Effect of intercropping carrot (Daucus carota L.) with french marigold (Tagetes patula nana L.) and pot marigold (Calendula officinalis L.) on the occurrence of some pests and quality of carrot yield

Intercropping combines different aspects of the interaction between organisms in ecosystems and may be classified as a pro-ecological method of plant cultivation limiting the harmful human interference in the environment, especially the use of chemicals. It also allows high yield, good quality, and economic productivity to be achieved. The aim of the present study, conducted in the years 2003–2004 in Mydlniki near Kraków, was to determine the effect of intercropping carrot Nardin F1 with French marigold (Tagetes patula nana L.) 'Kolombina' and pot marigold (Calendula officinalis L.) 'Promyk' on carrot yield, its quality, and the occurrence of pests. On average in both years of the study, intercropping did not reduce total or marketable carrot yield. In 2003 intercropping contributed to a significant increase in marketable yield compared with yield from sole cropping. In 2004 the dry matter content was higher in the roots of carrots grown with pot marigold. The treatments intercropped with both French and pot marigold were characterized by an increased content of sugars in carrot roots and in 2004 year – of carotenoids. Intercropping had a significant effect on the number of roots damaged by the carrot rust fly, Psila rosae, (the best in this respect was the combination with Tagetes) and by nematodes (the best in this respect was the combination with Calendula). The number of larvae of carrot psyllid, Trioza viridula, was significantly lower in the plots where carrot was intercropped. The study did not find intercropping to have a positive effect on reducing the occurrence of the root aphid.