紫色土坡地旋耕机耕作侵蚀特征

Rate and pattern of tillage erosion by rotary cultivator on the steep land of purple soil

耕作侵蚀的过程机制和防治技术研究是我国现阶段水土保持科学与技术的重点研究领域,关于小型旋耕机耕作的土壤再分布过程和影响因素研究较少。应用磁性示踪法研究旋耕机等高耕作、向下耕作和向上耕作的土壤再分布模式和强度,查明耕作速度对旋耕机耕作侵蚀的影响。结果表明:不同耕作方向下旋耕机单次耕作过程中均引起土壤同时发生向上坡和向下坡移动,且均导致土壤发生向下坡净位移;不同耕作速度时等高耕作和向上耕作土壤净位移与坡度均呈显著正相关(P<0.01),而向下耕作二者无显著相关性(P>0.05);土壤净位移量表现为快挡等高耕作(11.53 kg/m)>快挡向下耕作(11.40 kg/m)>快挡向上耕作(7.59 kg/m)>慢挡向下耕作(7.33 kg/m)>慢挡等高耕作(6.87 kg/m)>慢挡向上耕作(6.29 kg/m);快挡时上下坡交替耕作的耕作侵蚀速率小于等高耕作,但慢挡时二者相当。旋耕机耕作相比传统耕作机具的耕作侵蚀明显下降,其推广应用对于防治紫色土坡地耕作侵蚀和土壤退化有重要作用。

[ Background] The process mechanism and conservation technology of tillage erosion are the key research domains of science and technology for soil and water conservation at current stage in China. Most of researches on the tillage erosion have focused on the effect of towed or hanging mechanized tillage and manual or animal-powered non-mechanized tillage on soil translocation and soil loss. However, there is few researches about the processes and factors of soil redistribution by the direct-connected rotary cultivator tillage. [ Methods~ The magnetic tracer method was used to label soils of 84 experimental plots with different gradients ranging from 5.7% to 30.9% , and to quantitatively evaluate the rate and pattern of soil redistribution by rotary cultivator tillage on the steep land of purple soil in Sichuan Basin, southwestern China. Ilmenite powder was selected as magnetic tracer, because its contrasting color distinguished from the surrounding soil and high level of magnetic strength, and it could be closely adsorbed on soil surface and move simultaneously with the eroded soil. In order to determine effects of tillage speed and directions on tillage erosion rate, three tillage directions of i） parallel to the contour ii） downward along the slope and iii） upward along the slope, and two tillage speeds of high and 10w gear for each tillage direction were set up in the study. [ Results] The results showed that at each tillage direction, any single tillage by rotary cultivator caused soil moving in both upslope and downslope simultaneously, and net translocation of soil was in the downslope direction due to gravity. While at different tillage speeds, the net transloeation rates were significantly correlated with slope gradient in contour and upward tillage （P 〈 0.01 ） , respectively, but not significantly correlated in downward one （P 〉0. 05）. Net soil translocation rate decreased in the order： contour at high gear （11.53 kg/m）, downward at high gear （11.40 kg/m） , upward at high gear （7.59 kg/m） , downward at low gear （7.33 kg/m） , contour at low gear （6.87 kg/m） , and upward at low gear （6.29 kg/m）. Tillage erosion rates induced by upslope-downslope alternative were less than those by contour at high gear operation, however, they were equivalent at low gear operation. Tillage erosion rate （4.54 -7.68 t/hm^2 under downslope parcel length of 15 m conditions） by rotary cultivator was much lower than by traditional farming implements （52. 89 and 53.06 t/hm2 for hoeing tillage and ox-drawn ploughing, respectively） , i.e., more than 85% erosion rate decreased. [ Conclusions] Therefore the expanding application of rotary cultivator should play a critical role in reducing tillage erosion and preventing soil from degradation on the sleep land of purple soil.