Composting of Pig manure and its Application in Earthworm Culture

In recent years, with the rapid development of livestock and poultry breeding industry in China, livestock and poultry manure wastes have also increased. The untreated discharge of manure wastes from some livestock and poultry farms not only seriously pollutes the surrounding environment, but also leads to livestock and poultry infectious diseases. The use of earthworms to treat livestock and poultry manure wastes not only protects the environment, but also obtains certain economic benefits. At present, earthworms are widely used in earthworm breeding at home and abroad. Breeding earthworms with pig manure is rarely reported. In order to study how pig manure can be used as bait for earthworm culture, the following three aspects were studied: 1) to study the effects of different doses of Bacillus subtilis on the composting of pig manure and straw compost. 2) the effect of Bacillus subtilis on the maturity of pig manure and straw compost with different C / N ratio, and 3) the effect of different C / N ratio compost base material on earthworm culture.

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Materials

Pig manure, taken from pig pens of local pig farmers in Xinxiang City, Henan Province; wheat straw, taken from Qiaoxie Experimental Field of Henan University of Science and Technology; Bacillus subtilis (ACCC19743), purchased from China Agricultural microbial bacteria Preservation and Management Center; earthworms, purchased from Henan Shijia Trading Company.

Pig manure is dried naturally, the water content is about 20%, ground, sifted through 2mm aperture, and set aside. Wheat straw is dried naturally, the water content is about 6.3%, and the crushing length is 2.0~2.5cm.

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Method 2.1 effects of different doses of Bacillus subtilis on composting maturity

According to the different inoculation amount of Bacillus subtilis, Bacillus subtilis was divided into 5 groups: group 1, group 2, group 3 and group 4 added 1.0%, 1.5%, 2.0% and 2.5% (weight to volume ratio), respectively, and the control group was natural compost without bacteria. The ratio of carbon to nitrogen in each group was 25, the amount of compost was 200kg, the initial water content was 60%, the environmental temperature was controlled at (28 ±1) ℃, and the humidity was about 65%. Each group had 3 repeats. When the temperature exceeds 50 ℃, the pile is turned manually once every 3 days. Using the five-point collection method, three mixed samples were collected from each group for the determination of pH value, water content, total nitrogen and total organic carbon.

2.2 effect of Bacillus subtilis on composting of pig manure and straw with different C / N ratio

According to the different C / N ratio of pig manure and straw, they were divided into 5 groups: group A, group B, group C, group D and group E. the initial C / N ratio of composting base material was 20 ~ 25 ~ 25 ~ 30 ~ 35 ~ 40 respectively. Each group was inoculated according to the optimum inoculation amount of Bacillus subtilis.

2.3 effect of composting substrate with different carbon-nitrogen ratio on the culture of earthworm

The comparison of the effect of compost substrate on earthworm culture, including the comparison of growth and adaptability of compost substrate to earthworm. The control group (natural compost) in 2.1and each group of compost base material in 2.2were dried for about a week, then the ammonia was removed as earthworm bait, and put into indoor flowerpot (upper mouth diameter 17.5cm, lower mouth diameter 13.0cm, high 9.5cm), and put 1cm 4 pot earthworms (reduce earthworm stress). The height of the composting base material is not higher than that of the flowerpot 3. 4. The number of earthworms is 100 / pot, the temperature is (20 ±1) ℃, the humidity is 65%-70%, each group is repeated 3 times, and the composting base material is added once in 10 days, and the thickness is 3cm. The culture ends after 7 weeks.

2.4 determination of physical and chemical indexes of item 2.4.1 during composting

Temperature: the temperature of each group was measured at about 09:00 and 16:00 every day during composting; pH value: take the mixed sample of 5g dry weight, add double distilled water, shake the solid-liquid ratio of 1 ∶ 10180r/min for 2 hours, static 30min, take the supernatant, and determine the pH value by pH meter; water content: take 100g mixed sample in ceramic iron plate and put it in 95 ℃ oven until the total amount is less than 0.01g, and the water content is calculated according to the weight loss before and after drying. C / N ratio: the total organic carbon content was determined by potassium dichromate-concentrated sulfuric acid method, and the total nitrogen content was determined by Kjeldahl method, and then the C / N ratio was calculated.

2.4.2 effect of earthworm culture

The average individual weight of earthworms = total weight / survival number; the survival number of earthworms = total number-death number and escape number; the adaptability of earthworms was determined according to the best activity range of earthworms in the base material, the looseness of the base material and the surface area of earthworm manure.

