Soil Compaction: Why is it a Problem for Potatoes?

Written by Patrick Skilleter

Soil is one of the most vital parts of any crop field. It provides crops with nutrients and water, gathered by their roots. A large root system increases the plant’s ability to take up these vital materials, which in turn can improve their yield and yield quality; both vital for food production and profitability of the crop. However, what if the roots are impeded? When soil is compacted, it reduces the number and mean size of pores in the soil. These pores usually store water and allow roots to penetrate the soil with minimal effort. This reduces the soil’s ability to hold water, and restricts root growth. For root crops, it can create deformities in the crop, and reduce its size. Even in crops where the yield is formed above ground, the reduced nutrient and water uptake will reduce the yield. Overall, compaction can be a serious issue.

Compaction is caused by high pressures on the soil, particularly when wet. The most common, artificial example is that of heavy farming machinery driving over soil during or after rainfall or irrigation. Soil compaction forms a core part of my PhD, where I am investigating whether its effects on potato tuber yields can be mitigated. Potato yield in the UK totalled of 5.3 million tons in 2018, making it the second largest crop by total yield in the UK. For many crops, soil compaction can be avoided or reduced for many crops through managing the use of machinery, but in potato fields it tends to be far less avoidable. Potato plants are very drought sensitive, and have small root systems, even in loose soils. As such, potato fields tend to be kept continually moist to avoid problems arising from lack of water. Furthermore, potatoes are grown during the dry months of the year, meaning that when the field lies fallow, it is continually wetted by rainfall over the Autumn and Winter months which prevents the soil from drying. In fact, one research paper (Stalham et al. 2007) surveyed 602 fields across the UK, and found that two thirds of these fields had regions in the upper soil where root growth was reduced by over 90% due to compacted soil. Compacted fields had, on average, a 40% lower total tuber yield than those without compaction. Van Loon et al., (1985) found that compaction reduced marketable yield by 50% in compacted fields compared to those harvested in uncompacted fields. Together, these losses mean that tuber yield from a heavily compacted field can see a 70% loss of marketable yield compared to those grown in an uncompacted field.

Overall, it is quite apparent that, thanks to the potato plant’s small, shallow root system, underground yield and susceptibility to compaction in their fields, compacted soil is both easily formed in potato fields. As such, finding ways of either mitigating the effects or formation of compacted soil are vital in order to secure the future of potato as a key crop in the UK.

References:

STALHAM, M., ALLEN, E., ROSENFELD, A., HERRY, F., (2007). Effects of soil compaction in potato (Solanum tuberosum) crops. Journal of Agricultural Science. 145, 295-312

VAN LOON, C., DE SMET, L., BOONE, F., (1985). The effect of a ploughpan in marine loam soils on potato growth. 2. Potato plant responses. Potato Research. 28 (3), 315-330