Co-composting of chicken manure with rice husk biochar and its effects on the performance of Cucumis sativus L

Rice husk biochar (RHC) in this study is a major by-product of the rice processing mill, abundantly available (estimated about 32,000 tonne/ year) and very low in cost. It is found underutilized and often paid, approximately RM8,000 annually to be disposed of by mill owners in some area especially Kelantan state. RHC was observed to increase crop growth and yield when used as polybag or potting media by farmers. However, there are inadequate detailed quantification on local mill RHC have been documented in relation to its capability in increasing crop production and soil improvement in Malaysia. This study was therefore carried out to, (i) determine physico-chemical properties of locally milled RHC, (ii) evaluate the effects of selected rates of RHC amendmend in composting process and compost properties of chicken manure and (iii) assess the effects of RHC and developed RHC compost on fruity vegetable crop production and soil properties. RHC in this study was collected from a local mill which operates cyclone husk furnace to generate heat for rice drying activity. RHC was characterized for its physico-chemical properties such as to its particle size, ash content, nutrient contents, Methylene Blue adsorption capacity, Brunauer Emmett and Teller (BET) surface area, functional groups using FTIR and Scanning electron micrograph image (SEM). Selected RHC application rates of 5% and 10% were evaluated for its effects on chicken manure composting through determination of composting temperature and CO2 release pattern, moisture, pH, nutrient content and microbial population. The finished compost were analysed for its leaching rates through laboratory column leaching test and the leached composts were viewed under SEM/EDX. RHC compost and fresh RHC were assessed for its efficacy through field trial on Cucumis sativus for two cropping cycles. The evaluation was based on crop growth and yield performances, changes in soil physico-chemical properties, crop nutrient concentrations and crop nutrient use efficiency. Results from the study showed that RHC is highly alkaline with pH 8.9, with a total carbon content of 16%, low bulk density of 0.17 g/cm3, particle size < 1mm, possess moderately high surface area of 401 m2g-1 with numerous meso to macropores ranging from (2.7 nm- 10 μm), presence of functional groups such as carboxylic acids and Methylene Blue adsorption capacity of 38.5 mg/g. RHC amendments at 5% and 10% was found to accelerate the composting process. The composts with RHC amendments showed early drops from the plateaued thermophilic temperaturestage by 10 days supported by higher CO2 respiration. The final RHC composts contained neutral pH characteristics (7-7.1). It was identified that higher moisture retention of 8% and 4% was obtained in the matured RHC compost 10% and RHC compost 5% respectively as compared to control. RHC was also found to minimize nitrogen loss during composting in which minimum losses of 0.4% for RHC compost 10% and 0.47% for RHC compost 5% was quantified at 10 days of composting as compared to 10.3% for compost without RHC (control). Laboratory leaching tests and SEM micrograph on RHC compost at both rates has proven that RHC does physically trapped and chemically sorb organic and inorganic molecules containing C, N, P and K and retained them against leaching losses. Field assessment for two seasons on Cucumis sativus showed the plots treated with 10% RHC compost gave the highest yield in season 1 (51.2 t/ha) followed by 5% RHC compost (49.5 t/ha) and fresh RHC 3% applied into soil (49.4 t/ha). Meanwhile for season 2, the highest crop yield production was in 5% RHC compost (45.9 t/ha), followed by 10% RHC compost (45 %) and fresh RHC 3% (41 %). The yield achievement is strongly correlated with crop nutrient concentration of N, P, and K as well dry root mass which were significantly higher in plots under 5% RHC compost and 10% RHC compost and followed by fresh RHC at 3% amendment as compared to non-amended RHC compost plot. Meanwhile soil CEC, pH, water holding capacity and porosity were found the highest in plots treated with 3% RHC. Treatment of RHC 1% into soil showed lesser positive effects and plots without RHC treatment was showing significantly lowest values for crop yield, growth and changes in soil physico-chemical characteristics.

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