Good Soil: The use of compost to condition soil leads to healthy vegetables and flowering shrubs.

Published On:Tuesday, August 31, 2010

By Gardener Jack

Our Bahamian soil is young in geological terms and there is not a lot of it. Any help we can give to improve or condition the soil will be rewarded by increased plant production.

The Bahamas is a mountainous country but the mountains are below the sea and their tops are flat and composed of oolitic limestone, which is highly alkaline. The problem with alkaline soil is its reluctance to allow mineral salts to be in the right state to be absorbed by plant roots. This phenomenon is called 'tying up' and means that fertilisers applied to highly alkaline soil are unable to be used efficiently by plants.

Native plants in The Bahamas are adapted to alkaline soil and many exotics have a wide tolerance that permits them to grow well here. Many others, however, prefer acid soil and barely survive. One good example is ixora. Planted straight into the ground ixora will soon show signs of stress and the leaves will suffer from chlorosis.

Flowering will be reluctant and the whole vitality of the plant will be debilitated. Ixora needs help and that comes from conditioning the soil.

Alkaline soil can be treated with sulphur in the form of powder, or flowers of sulphur. If sulphur is worked into the soil around shrubs it can reduce alkalinity substantially and allow better absorption of fertiliser.

Another remedy is to apply Sequestrene 138-Fe, a specialised chelated iron that acts as a catalyst and promotes the absorption of mineral salts. This remedy is expensive but only a little Sequestrene is required for each treatment.

The applications of sulphur and chelated iron are temporary and the treatment must be ongoing. The best and more permanent way to condition the soil is to add rotted material that we generally refer to as compost.

I know as soon as many readers come across the word compost they will sigh and turn the page. Compost is a bugbear to many gardeners because the old fashioned ways of making it were time consuming and laborious, not to mention smelly.

These days you can buy a tumbler-type composter that gives you workable compost in a month. Even simpler, you can add your composting materials directly to the soil.

Have a small bucket by the back door and fill it with kitchen vegetable trimmings, coffee grounds and used paper towels - as long as they have not been used to mop up oil. Dig a hole in your vegetable garden as deep as you can and put your waste inside and refill the hole. Water it and mark the position with a stick, then work on your next bucketful.

Here in the subtropics organic material breaks down very quickly. Within a few weeks your fortified holes will contain a rudimentary form of compost that your vegetables will enjoy.

Ideally a compost is composed of green or nitrogen matter mixed with brown or carbon matter in the ratio of 3-1, though experienced gardeners will argue at length over their own favourite ratio.

Green nitrogen matter includes fruit and vegetable scraps, coffee grounds, tea bags, eggshells, green plant material, peanut shells, hair, grass clippings, and the shells of all peas and beans.

Brown carbon matter includes dry grass, sawdust, wood ashes, nutshells, shredded newsprint (use yesterday's Tribune!), kitchen towels, tissue paper, corncobs, and dry leaves.

This form of composting is about as easy as it gets. If you compost your garden in this way on a regular basis you will eventually have a vegetable garden that only needs the occasional application of fertiliser in order to produce the best vegetables possible.

* gardenerjack@coralwave.com