1 Introduction

Despite the significance of faba bean (Vicia faba, L.) as a legume crop, its growth is subdued in numerous agricultural land regions owing the infestation of broomrape reducing yield and returns (Amri et al. 2019). Faba bean is considered a multi-purpose crop, since it is used as a source of protein in human diets (Khazaei et al. 2019), as fodder crop for animals, and as a main component in crop rotation (Nebiyu et al. 2016; Rose et al. 2016).

Orobanche species are sophisticated and ruinous parasites to agriculture with the difficulty of controlling (Fernández-Aparicio et al. 2016). Broomrape is a terrible parasitic weed which causes huge losses in faba bean productivity worldwide (Ennami et al. 2020). Yield losses in faba bean could reach 41–95% (Bouraoui et al. 2016; Saudy et al. 2021b) due to the attacks of broomrape. Additionally, crop yield may be completely lost (Qasem 2019) under heavy broomrape infestation. Annually, Orobanche species cause losses in yield estimated at hundreds of millions dollars affecting the livelihoods of around 100 million farmers (Gevezova et al. 2012).

Despite using several solo applications for broomrape control, the coveted success was not enough (Rubiales 2014). Therefore, finding integrated and compatible approaches should be espoused for obtaining passable degree of parasite control and to obviate yield reduction under broomrape-infested fields. Owing to the concerns related to herbicides use (Saudy and Mubarak 2015; Saudy et al. 2021a), various strategies have been proposed in weed control (Samejima and Sugimoto 2018; Aisa et al. 2019; El-Metwally and Saudy 2021a; El-Metwally et al. 2022); however, other alternatives and eco-friendly methods are necessary (Saudy et al. 2020). For avoiding or at least decreasing the harmful impacts, herbicides use the clean and biological solutions are adopted in agriculture production (El-Metwally and Saudy 2021b; Saudy et al. 2021c; Saudy and El-Metwally 2022). There is no doubt that reducing the soil seed bank by damaging broomrape seeds in the soil is a crucial action for effective management program of broomrape. Owing to secretion of chemical substances by potential host roots, the parasitic seeds germinate (Brun et al. 2019). In addition to other metabolites, strigolactones are the compounds responsible for stimulating germination of Orobanche spp. seeds (Pouvreau et al. 2021).

As a cultural method, trap crops may effectively reduce Orobanche seed bank and could be used as a part of integrated Orobanche control approach. Trap species is a false host that stimulates parasite seed germination but not parasitized. It exhausts parasite seed bank in integration with other methods of parasite control while trap species or stimulatory natural chemicals (Ye et al. 2017; Samejima and Sugimoto 2018) may be incorporated in parasite management. However, heavily infested fields should be planted in crop rotation (absence of the true host) with trap species for 2 or 3 years to exhaust parasite seed bank. Using a type of mixtures of plant species (interplanting or intercropping) could reduce weed infestation (Saudy and El-Bagoury. 2014; Saudy 2015). Several plant species, i.e., fenugreek, lupine, and garlic (El-Mehy et al. 2022), were intercropped with faba bean achieving good control of broomrape; however, the use of flax was not sufficiently studied.

Biological control is one of many substitutional means for tackling the issues of parasitic weeds. Biologically, mycorrhiza as natural enemy could be used against broomrape. In this context, root exudates of arbuscular mycorrhizal (AM) fungi had a negative impact on the germination of O. cumana induced by germination stimulants (Louarn et al. 2016). Mycorrhizal colonization of tomato plants was shown to reduce broomrape seed germination (Tadayyon et al. 2018).

Using plant residues in the form of biochar or charcoal could be used as a practical tool to avoid the attacks of broomrape (Saudy et al. 2021b). Due to its active surface area, biochar is of great potential to reduce the bioavailability of the adsorbed organic compounds (Nartey and Zhao 2014). However, further studies are needed to understand the mechanism of biochar for affecting the weed seeds in soil.

