Producing compost, mulch, or organic fertilizers are suitable methods for utilizing pruning residues, which are effective in reducing environmental problems caused by the accumulation of pruning residues. Wood is a part of pruning residues that, due to decomposition and release of biochemical compounds, have allelopathic effects. Since limited reports have been published regarding the allelopathic effects of wood from trees and ornamental shrubs, in the current experiment, the biochemical compounds and allelopathic effects of wood from eight species of ornamental trees and shrubs were investigated. Pruned wood of Bougainvillea, Albizia lebbeck, Cordia myxa, Conocarpus, Dodonaea viscosa, Nerium oleander, Leucaena leucocephala, and Callistemon citrinus was soaked in water for 24 and 48 hours to prepare water elutes. The analysis of biochemical compounds showed significant differences in the phenolic compounds, tannin index (A280), flavonoids, non-structural soluble carbohydrates, total suspended solids, and electrical conductivity in the water elutes of wood samples, but the pH of the water elutes did not show significant differences. The duration of soaking wood in water (24 or 48 hours) affected the electrical conductivity and biochemical compounds in the water elutes. The Leucaena leucocephala extract had the highest tannin index (67.10 A280/ml) and soluble carbohydrates (81.1 mg/g), while the highest total phenol content was in Leucaena leucocephala and Conocarpus (1.107 and 55.114 mg/g, respectively). The highest electrical conductivity was in the Cordia myxa extract (87.2 ds/m), and the highest total suspended solids were in the Callistemon citrinus extract (0.61%). The highest level of flavonoids was found in Bougainvillea, Nerium oleander, Leucaena leucocephala, and Cordia myxa. The allelopathic effects of the water elute prepared from wood samples resulted in a reduction in germination percentage and germination index of cucumber seeds, as well as a decrease in the root and shoot length of cucumber seedlings, indicating the presence of allelopathic effects of biochemical compounds present in the wood of trees and ornamental shrubs. These results can be useful in selecting these species for designing landscape plantings to their allelopathic effects of residues on neighboring grasses and ornamental plants, or in managing pruning residues and producing compost or mulch from the wood of ornamental trees and shrubs. |
