IndexMaterials and methods1. Isolation of fungi associated with cowpea disease:2. Source of biochar, compost and mycorrhiza tested:3. Laboratory tests3.1. Preparation of compost water extract (CWE)3.1.1. Effect of biochar and compost on growth of R. solani mycelium:4. Greenhouse experiments:5. Field experiments:6. Statistical analysisDiscussionImpact of some soil amendments and mycorrhiza on cowpea damping-off caused by Rhizoctonia solani.Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Adding biochar to soil improves soil fertility and plant growth, especially when combined with organic compounds such as compost. This study was conducted to examine the effect of soil amendments with biochar, compost and mycorrhiza as biofertilizer alone or in combination on some growth parameters of cowpea plants and suppression of dampening disease caused by Rhizoctonia solani under greenhouse and field conditions. In vitro experiments have shown that biochar has no direct effect on the tested fungus even at the highest tested concentrations. In the greenhouse, Copmost was more effective than biochar in reducing dry-off diseases. In the field, mycorrhiza alone or combined with biochar or compost gave the lowest rates of disease mitigation. Furthermore, they significantly improved plant growth parameters (plant height (cm), root length (cm), number of leaves, pods and nodules/plant, fresh weight of leaves and roots (g) and dry weight of leaves. and roots (g )). Additionally, the tested treatments improved the cowpea plants' ability to absorb nitrogen, phosphorus and potassium from the soil. Mycorrhiza alone or combined with biochar or compost have been the most effective treatments in this regard. Keywords: compost, cowpea, mycorrhiza, rice straw biochar and macronutrients. The search for new strategies to control plant diseases and improve yields has led to the discovery of several new ideas, including amendments related to organic soil compounds such as biochar and compost. These compounds are well known for their suppressive effect against a wide range of soil-borne pathogens (Coventry et. Al., 2005 and Noble and Coventry, 2005). Biochar is a carbon-rich organic product produced by a heating process known as pyrolysis (Sohi et. al., 2010; Elad et. al., 2011 and Sparks, 2011). The type of organic compounds and the temperature used for its production determine its nutrient content and physicochemical properties (Antal and Gronli, 2003 and Gaskin et. al., 2008). The addition of biochar to the soil improves its characterization with consequent beneficial effects on the quality and quantity of plants (Glaser et. al., 2002; Steiner et. al., 2008 and Atkinson et. al., 2010). It is very stable in soil with a half-life of up to thousands of years (Zimmerman, 2010). Recently, it has been reported that soil amended with biochar can influence the development of plant diseases caused by foliar and soil pathogens (Graber et. al. 2014). Another soil amendment with suppressive effects is compost. It inhibits a wide range of plant diseases caused by various soil-borne pathogens. This could be due to increased competition and antagonism from soil biota associated with increased microbial activity in the soil (Pugliese et. al., 2011). Arbuscular mycorrhizal fungi are one of the most important microorganisms. Establishes symbiotic relationships with plantsand influences foliar and soil pathogens (Whipps, 2004 and Fritz et. al., 2006). Cowpea (Vigna sinensis Endl.) is the most important vegetable crop. Cowpea seeds contain approximately 23% protein and 57% carbohydrates (Belane and Dakora, 2009). Cowpea plants are subject to attacks of root rot and diseases caused by Fusarium solani, Rhizoctonia solani, Macrophominaphaseolina, Sclerotium rolfsii and Pythium sp. These diseases cause considerable losses suffered by cowpea plants worldwide (Shihata and Gad El-Hak, 1989; Ushamalini et. al., 1993; Rauf, 2000; Satish et. al., 2000; El-Mohamedy et . al., 2006). , considered the effect of compost, biochar and mycorrhiza, alone or in combination, on the control of cowpea spoilage caused by Rhizoctonia solani and on some plant growth parameters under greenhouse and greenhouse conditions. field. Furthermore, the study was expanded to evaluate the effect of these treatments on plant nitrogen, phosphorus and potassium (NPK) content. Materials and methods1. Isolation of fungi associated with cowpea disease: Diseased cowpea seedlings, which exhibited typical symptoms of cowpea disease, were collected from the Experimental Farm of Agricultural Fac., Cairo Univ. isolation, the infected roots were washed thoroughly