Sustainable production of fennel and dill by intercropping

Intercropping is claimed to be one of the most significant cropping techniques in sustainable agriculture, and much research and many reviews attribute to its utilization a number of environmental benefits, from promoting land biodiversity to diversifying agricultural outcome. In this sense, intercropping is thought to be a useful means of minimizing the risks of agricultural production in many environments, including those typical of under-developed or marginal areas. In order to validate this hypothesis in a representative area of the semiarid Mediterranean environment, we evaluated the possibility of growing dill and fennel, both belonging to the family Apiaceae, in temporary intercropping. Our trial was performed in Sicily in 2000-01 and 2001-02; in the first year, fennel and dill were cultivated in a mixture using a substitution scheme, whereas in 2001-02 we evaluated the bio-agronomical and chemical features of fennel alone. The biological efficiency of the intercropping system was evaluated by using the Land Equivalent Ratio and the Competitive Ratio, and an estimate of the interaction effects of both crops was performed by analyzing the major vegetative and yield traits of plants, along with the chemical profile of volatiles of the fruits. Both in grain yield and in biomass yield, the most efficient cropping system was the intercropping ratio with a higher proportion of fennel, in which the competitive ratio values calculated for dill reached 1.90 for grain and 2.59 for biomass. Our results also indicate that the presence of dill exerted a clear stabilizing effect on fennel seed yield of the following year: whereas no difference in fennel seed yield was detected from one year to the following on the previously intercropped plots, in the repeated pure stand a 50% yield reduction was recorded. In the trial environment, the technique showed a good potential to improve the efficiency of resource utilization; further long-term experiments will be necessary in order to demonstrate the application of such a technique to other medicinal and aromatic plant mixtures.