Effect of spent mushroom compost on yield and fruit quality of tomato

An experiment was conducted to observe the performance of the composted spent mushroom substrate (SMS) along with chemical fertilizers on the yield, fruit quality and nutrient uptake by tomato plant for using the mushroom waste through composting. The experiment was laid out in a randomized complete block design with seven replications. Treatments were T1: no fertilizer and compost application (control), T2: recommended dose of fertilizers (RFD), T3: 25% SMC-N+ 75% fertilizer-N, T4: RFD + 2.5 t ha -1 SMC, T5: 50% SMC-N + 50% fertilizer-N, T6: 100% SMC-N and T7: 100% SMC-N + 50% fertilizer-N. Application of SMS compost at 2.5 t ha -1 along with recommended fertilizer dose showed the best performance for number of fruits, fruit yield, fruit quality (total protein, vitamin C, total sugar, reducing sugar) and nutrient uptake by tomato. This treatment showed significantly higher fruit yield, quality and nutrient uptake not only over control but also RFD, SMS compost alone and combination of SMS compost & RFD. Though SMS compost alone proved less effective, however combined application of SMS compost at 2.5 tha -1 with chemical fertilizer of recommended dose had shown to be more effective.


Introduction
The use of agrowastes as sources of plant nutrients serve as environmental sanitation as well as reduction in craving for mineral fertilizers by farmers Ayeni (2014). The best alternative of the present day's environmental degradation is to make proper use of the available unutulized organic biodegradable wastes in order to convert them into compost within a short period (Chanda et al., 2011). Mushroom wastes are creating various problems as air pollution, ground water contamination and nuisance. Waste management program is not well organized in Bangladesh due to different causes. Many cities in Bangladesh are not able to manage it due to institutional, regulatory, financial, technical and public participation shortcomings. People use to pile it and then burn it, or just bury it in some out of-the-way place and forget about it. It is recognized that spent mushroom waste contains rich and valuable organic materials and is convenient for recycling in different forms (Danny, 1992;Szmidt and Convay, 1995). There is a good opportunity to reuse spent mushroom substrate through composting to produce vegetable crops. Tomato (Lycopersicon esculentum) is a major horticultural crop with an estimated global production over 120 million metric tons (FAO, 2007). It is one of the most popular and versatile vegetables in the world, because of its taste, color, high nutritive value and its diversified use (Verma et al., 2015) and ranked among the top vegetables of economic importance. Tomatoes need high levels of nitrogen and phosphorus. It requires nutrients such as N, P, K, Mg, Ca, Na and S for good production. These nutrients are specific in function and must be supplied to the plant at the right time and in the right quantity (Shukla and Naik, 1993). Tomatoes need to grow in soil with heavy organic matter incorporated into it. Tomato plants have high requirement, are heavy feeders, for macro-nutrient elements including potassium and calcium and some micronutrients such as iron, manganese and zinc (Abbasi et al., 2002). Research interest in tropical countries has shifted to the utilization of agro based industrial wastes and farm waste products which if not converted to other economic uses such as fertilizers might pose environmental hazards (Ayeni, 2014). Farmers spend generally excessive amounts of inorganic fertilizers to produce vegetables with high yield (Stewart et al., 2005). Continuous use of inorganic fertilizers cause imbalance in soil physicochemical properties and unsustainable crop production (Jeyathilake et al., 2006). Organic fertilization is important for providing plant with their nutritional requirements without having an undesirable impact on the environment (Njoroge and Manu, 1999). But organic manures alone are unable to give economic yield. Again huge quantity of organic wastes required for manuring. It has become necessary to combine different types. It is also necessary to integrate chemical fertilizers into the organic sources to reduce the quantity and enhance nutrient release (Ayeni and Adetunji, 2010). Combination of organic and inorganic fertilizers could produce better yields than organic manure alone. These result agreed with previous findings obtained on onion (Abbey and Kanton, 2004;Gambo et al., 2008) and broccoli (Ouda and Mahadeen, 2008). Use of organic manure is limited by the huge quantities needed to meet crop nutritional need, while the use of chemical fertilizer is limited by cost and scarcity (Akanbi et al., 2005). So, there is need to investigate the combined effects of organic fertilizer with inorganic fertilizers and also to find suitable ratio of inorganic fertilizers and compost, which could give an economic yield. Therefore, the goal of the present study was to devise ways and means for utilization of spent mushroom substrates instead of disposing them as undesirable waste. The study was planned to evaluate the effects of SMS compost with different levels of inorganic fertilizer on tomato and finding out suitable ratio of them which could give an economic yield of tomato.

Location and time
Compost of spent mushroom substrate was prepared at the Field Laboratory of the Department of Soil Science, BAU, Mymensingh during April to July 2010. Field experiment was also conducted in the Field Laboratory of the Department of Soil Science, BAU, Mymensingh during November 2010 to March 2011.

Compost preparation
Spent mushroom substrate was heaped into piles under a cover shed over a 12-week period. The compost pile was turned twice a month for the first 10 weeks and then the materials were allowed to attain maturity over a period of 4 weeks, with no turning. Moisture content of the feed was kept at around 60 -70% throughout the composting period by sprinkling adequate quantities of water. The composted material was allowed for curing over a minimum of one month to create more stable compost.

