玉米秸秆覆盖对坡面产流产沙过程的影响

通过室内土槽模拟试验,研究不同降雨条件下玉米秸秆覆盖对沙坡地产流时间和产流产沙过程的影响。处理分为8种降雨强度和5个水平的秸秆覆盖度:0、15%、30%、60%和90%。40组模拟降雨结果表明:华北保护性耕作研究区域沙壤土条件下的产流时间与降雨强度符合幂函数关系;秸秆覆盖能延缓地表径流的产生,自然降雨(雨强10~80 mm/h)过程中,15%、30%、60%和90%秸秆覆盖较无覆盖分别推迟产流时间1.0~15.4、2.1~22.1、3.4~48.2和5.9~73.6 min;秸秆覆盖对地表径流和产沙影响显著,降雨历时1 h,30%秸秆覆盖减少径流总量17.9~/o~38.7%,减少产沙总量34.1%~48.0%0 30%秸秆覆盖水土保持效果显著,考虑到过多的秸秆覆盖(80%)会造成播种机堵塞,所以在保护性耕作研究实践中,建议保持30%~60%(1 400~3 100 kg/hm~2)的玉米秸秆覆盖,以达到较好的水土保持效果和播种质量,该研究可为保护性耕作研究区域适宜的玉米秸秆覆盖量提供依据。

Effects of maize straw mulching on runoff and sediment process of slope

Abstract: Straw mulching is a main method to reduce soil erosion and improve soil moisture. However, overmuch straw mulching may lower the anti-blocking capacity of no-till planter, affecting seeding quality and grain production in conservation tillage system in North China Plain. So, more researches should be conducted to investigate the suitable straw mulching quantity in conservation tillage system. Aiming at achieving suitable straw mulching conditions for high-performance planting of no-till planter and efficient soil and water conservation, this paper studied the effects of straw mulching on slope runoff and sediment yield process under different simulated rainfalls, and quantified the straw mulching rate for different conditions. A rainfall simulation experiment was carried out at Zhuozhou Experimental Station of China Agricultural University, Hebei province, from October 2013 to May 2014. The soil-bin (length: 1m, width: 1 m, slope rate: 9%) was filled with sandy loam soils according to natural soil structure in North China Plain. The surface was covered by chopped (less than 100 mm) maize straws collected after maize harvesting (early October). A rainfall simulator (model: DIK-6000, made in Japan) was used to produce different rainfall intensity. In this experiment, eight kinds of rainfall intensity (10, 20, 30, 40, 50, 60, 70, and 80 mm/h) and five kinds of straw mulching rate (0, 15%, 30%, 60%, and 90%) were considered as two independent variables in experimental design (three replications). Each simulated rainfall lasted for 1 h. The results showed that under different straw mulching rates, runoff time and rainfall intensity varied as power functions in conservation tillage fields in North China Plain. Straw mulching significantly (P<0.05) delayed runoff time in each simulation, and compared with uncovered treatments, straw mulching treatments with a coverage of 15%, 30%, 60% and 90% delayed runoff time by 1.0-15.4, 2.1-22.1, 3.4-48.2, and 5.9-73.6 min, respectively. Furthermore, straw mulching restrained runoff and reduced total runoff and total sediment yield. Compared with no straw mulching treatment, 30% straw mulching treatments significantly reduced total runoff by 17.9%-38.7%, but the positive effect in 15% straw mulching treatment was negligent. For sediment yield, the value in >30% straw mulching treatments was 34.1%-48.0% lower than that in no straw mulching treatment under total 8 kinds of simulated rainfall conditions. However, significant reduction (15.6%-34.7%) in 15% straw mulching treatment could only be founded in heavy rainfall (50-80 mm/h) experiments. The results above demonstrated that >30% straw mulching rate could significantly reduce soil erosion and improve soil water retention capacity. However, in North China Plain, the annual output of maize straw is about 7000 kg/hm2. In conservation tillage fields, if the straw mulching rate is over 60%, and this heavy straw cover condition will affect no-till planter's anti-blocking capacity. So, in conservation tillage system, 30%-60% maize straw mulching (1.4-3.1 t/hm2) is recommended to achieve high performance of planting and high efficient soil and water conservation, which provides the valuble information for suitable straw mulching rate of maize in North China Plain during the application of conservation tillage practice.