Grassland soil biology guide

In grassland soils, the soil life below ground often weighs ten times more than the grazing livestock you can see at the surface. Soil organisms are hugely diverse and play a range of critical roles in most soil processes.  Soil biota is a collective term for all these living organisms, excluding plant roots, and is sometimes also simply called soil life.

In grassland systems, soil life:

• Forms an intricate food web which gets energy from inputs of carbon to the soil in organic matter through plant roots, crop residues and livestock excreta;
• Powers nitrogen fixation through the symbiosis between rhizobia and legumes;
• Drives phosphorus, nitrogen and sulphur cycling to recycle nutrients back into a plant available form;
• Stabilises soil structure and allows the soil to absorb intense rainfall through an open pore network;
• Develops a sponge-like pore network to hold on to water and support pasture growth through drought.

Farm management practices can both help and hinder the biological processes happening in the soil. Wherever possible farmers should seek to manage soil conditions to provide the best food and living conditions for soil organisms so that they can function in harmony and maintain fertile and productive soils.

The Problem:

Soil biology is now widely accepted to be a key driver of both soil function and pasture productivity. From both economic and environmental perspectives it is therefore important that grassland farmers understand the role of soil biology in driving the function of healthy grassland systems and that they are able to select sward management approaches that optimise ecosystem health and productivity both above and below ground.

Assessment of forage quality, soil pH and topsoil nutrient availability alone is now widely recognised to give an incomplete picture of soil quality.  Routine soil analysis approaches have been developed to quantify whether the chemical factors (pH, P, K and Mg) which affect soil-plant interactions with regard to root growth and nutrient availability are optimal or sub-optimal.  There are currently no robust methods to assess whether soil biology is functionally well.

Aims and Objectives:

• To help grassland farmers gather sufficient information about the biological status of their soils to make informed soil management decisions and to optimise grassland productivity and forage quality
• To provide clear accessible farmer-targeted information on the diversity of soil organisms from archaea to earthworms  and how interactions amongst these populations and their environment drive soil function and grassland productivity a providing a directory of relevant soil organisms, their habitat and their function within grassland soils
• To provide clear information on the direct and indirect impacts of agricultural grassland management (both positive and negative) on soil biology and soil function
• To provide a range of practical guides supporting the recognition, identification and quantification of soil organisms and the measurement of soil biological function (e.g. respiration, decomposition)
• To collate the existing data on soil biology and biological function in grassland soils derived from both research and farmer-based studies and share this information in a series of case studies (at least 5) that put information about soil biology into a practical agronomic context
• To develop a series of dissemination events, working with DairyCo and EBLEX, that effectively share information on soil biology within the context of soil assessment and management in grassland systems

Approach:

1. To review the available evidence on the role of soil biology in grassland systems and impacts of management practices.
2. An initial meeting with farmers and industry representatives will present the findings from the literature and specifically explore the most effective ways in which this information can be presented to the industry
3. Case study sites (at least 5) will be identified through existing contacts, recommendations from DairyCo / EBLEX and industry engagement
4. Review with key industry stakeholders both of the materials and the way in which they are presented
5. Delivery of a number of practical events arranged with key industry stakeholders (DairyCo / EBLEX, BGS, RADBF)
6. Delivery of technical guides