Sustainable reuse of rice residues as feedstocks in vermicomposting for organic fertilizer production

Abstract

Over the past decade, rice (Oryza sativa or Oryza glaberrima) cultivation has increased in many rice-growing countries due to the increasing export demand and population growth and led to a copious amount of rice residues, consisting mainly of rice straw (RS) and rice husk (RH), being generated during and after harvesting. In this study, Eudrilus eugeniae was used to decompose rice residues alone and rice residues amended with cow dung (CD) for bio-transformation of wastes into organic fertilizer. Generally, the final vermicomposts showed increases in macronutrients, namely, calcium (11.4-34.2%), magnesium (1.3-40.8%), phosphorus (1.2-57.3%), and potassium (1.1-345.6%) and a decrease in C/N ratio (26.8-80.0%) as well as increases in heavy metal content for iron (17-108%), copper (14-120%), and manganese (6-60%) after 60 days of vermicomposting. RS as a feedstock was observed to support healthier growth and reproduction of earthworms as compared to RH, with maximum adult worm biomass of 0.66 g/worm (RS) at 60 days, 31 cocoons (1RS:2CD), and 23 hatchlings (1RS:1CD). Vermicomposting of RS yielded better results than RH among all of the treatments investigated. RS that was mixed with two parts of CD (1RS:2CD) showed the best combination of nutrient results as well as the growth of E. eugeniae. In conclusion, vermicomposting could be used as a green technology to bio-convert rice residues into nutrient-rich organic fertilizers if the residues are mixed with CD in the appropriate ratio.

Instrumental characterization of organic wastes for evaluation of vermicompost maturity

“…EC measures the amount of salinity in an organic material and is a good indicator of vermicompost quality used in agriculture ). According to Shak et al (2014), the decrease in EC during vermicomposting may be due to the precipitation or leaching of soluble salts and mineralization of organic acids. Lasaridi et al (2006) observed that the plants have a maximum EC tolerance limit of 4.0 mScm −1 and below this value of EC, manure can be applied to soil for plant growth and development.…”

“…According to Suthar and Singh (2008), the loss of carbon and addition of nitrogen during the vermicomposting process reduces the C:N ratio in the end product. A C:N ratio of <20 confirms organic waste mineralization which indicates compost maturity; however, a C:N ratio of <12 is also preferred for agricultural purpose (Shak et al 2014). …”

Composting of olive processing wastes and tomato stalks together with sewage sludge or dairy manure

“…EC indicated the presence of soluble salts in the compost mixture. EC reflects the salinity of an organic amendment, in which high salt concentration may cause phytotoxicity (Shak et al 2014). EC values vary depending on the type of olive oil wastes and use of porous materials (Muktadirul Bari Chowdhury et al 2013).…”

Rice Husk and Its Applications: Review

“…Many researchers reported, RH is used to improve of nitrogen and other macro and micro-elements absorption which enhancing the production and translocation of the dry matter content from source to sink (El-Wehishy and El- Hafez, 1997;Awad, 2001;Ebaid et al, 2005;El-Refaee et al, 2006;Ebaid, et al, 2007). RH is bio transformed of into organic fertilizer through vermicomposting (Lim et al, 2012;Shak et al, 2014). Also it can be used as a source of potassium for growth and yield of cowpea (Priyadharshini and Seran, 2010).…”