Recycled paper and compost could both be key tools to control plant disease

New research by the University of Warwick should have gardeners and commercial growers competing for both recycled paper and organic waste composts. The University's plant research department, Warwick HRI, is finding that recycled paper based composts are proving to be a major weapon in the fight against a range of plant diseases.

A University of Warwick research team under Professor Ralph Noble has recently shown that the use of composts can reduce the incidence of some important plant diseases by as much as 72%. That research, funded by the UK government's Waste and Resource Action Programme (WRAP), found that the replacement of around 20% of the volume of soil or peat by compost gave major disease control benefits.

Professor Ralph Noble's latest research appears to add another ecological benefit. Early results from trials with conifers using compost made from paper waste shows that it is providing much the same disease suppressing effect as green compost made from plant waste. This provides an obvious additional commercial use for the vast amount of paper waste generated by offices and homes.

Professor Noble said: "During paper recycling production a large proportion of the fibres cannot be recycled. The useable fibres are taken out to make new newsprint, and the small fibres are no longer usable, they're a waste by-product. In Britain, about half a million tonnes of these small, unusable fibres are produced each year. They have a potential use in growing media because they hold a lot of water, just like peat and, being a waste product, they have no other value. Obviously materials that are going to replace peat have to be very cheap or waste by-products. So, paper wastes fit this bill in terms of being cheap and they also hold a lot of water, which is what you need for plant growth".

The suppression of plant diseases was particularly noticeable when the green and recycled paper composts were added to peat. Peat is used by many growers as it provides a clean and uniform material that is suitable for plant growth – but its very cleanliness makes the plants growing in it susceptible to quickly spreading plant diseases. In contrast compost contains a diversity of microbes that can suppress plant diseases. The ecological benefits of this are obvious: less fungicide has to be applied to plants, less peat is required thus preserving peat bogs, and green waste and paper waste that would otherwise be land-filled is recycled.

Professor Ralph Noble says: "This research shows that the use of such compost could provide clear commercial benefits to growers and ecological benefits for us all. There should be no additional costs involved but we must still test the reliability of using composts for a wide range of commercial crops. Those growers who do change from using 100% peat could literally reap significant rewards"

Note for editors: Professor Ralph's survey found that when added to peat, green compost suppressed plant disease by the following average amounts