不同水耕年限稻田土壤水分渗漏与保持特征

以江汉平原连续水耕年限大于100年(老稻田)和由旱耕改为水耕17年(新稻田)的稻田为研究对象,通过测定土壤剖面基本理化性质和水力学参数,揭示了2种稻田土壤水分渗漏和保持特征差异。结果表明:(1)新稻田土壤的平均饱和导水率(Ks)为32.05cm/d,显著高于老稻田(17.91cm/d)。新、老稻田土壤Ks均表现为耕作层底土层犁底层,新稻田耕作层Ks分别为犁底层和底土层的6.3倍和5.7倍,老稻田耕作层Ks分别是犁底层和底土层的6.9倍和4.0倍。(2)老稻田土壤持水能力高于新稻田,同一剖面不同土层持水能力表现为耕犁底层底土层耕作层。0.03mm当量孔径的孔隙比例随土壤剖面深度的增加而降低,新稻田各层土壤比例大于老稻田。(3)新、老稻田最大有效水含量随土壤深度的增加而降低,老稻田各土层(32.25%~46.59%)均高于新稻田(26.99%~36.74%)。老稻田平均总库容(135.8mm)大于新稻田(124.4mm),新稻田滞洪库容(11.21~38.74mm)大于老稻田(8.1~60.74mm)。旱耕改水耕加重了水资源的消耗,增加了浅层地下水污染风险。

Characteristics of Soil Water Percolation and Conservation in Different Aged Paddy Field

Based on the profiled soil physical/chemical and hydraulic properties measurement, the characteristics of water percolation and conservation in different aged paddy fields in the Jianghan Plain were investigated, and the paddy fields were of 17 years (new paddy field, NF) and more than 100 years (old paddy field, OF), respectively. The results were as follows: (1) Water percolation was more likely to occur in the NF. The higher average saturated hydraulic conductivity (Ks) in the NF (32.05 cm/d) was observed than that in the OF (17.91 cm/d). The highest Ks was observed in the plow layer, followed by the subsoil layer, and the lowest Ks was in the plough pan. The Ks of plow layer was 6.3 and 5.7 times of the plough pan and subsoil layer for the NF, and 6.9 and 4.0 times for the OF, respectively. (2) Higher water capacity was observed in the OF than that in the NF. The highest water capacity was identified in the plough pan, followed by the subsoil layer, and the lowest was found in the plow layer. However, the macropore distribution showed the opposite law. (3) The available water content decreased with the decreasing soil depth in the NF and OF, with higher values observed in the OF. In addition, higher total water capacity and flooding control capacity were also observed in the OF. The water shortage stress and groundwater pollution risk were increased by the land transformation from the non-irrigated farmland to the paddy field.