INTEGRATED MANAGEMENT OF IN‐FIELD, EDGE‐OF‐FIELD, AND AFTER‐FIELD BUFFERS¹

Abstract

This review summarizes how conservation benefits are maximized when in‐field and edge‐of‐field buffers are integrated with each other and with other conservation practices such as residue management and grade control structures. Buffers improve both surface and subsurface water quality. Soils under permanent buffer vegetation generally have higher organic carbon concentrations, higher infiltration capacities, and more active microbial populations than similar soils under annual cropping. Sediment can be trapped with rather narrow buffers, but extensive buffers are better at transforming dissolved pollutants. Buffers improve surface runoff water quality most efficiently when flows through them are slow, shallow, and diffuse. Vegetative barriers ‐ narrow strips of dense, erect grass ‐ can slow and spread concentrated runoff. Subsurface processing is best on shallow soils that provide increased hydrologic contact between the ground water plume and buffer vegetation. Vegetated ditches and constructed wetlands can act as “after‐field” conservation buffers, processing pollutants that escape from fields. For these buffers to function efficiently, it is critical that in‐field and edge‐of‐field practices limit peak runoff rate and sediment yield in order to maximize contact time with buffer vegetation and minimize the need for cleanout excavation that destroys vegetation and its processing capacity.

Managing ditches for agroecological engineering of landscape. A review

“…Finally, D'Itri and Belcher (1994) also mentioned that field drainage associated with water level regulation in ditches controls the minimum water table level during the dry season for crop subirrigation. In northern America, subirrigation, i.e., subsurface irrigation, has enabled increases of yields from 12 to 48 % for maize and soybean (D'Itri and Belcher 1994).…”

An assessment of vegetation characteristics and hydrologic flow pathways on the effectiveness of vegetated buffer strips for phosphorus reduction in an agricultural watershed

“…Additionally, they are designed to intercept contaminants at the source instead of as a final barrier before an adjacent waterway (Dabney, Moore, & Locke, 2006). In regions with steep hillslopes, multiple in-field buffers can be placed along the contours of the hillslope.…”

“…A secondary function of buffers is to reduce soil P through uptake by vegetation and to improve soil permeability and infiltration through root channels (Dabney et al, 2006;Syversen, 2005). To retain dissolved P, Barfield et al (1998) and Lee et al (2003) argue that infiltration is the most effective method, particularly when vegetation creates frequent vertical soil channels.…”

“…However, in flatter areas such as the Canadian Prairies and much of the LWB, the more common in-field buffer practices are vegetative barriers that are narrow but densely planted strips of vegetation that follow the edge of cultivated fields, and grassed waterways that run from upslope to downslope and are designed not to trap sediments, but to direct surface water to protect soils, and to prevent erosion (Dabney et al, 2006).…”

“…In a review of the conservation benefits of different types of buffers, Syversen (2005) and Dabney, Moore, & Locke (2006) outlined mechanisms by which buffers can improve water quality. These include P uptake by vegetation, entrapment of particulate P from overland runoff, slowing the rate of overland runoff, increased soil permeability through root channels, and retention of snow.…”