An inspection of the response surface for the LER indicated that the minimum density combination required to produce the maximum yield advantage within the density range considered comprised maize being planted at a density of 11 plants m−2 and bean being planted at a density of 39 plants m−2. Although this combination would provide the maximum biological productivity, it is considered unlikely to provide the maximum gross economic margin.
- 7The above methodology may provide a useful tool for managing competition, either between two or more crops in an intercrop, or within a crop–weed interaction.