A meshl-bag method for field assessment of soil erosion

ABSTRACT:

Field measurement of soil erosion is often desirable in soil conservation or management research. Conventional dyriamic methods (e.g., sediment and water collecting methods) are costly, laborious, and, in many cases, unavailable. This report from the tropical cropland in the Amazon region of Peru, describes a simple “mesh-bag” method for field assessment of soil erosion. A preliminay testing of nylon mesh-bags of 30 × 30 cm (12 × 12 in) with 5 mm (2 in) mesh on the top and 2 mm (.07 in.) mesh at the bottom were constructed and placed randomly in field plots and removed periodically to determine the quantity and quality of the eroded soil collected. Analysis of the variance indicated that the pooled coefficient of variation is seven percent within the side-by-side pairs; 24 percent within plots, and 42 percent within a management system. The efficiency of the bags stayed unchanged at least to the extent of 10 g (.35 oz) bag. Further testing of the method on 5 × 30 m (16.4 × 98.4 ft); 15–20 percent slope plots indicated that the amount of soil collected is independent of the position along the continuous slopes. The amount of soil collected in the bag correlated well with the product of rainfall × rainfall intensity (mm × mm/h). The mesh-bag method is reproducible and sensitive. By raking soil erosion under different practices in the field, it provides a simple means to sample eroded materials. Although the method is semi-quantitative at present. It has the potential to be developed into a truly quantitative method if rigorous evaluation under controlled environments and comparison with other conventional methods can be performed.