Soil assessment prior to a grassland reseed

Before reseeding grassland, it’s crucial to assess the soil's condition and suitability to ensure success. This involves checking the drainage system, soil fertility, structure and any potential barriers to successful growth. Find out what to assess and how to prepare.

It’s important to assess the soil up to six months before reseeding so you have time to make any necessary amendments.

Field drainage system: Ensure the drainage system is working properly. Poor drainage can lead to waterlogging, which can affect grass seed germination and establishment.

• Check for wet areas in the field, which can indicate drainage problems
• Look for indicator species, such as rushes, which thrive in poorly drained soil

Drainage ditches and outflows: Ensure that any drainage ditches are clear and functioning properly.

Soil testing: Conduct a thorough soil test to assess nutrient levels, pH and soil organic matter. For a better look at soil health, use the soil health scorecard.

Soil structure assessment: Evaluate the soil’s structure to determine whether ploughing or a minimum tillage approach is best for reseeding.

Soil testing is essential to understand the nutrient profile of your field and identify areas that may need adjustments, e.g. fertiliser or lime.

Follow the steps below to sample for a standard soil test. The soil health scorecard sampling uses a different approach, see the soil health scorecard resources for sampling information.

How to sample soil for a standard soil test:

1. Walk the field in a ‘W’ pattern: Start from one corner of the field and walk in a ‘W’ pattern to collect samples, avoiding gateways, feeding areas and tracks, which can have altered soil conditions.
2. Sampling depth:
   • If you plan to plough the field, sample to a depth of 15 cm
   • If you’re only cultivating the surface, sample to a depth of 7.5 cm
3. Collecting soil samples: Use a sampling auger or soil corer to collect soil plugs from various locations across the field. Aim for 25 plugs in total, evenly distributed across the ‘W’, to provide a representative sample.
4. Mixing the soil samples: Place the plug samples into a clean bucket and mix them thoroughly to ensure the sample is representative of the entire field.
5. Prepare the sample for lab testing: Take a subsample of the mixed soil, place it in a clean plastic bag and label it with the details of your field.
6. Send to a soil laboratory: Send the soil sample to a laboratory for testing. This can be done through a local co-op, fertiliser merchant or an independent company. Ensure that the sample is sent at least two months after the last application of manure, fertiliser and lime to avoid skewed results.

Assessing the soil structure is crucial for determining the type of tillage required for reseeding.

The visual evaluation of soil structure (VESS) is a straightforward and quick way to test soil structure in a few simple steps. The soil quality score produced can help highlight where soil structure needs to be improved and guide your reseeding approach.

How to assess soil structure:

1. Take a soil sample: Dig a soil pit or use a soil auger to extract a soil sample from the field.
2. Evaluate the soil: Examine the soil’s structure by looking at how easily it breaks apart.
3. Score the soil: Assign a score using the VESS descriptions and follow the recommendations below.

Recommended tillage method for reseeding based on VESS scores:

A score of 1–3 (good to moderate structure) indicates that the soil is well structured and requires minimal tillage. A ‘minimum-till’ reseed could be sufficient.

A score of 4–5 (poor structure) indicates that the soil is compacted or poorly structured. Consider the following tillage options:

• Plough and reseed where swards have less than 50% sown species or productive grasses
• If swards are still productive:
  • Use a surface slitter or aerator to address any compaction found less than 10 cm deep ahead of reseeding
  • Sward lift to address any compaction found more than 10 cm deep ahead of reseeding with the option to mole plough on clay soil

For guidance on specific grassland cultivation order a free copy of our Resilient grassland soils guide.