Technique for Using Spent Mushroom Substrate of Flammulina velutipes to Cultivate Volvariella volvacea in Idle Period of Greenhouse Summer Squash

Ziwen ZHONG, Ming SUN, Yan LI, Yongping JING, Yingpeng ZHANG

Institute of Agricultural Resources and Environment, Shandong Academy of Agricultural Sciences/ Key Laboratory of Agro-Environment in Huang-Huai-Hai Plain, Ministry of Agriculture and Rural Affairs, Jinan 250100, China

Abstract Greenhouse summer squash is a major type of greenhouse vegetable in Shandong Province. In summer, there is a three-month idle period of greenhouse summer squash. Volvariella volvacea is a high temperature resistant high-quality edible fungus. In practice, it is able to use the spent mushroom substrate of Flammulina velutipes to cultivate V. volvacea. In the idle period of greenhouse summer squash, cultivating V. volvacea using the spent mushroom substrate of F. velutipes has high economic and environmental benefits. The cultivation techniques mainly include the preparation of cultivation materials, preliminary preparation for the greenhouse, planting management of V. volvacea, and returning the spent mushroom substrate to the field. By comparison with the conventional summer squash planting, this technique has higher economic benefits and its application prospects will be broad.

Key words Summer squash greenhouse, Idle period, Spent mushroom substrate, Volvariella volvacea, Cultivation techniques

1 Introduction

In China, Shandong Province is a large greenhouse vegetable planting province. Its greenhouse vegetable planting area is about 0.466 million ha. Its greenhouse vegetable develops rapidly, the annual sown area exceeds 0.933 million ha, accounting for about 1/4 of the total greenhouse vegetable area of the whole country. Greenhouse planting is generally one cropping one year or two cropping a year. In summer, the temperature is generally high and it is usually the idle period of vegetable greenhouse. Summer squash is a major vegetable of protected cultivation in Shandong Province. In summer, the summer squash greenhouse is generally idle for about three months. Without considering the greenhouse mulching solarization for sterilization, there are about two months for planting other high-temperature resistant vegetables.

Volvariella

volvacea

, also known as straw mushroom or paddy straw mushroom, orchid mushroom, originated in Nanhua Temple in Shaoguan City in Guangdong Province. China started artificial cultivation of straw mushrooms 300 years ago. It was introduced to the world in the 1930s. It is an important tropical and subtropical mushroom and the third largest cultivated edible mushroom in the world. China’s yield of straw mushrooms ranks first in the world and the production of straw mushroom is mainly distributed in southern China. Straw mushroom meat is tender, crispy and tasty, delicious, nutritious, and has good health care value. In summary, straw mushroom is a high-quality edible fungus. Especially in the hot summer, when other edible fungi are produced very little, it is the peak season for selling straw mushrooms, while it is just the off-season for vegetables at this time. Therefore, planting straw mushrooms can enrich people’s vegetable types. In addition, the straw mushroom price is high, so it can provide growers with high economic benefits.Cultivation of straw mushrooms mainly uses straw, wheat straw, waste cotton, cotton husk, etc. as the main raw materials. On the one hand, as labor costs and raw material costs continue to rise, the prices of these raw materials have risen sharply, accordingly increasing the cost of cultivating straw mushrooms. On the other hand, the current factory production of

Flammulina

velutipes

is developing rapidly. The daily output of 10-80 t of spent mushroom substrate is up to 12-92 t. A large amount of spent mushroom substrate is mainly used as fuel, fertilizer and feed, and its added value is not high, leading to serious waste. Therefore, reutilizing nutrients of the spent mushroom substrate of factory production of

F.

velutipes

to cultivate straw mushrooms in summer squash greenhouses can increase farmers’ income and at the same time, the cultivation material can be used as organic fertilizer to reduce the cost of fertilizers, so as to realize high economic and environmental benefits.

2 Preparation of cultivation materials

The cultivation materials for straw mushroom mainly include the spent mushroom substrate of

F.

velutipes

and quicklime. The spent mushroom substrate of

F.

velutipes

comes from spent mushroom substrate from factory production of

F.

velutipes

, and the cost is low; quicklime is also relatively easy to obtain and is mainly used to adjust the pH of the cultivation materials. Generally, cultivation materials are prepared according to the volume-to-mass ratio of 1 mof spent mushroom substrate and 25 kg of quicklime. In addition, the amount of cultivation materials is determined according to the planting area of the greenhouse, and the amount of spent mushroom substrate of

F.

velutipes

is generally 300-600 m/ha. First, select a relatively flat site, and stack the spent mushroom substrate of

F.

velutipes

in long strips with the height not greater than 1 m. When stacking, spread a layer of spent mushroom substrate and sprinkle a layer of quicklime to ensure that the spent mushroom substrate and quicklime are fully mixed according to the volume-to-mass ratio. Conduct natural fermentation for 10-14 d, turn over 2-3 times during the natural fermentation. In order to maintain well ventilation and ensure effective fermentation, if necessary, use wooden sticks or bamboo poles with a diameter of 30-40 mm to pierce a row of ventilation holes every 20-30 cm on the top and side of the fermentation heap. The core temperature of the fermentation heap is kept above 65 ℃ for 5-7 d. When the temperature of the fermentation heap drops to 38-40 ℃, the spent mushroom substrate should be kept to the extent that there are water droplets falling if the spent mushroom substrate is tightly gripped. In addition, according to the monitoring data of the pH of the cultivation materials, properly add quicklime to maintain the pH of the fermentation heap at 8.5-9.0, so as to meet the requirements for cultivation materials of the straw mushroom.

