Allelopathic activity of the leaf powder of Ficus nitida on the growth and yield of Vicia faba and associated weeds

BackgroundFaba bean weeds are considered as serious pests that lead to pronounced damages to its agricultural production since they consume water and nutrients from the soil, reducing not only the yield but also the quality of the crops. So, the aim of this investigation is to control the weeds associated with faba bean plants.Materials/methodsTwo pot experiments were carried out during two successive winter seasons of 2016/2017 and 2017/2018 in the greenhouse of the National Research Centre, Dokki, Giza, Egypt. Treatments were applied by incorporating the dry leaf powder of Ficus nitida to the soil surface of pots at the rate of (0, 10, 20, 30, 40, 50, and 60 g/kg soil).ResultsAll concentrations used pronouncedly decreased the fresh and dry weight of both Phalaris minor and Malva parviflora. On the other hand, Vicia faba growth as well as its yield and yield components were increased with most concentrations used as compared to their mixed controls. Treatments of 20, 30, and 40 g/kg soil, from F. nitida leaf powder, respectively recorded the highest increases in the most growth characters of V. faba with both weeds (P. minor and M. parviflora) at the two growth ages when compared to the healthy control. Also, the best results in all V. faba yield components were recorded with 20 g/kg soil of F. nitida treatment.ConclusionThe results of the present study indicate the possibility of using the allelopathic activity of the leaf powder of Ficus nitida as a selective bioherbicide for controlling annual weeds accompanied Vicia faba plants.


Background
Allelopathy has beneficial or harmful effects on plants due to release of allelochemicals which are secondary metabolites, which is present in all plant tissues including leaves, stems, flowers, roots, and seeds (Manikandan and Jayakumar 2011;Mohsin et al. 2016). Allelochemicals are now being used as biopesticides, bioherbicides, and also as growth promoters. Therefore, it is another emerging area of research since most of the chemicals as biopesticides or bioherbicides are known to be specific variety of pests and weeds. The use of allelochemicals as secondary metabolites from plants for this purpose would be environmentally friendly, since natural chemicals are renewable and easily degradable (Manikandan and Jayakumar 2011).
Allelopathy is simply a natural process of inhibition or stimulation of plants by the action of allelochemicals which are produced and released to the environment by different plants (Zeng et al. 2008;Majeed et al. 2017). Moreover, the inhibition or stimulation efficiency of these allelochemicals depends on their type, concentration, and the plants which respond to these allelochemicals (Dawood et al. 2012;Majeed et al. 2012;Muhammad and Majeed 2014;El-Masry et al. 2015;Ahmed et al. 2018;El-Rokiek et al. 2018;Messiha et al. 2018).
Vicia faba (faba bean) is one of the most important legumes in the world especially in developing countries. It is a leading source of food protein. It is also a rich source of dietary fiber, minerals, and some vitamins (Gepts et al. 2008).
On the other hand, weeds are considered a serious pest that leads to pronounced damage to agricultural production because it consumes nutrients from the soil. Thus, reduces the yield of the crops, in addition it reduces the quality and quantity of the crop (Siddiqui et al. 2009;Messiha et al. 2018).
The aim of the present investigation is to assess the allelopathic potentiality of the leaves of Ficus nitida (a widely and common tree in Egypt) on the growth of Vicia faba associated by two annual weeds Phalaris minor and Malva parviflora.

Materials and methods
Two pot experiments were carried out during two successive winter seasons of 2016/2017 and 2017/ 2018 in the greenhouse of the National Research Centre, Dokki, Giza, Egypt, to study the possibility of controlling two weeds, i.e., Phalaris minor and Malva parviflora growing with Vicia faba by using the dry leaf powder of Ficus nitida. Vicia faba seeds (var. Giza 843) were obtained from Agricultural Research Centre, Giza, Egypt. Dry leaves of Ficus nitida was grinded to fine powder and was immediately incorporated to the soil surface of the pots before sowing at the rate of 0, 10, 20, 30, 40, 50, and 60 g/ kg soil. The pots, 30 cm in diameter and 30 cm in height, contained equal amounts of sieved soil (2: 1 v/v clay and sand). Seven seeds of V. faba were sown on 20th and 19th of November in the first and second seasons, respectively. The pots were infested with a constant weight from each weed, i.e., P. minor and M. parviflora. The seeds of both weeds were sown simultaneously and mixed thoroughly at a depth 2 cm in the soil. The experiment consisted of eight treatments for each weed including two untreated controls, healthy plant (weed-free faba bean), faba bean with P. minor or M. parviflora (unweeded treatment). The other six treatments were leaf powder of Ficus nitida at concentrations 10, 20, 30, 40, 50, and 60 g/kg soil. All pots were distributed in a complete randomized design. Faba bean seedlings were thinned 2 weeks after sowing so that three homogeneous seedlings were left per pot. Three replicates were collected from each treatment at 30 and 60 days after sowing and at harvest. The normal cultural practices of growing V. faba plants were followed especially fertilization and irrigation.

