Earthworms at the end of the rainbow
Driving home from the first winter meeting at the Truro Monitor Farm (meeting report), I had the chance to reflect on group discussions about the assessment of soil health. A twitter comment from @perkinseleanor, also had me thinking.
“What is your pot of gold at the end of the rainbow?”
During the meeting at Tregairewoon Farm, the group were tasked with counting earthworm numbers and conducting visual soil assessment scores. This information, in addition to yield and soil indices, were used to identify potential constraints on arable productivity, and possible solutions to yield limiting factors.
Earthworm activity enables crop roots to grow more easily through the soil, and increase water availability at depth, but they rely on a supply of organic matter. There is actually no clear relationship between increased earthworm populations and yield, but research has shown that the application of farmyard manure to increase soil organic matter, which has a positive impact on soil biology, can improve yields of barley grain and straw by more than 1 tonne per hectare each. The benefits can be achieved over a relatively short period of time, within two years following application.
So what is the target? The optimum level of soil organic matter is also somewhat elusive, as is the quantification of organic matter levels in your fields. The key factor for increasing soil biological activity is the application of fresh organic matter material.
At Truro Monitor Farm, although earthworm numbers were close to the average for conventionally managed arable field (150 per m2). Within the cover crops, earthworm populations were 300 per m2, which could suggest the improved soil environment, or the variability of earthworm populations within the field. Soil assessments were moderate to good, and the group identified that increases in the soil organic matter, achieved by the improvement of the rotation, is the starting point for overcoming low yields.
So you could say, that in this instance, it was earthworms we were searching for at the end of the rainbow. But when was the last time you stopped to ask yourself the same question?
It could be that you are searching for increasing soil organic matter for increased soil biology by growing cover crops, or reducing fungicide usage by varietal selection with greater disease resistance.
With the launch of AHDB’s cross-sector benchmarking system just around the corner, there has never been a better time to identify your end goal and monitor how decisions to reach this goal affect your business.