Mechanical loosening of grassland could reduce flood risk and increase grass output

Recent flood events devastated some parts of the UK. In response to mitigating future flooding, farmers are looking at land management practices to improve resilience to weather events on their farm. Mechanical loosening of grassland soils in moderate condition has been shown to dramatically increase water infiltration rates, increasing the amount of rainwater that could be stored in the soil. This could reduce surface runoff volumes and associated flooding risk in some grassland-dominated catchments.

Recent extreme rainfall events in parts of the UK had devastating impacts on rural areas in parts of North Wales, Northern England and Scotland with severe flooding and damage to transport routes, collapse of infrastructure (including bridges, walls and buildings), soil erosion and loss of livestock, outlined in a recent article.

The way soil and land are managed can influence water movement and some farming practices may have contributed to, or exacerbated the severity of flooding which occurred in December 2015. David Harris, a senior business management consultant at ADAS explained in a topical article the impacts of soil compaction on infiltration rates and surface runoff in arable land and grasslands.

Soil compaction in grasslands not only reduces agricultural productivity, but also has implications for flood management and water resources, biodiversity, soil, water and air quality. Farmers have the ability to improve soil surface drainage and reduce flood risk through grassland management, which has also been shown to reduce soil erosion, help retain soil nutrients, and improve yields in some instances.

A Defra funded research project (BD5001) led by ADAS investigated soil structural degradation under grassland. The project was managed by Dr Paul Newell Price, a senior soil scientist at ADAS, who explains that "a survey of 300 grassland fields in England and Wales found that about 30% of soils were in good structural condition; 60% were in moderate condition; and 10% were in poor condition. So a lot of farms have the potential to improve the condition of their soils".

The project identified mitigation methods with potential to alleviate soil compaction and have a positive impact on soil functions (e.g. productivity, water regulation and supporting biodiversity). The study looked at four sites with compacted soils to assess the impact of mechanical loosening on water infiltration rates.

The results from the project demonstrated that mechanical loosening (i.e. the use of 'top-soilers' with leading discs, tines and a packer roller, working at 25-35 cm depth) can considerably improve water infiltration rates and structural condition in grassland soils. "Mechanical loosening dramatically increased water infiltration rates. Furthermore, there was evidence of more roots in the lower topsoil with higher root density, improved soil structure, and the potential for reduced surface runoff and waterlogging" explains Paul. "If the increased water infiltration and improved soil structure also results in increased soil water storage, this could have an important impact on flooding risk within and downstream of grass-dominated catchments".

For the full article, visit www.adas.uk.