Weed characters studied
Three replicates were collected from each treatment at 30 and 60 days after sowing (DAS), fresh and dry weight of both P. minor and M. parviflora (g/pot) were recorded.

Vicia faba characters studied Plant growth
Samples from V. faba plants were collected from each treatment at 30 and 60 (DAS) to determine plant height (cm), number of leaves/plant, number of branches/plant, as well as fresh and dry weight of plant (g).

Yield and yield components
On April 27 and 25 in the first and second season, respectively, samples from V. faba plants were taken at harvest from each treatment to determine the number of pods/plant, weight of pods/plant (g), length of pod (cm), number of seeds/ pod, weight of seeds/plant (g), weight of seeds/10 pods (g), and weight of 100 seeds (g).

Chemical analysis
Determination of total phenolic contents and total flavonoids in the leaf powder of F. nitida Total phenol and total flavonoids were determined in the leaf powder of F. nitida according to Srisawat et al. (2010).

Statistical analysis
Data of the two seasons were subjected to analysis of variance (ANOVA) according to Gomez and Gomez (1984), using CoStat software program. The differences among means were compared using LSD test at 0.05 probability level.

Weed growth characters
The results in Tables 1 and 2 showed that all concentrations used from the leaf powder of Ficus nitida (10 to 60 g/kg soil) significantly decreased fresh and dry weight of both weeds, i.e., Phalaris minor and Malva parviflora at both growth ages (30 and 60 DAS), except the lowest concentration (10 g/ kg soil) with P. minor at 30 DAS, as compared to the mixed control. The rate of reduction in weed growth of both P. minor and M. parviflora depends on the concentration used. The maximum reduction in the fresh and dry weight of both weeds at both growth ages was recorded with the highest concentration (60 g/kg soil) of F. nitida leaf powder, that reached to 69.6 and 69.8% for P. minor and 79.5 and 80.3% for M. parviflora respectively, as compared to their corresponding control at the second growth age (60 DAS).

Vicia faba growth
The results recorded in Tables 3 and 4 illustrated that most V. faba growth characters, represented by plant height (cm), number of leaves/plant, number of branches/plant, as well as fresh and dry weight/plant (g), were significantly increased with all concentrations of F. nitida leaf powder (10 to 60 g/kg soil) as compared to their mixed control with both weeds, P. minor and M. parviflora at both growth ages (30 and 60 DAS). Treatments of 20, 30, and 40 g/kg soil, from F. nitida leaf powder, respectively recorded the highest increases in the most growth characters of V. faba with both weeds (P. minor and M. parviflora) at the two growth ages when compared to the healthy control. It is worthy to mention that the best results in most growth characters at the two growth ages with both weeds was recorded with treatment (20 g/kg soil) from F. nitida leaf powder as compared with healthy control. At 60 DAS, the increases in the dry weight of V. faba plant due to this treatment reached to 12.27 and 25.38%, respectively over the healthy control with P. minor and M. parviflora weeds.

