Building Soil Fertility

Well cared for soil is the foundation of organic growing and a priority for providing plants with fertility. The below introduces how to develop your soil to grow healthy crops using organic methods. These apply whether growing in open ground or raised beds. There is also guidance on feeding plants.

Understand soil

• Particles of weathered rock (soil ‘texture’), mostly clay, silt and sand
• ‘Organic matter’ (turns into ‘humus’), dead/decomposing plants/animals
• Living organisms, roots, worms, fungi, bacteria, other micro-organisms
• Air and water, in spaces between soil particles; drainage channels

The top layer of soil is most important for plants. This ‘topsoil’ has the most life and fertility - and where gardeners make the most difference.



Test your soil. Assess former cultivation

• Identify soil texture and main characteristics, eg drainage and fertility
• Estimate organic matter and living content
• Assess compaction and drainage (typical air and water content) 
• Measure the relative soil ‘acidity’ or ‘alkalinity’ (pH)

Start building soil fertility: Develop its structure

Add organic matter

Eg two shovels of compost per square metre. Boosts fertility; adds air; encourages living organisms; improves drainage (clay soil) and water retention (sandy soil).

Digging over soil

Quick way of adding organic matter and horticultural grit; reduces compaction (adds air/improves drainage).

Alter soil pH

Minor shifts in pH are possible by adding natural substances, eg dolomite limestone. This helps prevent some plant diseases, eg liming deters ‘clubroot’.

Keep improving your soil

Continue adding organic matter annually and dig as needed. Build and maintain soil fertility by using crop rotation and ‘green manure’.

Look after your soil once improved

Avoid wasting fertility and damaging soil structure, eg minimise cultivation and limit compaction by not treading on soil.