論文の公開元へVariations of Soil Properties and Crop Productivity with Local Fertilization Practices in Kampong Cham Province, Cambodia
概要
Chapter 1 Background and Objectives
Cambodian agriculture is occupying about 20.7% of the GDP growth. Agricultural systems in Cambodia are mainly based on inorganic fertilizer and pesticide applications. Inorganic fertilizer plays a key role in agricultural cultivation and production of major crops. However, high rate of applying inorganic fertilizer leads to unsustainable production systems as well as degradation of the natural environment. Inorganic fertilizer application currently increases due to high demands for crop production in Cambodia. Although many farmers are attracted by chemical fertilizers, there are some farmers who achieve a high yield of production by applying farmyard manure or compost. Farmyard manure is available all year round, as more than 70% of farmers are breeding cattle. When the amounts of cow manure or compost produced were less than the amounts required, they are depending on inorganic fertilizer. In addition, organic farming was proposed as an alternative farming practice to local farmers in Cambodia. Recently, local farmers in Cambodia would like to increase organic fertilizer application for decreasing the expenses of inorganic fertilizer. According to the situations mentioned above, research interests have been focused on examine the variation of soil properties and crop productivity with local fertilizer. For the research sites in this study, Kampong Cham Province was selected, as an alternative farming practice based on organic fertilizer application was promoted to local farmers.
Chapter 2 Rice Productivity in Relation with Farmers’ Fertilization Practices
Kampong Cham Province is in the central plain of Cambodia. The major activity of people in the province is agriculture, mainly cultivating rice and vegetables. Samraong and Baray Communes were chosen as the study sites. From 2006 to 2009, there was a project on promoting organic farming through composting and liquid fertilizer making in Baray Commune. Also, a similar project on promoting sustainable agriculture was conducted from 2011 to 2016 in the Samraong Commune of Prey Chhor District, Kampong Cham Province. After the project implementation till now, farmers in Baray Commune had experienced for more than 10 years applying organic fertilizer, and only 5 years passed in Samraong Commune.
Therefore, the study was conducted to identify farmers’ fertilization practices in Kampong Cham Province through questionnaire survey and to examine variation of rice productivity with farmers’ fertilization practices in Samraong and Baray Communes. As it was difficult to evaluate the yield among different upland crops, rice production was selected for the comparison. One hundred farmers were selected for an interview with questionnaire survey on agricultural practices in Samraong and Baray Communes Organic Fertilizer Dependence (OFD%) was developed for indicating degrees of organic and inorganic fertilizers dependence of local farmers. The results showed that most farmers combined 84% in Samraong and 76% in Baray Communes of organic with inorganic fertilizers for their agricultural productions. The current practice on the applications of organic and inorganic fertilizers also affects the rice production in Samraong and Baray Communes. Farmers in Samraong Commune applied more inorganic fertilizer than farmers in Baray Commune, while rice yields are lower. It was observed that excess application of inorganic fertilizers is not necessary to produce effective yield if farmers can supplement it from organic fertilizer. Correlation between OFD% and rice production was observed, indicating that OFD% can be used for describing the appropriate amount of mixing organic and inorganic fertilizers. The higher yield can be achieved by applying 35% to 40% of organic fertilizer in Samraong Commune and 60% to 80% in Baray Commune. However, using more than 80% of organic fertilizer may reduce rice production. In conclusion, longer periods such as 10 years applying organic fertilizer has positive effects on crop production with organic fertilizer application.
Chapter 3 Soil Properties in Relation with Farmers’ Fertilization Practices
From the outcomes of chapter 2, it was found out that changes in soil properties due to fertilizer practices may affect rice production as there was a positive correlation between OFD% and the rice production per nitrogen applied at 95% confidence interval in the farmlands of Samraong and Baray Communes. Accordingly, research interests moved to examine variations in soil properties in relation with local farmer’s fertilization practices. Forty samples of disturbed and undisturbed soils in Samraong and Baray Communes were collected for analysing soil physical, chemical, and biological properties. Organic Fertilizer Dependence (OFD%) was set as a key factor for evaluating soil properties. The results showed that combined application of organic and inorganic fertilizers had positive effects on soil quality, i.e., providing a higher permeability, organic matter, organic carbon content, EC, total P and N, available K and Ca. Correlation between OFD% and soil properties was not observed in Samraong Commune, while a strong correlation was observed in Baray where 10 years of applying organic matter has been conducted. The ions that derived from organic matter or organic matter may accumulate in the soil which led to the improvement of soil properties. Soil in Baray seems to have less coliform than in Samraong Commune, indicated local farmers’ fertilizers practices may affect pathogenic inhabitation.
Chapter 4 Survival of Pathogenic Bacteria in Relation with Farmers’ Fertilization Practices
Cow manure and compost has been used as fertilizer for many years to provide nutrients to crops and improve overall soil quality. Improperly processed manure or compost may contain pathogens (coliform and Escherichia coli) that are harmful to humans. Coliform and E. coli are both natural flora of humans and animals, and a major pathogen causing significant mobility worldwide. Coliform and E. coli was existed in farmland soil in Samraong and Baray Commune. Therefore, the study was conducted to investigate the survival rates of pathogenic bacteria with organic and inorganic fertilizers application in Samraong and Baray Communes. Twenty soil and compost samples, and 10 samples of irrigation water were collected for the analysis of pathogenic bacteria (coliform and E. coli). Instant-check was used for pretesting E. coli in the fields.
