Improving drainage with the addition of organic matter.

Press, 29 June 1983, Page 16

Improving drainage with the addition of organic matter.

Many problems occur in the garden during the winter months because of poorly-drained soils. Now is an excellent time, before the soil becomes too wet, to prepare planting beds or sites and avoid problems arising from wet puggy soils later on. Clay soils are particularly prone to water-logging problems in winter. These soils are made up of extremely small particles which pack together tightly. Roots find it difficult to penetrate between the particles and the soil moisture is held so tightly that it does not drain away easily. This is the worst type of soil for plant growth. In most home gardens, the addition of plenty of organic matter into the soil is often sufficient to improve the physical condition of the soil and help avoid diseased and unthrifty plant growth. Organic matter improves aeration, surplus water drains away, roots can penetrate the soil easily and plant nutrients are more available. (Organic matter is any form of material that was once living. Humus is organic matter that has decomposed). Sphagnum peat is superior to any other form of organic matter. A good peat is composed mainly of sphagnum moss, a fibrous spongy material. This moss is capable of absorbing 15 to 30 times its own weight of water but, at the same time, surplus water can drain freely, so that roots have adequate aeration. The addition of peat greatly improves the

condition of soil and enhances plant growth. Compost is a good form of organic matter but inclined to be variable. A good quality compost is easily broken with a fork, has a crumbly texture and a brownish black colour. Bark chips, sawdust and straw all improve drainage and aeration. Green crops, such as lupins, oats and ryegrass, can be grown during the winter and dug in during the spring. Raising plant beds in very heavy clay soils or low lying areas with a high water table is an easy,

effective way of improving drainage. Beds or mounds can be built up with compost, peat and good top-soil to at least 200 mm above surrounding soils. The plants are then able to establish themselves in well drained soils. Raised beds also have aesthetic appeal. Plants can be featured as flowers, and textures are shown better. Flat, monotonous contours of the land can be relieved. Well-drained soils have the added advantage of warming earlier in the spring, encouraging plant growth.