Competitive interactions in Ginkgo and crop species mixed agroforestry systems in Jiangsu, China

Abstract

Intercropping Ginkgo and crop species in southern China is receiving increasing attention because it offers potential advantages for resource utilization, higher economic income to farmers and increased sustainability in crop production, We carried out a 2-year field intercropping system composed of Ginkgo with wheat, broad bean, and rapeseed, respectively, to determine the competitive interactions between the different species, and productivity and the economic yield of each intercropping system. The density of Ginkgo and crop species was varied systematically in a two-way density matrix composed of three monoculture densities and nine intercropping of all possible pairwise combinations of monoculture densities. Intercropping systems were assessed on the basis of several intercropping indices such as land equivalent ratio, relative crowding coefficient, relative competition intensity and vector competition analysis. The results showed that the combined biomass production of the component crop species was significantly greater in the Ginkgo/crop mixtures than in monocultures crops (Ginkgo, broad bean, wheat, and rapeseed). Ginkgo: rapeseed ratio 24:12, Ginkgo: bread bean ratio 24:5, and Ginkgo: wheat ratio 24:200 had the best total biomass production. Ginkgo: rapeseed (and broad bean) ratio 24:5 and Ginkgo: wheat ratio 24:200 in respective Ginkgo/crop mixtures had the maximum economic yield. Vector competition analysis showed that Ginkgo/rapeseed mixture exhibited an antagonistic interaction type and therefore is not suitable for intercropping. Ginkgo/broad bean mixture demonstrated the most beneficial effects among the three intercropping systems.