Autumn grassland management advice for long-term productivity
As the grass growing season winds down, livestock farmers should still be thinking about strategic grassland management during autumn to benefit future productivity.
For example, results from the AHDB’s Strategic Farm programme showed that improved grassland management can shorten the winter housing period by up to a month, positively impacting farm profit margins through reduced costs, such as feed and bedding.
Taking steps to improve nutrient uptake and build a robust sward structure that is more resilient to winter stressors, such as frost and heavy rain, also provides a strong foundation for early spring growth.
The following blog sets out detailed agronomic advice on autumn grassland management, explaining strategies to help improve long-term regrowth and recovery.
Assessing your grassland nutrients
Before making any autumn grassland management decisions, soil testing is a crucial first step.
Soil tests provide precise information about the levels of essential nutrients, such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulphur (S), allowing for more precise and efficient fertiliser applications.
Determining soil pH level is also important, as this affects nutrient availability.
Most nutrients are optimally available to grasses in a pH range of 6.0 to 6.5. For example, in acidic soils (pH below 6.0), phosphorus becomes less available, and toxic metals like aluminium can become more soluble, harming grass roots.
If the pH is below the optimal range, lime (calcium carbonate) application can help to increase it and improve nutrient uptake.
Autumn is a good time to apply lime, to correct low pH soils ready for spring growth.
Autumn nutrient applications for grassland
When interpreting soil test results, it is important to compare the nutrient analysis with recommended nutrient levels for optimal grass growth.
The following recommendations are summarised from AHDB’s Nutrient Management Guide (RB209) for grass and forage crops.
These guidelines help ensure grasslands receive the necessary nutrients to promote strong autumn growth, improve soil health, and prepare for the following growing season.
Nitrogen (N)
Applying nitrogen in late summer supports an extended growing season into the autumn. This is particularly important for maximising pasture productivity and providing additional forage before winter sets in.
We recommend using OCI Nutramon, a calcium ammonium nitrate fertiliser, which delivers the highest nitrogen efficiency compared to other nitrogen fertiliser types.
For late autumn growth, farmers are advised to apply up to 50 kg N/ha in late July or August, and adjust these rates based on soil nitrogen supply (SNS).
Soil nitrogen supply refers to the amount of nitrogen available in the soil that plants can utilise for growth. It includes nitrogen from various sources, such as soil organic matter, previous crop residues, and applied organic or inorganic fertilisers.
For fields with low SNS levels, it is recommended to apply 30 kg N/ha more than their calculations across the season; for high SNS sites, apply 30 kg N/ha less.
This helps ensure grass receives the appropriate amount of nitrogen based on the soil’s existing nitrogen levels, preventing both deficiencies and excessive applications that could lead to leaching and environmental harm.
Phosphate (P)
Phosphate is vital for root development and energy transfer within grass plants, so autumn application ensures it is available for the critical root development phase, helping the grass to establish a strong foundation for the next growing season.
For grazed swards, phosphate should be applied based on the soil P Index. This typically ranges from 0 (very low phosphorous) to 9 (very high).
A P index of 2 is considered the optimal level for most UK grasslands.
If soil test results are below this target, additional phosphorus fertilisation is required to build up the soil phosphorus reserves to the optimal level.
For example, at a P Index of 1, 50 kg/ha of phosphate is recommended.
Growers should be mindful of preventing excessive phosphorus accumulation, which can lead to environmental issues, such as runoff and water pollution.
Potassium (K)
For grazed swards, potassium should be applied based on the soil K Index.
Similar to the phosphorus index, the soil K index ranges from 0 to 9 and guides the appropriate potassium fertilisation required for optimal plant growth.
For UK grasslands, the target soil K Index is generally index 2.
Growers are advised to apply additional potassium if lower than this – at a K index of 1, 30 kg/ha of potassium in the autumn is recommended to help regulate water balance, enzyme activation and photosynthesis.
For silage fields specifically, an additional 60 kg/ha may be needed after the last cut, or by the autumn to replace offtake. This is essential to restore nutrient levels depleted by the removal of biomass, ensuring the grass remains healthy and productive.
Sulphur (S)
Autumn is a key time to balance nutrient applications to ensure grass enters winter in the best possible condition. Sulphur application should be proportional to nitrogen to optimise nutrient uptake and efficiency.
Without sufficient sulphur, the efficiency of nitrogen use decreases, leading to poorer plant growth and protein synthesis.
This is why we have created OCI Dynamon, a nitrogen-sulphur fertiliser that combines nitrogen and sulphur in a single granule, for enhanced nitrogen use efficiency.
By adjusting sulphur application based on nitrogen levels, farmers can ensure both nutrients are available in the correct proportions, maximising their benefits for the autumn grass growth period.
Read more advice on applying sulphur for optimal grass growth.
Autumn fertiliser application restrictions
Proper nutrient application during the autumn ensures crops have adequate resources for the upcoming seasons while minimising environmental impact.
In England, the Farming Rules for Water provide essential guidelines for fertiliser application, aimed at preventing water pollution and promoting sustainable farming practices.
Under the Farming Rules for Water, applications of both organic manures and manufactured fertilisers must be meticulously planned to avoid pollution risks. Farmers must consider soil nutrient levels, crop requirements, and the potential for nutrient runoff or leaching into water bodies.
Guidance on applying manufactured fertilisers in autumn
Specific application rules apply to Nitrate Vulnerable Zones (NVZs), which are areas designated to protect water sources from the risk of pollution.
Within the Farming Rules for Water, there is a closed window for the spreading of manufactured nitrogen fertiliser from 15 September to 15 January.
This has been implemented to prevent nitrogen from leaching into waterways during times of the year when crops are less able to take up the nutrients due to reduced growth rates, colder temperatures, and higher rainfall.
Applying organic manures in autumn
The Farming Rules for Water stipulate that high readily available nitrogen manures must not be spread on any soil type from 15 October to 31 January.
On sandy or shallow soils, this extends from 1 September to 31 December.
Non-compliance with these regulations can result in enforcement actions by the Environment Agency. Farmers are encouraged to keep detailed records of soil tests and fertiliser applications to demonstrate compliance.
Autumn grazing management
Grazing management goes hand-in-hand with strategic nutrient management to benefit grassland through autumn and beyond.
Practising controlled grazing and systematically closing paddocks in autumn helps ensure pastures remain robust and productive throughout the winter and into the spring.
It is advised to to leave a residual sward height of around 5-7 cm, which is optimal for most grass species commonly found in UK pastures.
Overgrazing during autumn can severely weaken grass swards, by reducing carbohydrate reserves in the plant and hindering root development.
Teagasc provides further advice on autumn grazing management for livestock farmers.
Further guidance on autumn grassland management
It is common practice for farmers in the UK to reseed grass swards every 5-10 years, often in autumn, to allow time for the seedbed to settle before spring.
Read more advice on autumn grass reseeding.
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