Agricultural benefits of biosolids

This section outlines the major beneficial constituents of biosolids.

They are a valuable source of both plant nutrients, trace elements and organic matter and can therefore be used as both a fertiliser and soil conditioner.


Organic matter

Soil organic matter is a major determinant of soil fertility, water holding capacity and biological activity and diversity both below and above ground.

Loss of organic matter can lead to soil erosion and loss of fertility.

Consequently recycling biosolids to agricultural soils has an important role in replacing losses that can arise from intensive arable farming where there is no alternative organic matter source.


Depending on the crop and the product type biosolids will supply around 10% of the nitrogen needs of a crop.

The source of the nitrogen supplied is organic and consequently it is released slowly as the soil warms and is therefore present over the crops growth cycle.


Biosolids will provide the phosphate needs for cereals and oilseed rape removing the need for applying bagged phosphate fertiliser.

A standard application rate will supply two years of crop phosphate needs. Biosolids can successfully be used to build-up the phosphate soil index if required.


Sulphur has become increasingly important as a crop nutrient as deposition from the atmosphere has decreased.

Sulphur in biosolids will supply enough sulphur for cereal crops and in most cases for oilseed rapes at standard application rates.


Biosolids contain significant amounts of magnesium sufficient to prevent deficiency symptoms sometimes seen on light sandy, acid soils.

Trace elements

Trace elements are important in varying amounts depending on the crop and soil type.

Biosolids contain all the important ones notably boron, copper, zinc, iron, sodium, manganese, aluminium and molybdenum.