Saturday, 15 July 2006

Composting of Rice Straw and Hardwood Bark with Oilseed Sesame Cake and Rice Bran.

Sang-Beom Lee, National Institute of Agricultural Science and Technology, 249 Seodundong Kwonsungu, 441-707 Suwon, South Korea

Compost offers positive advantages on soil quality and can provide an important source of nutrients for plants. Small-scale composting becomes an alternative treatment method of organic materials, generated from different sources. The used organic materials in this experiment were rice straw, hardwood bark, oilseed sesame cake and rice bran. Rice straw and hardwood bark are rich in carbon content, whereas oilseed sesame cake and rice bran are rich in N. The mixtures for composting were prepared using these four organic materials at different ratios. The mixtures of C rich materials (rice straw and hardwood bark) and N rich materials (oilseed sesame cake and rice bran) were a ratios ranging from 50% to 80% C rich materials. The temperature during the composting process rose immediate after piling and maintained at a level between 50~65C. The patterns of temperature change in mixtures of hardwood bark were significantly a higher level than in mixtures of rice straw. The total N content of all treatments increased gradually during composting from an initial value between 0.16 and 1.53% to 1.00 and 3.68% by the end of composting after 14 weeks. Conversely, the C content decreased slowly until the end of the composting period. The C/N ratios dropped dramatically from 7 weeks onwards to 25~40 and were then maintained at a level of 20~35 until 14 weeks. The pH values of all treatments increased continuously throughout the entire composting period. Their pH values were observed from an initial 5.0~8.4 to 6.6~9.0 by the end of composting. The other chemical properties such as available P2O5, extractable K, Ca and Mg were also increased slightly during composting period. Composting rice straw and hardwood bark with high nitrogen contained organic materials (oilseed sesame cake and rice bran) creates a production that supplies plant nutrients. The mixtures of containing 70% to 80% rice straw and 60 to 70% hardwood bark were produced the most suitable compost in terms of nutrients and maturity. Keywords: composting, organic materials, rice straw, hardwood bark, organic farming.

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