Allelopathic Effects of Chinaberry, Silk Tree and Iranian Pine on some Growth Traits of Lolium prene and Festuca arundinaceae

As the population grows and cities expand, the demand for more green spaces has also increased. Grass is widely recognized as one of the most important ground covers in the world. However, the development of green spaces is hindered by a severe shortage of water resources and challenges associated with managing and maintaining grass. The composition of trees and plants may cause to inhibitory or stimulation effects on crops, called allopathic effects. Therefore, understanding the allopathic effects is important to determine appropriate methods of cultivation and product management to prevent interference of allopathic substances in the growth and production of products.
 This study was performed in two separate experiments as a factorial based on completely randomized design at Ferdowsi University of Mashhad. In the first experiment, the effect of three different levels of plant residue powder (zero, 0.46 and 1 g) of three types of trees (Pine, Silk and Chinaberry) on germination and growth of Lolium prenne and Festuca arundinaceae grasses with four replications in the greenhouse was investigated.  The second experiment, the effect of 5 ml of aqueous extract prepared from plant residues of the mentioned trees on germination and growth of the mentioned grasses in three replications in the laboratory was investigated. At the end of both experiments, some of morophology traits (weight, length, germination index) were measured. Minitab software was used to analyze the data obtained from both experiments.
 According to the analysis of variance table of the first experiment, the results show that the simple effect of grass treatment on plant and root length, fresh weight, germination percentage and rate are significantly different. In the simple effect of treatment the quantity of plant residues, all traits have a significant difference. Also, in the simple effect of treatment of plant residue kind, plant length, root length, fresh and dry weight, germination percentage and rate were significantly different. Interaction grass and the quantity of plant residues treatment and the interaction of grass and kind of plant residues treatment, all measured traits had a significant difference. The interaction triple treatments plant length, root length, dry weight, germination percentage and rate differences were observed. Therefore, in the interaction triple treatments, the most and least plant lengths were observed related to the treatment of Lolium grass with 0.46 gr of Pine residue powder and the treatment of Festuca with 1 gr of Chinaberry residue powder. Also, the most and least root lengths were related to Lollium grass with 0.46 gr of Pine plant residue powder and Festuca grass with 1 gr of Pine plant residue powder. In the triple of dry weight the most amount was related to Festuca with 1 gr of Chinaberry residue powder and the least was related to Lolium control. The most and least germination percentages belonged to the control Festuca and lollium with 0.46 gr of pine plant residue powder respectively, and in the trait of germination rate, the most amount belonged to the control Festuca and the least to the control lollium has been observed. The results of the second experiment demonstrated a significant difference in all measured traits including grass treatment, plant length, fresh and dry weight, germination percentage and rate, and simple effect of plant extract. Moreover, the interaction of grass treatment and plant residue extract showed significant differences in root length, plant length, fresh weight, dry weight, and germination rate and percentage. Comparison of the mean interaction of grass treatment and type of plant residues revealed that the control Festuca had the highest plant length, while Lolium with Silk residue extract had the lowest. The longest and shortest root lengths were observed in control Lolium and Lolium with Silk residues, respectively. The highest and lowest fresh weight were recorded in Lolium control and Lolium grass along with Silk residue extract, respectively. For the dry weight trait, the highest amount was related to the treatment of Lolium grass with pine residue extract, while the lowest dry weight was observed in Festuca grass and Lolium grass with Silk residue extract. In terms of the germination percentage trait, control Festuca and Festuca with pine residue extract had the highest germination percentage, while Lolium with Chinaberry residue extract and Lolium with Silk residue extract had the lowest.  The most and least germination rates belonged to Festuca control and Lolium with Chinaberry residue extract. From these discussions, it can be concluded that the allelchemicals in the powder extract of plant residues have had a significant effect on the yield of these two grasses and have reduced growth and germination. Decreased germination due to allelopathic stress can be due to different abnormalities in metabolic activity, seed saturation potential, death of some dividing cells and embryonic abnormalities.
 Based on the results of both experiments, it can be concluded that Chinaberry and Silk trees have a stronger allelopathic effect compared to Pine. Additionally, the performance of both grasses in response to residues and extracts containing allelochemicals was slightly different. For instance, in the second experiment, the impact of Chinaberry extract reduced plant length by 28%, root length by 89%, dry weight by 16%, germination percentage by 75%, and germination rate by 85% compared to the Festuca control treatment. Similarly, the effect of Chinaberry extract on Lolium grass resulted in a 96% reduction in plant growth, 97% reduction in root length, 98% reduction in wet weight, 50% reduction in dry weight, 89% reduction in germination percentage, and 89% reduction in germination rate compared to the Lollium control treatment.