湖南几种耕地土壤固定态铵释放的动力学研究

Kinetics of release of fixed ammonium from several types of cultivated upland soils and paddy soils in Hunan province, China

通过野外调查取样、室内培养试验与分析测定,研究了湖南省几种母质发育的旱地土壤和稻田土壤固定态铵释放的动力学。结果表明,供试土壤固定态铵的释放非常缓慢。水田土壤培养8周后,旱地土壤培养7周后均未达到最大释放量,其累积释放量随着时间的延长而增加;除开始2d内固定态铵的释放稍快外,整个培养期间土壤固定态铵的释放速率基本保持恒定。其中,土壤“新固定的”固定态铵的释放率远远大于“原有的”固定态铵。在水田土壤条件下,“新固定的”固定态铵经培养8周后,可释放出“新固定的”固定态铵的58.0%-80.8%,而“原有的”固定态铵仅能释放2.4%-8.8%。数学拟合结果表明,一级动力学方程和抛物扩散方程均能很好地拟合供试土壤固定态铵释放的动力学资料,零级方程也有较好的拟合效果,但Elovich方程较差。研究还表明,溶液中的阳离子种类会影响土壤固定态铵的释放,Ca^2＋的存在较K^＋更有利于固定态铵的释放。

The kinetics of release of fixed ammonium from several types of cultivated upland soils and paddy soils derived from chief parent materials in Hunan province, China, were studied with sampling on fields, and laboratory incubation and determination. The obtained results showed that release of fixed ammonium in the tested soils increased with the incubation time, and the rate of fixed-NH4^＋ release was very slow. Release of fixed ammonium still continued at the reaction time of 8 weeks for the paddy soils and of 7weeks for the upland soils and had not reached the maximum releasing capacity. The release rate of fixed ammonium did not change almost during the whole incubation period except the initial 2 days. The releasing rate of recently fixed ammonium is much larger than that of inherently fixed ammonium. For the paddy soils, recently fixed ammonium could release 58.0% to 80.8% of it, and inherently fixed ammonium only released 2.4% to 8.8% of it after 8weeks of incubation. The statistical analysis showed that both first-order equation and parabolic diffusion law equation were the most adaptable to describing the data of fixed-NH4^＋-release kinet- ics characterized by the larger correlation coefficient（r） and the lowest value of the standard error of estimate （SE）. The category of cation could also affect release of fixed-NH4^＋ from soil. Ca^2＋could help release of fixed ammonium perhaps as it could expand the space of the interlayer of 2 ： 1 type clay minerals.