Evaluation of Ficus nitida Allelopathic Potential and the Most Efficient Application Method for Controlling Weeds Associated with Sunflower Plant

Abstract

Allelopathy is a phenomenon by which plants positively or negatively affect neighboring plants by releasing allelopathic compounds. These allelochemicals are secondary metabolites found in different concentrations in shoots, roots, leaves, flowers, and even pollen grains. Allelochemicals have potential as natural bioherbicides for controlling weeds when applied in the form of extracts or through intercropping, cover cropping, and mulching. The present study was conducted to investigate the allelopathic potential of Ficus nitida leaves against Echinochloa crus-galli L. and Corchorus olitorius L weeds associated with sunflower plant via two application methods (mixing of F. nitida leaf powder with soil and foliar spray of F. nitida leaf powder alcoholic extract). Two pot experiments were carried out for the two summer seasons of 2020 and 2021 in the greenhouse of the National Research Centre (NRC), Dokki, Giza, Egypt. Nine treatments were applied in a completely randomized block design. Three treatments were applied before sowing, namely F. nitida leaf powder was mixed with the soil at rates of 15, 30, and 45 g/pot. The other three treatments of alcoholic leaf powder extract of F. nitida were sprayed twice on both plants and weeds at 10, 20, and 30% (w/v) concentrations. Additionally, three check treatments—healthy (sunflower only), unweeded, and both weeds only—were applied for comparison. The recorded results showed that F. nitida had an allelopathic bioherbicidal effect on both weeds. By increasing the concentration of F. nitida extract, the bioherbicidal potential increased. Moreover, the recorded results showed that foliar spray of alcoholic extract at 30% concentration was the superior application method for controlling weeds. Mixing of F. nitida leaf powder at 45 g/pot ranked second after this superior treatment. A noticeable result is that these two superior treatments improved sunflower growth parameters and yield traits. Quantitative estimation of phenolic compounds and flavonoids demonstrated that the concentration of these allelochemicals is higher in alcoholic extract than in water extract. Moreover, phenolic acid concentrations as detected by high-performance liquid chromatography fractionation are higher in alcoholic extract than in water extract.