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How can compost benefit my ?

Compost can improve overall soil health when incorporated into the soil or surface-applied as a soil conditioner. Despite differing in nutrient requirements, such as , , , , canola, lucerne and can all benefit from the addition of pasteurised and composted organic materials.

Give crops a kick-start and boost soil health Compost can improve your soil’s transforming, releasing and cycling Compost also plays a role in suppressing physical, biological and chemical of nutrients and essential elements. plant diseases and international properties and positively enhance Increasing soil organic matter promotes research has shown great results when actively growing crops. microorganisms that are essential for compost is incorporated into the soil. converting nutrients into their plant Quality compost naturally contains a Physical available forms and facilitating nutrient range of bacteria and fungi that can Replenishing soils with compost not uptake by plants. suppress organisms that cause disease. only adds valuable organic matter This can occur in a number of ways with to your system but also adds to the As the organic matter decomposes over the beneficial microbes: consuming the stock of soil carbon. Organic matter time it results in the development of pest fungi, producing antibiotics and/or contains organic carbon which plays more stable carbon compounds, made hormones than can be harmful to pest a central and fundamental role in soil up primarily of humus. Humus enhances fungi and competing for food and other quality and fertility. The organic matter mineral breakdown and in turn nutrient resources. Compost can also help plants acts as the ‘glue’ to bind soil particles availability. Highly mature and stable to fight off disease by boosting their into aggregates thus improving soil composts contain stable long-lasting immune system and providing more structure, infiltration, air porosity, water forms of carbon called humates (or favourable conditions for plant growth. and nutrient holding capacity. sometimes humic and fulvic acids). These are also recognised to be very In most cropping systems, carbon important for soil health and fertility. is taken off the farm through grain harvesting, stubble fed to stock or cutting of hay. Soil quality and fertility Total nutrient levels vs. available nutrients reduces over time as carbon is being continually removed from the farm Not all of the nutrients in the compost are immediately available for use by and not replaced. Applying compost plants and microorganisms - this is also the case with synthetic fertilisers and even within your soil. An initiative of Compost Australia replenishes the soil organic matter and helps to sustain soil quality and fertility and maximise production over time. The amount that is immediately available to the plant will depend on your soil For more information and a list of quality suppliers, go to type and its properties as well as the environmental conditions. Biological Adding compost to soil improves It is a good idea to check your soil nutrient test results and correlate that to microbial diversity and activity by your compost nutrient tests before application. Regular monitoring will help ensure you are not applying too much (or too little) of a particular nutrient the resource for compost users providing microbes with a food source: organic matter. Microbial and you can adjust synthetic fertiliser applications where necessary. You will populations are responsible for need to account for compost nutrient inputs in your nutrient budget. Chemical Many nutrients are removed from the $$ Value of Nutrients in Compost soil each year through cropping: Nutrient min–max kg/t $/kg** min–max $/t • Nitrogen (N) loss ranges from 17 kg/t compost*2 compost of yield with oats to 40 kg/t of yield Nitrogen 6 – 24 1.27 7.62 – 30.48 for canola Phosphorus 2 – 11 4.40 8.80 – 48.40 • Phosphorus (P) loss ranges from 2 Potassium 2 – 19 1.68 3.36 – 31.92 kg/t of yield with cereal hay to 6.5 Calcium 7 – 44 0.50 3.50 – 22.00 kg/t of yield for canola Sulphur 2 – 6 0.70 1.40 – 4.20 TOTAL $24.68 – $137.00 • Potassium (K) loss ranges from 3.7 kg/t of yield with wheat to 20 kg/t of * nutrient composition of compost will vary between products - your compost supplier can provide you with an analysis. The range here includes composts made from just garden organics (min) 1 yield for hay. and compost made from manures using a specialised process to concentrate nutrients (max). This range includes total nutrients, check your compost analysis for levels of available nutrients. As plants require a consistent supply ** based on March 2010 fertiliser prices, calculating the $/tonne by the % nutrient/tonne. of nutrients throughout the crop cycle The information in this document is based on the best available knowledge and understanding at to achieve high yields, these nutrients the time of publishing. No person should act on the basis of the contents of this publication without need to be replaced. Compost can first obtaining specific, independent professional advice. The authors, editors and publishers take no responsibility for the accuracy, reliability and correctness of any information in the document supply many nutrients to your crop. and it is the responsibility of the users to make their own decisions about the accuracy, currency Compost can also make the nutrients and reliability of this information. already in your soil more available to plants through increased microbial activity and nutrient cycling.

In the table above we have shown an example of the total nutrients (minimum and maximum) in compost and their value based on current fertiliser prices.

