Strategies to increase soil biology - Final Update
Key results
- Lower application rates of Goop have the potential to be as effective as higher application rates
- Microbial content remains in the soil for at least 7 months after application
- The nutrient value of the soil was greater in Goop-treated plots compared to untreated plots
Background
Attendance at an online soil health course run by Dr Elaine Ingram, an internationally recognised authority on soil microbiology, highlighted the importance to Sam of soil and maintaining soil health as the biggest asset on the farm. The course inspired him to try and understand more about promoting the microbiology present in his soil.
A new experimental compost extract product, 'The Goop' was selected for use, made by the Soil Ecology Lab (soilecologylab.co.uk).
'This product contains hundreds of species of beneficial bacteria, fungi, protozoa and nematodes grown using compost as an incubator in a controlled process. Together they compose a healthy soil ecosystem designed to support crops. Most agricultural soils have deficient or dysfunctional soil food webs, and this product acts as a shot in the arm for your soil. The Goop offers you all the benefits of compost without the need for learning, managing, extracting, or brewing. It's like having the best elements of compost in a convenient bottle’.
Purpose of the work
- Identify efficient ways to increase soil biology (bacteria, fungi, protozoa and nematodes) through re-inoculation with compost extracts
- Identify the amount of extract required to apply to soil to measure quantifiable improvements in soil biology levels
What we did
- 6 fields, (average 4.7ha) were used, each field divided in half
- Half of each field was sprayed with Goop, the other half was not
- Each field had varying application rates: 2, 4, 6, 8, 10, or 12 L/ha of Goop
- Application of Goop was in April 2024
- Soil samples were taken in November 2024 and sent off for analysis
Outcomes
Application rates of 2, 4 and 6 litres per hectare were grouped into a “low” application rate whilst 8, 10 and 12 litres per hectare were grouped into “high” application rates.
Graph 1: Available N, P and K in soil from different treatments
Graph 2: Soil Microbial Content (note different format of measurements)
There was slightly more available nitrogen in the Goop soil compared to the untreated fields, little difference between phosphorus levels, and only a difference between the low Goop application rate of potassium compared to the higher rate and the control (Graph 1).
As expected, Goop-treated fields contained more fungi, amoebae and nematodes compared to untreated fields, and these levels have been maintained over the 7 months (April to November).
However, there was no difference in the bacterial content. It is encouraging that there is no difference in amoebae and nematodes between high and low application rates of Goop. This suggests that the lower applications are just as effective as the higher ones. However, it is important to note that there were no amoebae found in fields treated with 4, 6, 8 and 10 L/ha.
Return on Investment
- Average of low application rate is 4 L/ha
- Average of high application rate is 10 L/ha
- With a Goop cost of £4/L:
- Low application costs ~£16/ha
- High application costs ~£40/ha
- Measurements of grass/crop growth would tend to indicate a return on investment but there is clearly a big difference in costs between the different application rates and a suggestion the lower application rates are as effective at promoting soil microbial content as the higher rates.
Graph 3: Nutrient Value of Soil
When comparing each application of Goop to its respective control (the other untreated half of the field), the higher application rates showed a greater available nutrient value in the soil.
It is difficult to put a value on the higher nutrient content without measuring its effect on grass/crop growth. If it can replace nitrogen fertiliser to some extent then savings could not only be significant but, with improvements in the soil health, could be long lasting too.
How to apply on your farm
The trial demonstrates the benefits of promoting good soil microbiology composed of a varied population of micro-organisms. It is possible to make your own compost teas and use starter cultures from several different outlets. Sam worked closely with Daniel Tyrkiel from Soil Ecology Laboratory who advised on the compost extract ‘The Goop’ and contributed with the form of tests available, such as the Soil Food Web microscopy assay.
If you would like more information on the project work, please contact timtechnegolcff@mentera.cymru.