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| Effect of phosphogypsum and gypsum as conditioners on rice husk and oil cake composting process and evaluation of their physicochemical character as a substrate |
| Received:May 16, 2020 |
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| KeyWord:composting;substrate;rice husk;phosphogypsum;gypsum |
| Author Name | Affiliation | E-mail | | ZHAO Bing | College of Resources and Environmental, Yunnan Agricultural University, Kunming 650201, China | | | WANG Yu-yun | College of Resources and Environmental, Yunnan Agricultural University, Kunming 650201, China | | | CHEN Xue-jiao | College of Resources and Environmental, Yunnan Agricultural University, Kunming 650201, China | | | XU Zhi | College of Resources and Environmental, Yunnan Agricultural University, Kunming 650201, China | xuzhi9910@126.com |
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| Abstract: |
| As composting conditioners, phosphogypsum and gypsum can increase the volume weight of loose material composting. At the same time, phosphogypsum also reduces the pH of composting products. The effects of phosphogypsum and gypsum on the utilization of rice husk matrix was evaluated from the perspective of substrate utilization, and the possibility of direct substrate utilization of rice husk by composting was discussed. Dry weight of 20% of phosphorus gypsum(T2)and gypsum(T3)were added as a conditioner to the test samples, and no conditioner was added to control(T1). The physical and chemical indexes such as temperature, pH, EC, water-soluble ammonium nitrogen(NH4+-N), water-soluble nitrate nitrogen(NO3--N), bulk density, and porosity of compost products were studied by aerobic composting. According to the requirements of composting harmless in the high temperature period of each treatment, the addition of phosphogypsum and gypsum can increase the seed germination index(GI value)in the late composting period and promote the composting and maturity process. At the end of the composting process, phosphogypsum and gypsum(T2 and T3 treatments)significantly increased the volume weight of composting products compared to that of the control(T1 treatment)(P<0.01). There was no significant difference between T2 and T3 treatments(P>0.05). The addition of phosphogypsum could significantly reduce the pH value of composting products(P<0.01), while the addition of gypsum could significantly increase the pH value of the composting products(P<0.01). The addition of phosphogypsum could also significantly reduce the content of water-soluble NH4+-N and increase the content of water-soluble NO3--N of the composting product(P<0.01). The weight density, venting porosity, and water holding porosity of the added phosphogypsum(T2 treatment) met the standard requirements of the vegetable seedling matrix(NY/T 2118-2012). Hence, the addition of 20% of phosphogypsum and gypsum to the rice husk-canola residue composting system can promote the composting and maturity process and complete the fermentation and maturity of the heap. The fermentation product on addition of 20% phosphogypsum in the rice husk composting system satisfies the requirements for volume weight, pH, and porosity in the substrate, and is a suitable substrate for vegetable seedlings. |
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