Journal of Integrative Agriculture
© 2013, CAAS. All rights reserved. Published by Elsevier Ltd.
Changes in Phosphorus Fractions and Nitrogen Forms During Composting of Pig Manure with Rice Straw
LÜ Dui-an 1, 2, Y AN Bai-xing 1, W ANG Li-xia 1, DENG Zhi-qiang 1, 2 and ZHANG Y u-bin 3
Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, P.R.China 2
University of Chinese Academy of Sciences, Beijing 100049, P.R.China 3
College of Plant Science, Jilin University, Changchun 130062, P.R.China
The study was conducted to reveal P fractions and N forms changing characters during composting of pig manure with rice straw. During composting, the NH 4+-N concentration decreased and reached at a relatively low value (<400 mg kg -1) in the final compost, while the NO 3--N concentration increased. Total N losses mainly occurred during thermophilic phase due to the high temperature, the high NH 4+-N concentration and the increase of pH value. Labile inorganic P was dominated in the pig manure and initial compost mixture. During composting, the proportion of labile inorganic P of total extracted P decreased, while the proportion of Fe+Al-bound P, Ca+Mg-bound P and residual P increased. The evolutions of the proportion of labile inorganic P, Fe+Al-bound P and Ca+Mg-bound P were well correlated with the changes of pH value, organic matter and C/N ratio. Therefore, composting could increase the concentration of N and P and decrease the presence of NH 4+-N and labile P fractions which might cause environmental issues following land application.
Key words : composting, nitrogen forms, phosphorus fractions, organic matter, pig manure
Pig manure has sufficient amount of nutrients, especially N and P, which are the main limiting nutrients in majority of soil for crop production. However, long-term manure application to agriculture lands will lead to N and P accumulation in soils and an acceleration of soluble N and P transfer into water bodies via runoff (Huang et al. 2011; Li Q et al. 2012). To address this problem, strategies such as composting has been adopted in many countries. During composting, labile organic compounds are stabilized and converted into products that could be used as organic fertilizer and soil conditioner.
The N forms are closely related to the degree of compost maturity (Bernal et al. 2009). Immature compost usually means high NH 4+-N concentration which can be easily lost through NH 3 volatilization following land application (Doydora et al. 2011; Vaddella et al . 2011). During composting, NH 4+-N can be immobilized or transformed to organic forms. Knowledge of evolution of N forms during composting is particularly important to assess agronomic and economic value of compost product, maturity of compost and risk following land application. The concentrations of P in animal manure and compost ranged from 1.5 to 39.3 g kg -1 (Sharpley and Moyer 2000). Most of the studies about P during composting only include total P (TP) content or the increment
Received 25 October, 2012 Accepted 6 March, 2013
LÜ Dui-an, Tel: +86-431-85542215, E-mail: email@example.com; Correspondence WANG Li-xia, Tel: +86-431-85542215, E-mail: firstname.lastname@example.org