Treatments and experimental design
There were seven treatments in the experiment and each treatment was replicated 3 times. Treatments were defined according to the different levels of inorganic fertilizer and SMS compost as basal application.

Tomato production
Healthy and uniform sized 25 days' old tomato (Lycopersicon esculentum; variety was Ruma) seedlings were transplanted to the experimental plots on 04 November 2010. Spacing of 50 cm between the rows and 50 cm between the plants were maintained. Urea, TSP, MoP, gypsum and zinc oxide were used as sources of N, P, K, S and Zn, respectively. All fertilizers except urea were applied as basal before sowing/planting of the crops. SMC and all fertilizers except urea were applied during final land preparation. Urea was applied in two split applications, the first split at seedling establishment stage and the second at flowering stage. Various intercultural operations were accomplished after seedling emergence for better growth and development of plants such as gap filling, weeding, staking, irrigation and plant protection. Tomato fruits were harvested when they became slightly red. Harvesting was done at 3-4 day intervals whenever necessary. After harvesting, data were collected on number of fruits per plant, fruit weight, fruit yield.

Chemical analysis
Plant analysis was accomplished to determine N, P, K and S contents. Further biochemical analysis was performed to measure protein, vitamin C and sugar contents. Digestion of plant samples were done with sulphuric acid and then the digest was estimated by distilling the digest with 10N NaOH followed by titration of the distillate trapped in H 3 BO 3 indicator solution with 0.01N H 2 SO 4 (Page et al., 1982). Wet digestion of plant samples with nitric-perchloric acid was performed for the determination of phosphorous, potassium and sulphur. Phosphorus was determined colorometrically using molybdovanadate solution yellow colour method (Yoshida et al., 1976) and the S concentration by turbidity method (Chapman and Pratt, 1964). The K concentration in the acid digest was determined directly by flame photometer (Yoshida et al., 1976).

Biochemical analysis
Biochemical analysis for total protein, vitamin C, total sugar and reducing sugar was done following standard methods. The principle of protein estimation is based on estimating the nitrogen content of the material and then multiplying the nitrogen value by 6.25. The estimation of nitrogen was made by micro-kjeldahl method, as described by Jackson (1973). Total sugar content was determined by the Anthrone method as per Dubois et al. (1951). Reducing sugar content was determined by following the method of Miller (1972). L-ascorbic acid was extracted with 6% Metaphosphoric acid and was estimated by titrimetric method (Reo, 1954).

Statistical analysis
Data on the yield and other plant parameters were statistically analyzed using MStat-C computer programme. Means were computed following DMRT at 5% level using the same computer programme (Gomez and Gomez, 1984).

Number of fruits per plant
Application of spent mushroom compost (SMC) with or without chemical fertilizers greatly affected the amount of fruits per plant (Table 1). The result revealed that the highest fruit number per plant in treatment T 3 (68) which was statistically identical to treatment T 2 (67), T 4 (65) and T 7 (65). The lowest fruit number per plant was obtained from control (T 1 ) treatment (23).

Fruit weight
Average fruit weight is presented in Table 1. The largest tomatoes were recorded in control (T 1 ) treatment (24.5 g) which was statistically similar to T 4 (RD+ 2.5 t ha -1 compost) treatment (22.2 g). The smallest tomato fruits were found in T 7 (Compost 100% + N 50%) treatment (15.5 g). Average fruit weight ranged from 15.5 to 24.5 g over the treatments.

Fruit yield
Fruit yield of tomato was significantly influenced by the application of spent mushroom compost (SMC) with or without chemical fertilizers (Table 1). Treatment T 4 (SMC at 2.5 t ha -1 along with RFD) recorded significantly higher fruit yield (46.0 t ha -1 ) followed by the treatment T 3 (75% N through chemical fertilizer + 25% N through SMC) (42.6 t ha -1 ) and T 2 (RFD) (41.5 t ha -1 ). The lowest yield was recorded in control treatment (T 1 ) (20.5 t ha -1 ). Fruit yield was found to vary from 20.5 t ha -1 to 46.0 t ha -1 across the treatments.

Fruit quality of tomato
From the data in Table 2, it appears that application of SMC at different amounts with different combinations positively influenced the fruit quality of tomato. Recommended dose of fertilizers application with 2.5 t ha -1 compost (T 4 ) showed the highest protein content (13.2%) and Vit C (25.4 mg Vit C 100g -1 ) with statistically similar Vit C content of T 3 (25.0 mg Vit C 100g -1 ). Total sugar and reducing sugar were found highest in treatment T 3 (4.08%) and T 5 (0.540%), respectively with statistically similar result of treatment T 4 (3.96%) for total sugar and T 2 (0.503%), T 3 (0.487%) , T 4 (0.533%) and T 6 (0.492%) for reducing sugar. Values having same letters in a column do not differ significantly at 5% level by DMRT. *= Significant at 5% level and **= Significant at 1% level. CV = Coefficient of variation

