不同利用方式及不同开垦年限白浆土的肥力变化

Baijiang Soil Fertility Changes under Different Land Use Type and Reclamation Years

以黑龙江省八五三农场白浆土为研究对象，以邻近的荒草地为对照，研究林地、旱田、水田3种利用方式及不同开垦年限（30～50年）旱地（大豆-玉米轮作）和水田的土壤肥力变化。结果表明：不同利用方式下，土壤表层（0～20era）的pH值大小为：荒草地〉林地〉水田〉旱田；旱田和水田表层土壤有机质分别减少44．17％和44．74％，但是亚表层（20—40cm）有机质提高。全氮含量分别减少19．92％和18．42％，全磷有所提高，全钾含量没有明显变化，旱田利用方式下土壤速效氮含量最高，水田速效磷含量最高；旱田、水田速效钾含量显著下降（37．84％和60．18％）。开垦30—50年后，旱田表层土壤pH值下降1～1．09个单位。有机质、全氮含量分别减少28．23％．43．78％、12．03％～31．20％；而全磷呈增加趋势，全钾含量变化不大。土壤速效氮、速效磷含量分别增加12-32％。42．15％和77％～195．35％．速效钾含量减少38．73％～43．08％，且随开垦年限增加，有机质、全氮减小幅度增大，速效氮的增加幅度降低。速效磷的增加幅度上升。水田表层土壤pH值下降0．62～0．84个单位，有机质含量减少33．16％～59．92％。；土壤的速效氮、速效钾含量均显著降低（24．25％～78．1％和49．95％～60．73％）；速效磷含量增加56．82％～281．9％，且随开垦年限增加，有机质、速效钾减小幅度上升而速效氮减小幅度降低，速效磷增加幅度增大。

Baijiang soil of northeast China is one of the main low-yielding soils. It has about 15cm organic matter layer. Below it is the baijiang layer. Taking barren as the control. We studied the fertility changes of Baijiang soil under three land use types （forest land, dry land and paddy field）, different reclamation periods （30, 40, 50years） of dry land with soybean-maize rotation and paddy field in Heilongjiang Province. The results were as follows：Marked changes of acid has taken place on topsoil （O- 20cm） of Baijiang soil under different land use types. There was no significant difference in forest soil compared with barren, the pH of barren〉forest land〉paddy field〉dry land. The topsoil pH was lower than that of the subsoil （20-40cm）. Compared with barren land, in dry land and paddy field, the organic matter and the total nitrogen declined sharply by 44.17%,44.74%, and 19.92%, 18.42%, but increased in the subsoil. Total phosphorus increased slightly by 2.1%, 2.8% and 4.1% in forest land, dry land and paddy field, respectively. There was no significant change of total potassium in three soils. The available nitrogen reached the peak in top soil of dry land, so did available phosphorus in paddy field. Compared with barren, and the available potassium in dry land and paddy field declined by 37.8% and 60.8%, respectively. Soil pH in the dry land soil declined byl.0 to 1.1 as reclamation year increasing from 30 to 50 years. After cultivated 30-50 years, in 0-20cm soil the organic matter and total nitrogen decreased by 42.2%-43.8% and 12.0-31.2% in top soil, total phosphorus increased by 1.1%- 5.5% and the total potassium had a slight change. Available nitrogen and phosphorus increased by 12.3%-42.2% and 77%-195.35%, but available potassium decreased by 38.8%-49.1% in topsoil compared with barren, respectively. With the increasing years of reclamation, the decrease amplitude of organic matter, total nitrogen increased, the increase rate of available N reduced, rate of organic P rose. In 20-40cm soil the organic matter increased. After the Baijiang soil being reclaimed as paddy field for 30-50 years, soil pH decreased by 0.62-0.84unit, soil organic matter decreased by33.16%-59.92%, available nitrogen and available potassium decreased by 24.25%-78.1% and 49.95%-60.7%, and available phosphorus increased by 56.82-281.9%, compared with barren respectively. And the decrease amplitude of organic matter, available K increased, the decrease rate of available N reduced, rate of available P rose with the increasing years of reclamation. In 20-40cm soil the organic matter and available nitrogen increased in the subsoil