Abstract
In this study we investigated the effect of the way inputting rice straw on nitrogen removal efficiency. We prepared 52 mm inner diameter and 400 mm height soil columns, and input rice straw by three different ways as follows: 1) mono-layered, 2) cutting rice straw into 20-30 mm pieces and then mix it with soil, 3) milling rice straw into under 1 mm pieces and the mix it with soil. We supplied potassium nitrate solution of 50 mg-N·l-1 to these columns at the rate of 200 ml·d-1. The column with rice straw input mono-layered showed steady nitrogen removal, the nitrate nitrogen concentration of its outflow did never exceed 20 mg·l-1 during 44 days of operation. On the other hand, other columns reveals poor nitrogen removal. The nitrate nitrogen concentration of their effluents came as high as 40 mg·l-1 in ten days. We concluded that if we use rice straw as a carbon source for denitrification to remove nitrogen from soil percolate, it will be better that rice straw be put into soil as mono-layer, not mixed with soil.
