Evaluation of faba bean (Vicia faba L.) and fennel (Foeniculum vulgare Mill.) intercropping advantage under row-replacement and additive series

Intercropping is an valuable cultivation system in all of the world due to the better use of resources and increase the quantitative and qualitative yield of plants. It also can be considered as one of the approaches to improve yield and stability in production. Recently, medicinal plants intercropped by legumes has been noticed. In order to evaluate faba bean and fennel intercropping advantage under row-replacement and additive series, an experiment was conducted in 2019.

This experiment was carried out at the research farm of the Azarbaijan Shahid Madani University, Tabriz, Iran, in a randomized complete block design with three replications. Treatments including 6:0, 4:2, 3:3, 2:4, and 0:6 of faba bean: fennel rows under replacement series and 6:3, 6:2, 2:6, and 3:6 of faba bean: fennel rows under additive series. After reaching a constant weight of fennel fruits, yiel and its components (number of umbels and umbellets and fruits per umbellet, 1000-seed weight, biological yield, seed yield, and harvest index) were measured in fennel plants. The essential oil content in fennel fruits was also measured using a Clevenger apparatus. Faba bean biomass was measured after harvesting plants in the flowering growth stage. Finally, the relative crowding coefficient, land equivalent ratio, actual yield loss or gain and intercropping advantage of faba bean: fennel mixed cultivation were calculated in the row-replacement and additive series.

The results showed that intercropping of faba bean and fennel had a significant effect on all studied traits. The highest number of umbels per plant was obtained from sole cropping (12.10). Also, the highest number of umbellets/umbel was related to intercropping of two rows of faba bean: four rows of fennel and three rows of faba bean: three rows of fennel by 22.05 and 19.62, respectively. The highest 1000-seed weight was obtained from sole cropping of fennel (5.62 g) and replacement intercroppings, especially from two rows of faba bean: four rows of fennel (5.56 g). The highest biological yield (1503.47 kg/ha) and seed yield (617.73 kg/ha) were obtained from the sole cropping of fennel. The maximum harvest index was related to the intercropping of three rows of faba bean: three rows of fennel, which shows that such a mixture ratio leads to the highest seed yield rather than biological yield produced. The highest fennel essential oil content was obtained from additive series. The highest faba bean biomass was found in the sole cropping (1933.02 kg/ha) and the lowest in treatments in which two rows of faba bean has been planted. Two rows of faba bean + six rows of fennel had the highest (3.96) relative crowding coefficient. The land equivalent ratio in all row-replacement and additive series was more than one or close to one, which indicates the usefulness of faba bean and fennel intercropping. The highest actual yield (0.07) and intercropping advantage indexes (0.17) were related to three rows of faba bean + three rows of fennel. Also, the lowest actual yield was related to additive series, especially treatments in which fennel had a higher mixture ratio than faba bean.

Based on the results obtained in this study, environmental resources including light, water, and nutrients have been used optimally in the three faba bean rows + three fennel rows and there was no effective competition to achieve them in this row-replacement series. In other words, ecological niche separation in this intercropping system has been done favorably, and subsequently the actual yield index increased. Therefore, the mixture ratio by 50:50 in the row-replacement series is recommended to achieve the highest benefit in semi-arid conditions where this experiment was conducted.