Recently, using of allelochemicals produced from different plant parts could contribute in parasite weeds control. In this respect, glucosinolate compounds are released from plant tissues, as in Brassica species, and convert into toxic compounds called isothiocyanate (Eisenschmidt-Bönn et al. 2019) which can suppress weeds (Ahmed et al. 2020). Therefore, the extracts of plant residues of the several individuals of Brassicaceae plant family could be exploited as effective tools to manage different types of weeds in many crops (Biswas et al. 2014; Ahmed et al. 2016; Messiha et al. 2018).

Dynamic scientific attempts and insights related to the efficiency different safe and ecofriendly methods of broomrape management should be adopted. Therefore, the current work hypothesized that soil application of mycorrhiza, charcoal, or rocket salad powder may manipulate the stimulating effect of faba bean root exudates in root rhizosphere to be unfavorable for growth and development of broomrape. Also, since mycorrhiza, charcoal, and rocket salad powder have different properties, they may interact differently with flax, as a trap crop, in managing broomrape weed in faba bean fields. Hence, the study aimed to investigate the relative efficiency of mycorrhiza, charcoal, or rocket salad powder under inter-planted faba bean with flax as clean methods of broomrape control in open field for sustaining the land productivity.

2 Materials and Methods

2.1 Study Site

In naturally broomrape-infested field located at El Nubaria experimental station, National Research Centre, Egypt (30°31′N, 30°18′E; 21 m above sea level), faba bean plants were grown along two winter seasons of 2018/2019 and 2019/2020. The experimental soil was sandy, and its physico-chemical properties, estimated by the method of Page et al. (1982), are presented in Table 1. According to soil taxonomy (IUSS Working Group WRB 2015), the soil is order Entisols and suborder psamments. The study site belongs to the arid zone conditions with rare rainfall and moderate winter. Along the two growing seasons of faba bean, the mean values of daily air temperature, relative humidity, wind speed, precipitation, and solar radiation were 16.9 °C, 62.2%, 2.59 m s−1, 0.51 mm, and 17.3 MJ m−2 day−1, respectively. The preceding crop was corn (Zea mays L.) in the first and second seasons.

Table 1 Physico-chemical properties of the experimental soil at the Experimental Station of Agricultural Production and Research, El Nubaria, Egypt
Full size table

2.2 Treatments and Design

Under two planting patterns (sole faba bean and inter-planting faba bean with flax), five broomrape control methods were distributed in a strip plot design with completely randomized block arrangement in six replicates. Broomrape control methods included mycorrhiza, charcoal, rocket salad seed powder, glyphosate–isopropylammonium herbicide, and weedy check (control).

2.2.1 Plant Material Preparation

Mycorrhiza

Mycorrhizal spores that contained a mixture of genera Glomus sp. and Gigaspora sp. were extracted from rhizosphere as the method described by Gerdemann and Nicolson (1963) and identified according to the key of Schenck and Perez (1990).

Charcoal

The used charcoal was prepared from dry plant wastes of casuarina (Casuarina equisetifolia) and passed through a 2-mm sieve. According to Page et al. (1982), some chemical properties of used charcoal were estimated and shown in Table 2.

Table 2 Chemical properties of used charcoal
Full size table

Rocket Salad Seed Powder

Seeds of Eruca sativa were grinded into fine powder. Total glucosinolates were measured by determining the liberated glucose which released during hydrolysis by myrosinase enzyme (Rauchberger et al. 1979). The resulting glucose were determined colorimetrically according to the method defined by Nasirullah (1996). Also, total phenolics of rocket salad seed powder were determined colorimetrically using Folin and Ciocalteu phenol reagent according to the method of Snell and Snell (1953). The analysis proved the detection of glucosinolates and phenols in rocket salad seed powder (See Table 3).

Table 3 Total glucosinolates and total phenolics detected in rocket salad (Eruca sativa) seeds powder
Full size table

2.2.2 Treatment Application and Procedures

Charcoal and rocket salad seed powders were added as a spot placement at a rate of 40 and 10 g hill−1, respectively (these amounts calculated based on the size of hole occupied by charcoal or rocket salad powders instead of the removed soil of hill before planting), after soil preparation, and then soil was irrigated (prior 15 days of planting). Faba bean hill rhizosphere was injected by mycorrhizal spores’ suspension at 21 days after sowing (DAS). The percentage of mycorrhizal colonization was estimated by the method of Trouvelot et al. (1986) at 65 DAS. Fig. 1 shows the success of mycorrhizal inoculation. Glyphosate–isopropylammonium, roundup 48% WSC (isopropylammonium N-(phosphonomethyl)glycinate), was applied twice during faba bean flowering stages (60 and 75 DAS, 0.18 L ha−1).

