Nottingham Organic Gardeners on why most soil can be improved with a bit of humus

Soil types are a bit of a mystery to many gardeners, but most can be improved with the addition of some organic matter. CAROLINE LOWBRIDGE finds out more from an enthusiastic member of Nottingham Organic Gardeners, who practise what they preach

UNLESS you have very poor soil which is inhibiting the growth of your plants, you may not have thought about what 'type' it is. It's often only when people start growing fruit and vegetables that they think about improving their soil.

Traditional gardening books advise on various costly and environmentally-questionable treatments such as artificial liquid fertilisers, but the group Nottingham Organic Gardeners (NOGS) has a simpler approach.

"If you get loads of organic matter like garden compost that's the best thing to do," says Karen Fry from the group. "Adding humus will improve most soils. It will make sandy soil hold onto its water better and have more nutrients, and will lighten clay soil."

A good example of the argument for organic gardening is two plots on the Whitemoor Allotments, taken on by members of NOGS last year.

Work on the plots is ongoing, but the group tried growing a few crops last year.

"We spent a year getting to know the plot and growing stuff on the plot as it was, and some didn't grow very well at all," says Karen. "We think the soil hasn't been fed and replenished with compost."

The soil may well have been fed with fertilisers in the past, and crops may well have grown successfully there. But while adding inorganic fertilisers to soil can produce good results in the short-term, the soil itself becomes less fertile over time.

The organic approach is to feed the soil rather than feeding the plants. So boosting the humus content of soil – by adding materials of animal or vegetable origin – will not only make the soil more fertile, but improve the structure over time.

The easiest way to do this at home is to make compost in a compost bin, available at a subsidised rate from most councils. NOGS needed big amounts for their plots, so they used municipal compost instead.

Another method favoured by organic gardeners is the use of 'green manures' – fast-growing plants which can be dug into the soil to improve fertility. NOGS used phacelia. "It's got deep roots which go down and get nutrients from deep in the soil, bringing it up into the plant body, and then you chop it up into the soil," Karen said.

Leaf-mould can also be made by collecting autumn leaves and leaving them to rot in a black bin liner, punched with a few holes. Spread it over the soil and let the worms dig it in for you. This will also prevent damage to the soil structure, which digging can cause.

As part of NOGS' efforts to promote organic gardening, they are one of many Nottingham groups and organisations taking part in a sustainable gardening event called the Great Spring Sowing later this month.

Karen and others will be on hand to give advice on soil and organic growing in general.

"You can tell what sort of soil you've got by getting a handful and seeing if it will roll into a ball or sausage," Karen says. "Clay will roll into a ball and will be shiny, while sandy soil won't hold a shape at all and will feel sandy.

"Sometimes soils come from silt and feel silky, and limestone soils will have bits of white stone in them. The nearest to an ideal soil is loam, which is dark and crumbly and is a balanced mixture of the different mineral sizes and humus."

The Great Spring Sowing is The Arboretum from 10.30am to 4pm on Sunday, March 22.

For more information on the event visit http://www.transitionnottingham.org.uk/greatspringsowing/

For more information on Nottingham Organic Gardeners visit http://www.nogs.btik.com/home.ikml