Better nutrition improves potato yield and quality
Making sure your potatoes are fully supplied with all the nutrients they require is the best way to improve crop yield and ensure good tuber quality
Just like any other crop potatoes need balanced nutrition and if any nutrient is limiting or unavailable to the plant when needed then growth will slow down and there will be a reduction in yield or quality.
Getting potatoes off to a good start is vital
Ensuring sufficient phosphate is available right from planting is one of the keys to unlocking the maximum yield potential.
How can phosphate management be improved?
Phosphate has an important role in the development of shoots and in particular roots and this is why a sufficient supply is key in the early stages of the potato crop. The problem here is that phosphate is relatively immobile in the soil and relies on the roots being able to grow towards it rather than the phosphate moving through the soil towards the roots. Couple this with the fact that potatoes are a particularly poor rooted crop and in the early stages often struggle to establish an effective root network capable of accessing water and other nutrients and you can see why this is an issue.
There are several ways to improve the management of phosphate in potatoes by using YaraMila compound fertilisers rather than more traditional 'straight fertilisers'.
Better timing of P and K applications ensures that the phosphate is applied close to when the plant requires it, so limiting the amount that becomes locked up by the soil. This is favoured by applying P and K as compound fertiliser at or just after planting rather than as separate 'straight' applications prior to planting.
Choosing a form of phosphate which not only supplies readily available phosphate but also maintains a supply of phosphate over time also avoids problems of 'lock-up'. Lock up is where the available phosphate becomes bound up in the soil as either iron or aluminium phosphate at low pH or as calcium phosphate at higher pH. YaraMila compound fertilisers contain phosphate in the form of P-Extend which supplies available phosphate over an extended period to avoid potential lock up in the soil.
Better distribution of phosphate through the soil profile also helps plant uptake. The best way to achieve this is to increase the number of fertiliser particles. Traditionally phosphate has been applied as relatively concentrated DAP di-ammonium phosphate, containing 48% P2O5 so there are relatively few concentrated particles.
However, if phosphate is applied as a compound fertiliser such as YaraMila Actyva S instead then every single prill or granule contains all nutrients and at a concentration of 14% P2O5 , there will be approximately three times as many particles.
Most aspects of quality can be improved by calcium
Calcium is a vital nutrient for potatoes and improvements in most aspects of tuber quality can be improved by having a sufficient supply of calcium during tuber growth.
How does calcium improve potato quality?
Calcium is a vital nutrient for potatoes and most aspects of tuber quality can be improved by having a sufficient supply of calcium during growth. It is required in the crop for the maintenance of cell walls, healthy leaf and tuber development.
Calcium deficiency is widely known as internal rust spot - a physiological internal defect in which small brown spots, due to cell death, appear in the tuber. This is directly related to a lack of calcium within the cell walls, meaning that they aren’t strong enough and when cell expansion takes place they collapse and necrosis occurs.
Once calcium is incorporated into cell walls it can’t be redistributed therefore it is important to have a sufficient supply as new cells develop. As mentioned already, calcium is integral to cell walls and give the cells, particularly the skin, strength. Therefore a sufficient supply will help ensure the skin has a good finish as well as helping against physical damage which can occur during harvesting and handling.
However, it’s not only the timing of calcium that needs to be right but also the source of calcium that is being applied. There is a misconception sometimes that liming materials will contain and provide enough calcium for the crop but many liming materials are calcium carbonate based. This means that they aren’t very water-soluble and consequently not freely available to the potato crop through the growing season.
Boron has important roles within plants and in cell wall has a synergistic relationship with calcium and also helps increase calcium uptake. Boron is involved in stabilising cell membranes and cell walls which can lead to less bruising during handling.
As previously mentioned the timing of application to the potato crop is essential to flush the developing tuber with soluble calcium therefore the optimum application period is at tuber initiation. The ideal source of fully soluble calcium is YaraLiva Tropicote which should be applied at tuber initiation.
Ca
Calcium is the key nutrient for tuber quality, it strengthens cell walls which improves many aspects of tuber quality
B
Boron is involved in stabilising cell membranes and cell walls which can lead to less bruising during handling
Can you really afford not to apply calcium?
Trials have consistently shown calcium can improve tuber quality by controlling or reducing a range of disorders. Specifically, calcium has improved tuber skin finish by up to 70%, reduced bruising by around 40% and shown a 75% reduction of internal disorders such as internal rust spot.
Calcium movement within the plant is by mass flow within the xylem system, which means calcium can only ever move upwards. Tuber calcium levels can only be increased by soil uptake not foliar. It is not possible for the plant to move calcium from leaves to tubers.
Solubility is the key to calcium uptake. Surprisingly most of the calcium in soil present in a form that is unavailable to plants. So it is important to apply calcium fertiliser in a form that is readily available to plants. Calcium nitrate is the most soluble form of calcium and the only fully available calcium fertiliser.
