耕作侵蚀磁性示踪的影响因素

Influencing Factors of Tillage Erosion Using a Magnetic Tracer

以钛铁矿粉作为磁性示踪剂,研究土壤磁化率背景值、操作方式、测定条件对耕作侵蚀磁性示踪的影响,确定耕作侵蚀磁性示踪技术的适宜测定条件。结果表明:紫色土研究样地的耕层土壤磁化率背景值和空间变异性都较小,对示踪剂磁性强度要求不高;土壤磁化率与示踪剂浓度可以利用线性方程拟合,示踪剂浓度在20~70g/kg时,拟合效果较好(R^2=0.999 6,P<0.001);当土壤颗粒组成中粗颗粒(粒径>5mm)占主导时,土壤磁化率与粒径<2mm和2~5 mm含量呈显著正相关,与粒径5~10 mm和10~20mm含量呈显著负相关,然而当细颗粒(粒径<5mm)占主导时,土壤磁化率与土壤颗粒组成无关;土壤磁化率与堆积厚度、土壤含水量和土壤紧实度呈正相关关系,与取样间距、示踪剂老化、土壤温度关系不明显。耕作侵蚀磁性示踪技术的适宜测定条件为:钛铁矿粉磁性示踪剂浓度为20~70g/kg,土壤磁化率测定时细颗粒占多数(>50%),堆积厚度在5cm以上,土壤紧实度在50~150N/cm^2,保持耕作前后土壤磁化率测定中堆积厚度、土壤含水量和土壤紧实度等条件基本相似。试验和应用表明钛铁矿粉的性能较适合作为耕作侵蚀磁性示踪剂。

This study chose ilmenite power as magnetic tracer to reveal impacts from background value and variability of soil magnetic susceptibility, layout and manipulation of sampling site, measuring conditions of soil magnetic on determination of tillage erosion, and then determined suitable conditions for magnetic tracer technology of tillage erosion. The background value and spatial variability on soil magnetic susceptibility of soil sampling sites were not obvious, which was not strict with strength of magnetic tracer. The soil magnetic susceptibility increased with increase in concentration of tracer and the linear fitting was the best when the tracer concentration ranged from 20 to 70 g/kg. When the diameter of soil particle larger than 5 mm was predominant, the soil magnetic susceptibility was positively correlated to diameters of smaller than 2 mm and ranged from 2 to 5 mm, but was negatively correlated to diameters of ranged from 5 to 10 mm and from 10 to 20 ram. When the diameter of soil particle smaller than 5 mm was predominant, there was not significant relationship between soil magnetic susceptibility and soil particle constitution. The soil magnetic susceptibility was positively correlated to soil accumulating depth, soil water content, and soil compaction, however, no highly significant correlations were found between soil magnetic susceptibility and sampling spacing, tracer aging, soil temperature. The suitable conditions for determination of tillage erosion using a magnetic tracer were that tracer concentration was 20-70 g/kg, the percentage of soil particle whose diameter was smaller than 5 mm was larger than 50%, the accumulating depth was larger than 5 cm, and the soil compaction ranged from 50 to 150 N/cm^2. And furthermore, soil accumulating depth, soil water content, and soil compaction should be similarities before and after tillage. Through experiment and application, it was proved that the properties of ilmenite power were more suitable for tracing soil in tillage erosion experiment as a magnetic tracer.