Approaches for Enhancing Composting Process of Farmyard Manure in Dhankuta District, Nepal

概要

Chapter 1 Background and objectives
Soil fertilization in mid-hills of Nepal is largely done with the application of locally made organic fertilizer in the form of farmyard manure (FYM). In recent years, use of chemical fertilizers has been in rise, but still considerable numbers of farmers use and are dependent on FYM to maintain soil fertility. However, FYM is often believed to be of inferior quality, lacking in essential nutrients, affecting the soil fertility status and agricultural productivity in mid-hills of Nepal.

Agriculture is a priority sector for uplifting prosperity of many farmers in mid-hills of Nepal, which can be achieved by better soil fertility management practices. Subsequently, it is of upmost importance to understand the prevailing conditions and constraints in low quality of organic fertilizers, so that strategies could be developed for overcoming the problems.

Chapter 2 Current conditions and constraints on maintaining soil fertility in Dhankuta District, Nepal
This study focuses on knowing the present conditions and constraints in productions, application of organic fertilizers for agricultural sustainability in Dhankuta District, Nepal focusing on maturity, nutrient content and pathogenicity of FYM. This study was advanced on the basis of questionnaire survey, interviews, group discussions and field visits. Additionally, manure samples were tested for their maturity, nutrient content and pathogenicity. The results showed that majority of famers in the used FYM; most of them also used chemical fertilizers. Loss of nutrients and heat through runoff or leaching was a major problem as most of the farmers used heap method for composting in open, with improper methods used. Self-heating test and C/N ratio of manure samples showed that farmers used immature manure resulting in low mineral contents with high pathogenicity. It was concluded that immaturity, low nutrient content and pathogenicity of the manure were three major problems in management and application of farmyard manure in the study area. Therefore, this research focused on understanding and developing strategies for overcoming these issues.

Chapter 3 Enhancing fermentation of farmyard manure using Bacillus sp. as a microbial inoculant
Microbial inoculation has been reported to have significant effects on composting process. Bacillus sp. is a thermophilic bacterium and has been reported to have positive effects in composting, providing high value compost and shorten the time of composting process. The objectives of this study were to see the effect of adding inoculant of Bacillus sp. for enhanced fermentation of composting materials, for better decomposed FYM. Bacillus sp. inoculant extracted from locally available rice husk, rice straw was added to raw material, and a composting experiment was conducted. Compost samples were sampled at regular interval for analysis.

The experimental results showed that Bacillus sp. was influential in increasing temperature, enhancing fermentation process with better decomposition and mineralization of organic matter. With the outcomes of this study, it can be said that Bacillus sp. as an inoculant can be effective in better decomposition, mineralization and shortening of composting time.

Chapter 4 Reducing nitrogen loss during cow manure composting with adding of rice husk biochar
Nitrogen losses in the forms of ammonia and nitrous oxide emission are major causes for low nitrogen content in cow manure compost, decreasing the agronomic value of it. In this study, rice husk biochar was added in cow manure composting to assess its effects on reduction of nitrogen emission. Gases released were measured periodically with static gas chamber method. In addition, total nitrogen content and C/N ratio were analyzed. According to the experimental results, loss of ammonia, which is peak during initial stages, were lower in the treatments added with biochar. Additionally, the addition of biochar reduced the emission of nitrous oxide. Furthermore, total nitrogen content and C/N ratio were better in biochar added treatments.

The obtained results may be attributed to the structural properties of rice husk biochar, which adsorbed the nitrogenous compounds. Additionally, biochar increased retention of moisture and nutrients enhancing microbial activity for better degradation and humification of organic matter. The results indicated that biochar could be a good medium in reducing the nitrogen loss and increasing agronomic value during composting of cow manure.

Chapter 5 Heat activation during cow manure composting using rice husk biochar and its effect on survival of pathogenic E. coli
Escherichia coli (E. coli) is a coliform bacterium, which is one of the most significant and common pathogens found in fresh cow manure. During composting process, biodegradable organic matter is broken down by microbial activity to produce heat which plays an important role in inactivation of pathogens. Therefore, degradation of organic matter has high significance on heat evolution during composting process for pathogenic free compost.

The objectives of this study are to see the effects of adding rice husk biochar in organic matter degradation and heat generation during composting process, subsequently, effecting the inactivation of pathogenic E. coli. Degradation rate of organic matter was calculated using first order kinetics. E. coli (cfu/g) and coliform bacteria were counted with serial dilution method and incubated in XMG Agar. Additionally, E.coli 0157:H7 was considered as a model pathogen present in cow manure and its’ survival was simulated using the D-value of the pathogen. The results showed that biochar addition helps in increasing degradation rate, thus increasing temperature. This increased temperature resulted in inactivation of pathogenic E. coli. The simulation of survival of E.coli 0157:H7 showed that temperature above 50º C for a period of 2 days can significantly decrease the population of pathogens. The results of the simulation can be beneficial while managing cow manure composting.

With the outcomes of this study, addition of rice husk biochar can be an effective strategy for better degradation and heat generation for inactivation of pathogens.

Chapter 6 Conclusions and recommendations
Soil fertility management practices are significant in maintaining and improving soil quality and fertility. In mid-hills of Nepal, organic fertilizers in the form of FYM are widely used for maintaining soil fertility. However, the quality of FYM used is considered low. Therefore, this study dealt in understanding the conditions and constraints in low quality FYM, so that strategies could be developed for enhancing the composting process for better quality FYM. According to the results of field survey and samples tested of the research site, it was understood that immaturity, low nitrogen content and pathogenicity were major problems associated with use of FYM. Use of immature fertilizers has resulted in low nutrient content and high pathogenicity. It was speculated that lack of microbes during the start of composting, loss of nitrogen and heat generation and loss during composting process are some of the problems associated with low quality of FYM in Dhankuta District, Nepal. Accordingly, an experiment was conducted to see the effect of adding inoculant of Bacillus sp. in enhancing compost quality. The results indicated that use of Bacillus sp. is a useful strategy for better and faster decomposition and mineralization of compost.

Rice husk biochar was used in composting of cow manure to see its effects on reduction of nitrogen losses through gaseous emission in the form of ammonia and nitrous oxide. Additionally, it was also speculated that adding of rice husk biochar enhances microbial metabolism resulting in increase of heat generation. The experimental results showed that rice husk biochar is efficient in reducing nitrogen loss and increasing heat generation during composting process. During composting heat generation is significant in degradation of organic matter and survival of pathogenic microbes E. coli.

For sustainable agriculture in mid-hills of Nepal, use of matured FYM is crucial; hence, farmers should be educated on importance of using fully matured compost. With the outcomes of this study, use of Bacillus sp. inoculant and rice husk biochar are recommended as strategies for better composting in mid-hills of Nepal.

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