Fig. 1
figure 1

Effect of mycorrhiza application in faba bean. Without inoculation (a); with inoculation (b) shows the presence of hyphae and spores

Full size image

The ordinary single super phosphate was applied (15.5% P2O5), 360 kg ha−1 during land preparation. Land was divided into 60 plots with net size of 10.0 m2 for each, comprising five furrows 3.5 m length and 0.65 m width. On November 13th, in both seasons (15 days after soil irrigation), Rhizobium-inoculated faba bean seeds cv. Sakha-1 were sown (3–4 seeds per hill), with 0.25 m space on the two sides of the ridge. Also, in interplanting treatment, flax seeds cv. Giza-3 were drilled between the two sides of faba bean, and then, soil was irrigated. At 35 DAS, faba bean plants were hand hoed and thinned, leaving two plants per hill. At 50 DAS, flax plants were removed to avoid the competition with faba bean plants. All experimental plots received ammonium nitrate (33.5% N) at a rate of 90 kg ha−1 divided into two equal parts and applied, 35 and 50 DAS. During growth stages, plants were irrigated through drip irrigation system using emitters of 2.0 L h−1 capacity.

2.3 Metrics

2.3.1 Broomrape Traits

At harvest (on April 30th and April 12th in the first and second seasons, respectively), the number of broomrape shoots and infected faba bean plants plot−1 were counted. Moreover, broomrape shoots were uprooted, air dried for 10 days and oven-dried for 24 h at 80 °C up to a constant weight for estimating the total biomass expressed in dry weight plot−1.

2.3.2 Agronomic Traits

At 110 DAS, plant height, plant dry weight, and branches number plant−1 were measured. At maturity, 10 faba bean plants were randomly uprooted from each plot to estimate pods number and weight plant−1 and weight of 100 seeds. Moreover, whole plants of the plot were harvested to estimate seed yield ha−1.

2.3.3 Seed Nutrient Uptake

Samples of seeds were grinded, oven-dried for 24 h at 60 °C, and digested by a mixture of H2SO4/H2O2; hence, total nitrogen was determined by micro Kjeldahl method using 5% boric acid and 40% NaOH as described by Chapman and Pratt (1961). According to Watanabe and Olsen (1965), phosphorus concentration was determined by ascorbic acid method using spectrophotometer. Potassium concentration was determined using flame photometer as described by Chapman and Pratt (1961). After that, nutrient uptakes were computed.

2.4 Statistical Analysis

The collected data were subjected to homogeneity test prior to analysis of variance (ANOVA). The outputs proved that the homogeneity and normality of the data are satisfied for running further ANOVA. Thus, data of each season were undergone to ANOVA according to Casella (2008), using Costat software program, Version 6.303, 2004. Seasons, broomrape control method, and planting pattern were considered as fixed effects while replications (blocks) were considered as random effect. At p = 0.05 level of probability, Duncan’s multiple range test (alphabetical lowercase letters) was used for distinguishing among the means of the main and interactional effects.

3 Results

3.1 Broomrape Traits

Analysis of variance revealed that broomrape number and weight as well as number of infected faba bean plants plot‒1 significantly influenced by broomrape control and culture pattern and their interaction in both seasons of 2018/2019 and 2019/2020 (Table 4). All weeded control treatments showed significant reductions in all broomrape traits compared to the unweeded (weedy check). Glyphosate is the effective treatment for controlling broomrape. Also, promising achievements owing to mycorrhiza, charcoal and rocket salad in broomrape control expressed in lower values of broomrape number and weight as well as number of infected faba bean plants plot‒1 than the weedy check. The broomrape control efficiencies of all applied weeded treatments are depicted in Fig 2.

