玉米季横垄坡面细沟侵蚀特征及其影响因素

通过野外人工模拟降雨试验,开展玉米不同生长期紫色土坡耕地细沟侵蚀特征研究,并分析玉米叶面积、雨强对细沟侵蚀过程的影响。结果表明:随玉米生长期推进,坡面产流时间、跌坎及细沟出现时间总体呈先增加后减少的趋势。苗期、拔节期跌坎与细沟出现的平均间隔时间分别为10′59″和15′30″,抽雄期、成熟期跌坎与细沟出现的平均间隔时间分别为20′16″和18′58″,玉米苗期坡耕地更易产生细沟侵蚀。苗期细沟形态发育完整,2.0 mm min-1雨强条件下,苗期最长细沟的长、宽、深分别为77.62、6.25和4.04 cm。随玉米生长期推进,细沟侵蚀阶段产流量表现为苗期拔节期成熟期抽雄期,苗期和抽雄期细沟侵蚀阶段产流量分别占玉米季径流总量的30.97%和19.01%,玉米各生长期细沟侵蚀阶段产流率均随降雨时间的推移呈波动上升。细沟侵蚀阶段产沙量表现为苗期拔节期成熟期抽雄期,苗期细沟侵蚀阶段产沙量显著高于其他生长期,玉米各生长期细沟侵蚀产沙率均随降雨时间呈波动变化。玉米季坡耕地细沟侵蚀产流量与雨强呈极显著正相关,产沙量与玉米叶面积指数呈显著负相关,产流率、产沙率与叶面积指数和雨强的回归方程均达极显著水平。

Characteristics and Influencing Factors of Rill Erosion in Slope Land with Contour Ridges during Maize Growing Season

Objective]Rill erosion is particularly serious on slope croplands of purple soil,where maize is the main crop. Therefore,it is a great significance to study how rill erosion occurs on the slope land during the maize growing season to evaluation and effective control of soil rill erosion. Method]To that end,a field artificial rainfall experiment was carried out for determination of characteristics of rill erosion on such slope croplands during different maize growing stages,and for analysis of effects of leaf area index and rainfall intensity on rill erosion process. Result]Results show that with maize growing in the field,runoff generation,drop-pit occurrence and rill formation varied temporally showing a rising-and-falling trend. Rills appeared earlier at the seedling stage(27′28″)than at the tasseling stage(48′03″). The average interval between drop-pit occurrence and rill formation was 10′59″,15′30″,20′16″ and 18′58″,respectively, at the seedling,jointing,tasseling and maturing stage,which indicates that rills formed much more easily during the seedling. When the rainfall was 2.0 mm min-1 in intensity,the rills developed best in morphology during the seedling stage,with the longest rill reaching 77.62,6.25 and 4.04 cm,respectively,in length, mean width and mean depth,and with the crop growing on,the volume of rill runoff at various growing stages displayed an order of seedling stage > jointing stage > maturing stage > tasseling stage. The volume of rill runoff during the tasseling stage and tasseling stage accounted for 30.97% and 19.01%,respectively,of the total of the entire maize season,and the runoff yield rate during the two stages was 751.48 ml m-2 min-1 and 461.23 ml m-2 min-1,respectively. However,the runoff yield rate,regardless of growing stage,displayed a generally rising trend,though fluctuating in the process with rainfall going on,and it fluctuated more obviously during the initial period of rainfall and gradually turned stable later on. Such fluctuation was higher in magnitude during the seedling stage than during the tasseling stage. The seedling stage was the highest among the four stages in rill sediment yield rate,reaching 6.96 g m-2 min-1 and followed by jointing stage, mature stage and tasseling stage. Rill sediment yield rate fluctuated with rainfall going on in all the stages and the fluctuation at the seedling stage was the highest in magnitude. Under rainfalls 1.5 or 2.0 mm min-1 in intensity,rill sediment yield varied sharply between maize growth stages while surface runoff did not much in volume,which indicates that the effect of maize plants conserving soil was realized through reducing sediment carrying capacity of the runoff. A significantly positive relationship was observed between volume of runoff and rainfall intensity during the rill erosion stage(r=0.93**)in slope maize fields,but negative ones were between rill sediment yield and maize leaf area index(r=-0.63*). The regression equations of runoff rate and sediment yield rate with leaf area index and rainfall intensity were rated at an extremely significant level (R2=0.95,R2=0.65). Conclusion]The findings in the study demonstrate that it is feasible to effectively control rill erosion on slope lands cultivated with maize at all its growing stages.