CANTERBURY arable farmers now have ready access to spent mushroom compost as a nutrient-rich source of organic fertiliser following the establishment of a commercial spreading service.
Agricultural services company, Winslow Contracting, has spent the past two years working with Meadow Mushrooms – New Zealand’s largest mushroom grower – refining the logistics of the program.
Winslow Contracting Managing Director, James Carr, says the new service is a ‘win-win-win’ for all stakeholders. “Our arrangement as a supplier of straw and exclusive compost disposal services to Meadow Mushrooms provides arable farmers with a ready market for their stubble,” he says. “In turn, we can provide Meadow Mushrooms with a consistent supply of quality straw and a professionally-managed compost disposal service. The spent mushroom compost will then be made available to arable farmers to replace valuable nutrients lost via the removal of stubble.”
Winslow has been supplying straw to Meadow Mushrooms’ growing facility at Prebbleton, south of Christchurch, for almost 30 years. Ironically, the compost spreading service was established primarily to encourage arable farmers to supply straw to Meadow Mushrooms. “Many producers have become reluctant to bale straw because it removes an important source of potassium,” James says. “Two years ago, we began a pilot program whereby we offered our customers two tonnes of compost for free in return for every bale of straw which meant they were compensated for any nutrients lost through baling. All they had to pay was spreading and transport costs.”
The program was so successful that Winslow Contracting and Meadow Mushrooms decided to expand it into a full-blown commercial operation. The compost is sold for $42.50–47.50/tonne, including delivery and spreading. “It’s one of the few products that pays for itself,” James says. “Its nutritional quality is fairly consistent, although the moisture content can vary from 28 to 33 per cent. It contains a good source of all the standard nutrients – nitrogen, potassium and phosphorus – as well as organic matter, which is good for soil structure and water holding capacity. All told, we think each tonne delivers about $40 worth of nutritional value, depending on the moisture content, as well as providing long-term benefits for the soil which are not always considered. Arable farmers in Canterbury are increasingly looking for organic alternatives to synthetic fertilisers. The availability of irrigation means many farmers have the opportunity to double-crop and this is really asking a lot of their soils.”
Winslow Contracting is already spreading more than 10,000 tonnes of compost a year and James expects this figure to triple or even quadruple within a few years. “We already have access to about 600 tonnes of quality compost each week and that amount is going to grow significantly as domestic demand for mushrooms grows,” he says. Industry data shows that the average consumption of mushrooms in New Zealand is about 2 kg per capita, compared to 3.2 kg in Australia.
Upon arrival at the Prebbleton facility, straw is shredded, soaked, treated with microflora and mixed with poultry manure before being stored in temperature-controlled enclosed bunkers for six weeks. The compost is then steam-pasteurised and moved to the growing room, where inoculated peat is spread over the top. Following harvest three weeks later, the compost is stockpiled on participating farms until it is spread using a high performance Pérard CL300 tracked spreader, which has a massive capacity of 35 cubic metres. Its hydraulic floor chain and PTO-driven twin double-helix rotors achieve accurate spreading rates of between 4 and 8 t/ha and a spreading width of up to 24 metres.
The spreader is towed by a new generation CLAAS AXION 930 tractor, which is equipped with a super-efficient 350 hp (257 kW) engine, continuously variable transmission, four-point cab suspension and smart on-board technology as standard. “The spreader weighs about 30 tonnes fully loaded, so we need about 350 hp to tow this and the AXION 930 is perfect for this,” James says. “It has an advanced electronic management system that enables the engine to deliver full torque at all speeds. There’s no powerboost and the fuel economy is very good. The CVT means we can maintain a precise ground speed to deliver exactly the desired application rate and the cabin suspension means it’s extremely smooth.”