基于染色示踪的农膜残留农田土壤优先流特征

随着覆膜农作的发展,农膜残留日益严峻,严重影响土壤水流运动。为了探索农膜残留对水流运动的影响机制,在河套灌区九庄节水综合试验站,设计3种残膜量,分别为0,300,600 kg/hm^2,于成熟期在各试验小区选择典型区域进行20,80 mm水量的染色示踪试验,共6个处理,研究不同残膜量对土壤物理特性的影响,基于染色示踪技术分析不同入渗量和不同残膜量对土壤水流运动的影响,并评价各处理土壤剖面的优先流特征。结果表明:随着残膜量增加,土壤容重、饱和导水率和土壤初始含水率呈下降趋势,而土壤孔隙度呈增大趋势,土壤中随机分布的残膜导致残膜处理(300,600 kg/hm^2)的各物理参数有较高的变异系数。基于土壤染色剖面二值化图像分析,土壤优先流发育程度随残膜量和入渗量增加而提高,300,600 kg/hm^2残膜量处理的最大染色深度(MDSD)和土壤染色剖面的变异系数(Cv)随残膜量增加而增大,与20 mm入渗量相比,80 mm入渗量下残膜处理的MDSD和Cv分别平均增加47.23%和27.34%。不同处理的优先流特征指标差异显著,5个优先流特征指标(染色面积比、基质流深度、优先流比、长度指数和变异系数)均显示残膜处理(300,600 kg/hm^2)的优先流程度高于无残膜处理(0 kg/hm^2),可见残膜量及入渗量的增加均会增大土壤优先流的发生几率和强度。

Soil Preferential Flow Characteristics of Agricultural Film Residual Farmland Based on Dye Tracing Method

Agricultural plastic film residual (PFR) increase quickly with the development of mulching cultivation, and have a strong impact on soil water movement. In order to study the influence of PFR on water flow movement mechanism, the experiment was carried out in water saving experiment station of Jiuzhuang, Hetao irrigation area. There were six treatments, including three PFR amounts(0, 300,600 kg/hm²) and two water infiltration amounts (20, 80 mm). The influence of different PFR amounts on soil physical properties was studied, the effects of different PFR amounts and different infiltration amounts on soil water flow was analyzed based on dye tracing method, and the preferential flow characteristics for each treatments were evaluated. The results showed that soil bulk density, saturated water conductivity, and initial soil moisture content showed a decreasing trend with the increase of PFR amount, while an increasing trend for soil porosity. The random distribution of residual film in soil lead to higher variation coefficient of each physical parameter of PFR treatment. The development degree of soil preferential flow increased with the increase of PFR amount and infiltration amount. The maximum dyeing depth (M_DSD) and the coefficient of variation of soil staining profile (Cv) of 300, 600 kg/hm² PFR treatment increased with the increase of PFR amount.Compared with 20 mm infiltration, the M_DSD and Cv for PFR treatment at 80 mm infiltration increased by 47.23% and 27.34%, respectively. In addition, the characteristic index of preferential flow of different treatments was significantly different. Five characteristic preferential flow indexes (dyeing area, uniform flow depth, preferential flow ratio, length index, and coefficient of variation) revealed that the preferential flow of 300, 600 kg/hm² PFR treatment was higher than that of 0 kg/hm² treatment. It can be seen that the increase of residual film amount and infiltration amount will increase the occurrence probability and strength of soil preferential flow.