Nutrient uptake by tomato fruit
Different treatments significantly affected the uptake of N, P, K and S by tomato (Table 3). The N uptake was increased due to the effects of different treatments of SMC. Among the treatments, significantly higher N uptake (136 kg ha -1 ) was observed in T 4 treatment followed by T 3 and T 2 showing the values of 104 kg ha -1 and 104 kg ha -1 , respectively. The highest P uptake was with treatment T 6 (24.62 kg ha -1 ) followed by treatment T 5 (23.73 kg ha -1 ) and treatment T 4 (23.01 kg ha -1 ). The highest K and S uptake were recorded in T 4 with the values of 191 kg ha -1 and 17.49 kg ha -1 , respectively. In all cases of nutrient uptake (N, P, K & S), the control treatment (T 1 ) showed the lowest uptake with the values of 47 kg ha -1 , 6.72 kg ha -1 , 83 kg ha -1 and 6.23 kg ha -1 for N, P, K and S, respectively. Nutrient uptake was calculated on dry basis, tomato contained 86% water. Values having same letters in a column do not differ significantly at 5% level by DMRT. *= Significant at 5% level and **= Significant at 1% level. CV = Coefficient of variation

Discussion
The effects of SMS compost alone and combination with inorganic fertilizer at different levels on tomato were evaluated to find suitable ratio of them which could give an economic yield of tomato. Application of SMS compost at 2.5 t ha -1 with RFD showed significantly higher fruit yield over control yield and also over RFD, combination of RFD with SMC and SMC. 2.5 t ha -1 SMC with RFD produced higher fruit yield along with higher number of fruits per plant. Baniuniene and Zekaite (2008) reported that application of enriched compost in conjunction with inorganic fertilizer increased rice productivity and enhanced soil fertility status than recommended fertilizer application alone. Addition of suitable organic manure improves the soil physical and chemical properties which encourage better root development, increased nutrient uptake and water holding capacity which leads higher fruit yield and better fruit quality (Suge et al., 2011). Organic manure activates many species of living organisms which release phytohormones and may stimulate the plant growth and absorption of nutrients (Arisha et al., 2003). Organic inputs alone will not meet the nutritional needs of crops because they contain a comparatively less quantity of nutrients compared to inorganic fertilizers, the need to integrate the two forms in order to achieve better crop yield. Organic manure alone is unable to give higher economic yield (Seran et al. 2010). SMS compost possesses the quality of good soil amendment for raising healthy vegetable crops tomato when applied with recommended dose of chemical fertilizers. When organic manure was applied with chemical fertilizer more nutrient uptake occurred in the plant system and so more plant biomass was recorded (Kavita and Subramanian, 2007). Jonathan et al. (2011) reported that SMS compost of Pleurotus pulmonarius mixed with depleted garden soil generally enhanced all the variables of growth considered when compared with control and significantly promoted height, stem girth, number of leaves, flowers and fruit production in all the vegetables investigated. Integrated use of organic manure and chemical fertilizers resulted in higher yield of onion in comparison with the exclusive application of chemical fertilizers (Jeyathilake et al., 2006). Seran et al. (2010) also reported that combination of organic and inorganic fertilizers could produce better yields than organic manure alone. Akanbi et al. (2005) observed a great increase in yield of tomato when nitrogen fertilizer was combined with compost manure. Application of SMS compost at 2.5 t ha -1 plus RFD also produced higher quality tomato fruit. Total protein, vitamin C, total sugar and reducing sugar contents of tomato fruit and potato tuber were found the highest in this treatment. This result is supported by the result of Ahlawat and Sagar (2007) who stated that composted SMS improved the firmness and ascorbic acid content. They also reported that mixing of soil with recomposted SMS enhanced the tomato quality with respect to higher fruit weight, ascorbic acid content, dry matter, total soluble solids and acidity. The composted SMS has been found to be a good growing medium for the vegetables and field crops and has shown multifaceted utilities in improving the yield and quality of the crop. Organic fertilizer supplemented with chemical fertilizer treated plants exhibited better results than the plants treated separately with different fertilizers treated plants (Chanda et al., 2011). Integrated use of organic and inorganic nutrient source of N is advantageous over the use of inorganic fertilizer alone. Use of organics could enhance efficiency of chemical fertilizer (Dulal and Roy, 1995). Combination of organic and inorganic nutrient sources result into synergy and improved conservation and synchronization of nutrient release and crop demand, leading to increased fertilizer efficiency and higher yields (Vanlauwe et al., 2002). Integration of organic and inorganic nutrient inputs could be considered as a better option instead of only inorganic fertilizer to increase fertilizer use efficiency and to maintain more balanced nutrient supply.

Conclusions
It can be concluded from the study that the reuse of spent mushroom substrate can be a value-added process, manuring vegetable crops. Combined application of SMS compost at the rate of 2.5 t ha -1 and recommended inorganic fertilizer could give higher yield of tomato along with high quality. The inorganic fertilizers appear to have compensated with slow release of nutrients from the compost and their combined effects would have increased the yield.