Influence of herbicides under biofertilizer application on fennel (Foeniculum vulgare) yield and quality with special reference to herbicide residues

Abstract

Abstract Background Weed occurrence and fertilization are considered two of the most factors influencing fennel yield. A two season’s field study was undertaken to investigate the response of fennel crop to two different herbicides under the application of biofertilizers. The two herbicides are pendimethalin (at reduced rate), fluazifop-p butyl and a combination of sequential application of both of them. The biofertilizers were used in 3 rates of 1:1:1, 2:1:1 and 1:1:2 (v/v/v) from atmospheric nitrogen-fixating, phosphorous-dissolving and potassium-solubilizing bacterial strains. Results The results indicated that under all rates of the biofertilizers, the two herbicides applied individually caused significant reduction in growth parameters of the fennel plant estimated. Hand weeding (untreated check) increased fruit yield by 63% and oil yield by 78% compared to unweeded control, while sequential application of pendimethalin + fluazifop increased fruit yield by 45% and oil yield by 83% under biofertilizers at the rate of 2:1:1. Slight decrease in protein content using pendimethalin + fluazifop (12.94, and 12.96%) compared to 13.56% for hand weeding was observed. However, fluazifop alone showed no significant differences (13.63 and 13.13%) during both seasons under the biofertilizer rate of 2:1:1. No detectable residues of pendimethalin and fluazifop applied alone or sequentially were found in the analyzed dry seeds. Conclusion The obtained results concluded that using proper level of biofertilizer combined with herbicides would increase the seed yield and oil content of fennel. Nevertheless, further investigation is needed to search for safer and effective weed control methods in medicinal plants.