Water Infiltration Demonstration with Growing Eastern Ontario Organic

On the evening of August 10th the Canadian Organic Growers (COG) hosted a gathering for Growing Eastern Ontario Organics (GEOO) participants and invited guests. The event was a mix of a virtual meeting on a Zoom platform and live face-to-face meetings at two locations. The hosts were Marshall and Kathleen Buchanan of Ottawa Valley Farm to Fork located near Douglas and Patrick and Anna Brunet of Dream Small Farm located near Alexandria. The purpose of the gathering was to discuss soil health and demonstrate water infiltration as one method of measuring soil health. 

The consulting agronomists for the GEOO program Rob Wallbridge, Valerie Yoder and myself, Ruth Knight were on hand to perform the live demonstrations and guide participants in a lively discussion. Alix Tabet and Jonathan Bruderlein hosted the virtual meeting using a pre-recorded video of the water infiltration demonstration we created a few days earlier at the farm of Paul DesRosier in St. Albert. Since soil health is such a passion of mine, I was pleased to be part of so much enthusiasm and curiosity about soil. It was also a welcome relief from the constraints of the COVID pandemic to meet people and make new connections with farmers. The comment from the participants at the live event was everyone really enjoyed the hands on learning. 

Soil Health Primer

We started with a small backgrounder on soil health. A simple definition is a healthy soil has the capacity as a living functional ecosystem to sustain humans, plants, animals and other organisms. The ability to allow water to flow through soil is one of those functions. Water has an interesting behaviour in soil. Water follows the law of gravity moving down into the soil and also defies gravity by moving upward through the soil. After water drains out of the soil by gravity, the water moves upwards against gravity from wet areas to dry areas by capillary action. A healthy soil improves the flow by capillary action. 

Snow or rainwater drains through the soil by gravity. The faster the water can infiltrate, the more rainfall can be absorbed and less erosion and flooding. The rainfall that can be infiltrated will be more effective at supporting life in the soil thus supporting a functional ecosystem. As the saying goes “It’s not how much rainfall you get, it’s how much you can keep” that sets apart a healthy or regenerative landscape from one that is degraded. The more rainfall that can infiltrate and replenish the water table, the longer the soil can continue to support plants and other life forms when there is no precipitation. The water that infiltrates into the soil will recharge the aquifers, result in less flooding, less wildfires, less pollution of waterways and provide more ecological services. For farmers healthy soil means less risk to crop productivity, greater economic resiliency, and more resilience in the face of climate change and other disruptions.

To demonstrate this relationship between healthy soil and water I like to use the analogy of a sponge. The sponge is an effective analogy because it has solid parts and pore spaces. And it’s really obvious how effective a sponge is at quickly soaking up liquid and how easy it is to squeeze out the liquid again. In healthy soil about 50% of the volume is made up of sand, silt and clay along with some organic matter. The other 50% is pore space that is filled with air and water. The roots are easy to see. They hold the soil together. More importantly the glues and slimes from the life such as fungi, bacteria, protozoa, etc. that feed from the carbon secreted by the roots, hold the solids together and create the pore spaces – by design not willy-nilly! Earthworms also create channels lined with nutrient rich carbon that persist for years if not disturbed. The pore spaces allow the exchange of oxygen, carbon and other gases as well as the flow of water and this is essential to support life. 

In return, the life forms or microbial life are essential partners in this sponge arrangement by gluing the soil particles together into larger crumb structures we call aggregates. These aggregates are also the storehouse for many nutrients as well as carbon. Think of the difference between flour and bread. The flour is the solid portion of soil which is the basic ingredient in bread. Then we add yeast, which is the life, and sugar that feeds the yeast, and this life creates the sponge-like texture in the bread. The same life forces create and regenerate soil. Our goal in soil management is to create conditions to support life. It’s not easy to directly measure that complex soil life so we choose other indicators that relate to the function or structure of soil.

Soil Health Indicators Help Discern Impact of Management Decisions

In choosing a soil health indicator we want something that will help us discern the impact of management decisions on the potential of the soil to function. Water infiltration is a soil health indicator that is relatively sensitive to management and relates to other soil physical, chemical and biological parameters. 

Management activities that disconnect the pores and earthworm channels such as tillage can reduce water infiltration and cut off capillary action. Adding diversity into crop rotations, intercropping and adding the maximum number of days of green plants and living roots to contribute more carbon to the soil, are all positive ways that support the life and water movement in the soil. Adding compost, manure and other organic amendments helps to build the organic matter that sequesters more carbon and creates more sponge in the soil. Heavy or continuous traffic on the soil, especially if it is bare, will compress the pores, squeeze out the air and prevent the water from infiltrating into the soil. Monocultures, pesticides, insecticides and fungicides all reduce the diversity and number of life forms in and on the soil that create the sponge. 

Comparing 4 Management Areas 

With the help of Marshall we chose the same soil type with 4 different management areas that are described as follows:

Lucky for us these management areas were in very close proximity to each other and we could mill around and observe each of the areas.

For the infiltration we used 4 metal rings 6” in diameter and 6” in height. The rings were pounded into the soil so that 3” is below ground and 3” is above ground. To simulate a rainfall event we poured the equivalent volume of 1” of water over the soil in the ring. A plastic sheet was used to cover the soil while pouring the water to prevent erosion and uneven flow on the surface. We measured the time in minutes and seconds for the water to soak into the soil. We repeated the pour 3 times in each ring and recorded the results. The participants were really helpful installing the rings, timing the water pours and sharing their observations. It amazes me what we can learn simply by watching water soak into the soil. The short pause in our busy lives brings us closer to the soil and the life forms it supports.

The results of the infiltration are attached here.  

Additional Observations from the Group

What did we see? – As the water soaked into the soil we saw air bubbles coming out of the soil. The bubbling activity varied from the different management areas as we added more pours. Soil in the grassy fencerow continued to release bubbles even on the third pour. Soil in the bare soil didn’t bubble after the initial pour

What did the soil look like after the exercise? – The bare soil from the tilled vegetable garden looked like pudding.T he soil from the grassy fencerow and the no till squash looked like chocolate cake. Which soil would you prefer?

A ‘AH HAH’ moment was shared – Water moves by gravity and also defies gravity!

What take home do you have that will result in a management change?  The foot traffic on the bare soil, although it appears to make a small difference to the infiltration, it’s enough to make me consider using strip tillage in my crop fields.

What did you enjoy about the event? Everyone enjoyed the hands-on learning, it’s a more effective way to learn. 

The general feel about the event – people enjoyed an opportunity to meet their neighbours and share their stories about their farm

Replicating On Your Farm

The water infiltration is a very simple measurement that can give you feedback on the impact of your decision making. There are other soil health measurements that we plan to incorporate into the GEOO project. Stay tuned for more info on that. If this has inspired you there are several water infiltration kits available for you to borrow and use to start measuring soil health on your farm. 

Every farm has a benchmark to compare your management to. Compare your fields or garden plots to an undisturbed fencerow, ditch or hedge. A word of caution the results don’t always come out the way you might predict which leads us to more curiosity and more inquiry. The innovative farmers I have met have very inquiring minds and take measured risks to try different ideas and follow up with measured outcomes, observations and modified plans to redo the trials. This curious mindset will lead us to more regenerative farming systems. We can do this!

by Ruth Knight PAg CCA