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Results and analysis 3.1 effect of different doses of Bacillus subtilis on composting ripening 3.1.1 temperature change

After the start of composting, the temperature of group 1 rose rapidly, entered the stage of high temperature fermentation (≥ 50 ℃) on the 4th day, and the composting temperature of ≥ 50 ℃ lasted for 14 days 16 days, while that of the control group increased slowly, reaching 50 ℃ on the 8th day, the composting temperature ≥ 50 ℃ lasted for 5 days, and the highest temperature reached 52 ℃. At the end of the experiment, the temperature of group 1 was close to the ambient temperature, while the temperature of the control group was slightly higher than that of the control group.

3.1.2 change of water content

In the process of composting, aerobic composting is both a process of oxidizing organic matter and a process of raw water, with water evaporation and generation at the same time. The water content of each group showed a downward trend as a whole, and at the end of composting, the water content of group 4 decreased to 33% 35%, which was higher than that of the control group (water content was 41%). It shows that the addition of Bacillus subtilis can accelerate the loss of water in composting.

3.1.3 pH value change

In the process of composting, the pH value of each group changed with the change of composting time and temperature. at the initial stage of composting, the pH value of each group was about 7.9, but in the process of composting, the pH value decreased at first and then increased, and then decreased slowly, and the final pH value of each group was 8.0-8.5.

3.1.4 change of C / N ratio

The composting base material of each group was prepared according to the initial C / N ratio of 25. After 28 days of composting, the C / N ratio of the four groups decreased to less than 20 and maintained at a relatively stable stage, while that of the control group was 21.

3.2 effect of Bacillus subtilis on composting maturity of Pig manure with different carbon / nitrogen ratio 3.2.1 temperature change

The temperature of each group reached more than 50 ℃ after 4 days of composting. Among them, the ≥ 50 ℃ of group A lasted for 18 days, the ≥ 50 ℃ of group B, C and D lasted for 15 days, and the ≥ 50 ℃ of group E lasted for 11 days. The cooling rate of group C > group B > group D > group A > group E was decreased to the ambient temperature (about 30 ℃) after 32 days of composting.

3.2.2 changes in water content

The water content of group B and C decreased rapidly because the carbon and nitrogen of these two groups were more suitable for microbial metabolism and growth, and the water content of group An and E decreased slowly because of less straw and anaerobic conditions in group A. the temperature was low, while the ratio of carbon to nitrogen in group E was high, which was not conducive to microbial metabolism and growth, and the water content in group E was the lowest (30.5%) at the end of composting.

3.2.3 changes in pH valu

The pH value of each group decreased at first and then increased and then decreased slowly. After 28 days of composting, the pH value of group A, B, C, D and E was 8.30, 8.10, 8.05, 8.10 and 7.80, respectively.

3.2.4 the change of C / N ratio

In the process of composting, the ratio of carbon to nitrogen tended to decrease as a whole, and all decreased rapidly in the initial stage. after 32 days of composting, the C / N ratio of group A, B, C, D and E decreased to 12.8, 15.6, 19.4, 21.5 and 29.6, respectively. The decrease of C / N ratio in each group was due to the decrease of total organic carbon, while the relative increase of total nitrogen caused the C / N ratio of each group to decrease gradually.

3.3 Culture effect of composting base material on earthworms 3.3.1 comparison of earthworm growth

Compared with group A (436.23 mg), the final weight of earthworms in group B, C and D (481.70510.67474.10 mg) was higher, and the number of initial escape and death in group E was more, so the growth index could not be measured effectively, so no statistics was made.

3.3.2 comparison of adaptability of earthworms

Adaptability mainly refers to the best range of activity, the looseness of substrate and the area of surface earthworm feces of earthworms. The number of escapes and deaths can indirectly reflect the survival rate of earthworms. Earthworms have a wide range of activities, large food intake, large feces and high survival rate, indicating that earthworms have strong adaptability; on the contrary, the adaptability of earthworms is poor. The adaptability of earthworms from strong to weak is group C > group B > group D > group A, in which group E is not suitable for raising earthworms.

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Conclusion

The main results are as follows: 1) in the process of composting, the addition of Bacillus subtilis can shorten the time of pig manure and straw entering the high temperature stage and accelerate the ripening process, of which 1.0% inoculation is the most cost-saving.

2) the maturity of compost was affected by pig manure and straw with different C / N ratio, and the composting effect was better when the C / N ratio of pig manure to straw was 25 ~ 30.

3) when the C / N ratio of pig manure to straw is 30, the effect of earthworm culture is the best after composting.

Author: song Gaojie, Li Han, Liu Xingyou

School of Animal Science and Technology, Henan University of Science and Technology

School of Resources and Environment, Henan University of Science and Technology

Xinxiang College

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