Table 4 Broomrape growth as influenced by broomrape control treatment and faba bean culture pattern in the 2018/2019 and 2019/2020 seasons
Full size table
Fig. 2
figure 2

Broomrape control efficiency based on dry weight as influenced by broomrape control treatment and faba bean culture pattern in the 2018/2019 and 2019/2020 seasons. Sole: pure stand of faba bean; Inter: interplanting faba bean with flax. Means not sharing the common letters for each factor in each bar differ significantly at p = 0.05 probability level based on Duncan’s multiple range; ±, standard error

Full size image

Association of flax plants with faba bean expressed in interplanting caused reductions in broomrape number plot‒1 by 33.7–12.6% and broomrape weight plot‒1 by 46.3–13.6% in the first and second seasons, respectively, compared to sole faba bean. However, the number of infected faba bean plants plot‒1 was lower with sole faba bean than interplanting treatment in the second season (Table 4).

In both seasons, glyphosate whether with sole or interplanting recorded the lowest values of broomrape number plot‒1 and broomrape weight plot‒1 without significant variation with charcoal and rocket salad applied in interplanted plots (Table 4). Moreover, in sole or interplanted plots (for both seasons) as well as in sole plots (in the second season), glyphosate, mycorrhiza, and charcoal achieved the lowest reductions in number of infected faba bean plants plot‒1. Broomrape control efficiency based on the dry weight as influenced by different interactions of weeded treatments and culture patterns are illustrated in Fig. 3.

Fig. 3
figure 3

Broomrape control efficiency based on dry weight as influenced by the interaction of broomrape control treatment and faba bean culture pattern in the 2018/2019 and 2019/2020 seasons. Sole: pure stand of faba bean; Inter: interplanting faba bean with flax. Means not sharing the common letters for each factor in each bar differ significantly at p = 0.05 probability level based on Duncan’s multiple range; ±, standard error

Full size image

3.2 Agronomic Traits

3.2.1 Growth Traits

Growth traits of faba bean, i.e., plant height, plant weight, and branches per plant significantly responded to broomrape control practices in the 2018/2019 and 2019/2020 seasons (Table 5). Charcoal showed the maximum values of all growth traits in both seasons, statistically leveled with mycorrhiza (in 2018/2019) and rocket salad (in 2019/2020) for plant height, with rocket salad (in 2018/2019) for plant weight as well as with rocket salad (in both seasons) and mycorrhiza or glyphosate (in 2019/2020) for branches per plant.

Table 5 Faba bean growth as influenced by broomrape control treatment and faba bean culture pattern in the 2018/2019 and 2019/2020 seasons
Full size table

Higher values of plant high and plant weight in 2019/2020 were obtained with sole plots than interplanted ones, while interplanting pattern produced heavier weight of plant than that of sole pattern in the 2018/2019 season.

The interaction between broomrape control and culture pattern had remarkable effects on plant height, plant weight and branches per plant in both seasons (Table 5). Under sole pattern, mycorrhiza in the 2018/2019 season, charcoal in both seasons, and rocket salad in the 2019/2020 season produced the tallest faba bean plants. The maximum plant weight was obtained with charcoal × interplanting pattern in both seasons and charcoal × sole pattern in the second season. Except glyphosate and weedy check × sole or interplanting patterns and mycorrhiza × sole pattern in the 2018/2019 season as well as weedy check × interplanting pattern in the 2019/2020 season; all other interaction treatments showed similar enhancements in branches per plant in both seasons.

3.2.2 Yield Attributes

Charcoal was the potent practice for improving all yield traits significantly equaling mycorrhiza and rocket salad for pod number per plant (in both seasons) and seed yield (in the second season), mycorrhiza for pod weight per plant (in the second season) as well as rocket salad for weight of 100 seeds (in both seasons).

Interplanting pattern surpassed sole pattern in pods number and weight per plant (in the 2019/2020 season) and weight of 100 seeds (in the 2018/2019 season), while in the 2019/2020 season, the weight of 100 seeds was heavier with sole than interplanting (Table 6).

