Abstract: To study changes in nitrogen forms in pig-bed litters and their impacts on physico-chemical properties of the underlying soil, water content, pH, and contents of different forms of nitrogen and organic matter in the 0-20 cm and 20-40 cm layer of litters and the >40-60 cm and >60-80 cm layers of underlying soil were determined in an experiment conducted of pig bio-bed from November 17, 2012 to May 24, 2013. It was found that with the litters kept in use longer, the contents of water and organic matter in the litters both displayed a trend of continuous decrease. As pigs kept on excreting urine and faeces, the content of TN, alkalytic nitrogen and NO₃^--N in the litters increased steadily, while pH and NH₄⁺-N displayed a different trend, rising first and then declining. In the underlying soil, because of infiltration, organic matter and nitrogen also followed a rising trend. It is, therefore, necessary to take some measures to prevent downward infiltration of effluent from the pig bio-bed for protecting underlying soil and water from pollution.

Key words: bio-bed pig rearing, bio-bed litter, nitrogen, organic matter