保护性耕作的不同因素对降雨入渗的影响

通过 2次人工模拟降雨试验 ,研究了机械化保护性耕作以及秸秆覆盖、表土耕作及机具压实 3因素对降雨入渗的影响。结果表明保护性耕作有延缓径流 ,增加降雨入渗的作用 ;秸秆覆盖和机具压实是影响降雨入渗的主要因素 ,表土耕作的影响相对较小。在土壤干燥 ,降雨强度为 72 mm.h-1的条件下 ,保护性耕作处理与传统翻耕处理比较 ,其地表产生径流的时间延迟 12～ 16 min,且稳定入渗率提高 1.5～ 1.6倍 ;分析各因素的影响可知 ,秸秆覆盖使径流延迟 8min产生 ,稳定入渗率提高 1.1倍 ;机具压实使径流早 7min产生 ,稳定入渗率降低 4 7.5。进一步研究压实程度和覆盖率对降雨入渗的影响 ,结果表明 :秸秆覆盖率越高 ,径流开始的时间和土壤含水量达到饱和的时间越晚 ,且稳定入渗率越高。在所试的秸秆覆盖率范围 (0～ 70 )内 ,同等降雨条件下 ,随着秸秆覆盖率的增大 ,径流量近似按二次曲线减少。随着土壤含水量的增大 ,秸秆覆盖对降雨入渗的作用减弱而压实的影响增强 ,压实可使表层土壤的体积质量增大 ,土壤入渗性能降低。在土壤含水量较高 ,降雨强度为 82 .5 mm.h-1条件下 ,压实使径流产生时间比无压实的早 13min,使稳定入渗率降低86 .8。机器质量越大 ,压实影响的深度越大。试验表明 ,小拖拉机和中型拖拉机都使

Rainfall Infiltration Related to Different Conservation Tillage Factors

Two rounds of field rainfall simulation experiments were conducted to assess the impacts of conservation tillage and its related factors, including surface tillage, residue cover and wheel traffic, on runoff and infiltration. The first test showed that conservation tillage can remarkably delay runoff and improve infiltration compared to conventional moldboard plough practice(CK). Among the three factors, residue cover and wheel traffic are more influential for infiltration, while the effect of surface tillage is not clear. Under low soil moisture and 72 mm/h of rainfall rate, conservation tillage could delay runoff 12~16 minutes and the final infiltration rate could be 1 5~1 6 times more than CK; Residue cover could delay runoff 8 minutes and increase the final infiltration rate by 1 1 times while wheel compaction produce runoff 7 minutes earlier and decrease infiltration rate by 47 5 % . The second test is to further investigate the effects of different levels of compaction and residue cover on infiltration. Within cover rate of 0~70 % , when residue cover increases, ponding and saturation will be delayed, the final infiltration rate will be higher and runoff amount will decrease along the conic curve vs cover rate. When soil is wetter, the effect of residue cover will be lower and the effect of compaction will be stronger. Compaction could increase surface soil bulk density hence worsen infiltration capability. Under the experimental situation with high soil moisture and 82 5 mm/h of rainfall rate, wheel compaction could produce runoff 13 minutes earlier and decrease infiltration rate by 86 8 % . Moreover, the heavier the machinery, the deeper the soil is compacted. Small tractor could compact soil within the surface of 10 cm and middle size tractor could affect the depth to 20 cm or more. Both the tractors could remarkably compact the surface 10 cm which is critical to rainfall infiltration.