Table 6 Faba bean yield attributes as influenced by broomrape control treatment and faba bean culture pattern in the 2018/2019 and 2019/2020 seasons
Full size table

Charcoal × sole pattern in the 2018/2019 season and charcoal, mycorrhiza, and rocket salad whether with sole or interplanting patterns in the 2019/2020 season revealed the maximum increase in pod number per plant. Charcoal × sole pattern in the 2018/2019 season as well as charcoal × interplanting pattern and mycorrhiza × sole pattern in the 2019/2020 season recorded the highest pod weight per plant value. Charcoal and rocket salad whether with sole or interplanting patterns in both seasons, in addition to mycorrhiza × interplanting pattern in the 2018/2019 season and mycorrhiza × sole pattern in the 2019/2020 season, were the most effective combinations for increasing weight of 100 seeds. The maximum increases in seed yield were observed with application of charcoal × sole or interplanting patterns and rocket salad × interplanting pattern in the 2018/2019 season as well as charcoal, mycorrhiza, and rocket salad with sole pattern in the 2019/2020 season.

3.2.3 Seed Nutrient Uptake

The most efficient practice for enhancing N, P, and K uptakes along the two seasons was charcoal. However, variations did not reach the level of significance with rocket salad for N and K uptakes (in the second season) and P uptake (in both seasons). Also, in the second season, charcoal was as similar as mycorrhiza for P and K uptakes and glyphosate for P uptake (Table 7).

Table 7 See nutrient uptake of Faba bean as influenced by broomrape control treatment and faba bean culture pattern in the 2018/2019 and 2019/2020 seasons
Full size table

N uptake in the first season and N and K uptakes in the second season recorded the maximum values with interplanting pattern and sole patterns, respectively.

Regarding the effect of interaction on nutrient uptake, data in Table 7 revealed generally that each of charcoal, mycorrhiza, and rocket salad has effective practices whether under sole or interplanting patterns, especially in the first season. In the second season, rocket salad with sole or interplanting patterns was the stable interaction for enhancing all nutrient uptake.

4 Discussion

Owing to its complex life cycle, controlling broomrape efficiently using conventional methods is almost hopeless (Eizenberg and Goldwasser 2018). Under high infestation of broomrape, faba bean cultivations could be completely prevented. This undoubtedly leads to huge reduction in crop production. In this connections, parasitic weeds like Orobanche crenata L. severely affect faba bean in several production regions (Pérez-de-Luque et al. 2016). Due to infestation with Orobanche spp., yield loss in beans could reach 50–100% (Aisa et al. 2019; Masteling et al. 2019). Since the parasitic weeds gain their nutritional requirements from photosynthetic assimilates of the host plant (Fernández-Aparicio et al. 2016), faba bean suffers a biotic stress. The accumulation of hexoses multiplies the osmotic pressure of Orobanche foetida, causing disturbance in concentration gradient in favor of the parasite and against faba bean (Abbes et al. 2019). Accordingly, Orobanche infestation decreased faba bean growth and yield and seed nutrients uptake. However, efforts and attempts to face the parasitic weeds should not be stopped.

An individual Orobanche plant can produce more than half million seeds, with high potentiality to remain viable for decades in soil in absence of the suitable host as well as genetic adaptability of the parasite to environmental changes, including host resistance, agricultural practices, and herbicide applications (Brun et al. 2019). This increases seed bank in soil every year making it difficult to eradicate. Accordingly, reducing weed seed bank in soil is a significant and effective tactic to avoid the negative effects of parasitic weeds such as broomrape, hence sustaining faba bean productivity (Saudy et al. 2021b). For effective management of broomrape weed, application of practices that reduce the soil seed bank by damaging broomrape seeds in the soil should be adopted. Findings showed the beneficial role of faba bean/flax interplanting for shrinking the issues of broomrape. Intercropping could reduce the infection of O. crenata on faba bean because of the allelopathic interactions (Abbes et al. 2019). Trap crops are non-host crops that can motivate the germination of parasite (Samejima and Sugimoto 2018). Different species stimulated seed germination of Orobanche spp. by more than 90%, and extracts of many plant species may be considered as trap, cover, catch species, or a source of natural germination stimulants for these parasites (Qasem 2019). However, heavily infested fields should be planted with trap species for 2 or 3 years to exhaust parasite seed bank. Such condition usually forced the farmer to abandon their cropland or delay their cultivation. The current study used flax as a trap crop (false host) in the presence of faba bean (true host) to stimulate the germination of the parasite seeds but cannot be infected and thus reduce the seed population in the soil. The crop rotation with certain non-host crop can reduce Orobanche seed bank in infested field (Hayat et al. 2020). Use of trap crop is one of the effective methods currently available to control agricultural root parasites (Aksoy et al. 2016). Thus, intercropping enhanced seed yield and reduced O. foetida infestation in faba bean (Abbes et al. 2019).

