BioCycle February 2011, Vol. 52, No. 2, p. 45
Project in the Hawkesbury-Nepean watershed in New South Wales is applying compost to 400 hectares of farmland to improve water retention and control nutrient runoff.
SINCE September 2009, growers from various industries across the Hawkesbury-Nepean Catchment (watershed) in New South Wales (NSW) have been opening their gates for deliveries of compost and mulch as part of the Nutrient Smart Farms project. The project is a joint initiative between Industry and Investment NSW (I&I) and the Hawkesbury-Nepean Catchment Management Authority. It is one of seven within the Hawkesbury-Nepean River Recovery Program, funded by the Australian government through its Water for the Future program.
The Hawkesbury-Nepean River System frames the region around Sydney, NSW, and contains the main water supply for Sydney while providing significant natural and recreational resources. One aim of Nutrient Smart Farms (NSF) is to improve water quality by reducing nutrient runoff from rural agricultural land. The target is to reduce the export of nitrogen by 27 metric tons/year and phosphorous by 6 metric tons/year. On-farm interventions include filter strips, detention ponds, off-river stock watering points and stock exclusion fencing. Another component of the project includes application of compost to 400 ha (about 988 acres) of farmland in the Hawkesbury-Nepean catchment.
By nature Australian soils are not very fertile, and the soils of the Hawkesbury Nepean catchment reflect this. Many are alluvial sandy loams. Farming has been undertaken in this region for more than 200 years, and much of the land has been continuously and intensively farmed. Large areas of agricultural land have become degraded, and would benefit from applications of organic matter to improve soil fertility, soil structure and productivity. In addition, the water quality in the Hawkesbury Nepean River has declined over time due to nutrient-rich runoff from a variety of sources including agriculture.
NSF’s compost application project seeks to capitalize on compost’s ability to improve soil structure and the related increase in the ability of the amended soil to hold nutrients and water. Increasing water-holding capacity will result in reductions in potable water use and river extractions. Increasing the nutrient-holding capacity will reduce nutrient levels in agricultural runoff.
Application of compost produced commercially and off-farm from vegetation and timber waste is a relatively new concept for agriculture in Australia. In possibly the largest project of its kind in the country, the NSF project utilized two companies – Australian Native Landscapes and Soilco – to supply more than 30,000 cubic meters of composted soil conditioner. This compost is produced from recycled organics from domestic green waste collections, timber and forest industry waste and commercial tree pruning operations that meet the Australian standard for pasteurized and mature composted soil conditioners. This standard does not specify products or processes to optimize performance for any particular application.
Typically, this compost has a particle size range of 10 mm to 30 mm and low nutrient content (0.5-1% N and 0.3% P). More than 400 ha of farmland received between 40 and 80 metric tons/ha (20 to 40 tons/ac) of compost. Most was incorporated, the exception being on grazing land. Vegetable farms, turf farms, orchards, grazing and dairy farms across a wide range of soil types were included.
Compost application rates used at each site were determined against initial background soil test results. Follow-up test results will show how the soils have responded to compost application. In addition, I&I NSW is monitoring eight of the 80-plus sites throughout the project area for changes in microbial activity and soil structure.
Education is a significant part of this project. For compost to be used as a regular input to agriculture, confidence needed to develop among farmers and the compost suppliers as far as the use of compost for agricultural application and the quality of compost available. This meant that the compost industry had to consistently produce high-quality compost and that the local farmers needed to recognize quality compost and understand its properties. Workshops held at muliple locations engaged local farmers and commercial composters discussing the role of compost in improving soil health.
In collaboration with the NSW Department of Environment, Climate Change and Water (DECCW), Compost NSW and compost researchers throughout Australia, specifications were drawn up for the compost so that it met the particular needs of each application site and guaranteed that the highest quality of compost was going onto agricultural lands (Table 1). These specifications have since become more widely used as benchmark specifications for compost applications to agricultural lands.
These specifications were followed to formulate compost for particular uses and particular soil types by describing the various chemical and physical parameters required. Stringent limits were set for physical contamination (Table 2).
I&I NSW also set up compost trials at the demonstration farm at the University of Western Sydney, Richmond to investigate and compare the response of growing vegetables with compost versus current farmer’s practice. Compost meeting the specifications was applied at rates of 20 m3, 40 m3 and 80 m3 in replicated trials. Overall water use and instantaneous water monitoring devices will ensure that growers see the water savings compost can deliver through improved water holding capacity. Soil physical, chemical and biological tests will provide data highlighting the positive addition of compost to all soil health parameters against current practice. Early results have shown improvements in soil organic carbon levels and soil structure resulting in increased soil water-holding capacity.
The research trials will provide scientific information to back up farmers’ individual experiences. While the project is only in its early stages, one grower, Valentine Micalef, expressed how the application of compost has helped with maintaining the structure of his formed beds after recent heavy rainfall. Another vegetable farmer, Tony Saad, had initially trialed compost on 5 ha and has now independently purchased compost to cover the other 30 ha of his farm. Both of these farmers have found significant reductions in water usage and advocate compost to other farmers in their industry. These positive experiences are spreading throughout the farming communities within the Hawkesbury-Nepean Catchment.
Virginia Brunton is a horticultural education resource specialist and is project officer for the Nutrient Smart Farms program sponsored jointly by the Government of New South Wales Department of Industry and Investment and the Hawkesbury-Nepean Catchment Management Authority.