What are soil amendments?

super-soil_490Soil amendments are also known as conditioners and include the familiar range of decayed organic materials like compost and leaf mould. Their role is to improve a soils structure and ultimately its ability to deliver water, air, and nutrients to plants. They encourage nutrient recycling by developing the innate structure of a soil. In comparison to fertiliser, soil amendments work over a long period and will benefit the entire garden. I’m always encouraging gardeners to concentrate primarily on their soil and growing conditions. At the risk of becoming a little technical, I hope to convince you that organic amendments are the safest and most effective means to promoting soil fertility.

The foundation of each soil’s ability to deliver effective plant nutrients can be described in terms of charged ions which must be gathered and held on particular locations within a soil’s structure. Depending on their electrical charge, individual ions will be attracted and loosely bound to the organic particles within a soil. For example, a zinc ion has a positive charge and is therefore attracted to organic particles with a negative charge. Any deficiency of organic soil particles may result in a nutrient supply which is wasted in terms of its sustained availability to plants. By increasing the overall quantity of organic material in your garden, the soil’s capacity to attract beneficial ions can be significantly enhanced.

Despite superficial similarities in outcome, the biochemical processes which underlie the distribution and availability of organic soil nutrients is distinct from those based on the inclusion of synthetic and chemical based fertilisers. The best example is nitrogen, which can be readily supplied to most gardens in the form of complex organic materials or as a synthetic ammonium compound or water soluble salt. In both instances the plant ultimately requires nitrogen to be supplied in the form of inorganic nitrates. With complex organic material, this process is dependent upon a range of soil micro-organisms which feed on the decomposing remains and break some of these into compounds of ammonium and ultimately nitrate which can be used by the plants. The process of decomposition is gradual, ensuring that organic materials provide a steady availability of absorbable nitrogen.