Connectivity might be the secret to healthy soils – Farmers Guardian

The more connected your pore space, the healthier your soils will be. This was the advice of Prof Andy Neal, micro-biologist and research scientist at Rothamsted Research.

Building a connected pore space starts with the inclusion of organic matter in the soil, as the complex process of breaking down the larger plant material into smaller plant material enables the soil to accumulate molecules and build biomass.

Speaking at Hutchinsons’ agroecological conference in late January, Prof Neal said: “This is the very important part for organic matter sequestration in soil, getting molecules which are small enough to associate with mineral surfaces and then become in tuned, so that no further microbial activity can happen.”

As the molecules are locked away into the soil through sequestration, the soil has the ability to create a ‘structure’. However, Prof Neal said to understand that structure, growers must first understand the scale.

When analysing pore space, the scale is somewhere between one and 100 microns.

“If that does not make much sense to you, it is smaller than the diameter of an average human hair,” said Prof Neal.

Pore space is important for a selection of soil health benefits including water holding capacity, as once the water drains, the reservoirs created by the pores increase the holding capacity of the soil.

Pore space is also where the greatest enzyme and microbial activity takes place and also home to fine crop roots.

The way soils behave is largely dependent on their texture.

Prof Neal compared two trial sites analysing the difference bet-ween clay and sandy connectivity between the pore spaces.

Each soil type also had a range of organic matters including a site that had less than 1 percent organic matter, as the trial had deliberately prevented any plant growth for more than 50 years.

“We intentionally starved the soil to test the limits and, at 1 percent organic matter, you have little porosity of about 5 per cent, so there is very little connectivity between those pores.

“The more connected your pore space, the healthier your soil will be,” he said.

As the organic matter is increased, Prof Neal said there was a sudden jump in the connectivity between the pores.

“Soils with a reasonable amount of clay have a very dynamic soil structure, but it is very dependent on the amount of organic matter you are pushing through the soil.”

However, another Rothamsted Research trial demonstrated that organic matter has very little influence on the structure of a sandy soil.

“That is because sandy soil is made up of large particles that are similar in shape and size, so you end up with huge voids which can-not form structure meaning sandy soils are very un-dynamic.”

A HUGE benefit of increased organic matter is the soil’s improved ability to hold water, this is due to microbes breaking down to a form that is able to stick to mineral surfaces and build pore structures, increasing the connectivity of the soil.

Using a rough calculation, Prof Neal explained that a 1 percent increase in organic matter could give the soil a 354,000-litrewater storage increase in the top 30cm per hectare.

“That is a real advantage to increasing your pore space, but that is just an example and do not go home and trust that number will be right on every soil,” said Prof Neal.