Controlled traffic farming to increase root growth of crops

Heavy farm machinery results in soil compaction, which can damage the root growth of crops and reduce crop yields. By using permanent lanes in the fields – known as controlled traffic farming – in the production system of organic vegetables, the yield can be increased. However, to what extent depends on both the soil type and the crop species, according to a study from the Department of Food Science, the Department of Mathematics and the Department of Engineering at Aarhus University in Denmark.

Field trial: random traffic farming and controlled traffic farming

The effect of two different traffic systems by tractors and agricultural machinery were tested in a field trial: random traffic farming (RTF) and controlled traffic farming (CTF) in permanent lanes that limits soil compaction to the lanes.

In order to be able to compare the effect of soil type, the experiment took place on two organic farms in Denmark – one with coarse sand in the period 2013-15 and the other with fine sandy loam in the period 2013-16.

Also read: Are light autonomous robots the answer to soil compaction?

In order to be able to compare the effect of crop species, both white cabbage, potatoes, beetroot and winter squash were examined. More specifically, the researchers investigated the impact of the two production systems on crop yield, root growth and nitrogen content under the conditions of the two types of management.

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The effect of two different traffic systems by tractors and agricultural machinery were tested in a field trial: random traffic farming (RTF) and controlled traffic farming (CTF) in permanent lanes that limits soil compaction to the lanes. – Photo: Hanne L. Kristensen, Aarhus University

Advantages associated with controlled traffic farming

The results showed that there are advantages associated with controlled traffic farming, but that both the soil type and the crop species matter. Most significant results were seen on the Skiftekær Økologi farm, which had fine sandy loam. The yield of white cabbage, potatoes and beetroot was, respectively, 27%, 70% and 42% higher (2015) and the yield of winter squash 43% higher (2016) when permanent lanes were used.

White cabbage (2015) as well as potatoes, beetroot and winter squash (2016) had between 2 and 25 times more roots when permanent lanes were used, says Hanne Lakkenborg Kristensen, Associate Professor and leader of the Science Team Plant, Food & Sustainability at the Department of Food Science.

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Most significant results were seen on the Skiftekær Økologi farm, which had fine sandy loam. The yield of white cabbage, potatoes and beetroot was, respectively, 27%, 70% and 42% higher (2015) and the yield of winter squash 43% higher (2016) when permanent lanes were used. – Photo: Hanne L. Kristensen, Aarhus University

On the farm, Vostrup Øko, which had coarse sand, there were also some positive effects of controlled traffic farming. The researchers found, among other things, that the use of this traffic pattern resulted in 1.4 times more roots on the beetroot (2016).

Nitrogen availability increased by controlled traffic farming

The mineral nitrogen content and potential mineralisation of nitrogen of the soil were either the same under the two traffic patterns – and in some cases higher when permanent lanes were used.

According to the researchers, this indicates that nitrogen availability was either maintained or increased by the implementation of controlled traffic farming, due to the increased plant growth and subsequent mineralisation of plant residues.

Permanent lanes can maintain or improve both crop yields and nitrogen uptake and can contribute positively to root growth

Overall, the results of the study indicate that controlled traffic farming, all other things being equal, can benefit organic farms. “Our study shows that permanent lanes can maintain or improve both crop yields and nitrogen uptake – and that permanent lanes can contribute positively to root growth. We have not found any negative effects of using permanent lanes in organic farming, regardless of whether it is coarse sand or fine sandy loam – and regardless of which vegetables are involved,” says Hanne Lakkenborg Kristensen.

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White cabbage (2015) as well as potatoes, beetroot and winter squash (2016) had between 2 and 25 times more roots when permanent lanes were used. – Photo: Hanne L. Kristensen, Aarhus University

She concludes: “Based on our research, we would, therefore, recommend the use of controlled traffic farming in organic farms. In vegetable production, it requires that the cultivation beds are fixed and that all machines have the same track width. Technologies for precise control of tractors and machines in permanent lanes are optional equipment that, according to Statistics Denmark, has become more widespread on agricultural holdings in recent years.”

The cost of compaction needs to count not only the investment in time, fuel and equipment required to take remedial action to repair the damage, but also the significant yield loss it often causes. What is the cost of soil compaction?