黄河泥沙充填复垦耕地表层土壤垂直入渗特性研究

Vertical infiltration characteristics of reclaimed farmland soils with Yellow River sediment fill

采用单圈入渗法,以当地原有长期耕种的耕地为对照,对引黄河泥沙充填复垦第2年的耕地表层土壤水分垂直入渗过程进行了现场测定,探讨复垦耕地耕种第2年的入渗特性,分析比较不同复垦时间的土壤入渗结果,并选用5种入渗模型对入渗特征曲线进行了拟合。结果表明:充填复垦第2年对照耕地的初始入渗率、稳定入渗率平均值分别是充填耕地的1.12倍和2.19倍,充填耕地呈上层表土入渗能力差、下层泥沙保水性能差的特性,有待改良;充填耕地各试验点间入渗率差别较小,入渗能力稳定;充填复垦第2年充填耕地初始入渗率、稳定入渗率平均值分别是第1年的1.51倍和1.43倍,充填耕地入渗率显著提高(P<0.05),耕种措施有改善充填耕地入渗能力的作用。Mezencev模型对充填耕地土壤入渗特征拟合效果最佳,Kostiakov模型对对照耕地土壤入渗特征拟合效果最佳;综合充填耕地和对照耕地而言,Mezencev模型具有最佳的拟合效果,其次为Kostiakov模型、NRCS模型、Horton模型和Philip模型;各模型的RMSE、R2、SSE和Ajust-R2指标显示,模型评价具有较好的一致性。

The technique of using Yellow River sediment to fill damaged farmlands in mining subsidence areas not only fully and rationally use Yellow River water and sediment resources, but also effectively increase farmland areas and improve re- gional environment. Infiltration is an important indicator for farmland soil and water conservation and nutrient retention. Lab infiltration apparatus was used to measure the vertical infiltration of reclaimed farmlands with Yellow River sediment fill, The aim of the study was to obtain the soil infiltration characteristics in Yellow River sediment fill farmland in the second year, and analyze and compare the experimental infiltration results of the first and second years of reclamation. Five infiltration models were selected to fit the characteristic curves of infiltration. The results showed that mean initial infiltration rate and mean sta- ble infiltration rate of control farmland were 13.95 mm,min-1 and 4.36 mm.min-1, which were 1.12 times and 2.19 times higher than that of fill farmlands in the second year of reclamation. The discrepancy was caused by the compaction effect of machinery used in the land reclamation process. The standard deviations of initial infiltration and stable infiltration rates of fill farmlands were 1.98 mm.min-I and 2.1 mm.min-~, significantly lower than those of control farmland （P 〈 0.05）. Thus the infiltration capacity of fill farmlands was steadier than control land. The mean initial infiltration rate and mean stable infiltration rate of fill farmlands in the second year of reclamation were 12.48 mm.min-1 and 1.99 mm.min-1, respectively; 1.51 times and 1.43 times higher than that in the first year of reclamation. This suggested that infiltration rate of fill farmlands increased significantly （P 〈 0.05） after two years of corn-wheat crop rotation. Thus farming practices, root development and the activities of soil microorganisms and small animals enhanced self-recovery capacity of fill farmlands. Therefore the study proposed cultivation of corps with well-developed root system to improve soil infiltration capacity in fill farmlands. In terms of the es-timation of soil infiltration rated, Mezencev model was the best for fill farmland, followed by Kostiakov model, NRCS model, Horton model and the Philip model. For control farmlands, Kostiakov model was the best, followed by Mezencev model, NRCS model, Horton model and Philip model. For both fill farmlands and control farmlands, Mezencev model had the best fit result, followed by Kostiakov model, NRCS model, Horton model and then Philip model. As the difference in assessment index between Mezencev model and Kostiakov model was small （P 〉 0.05）, both models had small fitting errors. However, because some of the parameters of Mezencev model （a semi-empirical model） had real physical meaning, Mezencev model was considered to be better than Kostiakov model. In addition, the rankings of the models based on different assessment indices were basically similar. This led to a considerable consistency in RMSE, R2, SSE and Ajust-R2 of infiltration models. This study provided research methods for determining farmland infiltration characteristics and the significant results were achieved. The results therefore provided the scientific basis for the reconstruction and improvement of fill farmland soils. The study as well provided certain guiding codes and practical values for the management of farmland irrigation and drainage.