LAND JOURNAL

Scorecard tool can help improve soil health

Better soil health can help offset carbon and increase resilience to climate change. A new scorecard based on research and agricultural trials can help farmers take timely, site-specific action

Author:

  • Elizabeth Stockdale

20 July 2022

Aerial view of tractor with tiller attached performing soil tillage in field

Even before the recent steep rise in input costs, there has been a growing interest in soil health on farms. Improving soils to support yields and reduce environmental impacts is vital in tackling the challenges presented by climate change and changing government support.

Each farm and field is different, however, and there is no single approach for ensuring healthy soils. Soils have a range of inherent properties, and the key factors are texture – that is the relative proportions of sand, silt and clay – depth, and stoniness. These properties are part of the assessment of land-use capability traditionally described using the grading system of the Agricultural Land Classification.

Texture plays a large part in determining the how easy the soil is to work during cultivation (workability) and to drive over (trafficability). Soil texture classes are therefore often used to indicate how resilient the soil is to structural damage.

Soil texture is also an important determinant of soils buffer capacity. Soils with a low buffering capacity are more likely to acidify quickly and to develop deficiencies in potassium (K+), magnesium (Mg2+) and other cations. The buffer capacity of soils tends to increase as the clay percentage increases and also depends on the type of clay, soil pH and also the amount of organic matter.

The chemical fingerprint of the soil is largely determined by the underlying parent material. These inherent characteristics of the soil determine both the yield potential and many of the environmental risks for any site.

Scientists describe and classify soil using a description of the number and character of the layers, in a profile from the surface down to this underlying material.The National Soil Map shows almost 300 groups of the most frequently co-occurring soil series. But while this map gives excellent background information, the data needs careful validation at field scale, where several distinct soils often occur.

Yield mapping over several seasons, together with satellite imagery and soil scanning, can help identify and map variation within fields. Identifying distinct soil management zones in these ways can enable farmers to target management measures and increase precision.

Measures such as application of fertiliser or manure, drainage, crop species or mixture choice and grazing management in each location interact with the soil character and determine its health. In the long term, healthy soil can maintain crop and livestock productivity and enhance environmental benefits.

Although farmers and their advisers have been assessing nutrient supply and soil compaction for years, with a range of indicators more recently developed to analyse soil biology, the necessary guidance and tools have not been provided to allow their routine use on farms.

Drawing on research to score soil health

The Soil Biology and Soil Health Partnership (SBSH) between the Agriculture and Horticulture Development Board (AHDB) and the British Beet Research Organisation (BBRO) has developed cutting-edge research alongside evaluation for indicators of soil health in research trials and on farms. The Partnership worked closely with farmers, growers and advisers to develop a soil health scorecard to enable them to better understand and improve their soil.

The process builds on the fundamental understanding of the physical, chemical and biological interactions governing soil health, as shown in Figure 1, and the practical constraints of measurement on farm.

More than 70 farmers volunteered to be part of the research in eight groups around the UK, covering a range of farming systems, climates and soil types. They tested and developed the scorecard approach between autumn 2018 and autumn 2021.

Experts worked together to reduce a list of 45 potential indicators to the following eight for ease of evaluation on farm:

  • physical: visual evaluation of soil structure (VESS)

  • chemical: pH and routine nutrients: available phosphorus (P) potassium (K) and magnesium (Mg)

  • biological: organic matter, earthworms, microbial activity.

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Figure 1: Physical, chemical and biological interactions governing soil health. © Agriculture and Horticulture Development Board

How the soil health scorecard works

To collect soil health scorecard data, observations of soil structure – VESS – and earthworm numbers are made at geo-referenced sites. Soil samples are collected for analysis at the same time. To benchmark the data between groups, the data must be collected in the same way and under similar soil temperature and moisture conditions. In the Partnership the data for soil health scorecards were collected:

  • after harvest

  • after the topsoil has wetted up in the autumn

  • at least one month after any cultivations or moderate soil disturbance.

The scorecard includes a traffic light system, providing a visual overview of the status of each indicator. The physical and biological assessments in the field are then linked with the results from a soil sample sent for laboratory analysis.

The final soil health scorecard gives the equivalent of a GP health check for soils giving a general overview of the health status of the soil and also identifying areas where improvement can be made through management, or where more detailed assessments or more regular monitoring is needed to deal with any problems.

Elizabeth Stockdale in the field. © Dr Amanda Bennett

Table 1: Sample scorecard

Investigate


Review


Continue rotational monitoring

Soil health monitoring from both existing trials and also on-farm was used in parallel to validate and optimise the scorecard and to evaluate the overall approach. These evaluations showed that all the indicators selected as part of the scorecard are important to provide the baseline for soil health assessment at a specific site.

Farmers in the test groups valued the data in the scorecard format, which prompted discussions about different management systems and their impact on soil health, as well as wider production and environmental outcomes. Farmers found it useful to revisit the basics of pH, drainage and organic matter addition, alongside discussions about the latest monitoring or application technologies.

In long-term experiments where soil-improving measures such as manure additions were being compared, the scorecard could distinguish the impacts of slurry – a good source of nutrients with a small benefit for soil organic matter – from those of farmyard manure – a good source of nutrients that also provides a small liming effect, and an increase in organic matter and microbial activity – and the soil conditioning benefits of green compost.

Impacts of tillage

As part of the SBSH Partnership's work, a field that has been converted to no-till as part of a strategy to improve soil health at the Game and Wildlife Conservation Trust in Loddington, Leicestershire, was cultivated by ploughing, and the impacts were compared with plots remaining untilled. Although the plough did reduce earthworm numbers, it wasn't devastating and the impact on soil organic matter after one year was negligible.

This indicates that occasional strategic tillage, for instance, as part of an integrated pest management approach to deal with weeds, could form part of regenerative farming systems. It also suggests that farmers growing root crops or other field vegetables can improve soil health by changing the rotation between crops such as potatoes and sugar beet. Improved soil health in root crop rotations will increase soil resilience and remove the need for one or more tillage passes, reducing the depth or speed of operations.

What data is needed to support better management for the farm? It doesn't need to be collected from every management zone in every field. On most farms, it is possible to identify 10–15 places that might provide the information needed.

A robust plan will then evaluate soil health at those geo-referenced monitoring sites once every three to five years at the same point in the rotation. The scorecard has been developed so farmers can use it to monitor the impacts of management and identify targeted interventions to maintain soil health themselves.

Scientific and site-specific strategies

Working together across the agricultural sector, the UK Soil Health Initiative and Championing the Farmed Environment have also developed sector guides to help farmers understand their soils and plan improvements.

Collecting data about soil, and even having an integrated assessment of physical, chemical and biological properties compared to relevant benchmarks, won't by itself improve soil health. The best soil husbandry uses site-specific understanding to select the most suitable combinations of management and then deploy them in a timely way.

The best soil husbandry is always site- and season-specific: there is no simple recipe of inputs, and each action needs to be informed by observation.

Elizabeth Stockdale is head of farming systems and agronomy research, NIAB

Contact Elizabeth: Email

Related competencies include: Agriculture, Management of the natural environment and landscape

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