3 Making preliminary preparation for the greenhouse

Before preparing the spent mushroom substrate, clean up the summer squash residues and weeds in the greenhouse where straw mushrooms will be planted in advance, and then water it. After the water is dry, level the planting furrow in the greenhouse. After the greenhouse mulching solarization for 2 weeks, ventilate for 3-5 d. Then prepare the furrow at the width of, 80-100 cm, and the height of the ridges on both sides of the furrow is 12-18 cm. Put a grass fence on the plastic roof of the greenhouse for shading. As necessary, add a layer of black shading net in the greenhouse to keep the visible light intensity in the greenhouse at 50-100 lx. After 10:00 am every day, according to the weather conditions, open the greenhouse roof properly for ventilation to keep the temperature in the shed at 28-34 ℃.

4 Planting management of straw mushrooms

Move the fermented straw mushroom cultivation materials into the furrow, and the covering thickness should be 15-20 cm. After pouring water through the furrow, spray moisturizing in the greenhouse to ensure that the humidity in the greenhouse is 80%-95%, so as to meet the normal growth conditions for straw mushrooms. Crumble the straw mushroom cultivars with hand, mix well, and then directly spread on the surface of spent mushroom substrate. The inoculation amount of cultivation materials is 500-1 000 g/m. After sowing the strains, monitor the temperature and humidity in the greenhouse every day to flexibly grasp the time and period of opening the greenhouse for ventilation. When the humidity is insufficient, spray water in the greenhouse or irrigate the furrow in time to ensure adequate humidity in the greenhouse. In addition, regularly monitor the pH of the cultivation materials to ensure that the pH is kept around 9.0, thereby inhibiting the growth of other fungi such as

Coprinopsis

atramentaria

. Once other fungi appear, remove them in time, and sprinkle quicklime on the plaque of the surface of spent mushroom substrate at the same time, to inhibit the growth of other fungi and reduce the nutrient consumption of the cultivation materials.

When the straw mushroom mycelium grows for about 10 d, the white sporocarp will be formed and exposed on the surface of the material. At the same time of keeping the humidity, avoid spraying water directly on the surface of straw mushroom cultivation materials. After the pH of the cultivation material drops, use lime water with a pH of about 10 to irrigate to adjust the pH, but the large water cannot flow over the straw mushroom sporocarp to avoid cold shrinkage of the sporocarp. After about one week, the sporocarp grows to greater than 2 cm, the straw mushroom can be picked. Fresh straw mushrooms are not easy to keep, and cap opening will influence their commerciality, thus it is necessary to make drying treatment. Dry the straw mushrooms at 80-120 ℃ and store them in a sealed container. Alternatively, it is feasible to quickly put the fresh mushrooms in boiling water and then freeze them at -18 ℃, or pickle them with more than 20% salt water and store them in cans. After a growth period of about one month, straw mushrooms may have 2-3 vigorous growth periods. As the nutrient of the cultivation materials is insufficient or the vigor of mycelium declines, the sporocarp growth of straw mushrooms in this period is completed.

5 Returning the cultivation materials to the field

After the straw mushrooms completely stop growing, replace the conventional organic fertilizer with the spent mushroom substrate and conduct in-situ tillage, and plow together with the lower furrow surface. When plowing, the spent mushroom substrate should be fully mixed with the greenhouse soil. At the same time, use 2 bags of 40 kg of compound fertilizers (15∶15∶15) as the base fertilizer for the planting of greenhouse summer squash, and the compound fertilizers should be put into the soil, and then prepare the furrow. After seedlings of summer squash grow well for transplanting, directly transplant them.

6 Picking and economic benefit comparison of straw mushrooms

As indicated in Table 1 for the straw mushroom-summer squash rotation experiment in Donggong Village of Liyi County in Shandong Province in 2019, the yield of summer squash in straw mushroom-summer squash rotation was slightly higher than that of the conventional summer squash control greenhouse. Besides, the straw mushroom-summer squash rotation additionally obtained 2 660 kg of straw mushrooms. Subtracting the 4 400 yuan planting cost of straw mushrooms, and taking the spent mushroom substrate after harvesting the straw mushrooms as the substitute of organic fertilizers, the fertilizer cost was 2 000 yuan lower than that of the conventional control greenhouse. Since the economic benefit of straw mushrooms is high, the total economic benefits of straw mushroom-summer squash greenhouse is much higher than the conventional control greenhouse. Using the idle period of summer squash greenhouse to plant straw mushroom can significantly increase income of farmers. Even in the year when the price of summer squash is low, this rotation method can increase the income up to 217%. The straw mushroom-summer squash rotation mode is a short-period but high-income rotation mode, so it is worth promoting.

Table 1 Economic benefit comparison of straw mushroom-summer squash rotation

7 Application prospects of the technique

In summer idle period of greenhouse vegetable, planting straw mushrooms can obtain high economic benefits. Besides, the spent mushroom substrate after planting straw mushrooms can be directly returned to the field to replace the organic fertilizer. In this way, it can reduce the input of organic fertilizer, improve the soil, reduce the occurrence of

Meloidogyne

incognita

, and facilitate the sustainable development of greenhouse vegetable. Thus, this rotation mode has bright application prospects.

However, the planting time of straw mushroom is in July to August, the hot temperature in this period results in a high difficulty for promoting the operation of this rotation. For example, there are certain difficulties in maintaining the temperature, humidity, and pH of the cultivation materials necessary for the growth of straw mushrooms in the greenhouse. In addition, fresh straw mushrooms are not easy to store at room temperature, and require processing such as drying or salting to have good commercial properties, and the sales market also needs to have a certain scale. Therefore, the technique promotion also needs energetic support of local government, so as to increase the income level of local farmers.