Using gypsum to improve soil health, water quality and fertiliser use efficiency
This field lab will explore the effect of liquid gypsum applications on nitrogen fertiliser use efficiency, soil health and water quality in the south Norfolk and north Suffolk ‘Claylands’ landscape.
The trial was inspired by the results of water quality monitoring, carried out at a number of arable farms in the Waveney Farming Cluster. These showed that nitrate leaching from arable field drains can be a significant ecological and economic problem over winter costing up to £1 per hectare per day in the value of lost nitrogen.
Coordinated by the River Waveney Trust, with Farm Carbon Toolkit as researchers, trials will be hosted on ten farms across ten fields within the Waveney Farming Cluster.
For updates on the trial, trial design and reports click on the brown/orange banner above.
How it works
- Nitrate and phosphate pollution from agriculture is a major cause of poor river water quality, and of economic importance to farm businesses.
- Nutrient leaching from arable fields is linked to soil health and fertiliser use efficiency.
- Gypsum is known to increase soil porosity, structural stability, workability, root exploration and drainage, but little is understood on how gypsum could be used as a tool to mitigate nutrient leaching from non-sodic, heavy clay soils in a UK context.
- In theory, gypsum should:
- Improve root system establishment, leading to increased nutrient uptake
- Reduce surface runoff through improved infiltration
- Reduce soil erosion by binding soluble nutrients in the soil
Trial design
The trial will be carried out on ten trial fields across 10 farms. Each field will be split into control and trial areas. Crop and field management will be identical in the control and trial plots in each field, except for the application of gypsum to the trial plots.
- Preliminary soil testing and soil health checks will be carried out on each field to inform gypsum application rate.
- Liquid gypsum will be applied post harvest 2024 and 2025 to the trial plots.
- Water and N testing (with chlorophyll meter) will be carried out on the fields over winter and spring both years of the trial
- Grain testing will be carried out at both harvests and will calculate fertiliser use efficiency
- Post application soil testing and soil health checks will be carried out on each field to evaluate the impact of gypsum on soil health.
Photo credit Emily Winter
Trial progress
So far 7 fields have received the gypsum since February, with 3 still to go, dependent on cultivations, crop establishment and grass cuts.
As yet there are no results that positively show the gypsum has affected either crop nutrition or growth, but it is early days.
Gypsum application due
The triallists are preparing to complete their first application of liquid gypsum. The original trial planned for this to take place in the autumn, but wet weather conditions meant that this was delayed until the spring.
The triallists will be using the following application guidelines:
- All rates are 10L/ha, and the product contains 6% calcium and 10% sulphur.
- For spring crops gypsum is best applied to the soil after/during the final cultivation.
- For growing crops the gypsum is best applied to the crop just before, or during, a rain. This sounds counterintuitive, but the aim is that the product be washed off the leaves so it reaches the soil.
- Liquid gypsum should not be mixed with liquid fertilisers, micronutrients in suspension or herbicides. These will all have to be applied in a separate pass.
- The product is highly soluble and at high risk of leaching, so triallists must ensure the weather conditions and soil temperatures are right. As the temperatures warm and biological activity increases an appropriate time to apply should be coming up.
- Gypsum will be applied only to trial plots, not to the control plot. The coordinator will ensure this is carried out correctly.
Soil tests carried out, gypsum delivered
In October the group met online to plan the next stages of the trial. and instruct the farmers on methods and timings of gypsum application. At this meeting a collective decision was made to postpone gypsum application to spring 2025, when its effectiveness will be enhanced due to warming soil temperatures and more active soil biology.
In November initial baseline soil testing for pH, P, K, Mg, Ca was carried out at each of the farmers' trial sites, along with soil health assessments completed by Farm Carbon Toolkit.
Gypsum has been purchased and delivered to facilitator and begun distribution to farmers.
The next step will be application of gypsum in the spring.
Pre-application soil testing and soil health assessments
Aug / Sep 24
First gypsum application
Sep/Oct 24
Continuation of water quality and crop nutrition data collection
Nov 24 - Jun 25
Farm walk / cluster event to discuss progress review and initial results
Jun/Jul 25
Second gypsum applications
Aug-Oct 25
Continuation of water quality and crop nutrition data collection
Nov 25 - Jun 26
Post application soil health assessments
Spring / early summer 26
Final report submitted
Oct 26
Results webinar and public event(s)
Winter 26/27
Group Coordinator
Emily Winter
River Waveney Trust
East of England
As well as working for the River Waveney Trust Emily is a mixed farmer. She runs a nutrient use efficiency programme for farmers and delivers farm advice on behalf of RWT. With eight years’ experience in aquatic ecology, her work includes a Broadland fish tracking project as part of her PhD research. She was raised on a family farm in the Waveney catchment, and has a broad knowledge and understanding of agricultural practices.
Researchers
Becky Wilson
Farm Carbon Toolkit
South West