Monitoring soil health provides us with a valuable opportunity to know how are we doing, if we are making progress toward our respective goals, is “it” working and are things improving? Here are 8 simple soil health measurements to get you started without the need to purchase expensive equipment, or to send soil samples away to the lab, making use of one of the most important tools on your farm – a spade
Compaction: This is often your #1 limit to production. Without a penetrometer, there are several ways to assess compaction. Using a spade to dig a cube of soil will tell you a lot. If you have to jump on the spade to penetrate the ground its either due to bone dry conditions, compacted soil or in some cases a very tight and sometimes deep thatch layers of undecomposed roots and litter. If the spade goes in several inches/cms and then stops, you will likely find a hard pan. Observing the cube of soil you can see if there are compacted layers of soil present. By considering history and management you will be able to determine if that is a plough or tillage pan at depth, or a more shallow ‘cow pan’ caused by pugging or overgrazing. Compaction is a good indicator that you have a lack of aeration which will restrict nutrient uptake and water infiltration.
Water Infiltration: See our fact sheet on taking an infiltration test. Knowing how long water takes to penetrate into your soil is an indicator of soil porosity and aeration or lack of it. If absorption of the 2nd 25mm/1inch takes longer than 12 minutes, your water cycle needs addressing, as a big percentage of your annual precipitation will be being lost through run off. Our ability to absorb and retain moisture is a key factor in building resilience.
Rooting Depth and Structure: Measuring plant rooting depths tells you how well those plants are able to penetrate the soil and access nutrients. We measure root depth to 80% density and 100%. Root depth also informs you about the effects of your grazing management. Do you have weeds that are tap rooted or spreading, with things such as Californian/Canadian thistles. Note how deep and fibrous those roots are and consider what they are providing. Weeds are natures healers; how can we assist with the remedial action they are taking to address the issues the soil is facing?
Root Rhizosheaths: Clean roots indicate there is a poor functional relationship between the plant and the soil biome. The presence of good rhizosheaths indicates that the mycorrhizal fungi are actively creating community networks to supply the plants with needed nutrients.
Nodules: Check the nodules on your legumes, are there any? What condition are they, large and plentiful? What colour are they? White, indicates they are not working. Pink they are working. Green they have been working and have stopped. Slice the nodules open to ascertain their true colour.
Dig a spade full of soil and sift through it counting the worms and other insects and pests as you go, pay particular attention to the upper layer and root mass. If you find more than 45 worms, things are looking good, 100 or more and your soil is humming. Often 10-20 or less worms are common numbers until the other limiting issues are addressed. Aeration and a functioning soil food web which are also dependent on the above ground biomass, are the key to good earthworm populations. If digging in hot, dry conditions do not fret, they do disappear in adverse conditions, so attend to keeping the environment conducive with good covers either living or as litter.
Soil Insects: In semi-arid environments these services instead are provided by termites, ants and other insects. While you are counting earthworms be sure to observe and count any other beneficial insects or pests you find. Root feeding insects such as mealy bug, grass grub, clover root weevil, wire worms all have a big impact on a growers bottom line. Knowing what is in your soil and in what populations is key to accessing management strategies and actions to take.
Structure: When you dig out a spade of soil does it collapse like a pile of sand or does it sit there like a brick and stay that way even after you have dropped it several times. Soil structure is like the frame work off a house. It creates rooms and walls, hallways and space for air, water, and organisms to move and thrive. Mycorrhizal fungi are key as they produce glomalin which forms soil macro aggregates holding our soil to the earth. Bacterial dominate soils are often very fine and structureless, making them prone to erosion, crusting and poor nutrient cycling as bacteria hold onto nutrients.
Colour: Comparing the soil from your paddock to that from under an old fence line that has not been subjected to animal impact, tillage and chemical applications can be telling. The darker the soil the higher the organic matter. Often, we find a considerable lighter colour in the paddock indicating degradation from past practices. Mottling, spots of colour that vary from the predominate soil colour indicate poor drainage, aeration and a loss in soil structure.
Smell: Is your soil is aerobic or anaerobic, let your nose be the judge. Fungal soils such as a forest have a distinct earthy smell which can be describes as sweet, rich or musty. Pasture soils with this aroma will have a good fungi to bacteria ratio. Highly bacterial soils on the other hand will be less aerated, with a less earthy odour or a mineral smell. Like a fine wine it is practice and exposure to the different aromas that will develop ones nose for a good soil. Anaerobic soils will have a putrid or sometimes chemical smell as they off-gas the build-up of alcohols, formaldehyde, sulphides and methane.
Getting out of the pickup and below the soil surface and measuring is a great way to get familiar with soil, measuring and recording over time will allow you to accurately assess the progress you are making over time. Photographs are a great way to record changes as our memories often fade and are inaccurate as record keepers. Ultimately, it is the actions we take from this information that make the difference. Identify where the opportunities lie to improve your soil function firstly by assessing where there are limitations. Take the guess work out of it, become the expert in your fields, apply new actions and enjoy discovering a whole world beneath your feet.
Without measurement there is no management. If you can’t manage it, you can’t improve it.
By Jules Matthews
Jules is available for coaching to help you achieve your regenerative agriculture goals and can be contacted by phoning +64 21 681 220 or by email email@example.com