Applying compost also increases the effective cation exchange capacity (CEC) of soil. An increase in CEC leads to higher soil adsorption of positively charged cations such as calcium, magnesium, potassium and sodium. The increase in cations translates into nutrients being held in the soil but made progressively available for plant uptake. This also leads to reduced acidity and higher soil pH. Soils with low CEC can lose nutrients easily through the movement of soil water. The Australian story: field trials and case studies Western Australia Soil bulk density decreased and porosity During the 2004 cropping season, increased with compost application field trials in Western Australia were as well as a significant increase in soil conducted by Organic Farming organic matter content as a result of Systems3. The aim of the field trials was increasing compost application rates. to demonstrate the practical benefits Six months after compost application, of using compost in existing farming potassium levels were significantly systems. Twenty farms were chosen for elevated - for every 10 t of compost the study and compost was broadcast applied there was an increase of around at two rates – 10 t/ha and 20 t/ha (wet 12 mg/kg (from a base of 360 mg/kg in weight) on each property. The field trials control treatment). were conducted on a range of crops including wheat, barley, lupins, canola Findings from the first year of the trial and oats. indicate that compost can improve growing conditions for crop production. Average wheat yields improved by 20% Increases in soil moisture retention, with the 20 t/ha compost application organic matter and porosity improve and 13% with the 10 t/ha compost conditions for plant development application. One farm reported and can reduce run-off and fertiliser yield increases of 39% above the loss. More water and nutrients are control at the higher rate of compost available for plant uptake, while at application. Compost application in the same time off-site environmental wheat production showed consistent impacts are minimised as run-off is improvements in soil moisture, plant dry reduced. Improvements in soil quality weight and tiller numbers. The use of associated with compost use will likely compost on broadacre farms during this have an effect on crop yield and farm trial improved soils by increasing soil sustainability in the long term. The benefits of using buffering capacity (pH) and moisture compost can still be holding, boosting the soil’s ability to New South Wales seen several years after retain nutrients and improving soil Recycled organics are being used chemical characteristics. on a demonstration site to assist in application. rehabilitating an overgrazed feedlot Victoria paddock in NSW5. Recycled organics • using compost soil conditioner A trial to study the effects of compost were applied in a 60:40 ratio of coarse over a three to five year period on soil quality and crop improvement in mulch:fine soil conditioner and trial is the best way to judge its raised beds was established to address plots were drilled with oats. benefits and effectiveness. inadequate soil drainage and organic matter levels in broadacre cropping soils Observations on plots with compost at • target compost applications to in south western Victoria4. the site to date show: poor performing areas in the • excellent initial germination first instance - these are likely Composted soil conditioner was applied • increased plant dry weights to benefit most. over three years at ten rates (ranging • increased plant available moisture from 0-90 dry t/ha) and incorporated and flowering and seeding • soil properties change over into the beds when they were reformed • excellent follow-up germination. time with compost use - to a depth of about 20 cm. In the first irrigation, spray programs, year, soil moisture increased significantly Further monitoring of the trial is cultivation and other farm with increasing compost application expected to demonstrate long term programs may need to be rates during May and July. benefits. adjusted as well. Global experience from research in the United Kingdom

The use of compost in broadacre wheat yields comparable to the The UK experience has demonstrated cropping is more developed in the standard UK fertiliser program. However, that compost can help to maintain United Kingdom, and detailed scientific the use of compost as well as a reduced and enhance soil organic matter and data is available from years of research fertiliser rate brought significant savings add value to cereal crops, particularly and field programs6. in bag fertiliser costs while still reaching those grown on lighter soils. Further similar wheat yields. field trials in Australia will strengthen Long-term cereal trials in eastern the local data set and provide valuable England have demonstrated significant Waste & Resources Action Programme information and guidelines for future yield increases from the use of compost (WRAP) data from the UK shows that 30 compost use in broadacre cropping. as well as increased soil organic t/ha (a typical UK field application rate) carbon, improved soil structure, plant of compost applies approximately 6-7 t/ establishment and water infiltration rate. ha of organic matter. A high proportion of organic matter in compost is lignified A trial conducted in southern Ireland (stabilised form), so it is likely to have over a three year period demonstrated a longer-lasting beneficial effect in soil that using compost at 22 t/ha, plus than other organic materials such as a reduced rate of inorganic fertiliser farm manures. nitrogen (100 kg/ha), produced winter

References 1 Grains Research and Development Corporation (2010). Recycled organic fertiliser fact sheet. www.grdc.com.au 2 Dorahy, C.G. and Yin Chan, K. (2010) Closing the loop - developing agricultural markets for recycled organics in NSW through targeted scientific research. Enviro 2006. 3 David, S. and King, C. (2005) Affect of improving soil organic matter with compost on broad-acre crop production, Organic Farming Systems. 4 Stokes, J., Cody, J., Maheswaran, J. B.E., Unkovich, M., O’Leary, G. (2003). A long-term study into compost applications for broadacre cropping. Solutions for a better environment: Proceedings of the 11th Australian Agronomy Conference, Geelong, Victoria, Australia, 2-6 February 2003. 5 Southern Rivers Catchment Management Authority (unknown). Case Study: Drought Feedlot Rehabilitation Trial. 6 WRAP (2009) Using quality compost to benefit cereal crops, www.wrap.org.uk/composting.

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