Loamless composts introduced the advantages of a uniform growing medium, but with components that are lighter, cleaner to handle, cheaper to prepare and which do not need to be sterilized (unless being used more than once). Many have low nutrient levels which enable growers to manipulate plant growth more precisely through nutrition, but the control of nutrients is more critical, as many components have a low buffering capacity. Peat has until recently been the basis of most loamless composts. It is used alone or in combination with materials, such as sand, to produce the required rooting environment. Peats are derived from partially decomposed plants and their characteristics depend on the plant species and the conditions in which they are formed (see Chapter 18). Peats vary and respond differently to herbicides, growth regulators and lime. All peats have a high cation exchange capacity, which gives them some buffering capacity. The less decomposed sphagnum peats have a desirable open structure for making composts and all peats have high water-holding capacities.
Was this article helpful?