Achieving high grass yields without the use of artificial fertilisers is one of the main challenges for organic livestock producers.
Understanding soil health is fundamental in order to create a bespoke management plan.
Below, Agscope consultant James Bretherton gives his top tips for how farmers can organically boost grass growth on farm.
1. Start with an in-depth soil test
The state of the soil influences everything we do and how livestock performs.
It is essential to understand exactly what it is made up of, and what nutrient levels it already holds, to be able to accurately give it what it needs to generate good grass growth.
Using a spade, dig a hole along the hedge line. Compare that with soil taken from the middle of the field.
The hedge line soil is an indicator of what the soil wants to be and is a cheap and easy place to start.
Carry out a test that goes beyond evaluating soil pH, phosphorus and potassium. Consider the mineral content, air and water levels, as well as organic matter.
- Minerals 46-47%
- Air 22-24%
- Water 22-24%
- Organic matter 5-7%. However, anything above 4% is great, and peaty soils will often be much higher than this.
2. Use the soil information to formulate a bespoke nutrient management plan
Once you have a good understanding of the state of the soil, it is possible to create a nutrient management plan around this.
Think about managing the soil like the rumen in a cow.
For example, the benchmark is for rumen is a pH of 6-6.2. Once this drops below 5.8, problems such as acidosis start to occur.
This is much the same for plants – as soon as pH levels start to drop, grass growth starts to decline.
Although nutrient levels will be dependent on the individual farm, there are key things to consider when formulating a nutrient plan.
These are soil type, levels of organic matter, calcium, magnesium and sulphur content, as well as trace elements and the biological status of the soil.
Calcium in particular should be a priority focus, as it is instrumental in plant cell formation and particularly beneficial for younger plants that lack vigour.
It is also essential for clover growth and forage palatability.
From a soil structure perspective, calcium is responsible for soil flocculation – whereby soil particles are bound together – and is the only mineral to do this.
The better the structure of the soil, the better the subsequent grass performance will be.
Magnesium has the opposite effect (dispersion), so it is important to closely monitor these levels too.
3. Consider the use of herbal leys
A study carried out in Scotland demonstrated the benefit of herbal leys in organic systems.
The study compared herbal leys with non-herbal leys and tested for 14 major/trace elements.
Only three of the 14 elements were lower in the herbals leys and there was an improvement in calcium and phosphorus levels within these plots.
These minerals are really important for livestock and key drivers of animal health.
In terms of specific plant species, what works best will come down to your individual location.
From a grass growth perspective, herbal leys have also proved to be much more resilient in drought situations – compared with monoculture leys – mainly due to the improved root architecture.
The ability to retain moisture during otherwise stressful growth periods no doubt helps contribute to increased yields.
4. Think about covering farmyard manure heaps to lock in the benefits
In practical terms, if a heap is outside and it gets rained on, that rain will wash away some of the key nutrients it contains.
As farmyard manure is a key fertiliser source for organic growers, retaining as much of these nutrients as possible is essential for promoting good grass growth, and covering the heap can help with that.
There are also benefits from an environmental point of view, as covering the heap can help control the amount of carbon dioxide being released.
Reducing farming’s impact on the environment is something that is being talked about a lot at the moment, and this approach can help to do just that while also benefiting grass production and growth.
Case study: Tim Downes, The Farm, Longnor, Shropshire
Shropshire organic farmer Tim Downes has a herd of 260 spring block calvers.
Over the past 10 years he has put a strong focus on developing healthy soils on his 148ha grazing platform to increase grass yields.
This has enabled him to achieve yields of 11t dry matter/ha last year.
The grazing area consists mainly of a red and white clover mix, with Aber grasses, as well as chicory and plantain where possible.
“We have one main grazing block for the milking cows that is rotationally grazed and has been overseeded for many years,” he explains.
“We are very keen on aeration – and subsoiling certain areas that need more lifting – and have also been focusing on repairing and regenerating our soils by increasing clover content with an overseeding disc drill.”
One of the key indicators Mr Downes looks at is organic matter, and he has found that there is a huge variation across the farm.
“Some of our best soils are 9% and some of the lowest are around 4-5%, though this has often been where cereals have been previously grown,” he says.
Improving drainage has also been instrumental. “This helped us identify that our lowest-performing fields actually had ditches that needed to be maintained and cleaned out, and so rectifying this has helped with overall performance,” he says.
More recently, Mr Downes – who has been advised by Mr Bretherton for a number of years – began looking at mineral values.
He explains: “We are part of AHDB’s Strategic Dairy Farm Network.
This has helped us understand what other growers are doing in terms of minerals and now we apply these annually to maintain the health of the soil.
“As well as the direct impact this has on animal health, this encourages biology to grow and encourages maximum uptake at optimum growth times.”
With calcium being such an important mineral for soil structure and grass growth, this has been a key focus.
“There is a balance to be found with calcium and magnesium levels and we look to target a 10:1 ratio to make sure we have got nice friable soils.”