Vicia faba yield and yield components
The results of yield and yield components, i.e., number of pods/plant, weight of pods/plant (g), length of pod (cm), number of seeds/pod, weight of seeds/ plant (g), weight of seeds/10 pods (g), and weight of 100 seeds (g) recorded in Tables 5 and 6, showed  that all applied treatments used of F. nitida leaf powder (from10 to 60 g/kg soil) significantly increased all yield parameters of V. faba, except the highest concentration (60 g/kg soil), as compared to their mixed control with both weeds, P. minor and M. parviflora. The best results in all V. faba yield components were recorded with 20 g/kg soil of F. nitida treatment. Not only this treatment alleviated the harmful effect of both weeds (P. minor and M. parviflora) but also significantly increased all plant yield parameters over the corresponding healthy control. The maximum increases in the weight of seeds/ plant (g) and weight of seeds/10 pods (g) of V. faba associated with P. minor weed reached to 41.28 and 36.0%, respectively, while with M. parviflora weed reached to 48.16 and 50.40%, respectively over the corresponding healthy control. Treatments with 30 and 40 g/kg soil from F. nitida leaf powder also achieved good results with all V. faba yield components, associated with both weeds, equal or exceed than the corresponding healthy control in some yield components. Therefore, it could be concluded that F. nitida leaf powder at (20, 30, and 40 g/kg soil) incorporated to the soil caused moderate reduction in the growth of both weeds (P. minor and M. parviflora) as shown in Tables 1 and 2 and consequently accompanied by the maximum increases in V. faba growth as well as yield and yield components (Tables 3, 4, 5, and 6).

Discussion
Our previous work at the Botany department of the National Research Centre of Egypt showed clearly that using the dry leaves and seeds powder of some allelopathic plants achieved good results in controlling some annual, perennial, as well as parasitic weeds associated different economic crops and could improve their growth as well as yield (El-Masry et al. 2015;Ahmed et al. 2018;Messiha et al. 2018).
The results of the present investigation reveal that Ficus nitida leaf powder possess to great extent allelopathic effect in controlling the growth of the two annual weeds Phalaris minor and Malva parviflora associating Vicia faba plants when added to the soil. The rate of reduction in the fresh and dry weight of both weeds at the two ages increased by increasing the F. nitida leaf powder concentration. Maximum reduction recorded with the highest F. nitida leaf powder concentration (60 g/kg soil) reached to 69.8 and 80.3% respectively in the dry weight of P. minor and M. parviflora at 60 DAS as compared to their mixed control (Tables 1 and 2). These results are in agreement with the results reported by Manikandan and Jayakumar (2011); they showed the inhibitory effect of the methanolic leaf and bark extracts of F. bengalensis on seed germination, shoot and root length, as well as the biomass weight in Ipomoea pentaphylla seedling. They concluded that the inhibitory effect on weed species is directly proportional to increase the concentration used and this may be due to the presence of methanolic soluble allelochemicals  like phenolic acids. Analysis of the dry leaf extract of F. nitida in the present study revealed the presence of total phenolic acids content (53.90 mg/100 g dry weight) and total flavonoids (18.83 mg/100 g dry weight). The reducing effect of F. nitida leaf powder on the growth of both weeds, i.e., P. minor and M. parviflora, could be attributed to these natural allelochemicals. These results were confirmed by El-Rokiek et al. (2016). Another confirming results were found also by some researcher that leaves and bark extracts of F. bengalensis have different allelopathic effect on seed germination percentage and early seedling growth parameters of some economic crop plants as maize (Zea mays), mung bean (Vigna radiata), and sunflower (Helianthus annuus), and these allelopathic effects are due to their allelochemicals mainly the total phenolic acids content that proportion to the concentration (Mohsin et al. 2016;Muhammad et al. 2018).
The results of the present study confirm this idea and reveal that different treatments of F. nitida leaf powder not only achieved good results in controlling the two annual weeds, i.e., P. minor and M. parviflora, but also increased V. faba growth and consequently improved its yield and yield components (Tables 3, 4, 5, and 6) especially at 20, 30, and 40 g/ kg soil concentrations. It is worthy to mention that improving the plant growth and consequently increasing its yield is not only due to the inhibition of weeds growth by chemical or biological means, that lead to increase the competitive ability of the plant, but also due to the selectivity of the allelochemicals in their action and the plant in their responses (Einhellig 1995). Allelochemicals which inhibit the growth of same or different species at certain concentration may stimulate the growth of same or different species at different concentrations (Ahmed et al. 2014;Bashen 2014;El-Masry et al. 2015;Messiha et al. 2018).

Conclusion
The results of the present work indicate the possibility of using allelopathic activity of F. nitida leaves powder as selective bioherbicide in controlling weeds.