GREEN COMPOST waste can help control weeds and improve soil structure, delegates at a recent Henry Doubleday Research Association talk have heard.

Good weed control from such practices has been achieved in organic baby leaf salad crops, said Keston Williams, agronomist for Vitacress salads.

“Last year we used 20,000t of compost on our organic and conventional crops. It works well on annual weeds, but not on perennials or polygonum species,” he said.

Applying compost as a mulch can not only help suppress weeds, but it also provides a source of readily available phosphate and potassium, said Francis Rayns from the HDRA.

But the nitrogen content from composts is relatively unavailable in the short term, he advised growers.

Growers concerned about composts carrying over diseases should be assured that the risk is fairly low, said Steve Roberts, a plant pathologist working with the HDRA.

“The majority of pathogens are eliminated if the composting process sustains 55oC for at least seven days,” he said.

But growers of high risk crops like brassicas or tomatoes should achieve higher temperatures of 65oC, or use disease testing to ensure pathogens such as club root and fusarium wilt are not transmitted, he said.

One study has found that compost can actually help suppress diseases such as root rots, club root and onion white rot, noted Ralph Noble of Warwick HRI.