Potato Review Group

Contents

Background

Influence of cultivar

Differences between nutrients

Further information

Nutrient use efficiency notes

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Background

  1. Nutrient use efficiency can be considered in three ways:
    • Uptake efficiency: how efficiently the plant takes up nutrient from the soil;
    • Physiological use efficiency: how efficiently the plant uses nutrient in terms of total biomass production;
    • Agronomic use efficiency: how efficiently the plant uses nutrient in terms of agronomically valuable yield.
  2. Uptake can be influenced by:
    • The plant itself, in terms of how quickly nutrient uptake occurs (faster uptake initiates faster replenishment of soil solution concentration from the solid phase, depending on the soil);
    • Root exploration volume, which depends on the plant’s inherent characteristics as well as speed/extent of establishment, plant health, soil moisture and soil structure;
    • Spatial distribution of nutrient in the soil in relation to location of roots;
    • Soil chemistry affecting availability of nutrient, both in terms of absolute concentration at any one time and buffer capacity to replenish soil solution concentration.
  3. Compared to other crops, potato has a relatively low root:shoot ratio but rapid influx of soil solution. However uptake efficiency varies from nutrient to nutrient, depending on its specific uptake mechanism.
  4. Weather and growing conditions can be extremely influential on nutrient use efficiency, due to influences on biological activity in the soil, establishment and health of the plant, and chemical availability of the nutrient. Therefore use efficiency is likely to be very variable between years, as well as with location and cultivar.

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Influence of cultivar

  1. An Indian field trial showed that the magnitude of influence of potato cultivar (how much yield varies due to cultivar) can be similar to (although slightly smaller than) the magnitude of influence of nutrient supplied; i.e. that changing cultivar may have almost as much effect as supplying additional nutrient.
    • For nitrogen, the influence of nutrient was slightly larger than influence of cultivar.
    • For potassium and phosphorus, the influence of cultivar was much greater than the influence of nutrient supplied.
    • Remember that this was only one trial (although over three years) and was based in India where conditions are markedly different to the UK, so should be taken as an example of what may occur, rather than a prescription of what will occur.
  2. Canadian and American field trials also show marked influence of cultivar on nitrogen use efficiency, although the size of the effect changed from year to year. Greatest difference was double efficiency from the most efficient compared to least efficient cultivar.
  3. Longer/later maturing potato cultivars may well have better nutrient use efficiency.
  4. Financial return differences between cultivars are more likely to be seen at higher fertiliser rates.
  5. A glasshouse study showed that potato cultivars which used K most efficiently, made greater use of the non-exchangeable pool [link: see ‘potassium chemistry’] compared to the less efficient cultivars. Most cultivars took up significantly more K than was present in the initially present exchangeable pool, however it is important to remember that if the soil has only a small non-exchangeable pool (e.g. very sandy soils), the difference between cultivars will be less noticeable.

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Differences between nutrients

The following observations are based on one set of field experiments (six cultivars over three years):

  • The influence of cultivar on uptake efficiency is much greater for K than for N or P. Also uptake efficiency tends to be greater for K than for N or P.
  • The was a reasonable correlation between uptake efficiency and agronomic use efficiency for N and K, but not for P; this suggests other factors influence how the plant uses P compared to N and K.
  • Within the ranges reported, for every unit increase in physiological use efficiency, there was significantly less increase in agronomic use efficiency for N and P, compared to K. In other words, a greater proportion of the K taken up by the potato plant ended up in the tuber, compared to P and N. However this does not mean that K is more important than N or P; all are required in the correct amounts to create a healthy, productive plant.

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Further information

Notes on nutrient use efficiency

Nutrient use efficiency 2016 (Efficiency of uptake is influenced by root growth; efficiency can differ between cultivars)

Tuber nutrients 1997 (The potential for foliar applied nutrients to be transported to tubers)

 

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