Crop rotation, seaweed extracts, lime, and a range of organic materials can all improve soil health and crop yields. Professor Geoff Dixon shows you several ways to improve your soil.

Rapidly rising costs of living are affecting all aspects of life. Increasing costs of fertilisers are affecting food production, both commercially and in gardens and allotments.

Wholesale prices of fertilisers have jumped four-fold from £250 to £1,000 per tonne within six months. All forms of garden fertilisers are now much more expensive. Crops, especially vegetables, only thrive if provided with adequate nutrition (see nitrogen-deficient lettuce below). Consequently, fertiliser use must become more efficient.

Nitrogen deficiency in lettuce.

Healthy, fertile soils achieved through good management are key to this process. That ensures roots can take up the nutrients needed in quantities that result in balanced, healthy growth.

Soil pH is a major regulator of nutrient availability for roots. Between pH 6.5 to 7.5, the macro nutrients, nitrogen, phosphorus, and potassium are fully available for root uptake. Below and above these values, nutrient absorption becomes less efficient.

>> How much soil cultivation do you need for your vegetables? Find out more in Prof Dixon's blog on cultivation.

As a result, soluble nutrients are wasted and washed by rainfall below the root zones. Acidic soils can be improved by liming in the autumn. Sources of lime derived from crushed limestone require up to six months to cause changes in soil pH values. Lime should be used in ornamental gardens with caution as it can result in micronutrient deficiencies.

Iron deficiency in wisteria.

Soil health and fertility are greatly increased by adding organic materials such as farmyard manure and well-made composts. Increasing soil carbon content helps mitigate climate change while raising fertiliser use efficiencies.

Beneficial soil biological life such as earthworms, insects, benign bacteria and fungi are greatly encouraged when you increase soil humus content. Using crop rotations, which include legumes, raises natural levels of soil nitrogen. This is a result of legumes’ symbiotic relationships with nitrogen-fixing bacteria.

Leafy vegetables such as brassicas require large amounts of nitrogen and, hence, should follow legumes in a rotation. Avoiding soil compaction encourages adequate aeration, benefiting root respiration and providing oxygen for other organisms.

Organic materials are of great value in ornamental gardens when applied as top dressings in late autumn or early spring. This provides two benefits: a slow release of nutrients into the root zones as decomposition occurs, and prevention of weed growth.

Inorganic fertiliser use can be further minimised by using proprietary seaweed extracts. These contain macro- and micro-nutrients plus several natural biostimulant compounds that aid healthy ornamental plant growth and flowering (illustration no 3 rose Frűhlingsgold).

Rose frűhlingsgold

Written by Professor Geoff Dixon, author of Garden practices and their science.