Mushroom growing is an eco friendly activity as it utilizes the waste from agriculture, poultry, brewery etc and in turn produces a quality food with excellent and unique nutritional as well as medicinal attributes. The spent mushroom substrate left after final crop harvest is a matter of concern as it creates various environmental problems including groundwater contamination and nuisance if not handle properly. Compost is considered spent when one full crop of mushroom has been taken or when further extension of cropping becomes unremunerative.
The material has been found to be a good nutrient source for agriculture because of its nutrient status. It contains 1.9 -0.4 -2.4 per cent (NPK) before weathering and 1.9 -0.6 -1.0 per cent (NPK) after weathering for 8 -16 months. It has a high cation exchange capacity, a measure of the amount of nutrients a medium can hold and a slow mineralization rate retains its quality as an organic matter.
Spent mushroom substrate can be utilized for the following –
1) Reclamation of soil:
Addition of spent mushroom substrate in nutrient poor soil helps in improvement of soil health by improving its texture, water holding capacity and nutrient status. It does not have any adverse effect on its alkalinity but leads to an increase in ph as well as the organic carbon content. The phosphorus and potassium requirements of crop plants can be fulfilled by incorporating 5 per cent of it by volume, while nitrogen requirement can be fully met by incorporating 25 per cent of it by volume.
2) Organic mineral fertilizer: Spent mushroom substrate is still nutrient rich and contains about 80 per cent of the total nitrogen in bound form with high molecular weight fractions of lignin and humic substances. Nitrogen release from the compost is very slow, therefore addition of some easily available form of nitrogen may be required. Conversion of spent mushroom substrate into an organic-mineral fertilizer seems to be an alternative way for soil amelioration and plant nutrition.
3) Manure for horticultural crops.
Suitable treatments like rapid salt leaching and weathering in open for 18 to 24 months make spent mushroom substrate more suitable for either complete or partial substitution of growing media for growing flowers, vegetables, fruits, saplings, ornamental shrubs and other horticultural plants of economic importance. The findings given below are the outcome of re search conducted at Directorate of mushroom research, Solan.
Tomato (Lycopersicon esculentum)
Spent mushroom substrate dose: 18.5 ton/ha
Superior yield: 6-24 months old naturally weathered spent mushroom substrate and 12 months old anaerobically recomposted spent mushroom substrate.
Superior quality: Superior fruit weight, ascorbic acid content, dry matter, total soluble solids (TSS ) & acidity in anaerobically recomposted spent mushroom substrate.
Pea (Pisum sativum)
Spent mushroom substrate dose: 20 ton/ha.
Superior yield: 12 months old anaerobically recomposted spent mushroom substrate.
Superior quality: Higher contents of protein, ascorbic acid, dry matter & total soluble solids in 18 months aerobically/anaerobically recomposted spent mushroom substrate.
Cauliflower (Brassica oleracea var.Botrytis)
Spent mushroom substrate dose: 25 ton/ha.
Superior yield: 12 months old anaerobically recomposted spent mushroom substrate.
Superior quality: Superior stalk length, curd length, curd dia, dry matter, ascorbic acid content, curd appearance in 12 months old anaerobically/aerobically recomposted spent mushroom substrate.
Ginger (Zingiber officinale)
Spent mushroom substrate dose: 30-32 ton/ha.
Vegetative growth and yield: 18 months old aerobically recomposted spent mushroom substrate + basal dose of chemical fertilizers.
Superior quality: Superior rhizome length, breadth, thickness, dry matter, total soluble solids, fibre & NSS in 18 months old aerobically/anaerobically recomposted spent mushroom substrate + chemical fertilizers.
Onion (Allium cepa L)
Spent mushroom substrate dose: 25 ton/ha.
Vegetative growth and yield: 12 months old anaerobically recomposted spent mushroom substrate + basal dose of chemical fertilizers.
Superior quality: Superior length and diameter of bulb, total soluble solids, dry matter, pyruvic acid and ascorbic acid contents in 12 months old anaerobically recomposted spent mushroom substrate + basal dose of chemical fertilizers.
Brinjal (Solanum melongena)
Spent mushroom substrate dose: 25 ton/ha
Superior yield: 12 and 24 months old anaerobically recomposted spent mushroom substrate.
Number of fruits: Highest in 24 months old aerobically recomposted spent mushroom substrate followed by control and 12 months old aerobically recomposted spent mushroom substrate.
Fruit quality: Best in standard fertilization followed by spent mushroom substrate treatments.
4) Disease management of crop plants.
The actinomycetes, bacteria and fungi inhabiting the spent mushroom substrate exert some antagonism to the pathogens surviving and multiplying in the soil. It helps in lowering blossom end rot and leaf curl in tomato, fusarium wilt and powdery mildew in pea, black rot in cauliflower and rotting in ginger.
5) Animal feed.
Cellulose made available after Pleurotus spp. ( Oyster mushroom ) cultivation can act as energy source for animals as they have sufficient quantity of enzymes / microbes in rumen, which can degrade it further. Besides availability of cellulose, oyster mushroom cultivation also improves protein value and digestibility of the substrate. The spent mushroom substrate of oyster mushroom can substitute about 30% of the total feed without affecting the growth of animals.
6) Vermicomposting.
The spent mushroom substrate from paddy straw and oyster mushrooms are better substrate for vermicomposting. The vermicompost produced from spent mushroom substrate is of same quality as from FYM and it takes 2-3 months in vermicompost preparation. The overall cropping results have shown that spent mushroom substrate requires early treatments like desalting/prolonged leaching and recomposting before using as it has shown several advantages over fresh.
The spent mushroom substrate quality parameters like its conductivity, load of heavy metals and phosphate should be given due consideration before using it in the field. So in the era of growing environmental awareness and strict legislations, exploitation of spent mushroom substrate for managing environment and agriculture requires strict watch on its physical, chemical and microbiological properties. The diversified uses of spent mushroom substrate may lead to a change of its name from spent mushroom substrate to used mushroom substrate.
Sentimenla Jamir, SMS (Soil Science), KVK : Zunheboto, Nagaland University: Lumami.