Streamside management zones for buffering streams on farms: observations and nitrate modelling

Environmental Science and Management not elsewhere classified

Smethurst, Philip ; Petrone, Kevin ; Baillie, Craig ; Worledge, Dale ; Langergraber, Guenter

Landscape Logic CERF Hub

RP-ID  :  EP105960

学科分类：地球科学(综合)

澳大利亚|英语

来源: CSIRO Research Publications Repository

【 摘 要 】

atural resource managers need quantitative information on the effectiveness of streamside management zones (SMZ) in agricultural landscapes for protecting water quality. Analysis of buffer experiments internationally had previously suggested that a buffer width of 15 m would remove about 80% of nitrogen (N). Nitrate is the main form of N of interest, but until recently there were few Australian data or model predictions available on buffer effectiveness. In 2007, a research project commenced in the Landscape Logic CERF Hub that focused on buffering a headwater stream from N contamination, with the aim of (1) quantifying the N-buffering effect at a small catchment scale, and (2) developing a model that integrated the salient processes and that potentially could be applied to other catchments. This research complimented a related project in the CRC for Forestry that included a much lower level of nitrogen monitoring. This report summarises our progress on these two aims. Measurements were made in a previously-established, steep, paired-catchment experiment with adjacent buffered and unbuffered headwater streams in a low-intensity grazing system. Modelling utilised the HYDRUS model, which has wide acceptance internationally for mechanistically simulating soil water and solute processes. We also used its N module (CW2D) that was developed for simulating nitrate removal by constructed wetlands. The 10 ha buffered catchment had an area of grazed pasture (62%) low in the landscape, and the rest was native forest. Approximately 10% of the pasture was fenced around the stream to exclude stock and to allow the establishment of a forest plantation. The adjacent 4 ha catchment in the same paddock was 99% grazed pasture and cattle had free access to its stream when stock were in the paddock. Stream water from both catchments was monitored for various forms of N. No fertiliser was applied to the pasture and only a small amount of hay was used as a feed supplement. A small amount of diammonium phosphate fertilizer was buried beside each tree seedling in the plantation soon after planting. Pools and fluxes of N measured in the buffered catchment were: pasture N uptake, N mineralisation and nitrification, and N concentrations in rain water, soil water, soil leachate, and the watertable.