Impacts of rehabilitating degraded lands on soil health, pastures, runoff, erosion, nutrient and sediment movement. Part I: Rehabilitation methodologies to improve water quality flowing from grazing lands onto the Great Barrier Reef.

Abstract

The project RRRD.024 investigated the potential to mechanically rehabilitate degraded, bare, D-condition grazing lands to improved condition in the Burdekin and Fitzroy River catchments of north-east Queensland. With successful rehabilitation there will be increased pasture health and productivity which will reduce water, sediment and nutrient runoff, with the aim of improving the quality of water flowing into the Great Barrier Reef lagoon from grazing land. There were six set objectives of the study and a three-way research approach was developed to identify and quantify mechanical rehabilitation information for these objectives. Seven key findings were identified from the study.
Summary of seven key findings
The success of rehabilitation of D-condition, severely eroded grazing lands was highly correlated to seven key aspects:
1. a high degree of mechanical disturbance (intervention) is required (deep ripping, blade ploughing or, adding mulch after heavy disturbance) to increase water holding and infiltration: disturbance includes overland water flow control measures
2. selecting the most suitable and responsive soil types (non-sodic clays, clay-loams and loams)
3. sowing well-adapted pasture species (tropical grasses and legume cultivars)
4. long-term total grazing control to allow for rainfall-dependent pasture establishment, seeding and spread over the first 3-7 years, depending on rainfall
5. conduct mechanical disturbance and seeding rehabilitation programs in years of predicted above average seasonal rainfall conditions (la Niña years preferably)
6. start rehabilitation before all topsoil is lost, and exposing more serious chemical and physical constraints to pasture development; and
7. plan and monitor grazing management strategies early to prevent the development and spread of bare D-condition areas by maintaining healthy soils and pastures. Grazing land management training is desirable.