Written by Patrick Skilleter. The issues associated with compacted soil have been well known for many years now, and whilst efforts are made to reduce the amount of soil compaction and the chances of it forming, the problem continues to plague cropland. Understanding how compaction can occur on cropland, its effects, and how to use this information to reduce the risk of soil compaction affected crop yields is of great importance. Soil compaction causes yield losses. Trials have found that compacted soil can reduce potato yields by up to 66% in extreme cases, although the number of typically closer to 40% (Stalham et al., 2005). Understanding how to mitigate the effects of soil compaction are therefore vital for ensuring yields remain sustainable as global food demands continue to increase.
The increasing reliance on irrigation to maintain yields encourages compaction, as wet soils are more susceptible to compaction than dry soils (Batey, 2009). Dry soils are very difficult to compact, as they are not malleable. Compaction is most easily produced through compression of wet soil on top of dry soils, as the dry soil provides a solid base against which the wet soil can be pressed. Irrigation is primarily applied to the topsoil, which tends to cause deeper soil to become dryer as the growing season progresses, as you can see in the below graph.
Of course, being susceptible to compaction does not mean that soil compaction will occur. In order for the soil to become compacted, pressure still needs to be applied to the soil. In a lot of cases, soil compaction is ascribed to increases in both farm machinery weight and usage (Dukier, 2004). However, as I have found in my own PhD, even minor amounts of soil compaction can have a major effect on the soil throughout the growing season. In a recent field trial, I applied mild compaction to two potato varieties (Maris Piper (MP) and Inca Bella (IB)) by simply walking across some of my plots. As you can see below, the compaction was minimal, with most plots have a maximum resistance of 0.5 MPa in the topsoil (<20 cm), which is not considered restrictive to root growth.
However, something unexpected was observed when the soil resistance was measured at the end of the growing season in Mid-September. Soil resistance increased greatly in all plots, which was expected and is quite a common phenomenon in agricultural fields (Marinello et al., 2017), (Huntenberg et al., 2021). However, what was notable was that there was a very clear and significant different in soil resistance values between the two varieties, shown in the graph below.
This difference in soil resistance is clearly related to the variety planted within the plot, and this raises a possibility for reducing soil compaction. Instead of having to rely on cultivars well adapted to compacted soil, is it possible that the amount of soil compaction can be mitigated simply by choosing certain varieties that do not have such a great effect on the soil resistance throughout a growing season? In the final year of this PhD, I hope to provide an answer to this question.
BATEY, T., (2009). Soil compaction and soil management – a review. Soil Use and Management. 25, 335-345.
DUIKER, S., (2004). Effects of Soil Compaction. Penn State College of Agriculture.
HUNTENBERG, K., DODD, I., STALHAM, M., (2021). Agronomic and physiological responses of potato subjected to soil compaction and/or drying. Annals of Applied Biology. 178 (2), 328-340.
MARINELLO, F., PEZZUOLO, A., CILLIS, D., CHIUMENTI, A., SATORI, L., (2017). Traffic effects on soil compaction and sugar beet (Beta vulgaris L.) taproot quality parameters. Spanish Journal of Agricultural Research. 15 (1).
STALHAM, M., ALLEN, E., HENRY, F., (2005). Effects of soil compaction on potato growth and its removal by cultivation. British Potato Council. Ref R261.