with tap water and cut into small fragments (0.5–1.0 cm), surface sterilized with 1% sodium hypochlorite for 3 minutes, then rinsed several times in sterilized water, dabbed dry between folds of sterilized filter paper. Small pieces were transferred to PDA medium in Petri dishes and incubated at 26±2°C for 7 days. Observations were recorded daily and the emerged fungi were collected and grown on average PDA slopes and their frequencies were calculated. Fungal growth was examined microscopically and purified using the single spore and/or hyphal tip technique (Dhingra and Sinclair, 1985). Purified fungi were identified based on their morphological characteristics, both at the genus and species levels, according to Booth and Waterston (1964) and Barnett and Hunter (1972). The most frequent fungus was used in vitro and in vivo (pot experiments) after confirming its pathogenic capacity.2. Source of tested biochar, compost and mycorrhiza: Rice straw biochar and commercial compost were kindly obtained from soil, water and the environment. Res. Ist., Agric. Res. Center, Giza, Egypt. The characteristics of rice straw compost and biochar are mentioned in Table (1). For mycorrhiza inoculation, Mycorrhizen was used as a commercially available inoculum. This mycorrhiza product was purchased from Soil, Water and Environ. Res. Inst., Agric. Res.Center, Giza, Egypt.3. Laboratory tests3.1. Preparation of compost water extract (CWE) CWE was prepared by vigorously stirring mature compost, at the rate of 1:2 (w/v) of compost (500 g) in sterile water (1000 ml), for 20 minutes . To be removed Table 1. Selected characteristics of rice straw compost and biochar used in this study pH of the tested compost Total carbon (%) Total N (%) Total P (%) Total K (%) Biochar 9.0 36, 60 0.52 0.54 0.88 Compost 8.19 25.05 1.31 1.65 -large particles from the compost mixture, a 250 ml aliquot of the mixture was filtered by passing through 3 sterile layers of gauze and then the filtrate was centrifuged at 500 rpm for 10 min to obtain the active supernatant as stock solution. Four different concentrations were tested against the tested fungus, namely 0, 5, 10 and 15%.3.1.1. Effect of biochar and compost on growthof R. solani mycelium: The inhibitory effect of the tested compost as aqueous extract (CWE) was examined in vitro against the tested pathogenic fungus using the well diffusion method according to El-Masry et. al. (2002). The CWE was filtered through a sterilized 0.22 μm Millipore membrane filter. Fifteen ml of sterile PDA medium was used for each plate, a well was then punctured on one side of the plate using a 0.5cm sterile cork probe and the bottom of the well was sealed with two drops of sterile PDA medium . One hundred ml of each CWE concentration was transferred to each well separately. Sterile water was used as a control. Five Petri dishes were used as replicates for each treatment and the control. All plates were incubated at 25°C for 7 days and then the reduction in mycelial growth was recorded. The direct toxicity of biochar was studied using an in vitro contact test to evaluate the growth reduction of R. solani. The PDA medium was amended with varying concentrations of biochar, i.e. 0, 5, 10 and 15%, p: v before autoclaving and then dispensed into Petri dishes (9 cm diameter). Agar plugs (5 mm in diameter), covered with actively growing mycelium, were transferred to the center of Petri dishes amended with one of four concentrations of biochar and then incubated at 25°C for 7 days, whereby fungal growth was been analysed. calculated. Inhibition of fungal growth was calculated using the following formula: I = CT/CX100Dove; I= Reduction (%) in fungal growth; C= Fungal growth in the control treatment and T= Fungal growth in the treatment4. Greenhouse experiments: Effect of compost and biochar at different concentrations on cowpea disease under greenhouse conditions: In order to determine the most effective concentrations of the tested compost and biochar, cowpea seeds (cv. Tiba ), obtained from Agric, Res. Centro, Giza, Egypt, the surface was disinfested in 2% sodium hypochlorite, rinsed in sterile distilled water and then 5 seeds were sown in each plastic pot (40 cm3) filled with a sterilized mixture of sand and clay (2:1, v /v) containing compost at 0, 5, 10 and 15% w/w or biochar at 0, 5, 10 and 15% w/w. One day later, the treated soil was infested individually with the tested fungal inoculum at the rate of 3% w/w, previously grown on barley sand soil (1/1, w/w 40% water) at 25 ±1ºC for two weeks. For each treatment, five randomly replicated vessels were used.5. Field experiments: Effect of