红壤水稻土肥力性状的演变特征

大田条件下 ,通过选点采样分析 ,研究了不同利用年限红壤水稻土的物理、化学和生物学性质的动态变化特征。荒地红壤水耕利用后 ,土壤颗粒组成呈现规律性变化 ,粘粒 (<0 0 0 2mm)含量从荒地红壤的 3 9%下降到 80a稻田土壤的 1 7% ,而粉砂 (0 0 2～ 0 0 0 2mm)含量升高。土壤pH一般增加 0 5～ 1个单位 ;0～ 1 0cm土壤有机碳和全氮含量从荒地红壤的 4 5 8gkg- 1和 0 3 9gkg- 1增加到 3 0a红壤稻田的1 9 6gkg- 1和 1 62gkg- 1,其后 ,即使利用时间长达 80a ,土壤有机碳和全氮含量并没有显著差异 ;土壤全磷含量 ,经 3a水耕利用后可从荒地红壤的 0 5gkg- 1提高到 1 3gkg- 1,表明通过施肥可使红壤磷素快速积累 ;而在水耕利用过程中 ,红壤稻田土壤的钾素含量呈下降趋势 ,经 80a利用的红壤稻田 ,0～ 1 0cm土壤钾素含量仅为荒地红壤的 80 % ;全铁和游离铁的含量也呈下降趋势。随着水耕熟化过程 ,细菌数量和脲酶活性也明显升高。不同利用年限红壤稻田土壤的各项性状指标的变化结果还表明 ,荒地红壤水耕利用后要达到高度熟化的稻田土壤肥力水平 ,需要经过 3 0a的时间

DYNAMICS OF SOIL PROPERTIES OF PADDY FIELDS IN RED SOIL REGION

In the present study, changes in soil physical, chemical and biological properties in paddy fields of a cultivation chronosequence were observed by field sampling in a typical red soil region in subtropical China, Jiangxi Province.After cultivation, clay (< 0.002 mm) content decreased from 39% of the orig-i nal uncultivated wasteland to 17% of the 80 a paddy field, while silt (0.02~0.002 mm) content increased.Soil pH increased generally by 0.5~1 units, the 0~10 cm soil organic C and total N contents increased respectively from 4.58 g kg^-1 and 0.39 g kg^-1 of the original to 19.6 g kg^-1 and 1.62 g kg^-1 of the 30 a paddy field, and then remained stable.With 3 a cultivation for paddy field, total P content increased from 0.5 g kg^-1 to 1.3 g kg^-1, which suggested that fertilizer application can accelerate phosphorous accumulation in paddy field.0~10 cm soil total K content showed a decrease by 80% with a 80 a cult ivation.Total Fe and free Fe contents also showed a decreasing tendency.Bacterial population in-creased and urease activity intensified obviously.In this chronosequence it appeared that it took 30 year to raise fertility to a relatively constant value, seen after 80 a cultivation.