Real Results Roadshow - Jenni Dungait Soil Paper

Professor Jenni Dungait, Soil Health Expert.

Climate change is here, and this, coupled with a shift towards new Environmental Land Management schemes by the UK Government, where some farm payments are likely to be determined by soil health, will affect the way growers manage their soils.

Professor Jenni Dungait who runs an independent soil science consultancy, Soil Health Expert, said, “Climate change is affecting us all. With UK rainfall in February 237% more than the average, we really have to think about using soils to help us solve flooding problems. Going forwards we are going to have to farm in a different way to manage these extreme conditions. As farmers, if you are looking after the land and you can get paid to moderate and manage this then it is a positive. Water is a resource that we are lucky to have, we have to learn to manage it better.”

Soil consists of minerals, organic matter, water and air. The ideal soil has the same amount of air as water in it, approximately 20-30%. If soils are managed to maintain these air and water contents then they will function better, providing an environment that roots grow in and other biological agents thrive in, including those important in nutrient cycling. Jenni said, “If there is more air in the soil, waterlogging and flooding can be prevented, just 20% airspace in 30 cm depth of soil can absorb 60 mm of rain before reaching saturation.”

There are three major pathways for water to take when it falls on soil. The first, surface flow is the most rapid. Jenni said, “We want to manage things so the water is not moving rapidly across the soil. If you are managing your soils poorly you are giving water every opportunity to flow quickly over the soil surface and into outflow.”

Subsurface flow, however, is desirable. “Here, it is supplying water and nutrients to your plant roots and it is moving much more slowly.”

The third, groundwater flow, is needed as an aquifer for drinking water and also as the source of water during drought.

So, what can growers do to affect these pathways and make the soil absorb as much water as possible?

Jenni said, “When it comes to increasing soil porosity, biology is your friend. Almost all water that moves through soil moves through macropores, many made by biological organisms. All these organisms want is some organic matter as a food source and minimum mechanical soil disturbance. These are the kind of fundamentals that underpin the idea that you can regenerate soils and your farm by using zero and min till.”

Soil organic matter also creates and stabilises soil aggregates. Jenni said, “Even a small increase in the amount of carbon in the soil can make a big difference as it feeds the soil biology, which produce the gums and exudates to hold the soil structure together. In times of flooding, the soils with lots of carbon will stay intact and will regenerate and recover more quickly once the water drains through.”

In comparison, a soil that has been poorly managed, losing soil organic matter through tillage and compacted and compressed from repeated use of heavy machinery, will have water move across the top, rather than down through the profile. Jenni added, “Drainage is also really important, so mechanical drainage is entirely necessary in most soils in this country. Check your drains and outflows to make sure they are functioning as well as possible. If your soil gets flooded it is not good for anything on or in the soil.”