As the results, high presence of coliform and E. coli was found in farmland soils, compost, and irrigation water in Samraong and Baray Communes. The survival rate of coliform in farmlands mostly related to fertilization practices. However, the survival rates of coliform became lower in the dry season. The use of immature compost was one of the causes of high pathogenic bacteria in soils. In conclusion, long-term use of organic fertilizers provides a better soil biological quality, which result in less pathogens in Baray Commune.
Chapter 5 Lime Material Application for Eliminating Pathogenic Bacteria (E. coli) in Kampong Cham Province
Coliform and E. coli was found in farmlands soils, compost, and irrigation water in Samraong and Baray Communes (Chapter 4). For producing high-quality and safer food products, it is necessary to eliminate pathogenic bacteria such as coliform or E. coli. The inactivation of pathogens in biosolids depends on several factors such as temperature, moisture content, pH, oxygen, soil type and texture. In all cases, pH has been reported to play a major role in bacterial death in the eutrophic areas, where the pH is close to or greater than 9.0. Increasing pH can be achieved by adding agricultural limestone (CaCO3) or quicklime (CaO). Agricultural limestone (CaCO3) is one of the basic inorganic and inexpensive materials that were applied in agricultural industries to stabilize soil pH. About 95% of CaCO3 can be obtained from shellfish and the rest is organic matter and other compounds. Therefore, the objective of this chapter is to evaluate the effects of different lime materials on the survival rate of pathogens and soil properties. Pot experiments were conducted with CaCO3 and CaO applied to the soil. CaO obtained by burning the lime materials at 800 was compared with other lime materials such CaCO3 powder, eggshells, clamshells, and wood ash at 5 g, 10 g, and 15 g to the soil. The results showed the increase in soil pH due to lime addition. However, there’s no significant difference of soil pH responding to amounts of lime added and similar trends were also observed between the unburned and burned lime material. The survival rate of coliform and E. coli were decreased with unburned and burned lime added, the pathogenic bacteria can be eliminated at 7 days after addition of lime. Lime additions help to increase in soil pH, EC and other nutrients component which affects to the survival rate of coliform and E. coli. There is no different between unburned and burned lime on the survival rates of pathogenic bacteria. Therefore, farmers no need to burn the eggshell, clamshell and wood ash to use in the farmland soils, and the amount of lime added should be less than 5 g or 22 kg/ha.
Chapter 6 Conclusions and Recommendations
This research was conducted to examine the variations of soil properties and crop productivity with local fertilization practices in Kampong Cham Province, Cambodia which can contribute to the promotion of organic farming in Cambodia. From this study was showed that most farmers combined 84% of organic with inorganic fertilizers in Samraong Commune and 75% in Baray Commune for their agricultural production. Farmers in Samraong Commune applied more inorganic fertilizer than farmers in Baray Commune, while the rice yields are lower. Correlation between OFD and rice production was observed, indicating that OFD can be used for describing the appropriate amount of mixing organic and inorganic fertilizers. Also, excess application of inorganic fertilizer is not an efficient fertilizer practices for increasing crop production. The higher yield can be achieved by applying 35% to 40% of organic fertilizer in Samraong Commune and 60% to 80% in Baray Commune. Correlation between OFD and soil properties was not observed in Samraong, while a strong correlation was observed in Baray Commune where 10 years of applying organic fertilizer. The combined application of organic and inorganic fertilizers had positive effects on soil quality such as providing a higher permeability, organic matter, organic carbon, and ions to the soil. Local farmer’s fertilization practices affect soil properties, and long-term of applying organic fertilizer in combination with inorganic fertilizers provided a better soil quality. However, there were high presence of coliform and E. coli was found in farmland soils, local compost, and irrigation water in Samraong and Baray Communes. The soils in Baray Commune seem to have less coliform compared to the soil in Samraong Commune. Long-term use of organic fertilizers provided a better soil biological quality, which result in less pathogens in Baray Commune. Local farmer’s fertilization practices affect the survival rate of pathogenic bacteria. The laboratory experiments were conducted to evaluate the effects of different lime materials on the survival rates of pathogenic bacteria and soil properties. Adding lime material increase soil pH and similar trends were observed between CaCO3 and CaO materials. Coliform was eliminated at 7 days after the addition of lime materials even the soil pH was less than 8. Also, there is no significant difference of soil pH, and the survival rate of coliform and E. coli to the amount of lime added. The amounts of less than 5 g should be considered. Increases in soil pH by adding CaCO3 materials can eliminate pathogenic bacteria effectively. Farmers can directly use eggshell, clamshell, and wood ash without burning for eliminating pathogenic bacteria in soils. Further, local farmers should be trained on production and application of these lime material.
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