Soil compaction by machinery

By David Jones, Broad Acre Agronomist, Msc. Agriculture

In part of 3 of our series looking into Controlled Traffic, we look at how it can still work on smaller farms and without spending large amount of money replacing equipment. Any farmer should be able to enjoy the benefits of farming without compacted soils.

Start with the planter

Build the system in multiples of the planter. The sprayer is usually easier to adapt give or take a few nozzles on either end of the boom. If you have a 6m planter and a 24m sprayer, a 4 into 1 system is the obvious place to start.

Harvester width

Usually the heaviest axle that will run over the field, the combine header needs to match the width of the planter in the vast majority of CTF systems. But remember that a 6m header needs to cut MORE THAN 6m of crop to avoid leaving unharvested strips.

Often the harvester is the most expensive part of the system to change, so a smaller operator might consider changing out the equipment in stages; if the planter is close to worn out and you have an 8m harvester, it might make sense to change the planter to 8m instead of both the harvester and planter.

That said, if you are committed to making the journey to full notill, using a 7m combine to cut a 6m width of crop is perfectly acceptable if you are prepared to sacrifice a bit of output for controlling compaction.

Another option to just get the system going is to contact someone like Ndume to add a tine onto each end of the planter – this can make the system work when the combine header width is just too wide.

Track Width

Probably the hardest aspect of reducing your wheelings with CTF is track width. The good news however is that it is easier for smaller farmers, relatively speaking.

Consider this; you have your planter width, harvester header width matching in size, and they fit perfectly into the sprayer and fertiliser spreader width…

controlled traffic farming

The harvest however runs on a wider track width of 2.8 – 3m so it makes wider tracks, shown in red in the picture. More compaction.

There are three options; for smaller farms, a small combine will almost sit on the wheelings of a 2.3m tractor, so just persevere. Second option is to widen the wheel widths of the tractors and sprayers which can add significant up front cost. Third option is to use large, low pressure tyres on the combine and accept that you will have extra wheelings, but this can be addressed over time as sprayers and tractors are replaced.

controlled traffic farming

Inevitably with 2.8-3m wheel track combines, you will need to alter the track width of your sprayers and planter tractor. But measure all of your machinery properly – they will often be different from that the manufacturer claims!!!

Guidance

The cornerstone of accurate Controlled Traffic farming is RTK, where pass to pass accuracy of 5cm and most importantly, repeatability so that the wheelings stay in exactly the same place every year.

For larger farmers an RTK base station makes sense; for smaller growers systems such as Omnistar or John Deere’s SF3 which now gives 9 month repeatability. If you are on a budget this is enough to get you going before resetting your A-B lines on your existing wheelings perhaps once a season.

Wheel widths

I have come across several growers insistent on using dual wheels on combines and pointing out that they are not compatible with CTF. The evidence supporting the use of duals to reduce compaction is limited; modern tyre technology means that contact area can be increased by effectively lengthening the footprint of the tyre. A very interesting demonstration of this is a Michelin Xeobib 650 compared to a budget brand 650 below:

Soil compaction

Courtesy of Michelin Agriculture, France

 Flex in the sidewall means that the tread in contact with the ground is far longer, providing a greater contact patch on the soil.

Filling in wheel ruts

The biggest fear of many farmers I worked with in Europe, yet with a very simple tramline renovator this is easily surmountable.

Do not fall into the trap of subsoiling tramlines in order to level them; this breaks up the firm, trafficable layer that will help your sprayer travel in wet conditions, and is shear madness.

controlled traffic farming

Residue spread and straw chopping

We often consider residue management as an afterthought, but even straw spreading is crucial for good establishment and slug management.

We may not have serious slug problems in Kenya, but we can have significant volumes of residue that we want to make the most of, for protecting the soil and sealing in moisture.

Using a straw rake to spread residue requires a pass diagonal to the combine lines, so this is not compatible with CTF. The answer, a sensible straw spreader on the combine.

crop residue

Poor residue spreading (on the right hand side) does not help soil cover, and misses out the opportunity to retain moisture close to the surface or control erosion.

Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the future of how we feed the planet.

Agventure Ltd set up the Center of Excellence for Crop Rotation to help farmers diversify cropping systems and introduce techniques which have a long-term outlook to improve soil health.

The Center of Excellence for Crop Rotation works extensively with Crop Nutrition Laboratory Services Ltd (CropNuts).

Till next time,

Happy farming,

David,

About David

David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.