Data of the current research introduced several applicable practices which achieved acceptable levels of broomrape control compared to the weedy check. In this respect, the charcoal properties could be exploited, however its significance for combating Orobanche did not investigated well. It is well known that strigolactone compounds secreted by host plant motivate the seed germination of Orobanche spp. (Pouvreau et al. 2021). Being charcoal or biochar is an energetic adsorbent substance, its application to the soil could affect the root exudates of faba bean. Organic compounds can be strongly adsorbed and their bioavailability is reduced due to the adsorption forces and surface activity of biochar (Nartey and Zhao 2014). Also, application of biochar as a spot placement may represent a barrier that impedes the access of faba bean root exciter to broomrape seeds preventing their germination (Saudy et al. 2021b). In addition, water retention potential, cation exchange capacity, and microbial activity of soil were improved with charcoal or biochar supply (Tan et al. 2017). Furthermore, Manirakiza and Şeker (2020) stated that application of biochar improved the water status, acidity and aeration while increased the organic matter and soil aggregation. These edaphic changes could influence nutrient availability to plants and nutrient cycling in soils (Charles et al. 2017). Therefore, charcoal not only improved broomrape control but also kept the faba bean yield.

Findings also revealed the success of inoculation with arbuscular mycorrhizal (AM) fungi. Herein, AM fungi root exudates had a suppressive impact on O. cumana germination (Louarn et al. 2016). Since the early fungal development and metabolism are strongly stimulated by strigolactones (Lanfranco et al. 2017), the released germination stimulants from host to parasitic seeds medium were reduced (Louarn et al. 2012). This could interpret the reduction of broomrape growth associated with faba bean plants due to AM inoculation. Moreover, production and exudation of strigolactone were significantly reduced by AM fungi symbiosis in tomato and the germination-inducing activities of Pinguicula ramosa were significantly lower in tomato plants colonized by AM fungi than in free tomato plants (Lopez-Raez et al. 2011). In addition, AM fungi can supply their host plant with water and nutrients, while provide a specific level of protection against biotic and abiotic stresses (Spatafora et al. 2016; Pérez-de-Luque 2017). Accordingly, mycorrhiza reduced the number of attached O. crenata and improved the faba bean growth specially in susceptible cultivar (Komeil and Badry 2021).

Advanced scientific works seek to exploit the allelopathic potential as an eco-friendly safe method to suppress weeds. In this respect, rocket salad powder showed allelopathic inhibitory effect that can be utilized in controlling O. crenata infesting faba bean. Since seed powder of rocket salad contains natural allelochemicals mainly glucosinolates and phenolic compounds, better broomrape control was obtained. The endogenous active myrosinase enzyme acts in hydrolyzing glucosinolates into other products mainly isothiocyanates (Bones and Rossiter 2006). It has been proved that 2-phenylethyl isothiocyanate is an active germination stimulant for parasitic weeds such as P. ramosa (Pouvreau et al. 2021). Therefore, isothiocyanates have been applied as bioherbicides for weed control (Ahmed et al. 2016; Messiha et al. 2018; El-Wakeel et al. 2019).

5 Conclusions

Despite the slight effect between sole planting of faba bean and interplanting with flax in crop yield, lower infestation by broomrape was obtained with interplanting pattern. This certainly will prevent new broomrape spikes to flower, hence less accumulation of seeds in soil. Moreover, dual benefit of mycorrhiza, charcoal, and rocket salad powder was obtained. Such practices not only restricted the attacks of broomrape against faba bean but also improved the crop productivity in the infested soil. Accordingly, this study provides faba bean growers with several new and safe options that could be applied to ensure that yield losses are avoided as much as possible under broomrape infestation.