compost, biochar and mycorrhiza alone or in combination on dripping-off disease of cowpea plants under field conditions during the 2013 and 2014 growing seasons: The most effective concentrations of compost and biochar tested were selected to study their effect on the environment. disease suppression when mixed together in the presence or absence of mycorrhiza. Sterilized cowpea seeds were coated with mycorrhiza inoculum before sowing. The following treatments were used in the experimental setup: Compost; Biochar; Mycorrhiza; Compost + Biochar; Compost + Mycorrhiza; Biochar + Mycorrhiza; Compost + Biochar + Mycorrhiza; Rhizolex-T; Control. The experiment was carried out at the unit experimental of Department of Plant Pathology, Faculty of Agriculture, Cairo University, Giza, Egypt during two successive seasons of 2013 and 2014. The soil was divided into ridges (70 cm wide). Seeds were sown 15 cm apart in a row on the ridge, two seeds in each position. Seeds were sown on April 15, 2013 and 2014 seasons. All practicesagricultural were carried out according to the recommendations of the Ministry of Agriculture, Egypt. The experimental treatments were arranged in a complete randomized block design with three replications. The plot area was 4.2 m2 (6 m long and 0.7 m wide). Pre- and post-emergence damping-off percentages and surviving healthy plants were performed 15, 21, and 45 days after planting, respectively, using the formula described by Mikhail et. al. (2005) and Abd El-Moneim, et. al. (2012) as follows: Pre-emergence (%) = Number of non-germinated seeds / Total number of seeds sown × 100 Post-emergence (%) = Number of dead seedlings after emergence / Total number of seeds sown × 100 Plants survived (%) = No. of surviving plants / Total No. of seeds sown × 100 Survival efficiency (%) = D1-D2 / D1 × 100 Considering that: D1 = Damping-off (%) in the control treatment and D2 = Daming-off (%) in control treatment treatment5. Effect of compost, biochar and mycorrhiza alone or in combination on some parameters of cowpea plants under greenhouse conditions during 2013 and 2014 growing seasons: The vegetative growth parameters of cowpea plants, i.e. height of the plant (cm), root length (cm), number of leaves, pods and nodules/plant, the fresh weight of leaves and roots (g) and the dry weight of leaves and roots (g), were determined 90 days after sowing. Five random samples of cowpea plants representing each treatment were carefully removed from the soil and then washed under running water to remove any remaining particles.6. Effect of compost, biochar and mycorrhiza alone or in combination on the nitrogen, phosphorus and potassium contents of cowpea plants under field conditions during the 2013 and 2014 growing seasons: The nitrogen and phosphorus contents were analyzed according to Jackson (1973), where the potassium content was determined using atomic absorption spectrophotometer (Barkin Elmer, 3300) according to (Chapman and Pratt, 1961), the results were calculated as g/100 g dry weight.6. Statistical analysisMost data were statistically evaluated according to Snedecor and Cochran (1967). Means were compared at a 5% probability level using least significant differences (LSD) as mentioned by Fisher (1948). On the other hand, percentage data were arcsine transformed and then subjected to statistical analysis to determine least significant differences (LSD) to compare variance between treatments (Gomez and Gomez, 1984).DiscussionBiochar not only improves the yield of crops (Kloss et. al., 2014) but also has the ability to control diseases caused by different pathogens (Matsubara et. al. 2002; Nerome et al. 2005; Elmer and Pignatello 201; Zwart and Kim 2012; Graber et al. al., 2014 Jaiswal et al. 2014) but no information is available on the impact of biochar on cowpea disease caused by Rhizoctonia solani. On the contrary, many authors have reported a suppressive effect of organic amendments such as compost against R. solani and other pathogens present in the soil (Borrero et. al., 2004; Bonanomi et. al., 2007). This study is the first report on the effects of compost and biochar alone or in combination with mycorrhiza on the growth of cowpea plants and the incidence and development of attenuation caused by R. solani. In the presented investigation, the in vitro study indicated that biochar had no direct effect on the tested mushroom, while the compost extract had a greater effect on reducing the growth of the mushroom mycelium. These results are, somewhat, in harmony with those reported by Bonanomi et al. (2007); Elmer and Pignatello (2011); Jaiswal et al. (2014). Different,.