Один тест не дает полной картины: почему инфильтрация воды не всегда отражает здоровье почвы

Advertissement What a water infiltration test can, and can’t, tell you about your soil health Healthy soil generally absorbs water faster, but a soil scientist says that no one field test can give a true diagnosis of how healthy your farm’s soil is By Geralyn Wichers Digital editor, news and national affairs September 8, 2026 7 min read What can a water infiltration test actually tell farmers about their soil health? Farmers who’ve been to a soil health field day have probably seen this demonstration: one of the speakers will pour water into a ring that’s been hammered into the soil. Someone uses a stopwatch to see how long the water takes to dissapear underground. They then move to a different spot — perhaps a nearby field with the same soil but a different type of cropping — and run the test again. The understanding is that healthier, less compacted soil usually sucks up water faster. For example, on an ALUS Canada tour, held mid-July in southeastern Manitoba, tour leaders poured a bottle of water into a ring stuck in pasture filled with a diverse forage blend. This was contrasted with a ring on the fence line. In the time it took for the water to infiltrate in the pasture, the water on the fenceline had hardly moved at all. Read Also Crops Does this mean the pasture soil is healthier than the fenceline? It might, but soil experts also warn that the devil is in the details. WHY IT MATTERS Sustainable farming movements argue that better soil health leads to better performing, more resilient land against severe weather shocks, like quick infiltration of heavy rainfall to help draw down flood risk. Soil snapshots For one thing, the test is measuring results on one spot in one moment in time. Yes, farm practice weighs on it. The soil may be tilled, which would give different results from when its covered and there are living roots in the soil — the type of contrast the demonstration is looking to make. But that same test, in the same spots, might show different results if the field tour happens during spring, when soil is already holding a lot of water due to snowmelt. During the heat of the summer, the soil may be very dry and suck water up quickly — or it may be cracked, allowing the water to bypass the soil structure entirely. “If you’re going to do infiltration tests to see the status of the soil, you have to do it at critical points,” said Afua Mante, an assistant professor of soil science at the University of Manitoba. Mante researches the physical properties and processes of soil. She suggested testing right after the snow melts to capture spring thaw and saturation conditions while there’s a high risk of runoff. Then check again once the crop is in. Check when there is heat and too little rain, which would capture stress points where the soil may crust or repel water, and again after harvest to assess the impact of machinery traffic and tillage. This should give an average or perhaps worst-case scenario. Pouring one small bottle of water into the ring may also not give the full picture, she said. When soil is dry, water may infiltrate quickly at first and then slow down. It’s only after prolonged wetting that the soil will approach the steady infiltration rate. Unfortunately for the flashiness of a display, Mante described that point as the lowest possible rate at which water will enter the soil. Testing in two different spots might show one initially infiltrate much faster, but if the underlying soil profile is fundamentally the same, things could ultimately settle into the same steady infiltration rate. The United States Department of Agriculture’s soil testing kit guide suggests doing the water infiltration test twice. “The first inch of water wets the soil, and the second inch gives a better estimate of the infiltration rate of the soil,” the guide said. The test doesn’t tell you where the water goes An infiltration test shows how fast the water leaves the surface. It doesn’t show where the water goes after that and the soil below the surface is probably not homogenous. Mante said she recently visited a farm in the Stonewall, Man., area in which the first 10 to 15 centimetres of soil looked great and was growing oats. However, when they dug past the first layer, the soil underneath was “super, super dry.” The first layer of soil had about 23 per cent moisture. Beneath it, at about 40 cm, the soil had about four per cent moisture. “Water is not going through,” Mante said. It wasn’t a matter of bad farming practices. It was a soil with a high concentration of calcium and magnesium. It was naturally hard. As a result, water moved laterally beneath the first 15 cm of soil, Mante said, and settled in the low areas. It makes for a different kind of compaction risk. The surface may look dry, but the upper level of soil might be a bit like an air mattress floating on water. Machinery may drive comfortably but still create compaction beneath the first layer of soil. How can you know where the water goes? Topography can help. However, in flat or sandy areas where the water disappears quickly, it can be more difficult. “Knowing your soil profile is very important,” Mante said. She encouraged farmers to try digging a small pit in a field of 60 cm to one metre deep, enought to see the strata of the soil profile. When it rains, they can then watch how water moves from layer to layer in the pit. What the test can tell you However, not every farmer is a soil geek with time and interest to dig a soil pit or do lengthy infiltration tests. When extension experts demonstrate the water infiltration, finding the steady infiltration rate of a field is beside the point—as it is for many farmers. They don’t need a hard number for how much water the soil can absorb. “We need to find other ways that are kind of simpler, easier, faster to tell a story,” said Marla Riekman, soil fertility specialist with Manitoba Agriculture. The test will still demonstrate that how they manage their soil affects how fast water infiltrates, said Megan Westphal, soil health specialist with Manitoba Agriculture. Generally, when speakers talk about healthy soil, they mean soil with a good structure, aggregate stability and higher organic matter. “A healthy soil with all of those things, they generally will allow water to infiltrate into it a lot quicker,” Westphal said. Whereas, compacted soil will slow water down. Poor aggregation may allow water to break apart aggregates into individual particles, which can clog the pores in the soil and slow the water. Farmers on the same soil health tours may see other tests, where soil samples are submerged to measure how well it holds together, that illustrate that effect. For farmers, the important part is often that “they’re just seeing that water is soaking in… my land can handle the heavy rains a little bit better. It doesn’t crust over and seal over quite as bad,” Riekman said. If farmers want to go into more depth on their own soil, the USDA has extensive information online about different types of soil tests and how to do them. Tests don’t stand alone Farmers also need to understand that no individual test of soil health can stand on its own, except maybe those addressing individual nutrient needs, Mante said. With water, it’s not just if the water infiltrates, but if there’s capacity to hold it, and if it percolates and reaches the spots where it may be held. “Soil health starts with the structure of the soil,” Mante said. “The structure allows us to understand the soil as a whole system and that requires doing multiple tests and interpreting them as a collective.” Get more in your inbox Get insights from our experts delivered to your inbox. Free • Unsubscribe anytime