Erosion control using soil surface treatments and native grasses at Craig Creek, Northern Territory
Creators: name: Calnan, Taegan
Publisher: name: Charles Darwin University
Year: 2006

description: The loss of resources from an ecosystem caused by soil erosion affects both the function of the immediate surrounds and those systems downstream. Stemming this loss from an area using local grasses and soil surface stabilisers to capture nutrients can stabilise the system and restore ecological function to a degraded area. The overall aim of this project was to develop practical techniques for controlling erosion at the Craig Creek site of Mt Bundey Training Area in the Northern Territory, through the use of soil surface treatments and grasses local to the area. The research is in three linked stages that specifically address the following three aspects of rehabilitation: (1) the germination and dormancy characteristics of local grasses; (2) the use of various soil surface treatments for stabilising the soil surface and promoting grass establishment and persistence and; (3) the growth characteristics of perennial grasses from the site and responses to soil amelioration and watering treatments. Fifteen grasses were assessed and seven had germination rates greater than 40% in at least one of the treatments. Low viability was a factor in the low germination rates of some grasses. Dormancy was a factor with potassium nitrate significantly increasing thegermination of Era grostis rigidiuscula (from 1 % to 28%) and Brachyachne con vergens (7% to 27%). Germination was most successful in sand, in shadehouse conditions, compared to laboratory tests with seeds on filter papers, and three species had germination &gt; 90% (Era grostis sororia, E. rigidiuscula and Vacoparis laxiflorum). The use of soil surface stabilisers over the course of a wet season (October—April) resulted in soil accrual on the jute and wire+mulch treatments, while soil was lost from plots with the log mulch. Vegetation establishment on the vegetation plots was high following the wet season (1233 individual grasses established on 336 m2); in contrast, persistence through the dry season drought was very low. Aristida macroclada was the only grass still present in the plots in November (9 grasses on 336 m2 remaining). Sodicity was very high in the eroded area, with 70% exchangeable sodium in the fine sediments in the centre of the scald zone. Growth responses of A. macroclada, E. rigidiuscula, E. sororia and Panicum decompositum to shadehouse trials investigating soil amelioration and watering treatments were positive for the fertiliser addition and waterlogging. There was no response to gypsum. Eragrostis rigidiuscula displayed the best traits for erosion control, with the highest growth rates and foliage cover of all the species. Aristida macroclada had low growth rates and low foliage cover, however it was the most persistent of the species. In summary, jute and wire + mulch are effective soil stabilisers for the Craig Creek area. Aristida macroclada and E. rigidiuscula both establish on the site without assistance, and with the addition of fertiliser, persistence rates and vegetation cover should increase providing protection to the dispersive sodic soils during the erosive wet season rain.