秸秆覆盖对干湿态红壤坡面流水力学参数的影响

Effects of straw mulch on surface runoff hydraulic characteristics of dried and wetted red soil

秸秆覆盖对地表径流的水力学参数有重要影响。在江西省余江县中国科学院红壤生态实验站附近的坡耕地,利用人工模拟降雨研究秸秆覆盖对坡耕地干湿态红壤地表径流水力学参数的影响。结果表明,有无秸秆覆盖对土壤地表径流速度和曼宁系数影响明显：1）0~30%覆盖度之间,流速随着覆盖度的增大迅速降低,而曼宁系数随着覆盖度的增大迅速增大;30%~90%覆盖度之间,流速随着覆盖度的增大降低缓慢,但曼宁系数随覆盖度增大而在高位小幅振荡。2）在同一覆盖度下,湿态土壤流速比干态土壤流速大,在0、15%和30%覆盖度时,这种现象较为明显,当覆盖度大于30%时,这种现象不明显;在0~30%覆盖度范围内,干态土壤曼宁系数比湿态土壤大;在30%~90%覆盖度范围内,干态土壤曼宁系数比湿态土壤小。3）30%覆盖度秸秆覆盖可以有效降低地表径流流速,增大地表糙率。从经济实用和水土保持效果来看,30%的秸秆覆盖是该区农地水土保持的最佳选择。

Mulching soil surface with a layer of plant residue is an effective method for conserving water and soil.A laboratory experiment was conducted to evaluate the effects of antecedent moisture content（AMC） and straw mulch on surface runoff hydraulic characteristics using rainfall simulator.The rainfall simulator was used to create rainfall intensity of 60 mm/h for 1 h.The study site was located at the Ecological Experimental Research Station of Red Soil,Chinese Academy of Sciences,in Yujiang County,Jiangxi Province of China.The soil used in this study was red soil derived from quaternary red clay.The runoff plot was 12 m in length and 3 m in width with a slope of 14%.Antecedent moisture content levels（dried,wetted） and percentage of straw mulch（0,15%,30%,60% and 90%） were considered as two independent variables in this experiment design.The results showed that straw mulch affected the velocity and Manning coefficient significantly.The velocity decreased quickly with increasing the mulch in the range of 0 and 30%,and decreased slowly with increasing the mulch in the range of 30% and 90%.The runoff velocity of wet soil was larger than that of dry soil under the same mulch rate,especially with the mulch rate of 0,15% and 30%.The Manning coefficient increased quickly with increasing the mulch in the range from 0 to 30%,and changed slowly with increasing the mulch in the range from 30% to 90%. The Manning coefficient of the dried soil were larger than that of wetted soils between the mulch rate of 0 and 30%,and were smaller between the mulch rate of 30% and 90%.By reduced the velocity and increased the Manning coefficient,the straw mulch could protect the soil and water from erosion.The mulch rate of 30% could have the best effect of soil and water conservation from the view of the economy.