Advice for farmers

Advice from Portsmouth Water

We offer free advice to farms within high-risk areas of our Safeguard Zones on the best farming practices to reduce agri-chemical losses to groundwater. See map below to check if your farm is eligible.

What are safeguard zones?

All of our groundwater abstractions have a catchment area, and we work within these areas to understand and mitigate the risk that land-use practices pose to the groundwater quality.

Safeguard zones are specific catchment areas where we have identified higher levels of nitrate contamination within the water that we abstract. Therefore, we aim to work with farmers within these catchments to help reduce nitrate losses to protect the quality of the water we abstract.

Law and legislation on agricultural pollution

Agriculture is responsible for around 40% of waterbodies failing to meet good ecological status (Environment Agency, 2024). The Reduction and Prevention of Agricultural Diffuse Pollution (England) Regulations 2018, also known as the ‘The Farming Rules for Water’, were introduced to reduce and prevent diffuse water pollution from agricultural sources.

EA Pollution Prevention Leadflet

Farming rules for water - updated July, 2025

You are required to follow these regulations if you are a land manager in England and also if you are in a Nitrate Vulnerable Zone (NVZ).

These regulations apply to agricultural practices, such as:

Use of organic manure or manufactured fertiliser
Storing manure
Preventing erosion: manage livestock and soil
Managing livestock

Below is a summary from the much more detailed rules found here:

Farming rules for water

Best practice to protect groundwater quality

Creating nutrient management plans helps identify where improvements could be made to maximise the uptake of nutrients in the soil providing both economic and environmental benefits. Improving the efficiency of nutrient uptake lowers fertiliser applications and decreases losses to groundwater.

When creating nutrient management plans for your farms the AHDB recommend a four-step plan:

Sample and test the soil in each field every 3-5 years to determine your soil nutrient supply.
Calculate the crop nutrient requirements.
Calculate the nutrient levels that will be supplied from organic manures.
Calculate the amount of fertiliser required, including product and rate.

For more advice on creating nutrient management plans:

AHDB Nutrient Management Plans

The Fertilizer Institute - The 4Rs

Nitrogen testing and application advice

Soil mineral nitrogen (SMN) testing

What is SMN?

SMN is the nitrate (NO3) and ammonium (NH4) in the soil; this is the immediately available nitrogen (N).

SMN is one component of the soil N supply (SNS):

SNS = measurement of SMN + an estimate of crop N (at time of sampling) + an estimate of subsequent soil N mineralisation:

Soil can also be sampled for Additional Available Nitrogen (AAN), which analyses SMN plus organic N that will become available:

AHDB Arable crops

Soil Mineral Test

How to sample for soil nitrogen

You will need to sample shortly before sowing. Sampling should be to a depth of 0-30cm and 30-60cm and should be carried out in at least 5 places across the field - in a W shape. Samples should be ≥ 250 g.

Organic material nitrogen testing

Nitrogen in organic materials

Organic materials contain both mineral and organic nitrogen (N). Mineral N is immediately available, whereas organic N mineralises over a period from months to years.

The material should be tested for immediately available N. However, the organic N from previous organic applications should be considered when calculating N fertiliser rates:

How to sample organic materials

You need to sample organic materials shortly before field application. Multiple samples should be taken at depth from different places from across the heap/store. Samples should be ≥ 250 g/250 ml.

AHDB Organic Minerals

Nitrogen fertiliser application rates

To calculate the synthetic nitrogen fertiliser requirement, you calculate the SNS index based on the mineral nitrogen in the soil plus nitrogen supplied from organic material:

The SNS index is then linked to crop nitrogen fertiliser requirement in a look-up table e.g.

Nutrient Management Guide

See the RB209 guide from AHDB (Section 4) for guidance:

Advice from Catchment Sensitive Farming (CSF)

Catchment: Know your catchment, key issues and priorities to help understand risks to water quality and where to put your focus.

Local Environment: Know your local environment and map your farm; soils, topography, water flow paths, locations of water bodies, woodlands and hedgerows. This will help you better understand where water flows from you farm and where contaminants may be at risk of entering water.

On Farm Activities: Map activities on farm over your local environment to visualise your risks.

Plan and Actions: Develop, plan and review actions to address risks to water quality, to help you reduce and monitor contaminant losses to water bodies.

CSF Website

Online mapping tool for your farm:

ALERT is a free mapping tool created by the Environment Agency on behalf of Catchment Sensitive Farming to help farmers and our local advisers analyse the landscape and reduce pollution from agriculture. This includes information on overland flow pathways, soil classification and slope threshold.

Alert Mapping Tool

Pesticide guidance

Its important to always use pesticides according to the label to increase their efficiency to ensure you’re getting the most benefit from them and to also minimise losses to groundwater.

Legal requirements:

Since 1999 any disposal to land of surplus spray and washings that does not take place ‘in the crop’ requires a ‘groundwater authorisation’ from the Environment Agency.
Since May 2006 the burning or burial of pesticide containers is prohibited in England and Wales.

All farmers should use a ‘crop protection management plan’ to review their operations and to ensure that they comply with the law and follow best practice when disposing of pesticide wastes.

Disposal of empty pesticide containers

Always empty and clean containers before disposal.
Do not rinse containers that have held sodium cyanide or aluminium, magnesium or zinc phosphides. Fill these containers with dry earth, sand or other inert material instead of rinsing.
Clean all containers and foil seals thoroughly and drain the washings into the spray tank.
Use pressure rinsing devices or triple rinsing with water to reduce and pesticide residues in the container to insignificant levels.
Store empty containers upright with lids in place awaiting disposal in a dedicated secure compound
Read the CPA guide on ‘container cleaning’ for more detailed advice.