Manure benefits - a case study in patience
GroundCover™ Issue: 100 | Author: Tony Craddock, Clarisa Collis
Spreading chicken manure as an alternative source of nutrients for grain and hay production has allowed a South Australian family to scale back its use of conventional fertilisers.
However, the long-term benefits of improved nutrient levels in the soil were slow to emerge on the Schuster farm in the Freeling district, about 60 kilometres north of Adelaide.
Three generations of the Schusters, including Merv, Gavin, Corbin and Leighton, have been spreading chicken litter across their grain and hay paddocks for 12 years.
“We didn’t notice any visual benefits at first, but as the years went by we began to notice an improvement in our soil tests results, especially in phosphorus levels,” Gavin says.
After initially applying the byproduct from broiler sheds to just over 60 hectares a year, the Schusters now annually spread between 1500 and 2000 tonnes of chicken litter over 600 to 800 hectares.
These rates were guided by the Schusters’ estimate that 2.5t/ha of chicken manure is roughly equivalent to the amount of phosphorus contained in 125 kilograms of diammonium phosphate (DAP).
Gavin says the cumulative benefits of using chicken litter over more than a decade has led to them reducing their DAP fertiliser rates by up to 30 per cent.
In the past, they typically applied 2.5t/ha of chicken manure in conjunction with 100 to 120kg/ha of DAP at seeding. More recently, this base rate was cut back to 90kg/ha, which saved them almost $26,000 on DAP in 2010.
Gavin is confident that their soil phosphorus levels are now high enough to reduce their DAP applications to 40kg/ha on individual paddocks where chicken litter has been applied – saving a further $24,000 a year.
“We were originally targeting 40 parts per million of Colwell P as a measure of plant-available phosphorus in the soil; however, our soil tests now indicate these levels are between 50 and 60ppm,” he says.
The possible saving on DAP fertiliser, estimated at $50,000 a year, is supported by a trial on the Schuster property funded by the Rural Industries Research and Development Corporation in 2010. This study showed there was no yield penalty in wheat paddocks where chicken litter was applied and DAP rates were reduced (see Figure 1).
Nitrogen is another major component in chicken litter so the Schusters spread it on their paddocks before sowing wheat and canola from late March until early April.
“We find it necessary to decrease our conventional nitrogen applications in areas where we’ve spread the manure to avoid burning crops,” Gavin says.
On their sandy country, higher manure rates of 3t/ha are applied, along with lime and gypsum, as part of a strategy to improve soils.
Gavin says, apart from providing essential nutrients such as phosphorus and nitrogen, the fertiliser alternative has proved a valuable source of trace elements, particularly zinc and copper.
The Schusters use a French-manufactured Rolland machine with a nine-metre-spreading width, but Gavin is keen to upgrade to a 20-metre width. He says the ability to spread the chicken litter more evenly using a wider spreader would increase efficiency and, ultimately, the plant uptake of essential nutrients and trace elements.
He says a spreader equipped with a chopper system and a chain base that breaks up the manure and uniformly feeds it onto the spinner deck is also important for even applications.
The size of the spreader bucket used for loading the litter is another feature of the Schusters’ equipment that helps avoid downtime. They use a telescopic handler (a forklift and crane hybrid) with a 3.5 cubic metre bucket, meaning the spreader can be fully loaded with four scoops.
Gavin says positioning piles of chicken litter in the centre of paddocks has helped minimise downtime when loading the spreader. For long-term storage, he suggests arranging the product in long rows, no higher than two metres, in the corners of paddocks to avoid sterile cropping areas caused by leaching.
To support local industry, the Schusters buy straw-based manure from a local chicken farmer, but they also source composted product, which has a relatively subdued smell, for spreading within 500m of Freeling.
Gavin urges growers to carefully assess the expenses of spreading and carting chicken litter. “These costs can often be as much per tonne as the product itself.”
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