How to find and repair compacted soil
Often called plow pan, compacted soil is that cement-like layer on or below the surface that’s impossible to plow through. Soil compaction is considered the “costliest and most serious environmental problem” facing agriculture. It occurs when soil particles are compressed together — especially when the soil is wet — destroying soil structure, reducing porosity, and leading to a more dense soil that is hard for crop roots and water to penetrate. Compaction can reduce crop yields as much as 60%. Learning how to find and repair compacted soil is crucial to a farmer’s success.
What causes compaction?
Simply put, compaction is caused by weight. Pressure on the soil from the weight of farm machinery squeezes the air from between the soil particles. The soil’s density increases and its pore spaces are reduced. The denser the soil becomes, the harder it is for water to infiltrate it, for organisms to dig through it, and for plant roots to penetrate it.
Since water can’t get through compacted soil, it stays near the surface and creates runoff that can carry pollution, leaves standing water for mosquitoes, and increases flooding. And since roots can no longer grow down, they spread out or hardly grow at all. And without water, microorganisms and roots, crop yields drop quickly.
Biggest contributors to compaction
These three items are the biggest contributors to soil compaction. Controlling these factors is the best way to keep compaction from controlling your fields.
- Use of heavier machinery — unsurprisingly, heavier harvesters, tractors and trucks lead to soils being subjected to heavier loads and rapid compaction
- Frequent cultivation — this can result in the formation of plow pan, a hard or cemented layer of soil at the plow depth. Plow pan is similar to hard pan, except that while hard pan can occur naturally, plow pan is always man made.
- Tillage when the soil is wet — soil is more plastic when wet and therefore more susceptible to shearing and compression.
Some soils have natural compacted layers which limit water entry, cause waterlogging and restrict plant growth. However continual plowing at the same depth and heavy machinery traffic on wet soils can produce similar compacted layers.
Soil compaction can have an impact over a range of soils and climatic zones and can affect different industries, e.g. cropping, grazing and forestry.
Compaction effects on different soils
Silt and clay soils are most susceptible to compaction, because their particles hold more water for a longer time than either sandy or loamy soils. As a result, clay soils remain in a plastic state, sometimes for the whole year, which means they will compress and shear when a load is applied to them.
Soil compaction can lead to:
- Increased soil erosion
- Decreased infiltration
- Decreased water storage — Without
- Decreased root growth
- Decrease in water entering the soil either as rain or irrigation
- Decline in soil structural stability
- Decline in N uptake and overall fertilizer efficiency — Large blocks of compacted soil provide few surfaces to retain and release fertilizer
- REDUCED YIELD — Compaction can reduce yields of some crops by as much as 60%
Warning signs of compaction
How do you know whether your soil has become compacted? Look on the soil surface for the following symptoms.
- Increased soil cloddiness
- Surface clods that resist breaking down after rain or cultivation
- Water ponding in tracks and headlands
- Wheel tracks with a smeared appearance
- Poor crop establishment in wheel tracks
- Crop lodging, uneven plant growth and uneven ripening of the crop.
You should also check under the surface for these signs. (Use a shovel to clear back the loose topsoil and dig into the subsoil.)
- A hard zone below the depth of cultivation (keep in mind that compacted soil may still appear soft when it’s moist)
- Soil remains in hard clods when you try to break it apart
- Soil appears to have no structure
- Flat, dull faces on soil peds
- Distorted crop root systems (referred to as right angle disease).
Preventing compaction
There are a number of ways you can minimize and manage soil compaction. These include:
(1) Reducing the frequency of tillage — adopting a no-till farming system is arguably
(3) Using the plastic limit test (if you can roll out a rod of clay soil with a 3mm [1/8″] diameter, then the soil is too wet for cultivation)
(5) Using large diameter, narrower tires, (which compact less surface area than small wide tires or dual tires)
(6) If narrow tires aren’t feasible, using flotation low-pressure tires instead on all equipment, especially tractors, harvesters and trucks
(8) Encouraging organic matter build up – pasture rotation is recommended.
1) Avoid traffic and tillage when the soil is moist or wet
Breakdown of the soil structure is greatest when the soil is wet, so stay off the field completely if possible. Restrict the use of any vehicle in the fields to times when the fields are at their driest.
2) Practice controlled traffic throughout the farm
Establish permanent travel lanes for farm traffic. Mark out your lanes and stay on the path. Limit wheeled traffic to no more than 30% of the soil surface, and once you’ve set up a traffic pattern, don’t till deeper than 4 inches. And always use the smallest vehicle possible for the job.
3) Use as many radial tires as you can
Tractor tires distribute forces into the soil, which can start the compaction process. Getting the right type is a key step in fighting compaction. Larger tires distribute weight more evenly than small, skinny ones. Since tractor weight is divided between its tires, extra tires in duals and triples (or tracks) spread the weight more evenly and reduce downward pressure. Also, radial tires help combat compaction because the footprint gets longer as you load it up (giving you less slip and better traction as a bonus).
4) Speaking of tires, be careful not to overinflate
Check your tires’ pressure before taking a vehicle into the field, and make sure they’re all set at the recommended rate. Inflating tires to higher than recommended rates has been shown to increase compaction and lead to relatively less tire traction. Lower pressure, on the other hand, creates a larger footprint, which takes some of the pressure off your soil.
4) Go no-till, or at least low-till
No-till farming may not always be practical, but the more you can reduce the amount and frequency of tillage, the more opportunity your soil has to begin healing itself. When tillage is necessary, make sure it’s variable-depth tillage.
Repair Compacted Soil
Your options to repair compacted soil can be biological, mechanical or both.
While clay soils are most susceptible to compaction, many have an in-built mechanism to repair structure degradation. They swell and shrink on wetting and drying, which causes cracking and breaks up the compacted soil.
Crop roots create soil pores and promote the formation of cracks in cracking soils. This biological ripping is a risk-free form of repairing soil compaction. The best response is gained by rotating crops or growing break crops to give different rooting patterns.
Cultivation
Cultivation when the soil is dry will hasten the natural breakdown of clods. This tillage needs to be shallow so that deeper (and usually wetter) soil is not compacted. Before starting, check the soil moisture profile to at least cultivation depth to ensure the soil is dry and that it will fracture rather than smear.
Ripping
Deep ripping should only be used as a last resort. Ripping moist to wet soil will cause further smearing and compaction. If the soil is dry enough to deep rip, the paddock should be cultivated first to leave some loose soil on the surface. This makes subsequent tillage operations more comfortable for the operator and helps restore the seedbed to a reasonable tilth quicker.
MultiFIX
The Optimum Food for Microbes not only builds up healthy microbes already in your soil, it also helps them venture into new areas — like compacted soil. The microbes then get to work, releasing gases that aerate the soil, creating air pockets that allow water and roots to expand and rejuvenate compacted soils. Whether or not your soil is becoming compacted, MultiFIX can help your native microbes reach their full potential. Send us a message or give us a call, and we’ll show you to help your crops reach their full potential.
...Worth a thousand words
Take a look at this short (2:23) video showing MultiFIX at work fighting soil compaction. Then you’ll understand what we mean.
And if you want to see the same results on your fields, give us a call.
