As the weather in the Northern Hemisphere gets rainier going into the Autumn months, the question of our soils’ relationship with water springs to mind. We know that healthy soils absorb much more water than unhealthy soils, and that healthy soil is less likely to degrade into runoff, but what’s the science behind this?
We’ve done some reading around the literature on this subject, to learn how to keep our soils in top shape with regenerative agriculture, and to build a greater resilience to climate extremes like flooding and droughts.
First, leaving soils uncultivated has been shown to increase the structure of macroaggregates within the soil – many studies show an improved macroaggregate stability in soils under no-till compared with ploughed soil (1,2). This is because the net of undisturbed roots and mycorrhizal hyphae entangle smaller aggregates together, reducing the likelihood of soil runoff during heavy rain, and increasing porosity. You can easily assess the macroaggregate stability of your soil with the VESS test or the Slake test (and the results can then be recorded within our Soilmentor app!). Hopefully, having an awareness of how your soil scores on these tests will help you to understand how to improve your soil health!
A long-term study found that conservation agriculture plots retained ⅓ more water under both wind and water erosion compared with conventionally tilled plots (3). Reducing wind and water runoff is significant – we know for example that the devastating US ‘Dust Bowl’ in the 1930s was caused by intensive cultivation, and hugely impacted food security at the time – it’s estimated that 300 million tonnes of topsoil was swept up by the wind, destroying crops and killing livestock (4). With extreme weather events increasing due to climate change, building soil resilience is of utmost importance.
In the same vein, agricultural runoff causes massive ecological damage, and is a major source of nonpoint source pollution in water systems – with runoff likely containing fertilisers, pesticides, nutrients and topsoil. A study comparing four streams with catchments from land under different management, found streams feeding from land under conservation agriculture had a higher diversity of invertebrates and more ‘clean water’ species than streams under tilled land, which was attributed to improved soil structure reducing agricultural runoff (5). The reduced topsoil runoff into nearby rivers and streams also reduces sedimentation, which increases the river’s capacity, as well as the clarity of the water – allowing sunlight to benefit the wildlife and photosynthesis in aquatic plants. Rivers with high sedimentation also absorb more heat from the sun, causing local warming which potentially causes further damage (6).
Soil erosion in the UK is clearly visible from space. Credit: NEODAAS/University of Dundee
We loved seeing the rainfall simulator at Groundswell this year – it really helped us to visualise the ability of healthy soil to absorb rain! You can watch a video of a rainfall simulator in action here.
Rainfall simulator in action at the 2019 Groundswell show – the bottles on the ground show the water that filtered through the soil in each plot, while the hanging bottles show the ‘runoff’ water.
So, to wrap up, healthy soils absorb and hold more water than degraded soils, which helps to reduce flooding, aquatic pollution, and resistance to drought conditions and wind erosion! Keeping your soil optimally protected involves minimal disturbance, continuous cover with mulch and living roots, and root diversity (from crop diversity) allows for increased microbial populations which help to aggregate soil. All of these come under the soil health principles.
We developed Soilmentor as a simple solution to help farmers monitor their soil health progression – seeing your soil health improve over time helps you to understand which farming methods are working for you, and hopefully give you an incentive to stay on a regenerative journey!
Learn more about making your soil rain-ready here.
Paper references:
- Congreves, K.A., Hayes, A., Verhallen, E.A., Van Erd, L.L. 2015. Long-term impact of tillage and crop rotation on soil health at four temperate agroecosystems. Soil and Tillage Research. 152: 17–28.
- Parihar, C.M. Yadav, M.R., Jat, S.L., Singh, A.K., Kumar, B., Pradhan, S., Chakraborty, D., Jat, M.L., Jat, R.K., Saharawat, Y.S., Yadav, O.P. 2016. Long term effect of conservation agriculture in maize rotations on total organic carbon, physical and biological properties of a sandy loam soil in north-western Indo-Gangetic Plains. Soil and Tillage Research. 161: 116–128
- Van Pelt, R.S., Hushmurodov, S.X., Baumhardt, R.L., Chappell, A., Nearing, M.A., Polyakov, V.O., Strack, J. 2017. The reduction of partitioned wind and water erosion by conservation agriculture. CATENA. 148: 160–167
- Baveye, P.C., Rangel, D., Jacobsen, A. R., Laba, M., Darnault, C., Otten, W., Radulowich, R., Camargo, F.A.O. 2011. From dust bowl to dust bowl: soils still a frontier of science. Soil Science Society of America Journal. 75: 6
- Barton, D.R., Farmer, M.E.D. 1997. The effects of conservation tillage practices on benthic invertebrate communities in headwater streams in southwestern Ontario, Canada. Environmental Pollution. 96: 207-215
- Lal, R., Reicosky, D.C. & Hanson, J.D. 2007. Evolution of the plow over 10,000 years and the rationale for no-till farming. Soil and Tillage Research. 93:1–12