Potatoes can only use calcium when it is delivered in a water-soluble form. YaraLiva Tropicote Calcium Nitrate is the only fully soluble calcium fertiliser. Other forms of calcium are much less soluble than calcium nitrate so they are unable to supply sufficient calcium to meet plant needs.
Available calcium
99.5% of the calcium in the soil is unavailable to plants but 100% of calcium in Tropicote can be used by plants.
Fully soluble calcium
100% of calcium nitrate dissolves in water so it is the only fully soluble calcium fertiliser, unlike other calcium fertilisers.
Still not convinced ? - listen to some other farmers
Here are short videos where some other farmers talk about how to achieve quality potatoes
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Foliar nutrition keeps the canopy greener for longer
Keeping the potato canopy greener for longer allows more photosynthesis which means more bulking of the tubers so leading to higher yields.
How does foliar nutrition improve potato marketable yield?
The potato plant is inefficient at utilising soil nutrients, therefore additional nutrition in the foliar form is an ideal way of getting additional nutrition into the leaf.
There is a general consensus amongst plant physiologists that the potato crop yield is limited by the source of photosynthate as opposed to the size of the ‘sink’ i.e. the number of developing tubers following ‘tuber initiation. It helps us consider what is important in ensuring we maximise the plant’s ability to fill the ‘tuber sink’ thus producing as many marketable potatoes as possible, and improving profitability.
In practical terms, we should ensure that:
- Plants produce a full canopy of leaves as quickly as possible (rapid early emergence)
- This full canopy is healthy, maintaining its ‘greenness’, for the duration of the tuber bulking phase
- The plant is able to translocate the sugars (sucrose) produced in the leaf down to the developing tubers as they ‘bulk’
This is achieved partly through the use of fertiliser applied prior to, or ‘placed’ at planting. Once the canopy, or Leaf Area Index (LAI), is at approx. 4, 90% of incoming solar radiation will be intercepted by the green leaves. This is converted by photosynthesis into ‘chemical energy’ known as ATP. This chemical energy is used during photosynthesis to produce sugars that are utilised to maintain the leaf canopy, and most importantly are transported to the developing tubers as they expand or ‘bulk’.
Mg
Magnesium is essential for photosynthesis and starch metabolism
P
Phosphate provides the energy for all plant metabolic functions.
K
Potassium is needed to move carbohydrates from the leaves to tubers
Which foliar nutrients are most important?
The potato plant is inefficient at utilising soil nutrients, therefore additional nutrition in the foliar form is an ideal way of getting additional nutrition into the leaf.
Phosphorus provides the energy for all plant metabolic functions. When applied at potato tuber initiation P increases the number of tubers set and when applied during bulking it increases tuber size. Potatoes are highly responsive to foliar phosphorus, marketable yield and tuber size can be improved by applications during bulking. Recent trials work carried out by ADAS confirms that foliar phosphate, when applied after tuber initiation, has a positive effect on tuber yields by increasing the tuber size.
Magnesium is essential for chlorophyll production as it is present in the centre of each chlorophyll molecule. Low levels of magnesium during the bulking stage will reduce the starch content of tubers. Magnesium is needed during tuber bulking and if supply is restricted tuber size and yield will both be reduced by up to 15% in severe cases.
Potassium is needed for the movement of carbohydrates from the leaves to the tubers and so contributes to increased yield. Too much K, especially in the chloride form, can reduce potato specific gravity.
Phosphorus, magnesium and potassium can conveniently be supplied as foliar nutrients by YaraVita Magphos K. To increase tuber bulking this should be applied during bulking at a rate of 5 l/ha with up to 2 applications.
Nitrogen is vital during tuber bulking to maintain the greenness of the leaf canopy and ensure optimal photosynthesis.
The bulk of nitrogen applications should have been applied by tuber initiation but if necessary nitrogen can be applied during bulking through foliar applications of YaraVita Croplift Pro.
More Tubers
Phosphate applied at tuber initiation increases tuber numbers
Bigger Tubers
Phosphate applied during tuber bulking increases tuber size
Maximising potato yields with a boost from foliar phosphate
The latest advice on maximising potato crops by using foliar nutrition from Phil Burrell, YaraVita Technical Manager.
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Recommended potato fertilisers
The following fertilisers are recommended for potatoes
Where can I buy Yara fertilisers ?
Yara supply our solid and liquid fertilisers and micronutrients through a network of local suppliers Use our interactive map to locate your nearest suppliers.
Related publications
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Potato webinar - can the right nutrition help suppress tuber disorders?
With potato quality being so important it's vital to give the crop the best nutrition to help suppress tuber disorders. Join our webinar to help answer your questions. Eva Ross of Yara is joined by Mark Tucker and Tom Decamp to discuss how effective nutrition helps control disease in potatoes.
Listen to the latest potato podcasts
If you are short of time why not check out our bite-size podcasts for the latest thoughts on potato nutrition.
Read more about improving nutrient efficiency
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