Potato nutrition – building from the basics, adding the best of the new

Achieving potato yield and quality requirements, requires a site-specific approach and a continued but more efficient use of fertilisers to achieve sustainable production. Excess nitrogen (N) supply can restrict yield but relationships between N uptake and yield, and between soil supply and N uptake, are not strong. Getting the rate of N application right is therefore an important, but not a simple, management decision. Data also suggest that lower N fertiliser rates could be used without impact on yield or potato tuber quality.

Rapid expansion of the potato canopy maximises capture of solar radiation driving total dry matter (DM) and tuber yields. N uptake supports canopy expansion but has limited effect on radiation use efficiency. As rates of applied N increase to the optimum, canopy persistence increases, with increases in radiation captured and DM yield. Indeterminate varieties partition less DM to tubers and, at high rates, N application can generate very large canopies, to the detriment of tuber production. Understanding the determinacy of varieties is now a key part of fertiliser recommendation systems. Peak rates of N uptake in potatoes occur only c. 30 days after emergence. Restrictions to early N uptake impact yield potential, giving only a very short window of opportunity to correct problems. To further optimise N management, more understanding is needed of: factors controlling the amount and timing of N uptake partitioning of N from the canopy to tubers, the role of continuing soil N uptake and how these are affected by management.

The C footprint associated with the field production of potatoes shows that 50-60% of greenhouse gas emissions is linked to N fertiliser use; with about half linked to nitrous oxide (N20) emissions in the field and half to fertiliser product emissions. Investment in improved technology within fertiliser production are reducing embedded C emissions in mineral N fertilisers. In parallel, commercial developments of waste-based fertilisers are allowing effective nutrient recycling.

The rapid and accurate measurement of the plant ionome, including micronutrients and their interactions, is increasing understanding of plant processes. For example, the role of calcium and boron, and their interactions in determining cell integrity is being revealed. Soil measurement can support a risk-based approach that identifies fields at highest risk of deficiency and enables agronomists to take action based on careful empirical observation even without a full understanding of the underlying mechanisms. Given the small amounts of micronutrients needed by crops, a focus on good soil structure and water supply, achieving effective rooting and getting pH right will largely address many of the issues.

More efficient N use will also help farms to achieve net zero for greenhouse emissions at farm scale, by reducing N2O losses and improving nutrient use efficiency. Lower carbon fertilisers and best practice nutrient management must go hand in hand to address sustainability.