Best Time to Spread Biofertiliser and the Regulations for Digestate Spreading
- Education
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Farmers worldwide are dealing with the challenge of maximising their crop yields to match the growing population. In the past, this was achieved through the application of chemical fertilisers. However, that practice is becoming less popular due to sustainability issues.
Key Points
- Digestate has more available nitrogren than chemical fertilisers
- Digestate must be spread at key times according to crop needs
- Specific digestate spreading rules must be followed
- Despite this, it's described as rocket-fuel for crops
Bagged fertilisers have a high carbon footprint because they are manufactured in specific places and transported to farms across the world. They also offer very specific nutrients to the soil. That’s good in a way because you know exactly what you’ve put in and how much.
On the other hand, you’ve spent all that money only on a specific nutrient. The formula doesn’t take into account anything that the plant would need to absorb and process in order to successfully use the chemical.
For example, nitrogen requires the presence of sulphur in order to be useful to a wheat plant. Without it, the plant won’t be able to pick up this important nutrient even if it is present in the soil.
In an ideal world, these necessary chemicals would already be in your land. However, if you keep adding chemical fertilisers that replenish one nutrient but not the others, the soil is eventually going to run out of everything else.
That’s why farmers across the UK are warming up to the benefits of biofertilisers, especially digestate created from anaerobically digesting food waste.
Categories of Digestate
Anaerobic digestion of food waste is a process where once-edible material (rotten or discarded vegetables, meat and its byproducts, milk and other dairy products) is made into a slurry and undergoes a series of biological processes to create biogas. However, once the process is complete, the slurry turns into a nitrogen-rich digestate.
This digestate has more available nitrogen than chemical fertilisers, other organic fertilisers, like manure, and even digestate made from farm waste and animal waste. There are several types of digestate that can be produced, the preferred option being Whole Liquid Digestate which is made up of 95% water and 5% dry material and is what we at BioteCH4 produce.
Factors Affecting When Digestate Can Be Spread
Crop Needs
As we said earlier, digestate has a lot of available nitrogen. In addition, it also contains potassium, phosphorous, and sulphur, all of which are nutrients that plants require. The easy availability and the complete nutrition profile are what make digestate a superfood for plants.
Unfortunately, the readily available nitrogen is so easily accessible because it is very volatile. If exposed to air for too long, the nitrogen in the mix escapes into the atmosphere in the form of noxious ammonia gas.
As a result, it needs to be added to the soil when the plants need the nutrients. That’s why it’s applied between the end of winter and the end of summer, when crops are growing and require nitrogen to thrive.
In fact, here’s a handy table to see when you can spread it in your fields.
Land Use: Tillage land
Soil Type: Shallow or sandy soils
Land Use: Grassland
Soil Type: Shallow or sandy soils
Land Use: Tillage land with crops sown on or before 15 September
Soil Type: Shallow or sandy soils
Land Use: Tillage land
Soil Type: All other soils
Land Use: Grassland
Soil Type: All other soils
Digestate Spreading Rules and Regulations
When spreading digestate, you need to bear in mind not just when it would be most beneficial for the crop but also the regulations controlling how, where, and when it can be spread. As of March 2022, these regulations have become more stringent to protect water bodies. They can be found in the Cross Compliance Guidelines.
In addition to adhering to the digestate application time frames, you also need to be aware of the weather requirements and restrictions. Digestate spreading should be avoided under the following circumstances.
- On waterlogged soil or land
- During periods of heavy rainfall or when this is forecast within 48hours
- On top of the frozen ground or during periods of snow covering
- Where soil has cracked down to the field drains
- Where a field has been pipe or mole drained
- When a field is sub-soiled over drains within the past 12 months
Besides the time of the year and weather conditions, the other factor that is regulated for digestate spreading is if the farm is located in a nitrate vulnerable zone (NVZ). This is a consideration because any excess nitrogen (or other elements) can get washed out into water bodies.
Once in the water, these can cause excess plant growth, leading to overcrowding which kills all animal life. That’s why digestate or high readily available nitrogen manures (those that have more than 30% of their total nitrogen content available immediately to the crops) are not allowed in the following circumstances.
- Where the land is located within 10 metres of a ditch, pond or water surface
- Where the land is located within 50 metres of a water supply used by human or dairy farms, including springs, boreholes or reservoirs
- Where fields are located on steep slopes
