Cotton-basil intercropping: effects on pests, yields and economical parameters in an organic field in Fayoum, Egypt

Summary

In many countries, cotton is traditionally intercropped with other plants in order to increase yields and to control pests. We tested the effects of intercropping cotton (Gossypium barbadense L.) and basil (Ocimum basilicum L.) during one field season on pest infestation, yields, and economical parameters in the Governorate of Fayoum, Egypt. Basil, which is known for its repellent effect on various insect pests, was mixed with cotton in three different intercropping rates (no, medium and high basil area fraction) and two row distances (60 and 90 cm) using a substitutive design with four replicates. Compared with the non-intercropped plots, cotton-basil intercropping significantly reduced total pest infestation and led to a 50% reduced abundance of the pink bollworm (Pectinophora gossypiella Saund.). Basil affected also the movement and abundance of the beneficial epigeic fauna (e.g., Coleoptera, Araneae, Gryllidae, Salientia). Abundance of the epigeic fauna was 30% higher adjacent to basil strips than in the centre of the cotton plots. Since neither basil intercropping nor different row distances affected microclimatic parameters in the experimental plots, we assume that both a basil-induced repellence against pest insects and a stimulation of beneficial epigeic fauna might be responsible for the lower pest infestation observed in intercropped plots. No correlation between pest infestation and cotton yields could be detected. Despite an up to 33% reduced area of cultivated cotton in the intercropped plots, seed cotton yield was not affected by intercropping. The wider row distance significantly reduced the number of cotton bolls per area, but increased boll mass and cotton yield per plant, thus resulting in similar seed cotton yield per hectare than at narrow row distance. The wider row distance also increased the abundance of spiders and crickets but did not affect weed abundance. With the exception of the treatment ‘intercropping with low basil fraction and wide row distance’, higher total revenues and gross margins were determined with intercropping than with cotton monocropping. These results demonstrate the high potential of intercropping cotton with basil in order to achieve a reduced pest infestation while concurrently increasing gross margins for the farmers.