N
Can be rescued through the leaves
Plants take up nitrogen through the leaves quite efficiently. When nitrogen is short, 10–20 kg of nitrogen can be applied through the leaves.
Science
For a plant, what matters is not only how much, but also when
In wheat nutrition, it is not enough to know whether the soil holds the nutrients the crop needs. It also matters when the plant gets them. Each nutrient has its own job, and a shortage at different growth stages can hit different yield components: leaf area, the root system, the number of productive tillers, ear formation or grain set.
How our study was done
Each wheat plant grew in its own container with a solution that lacked one nutrient. This lets us see exactly what happens to the plant when that particular nutrient is missing – and how long it can wait.
A deficiency is not always visible right away
Plant physiology can change before clear symptoms appear, and similar symptoms can be caused by different nutrients or other stresses. That is why a visual check helps you suspect a problem, but a reliable diagnosis often needs plant and soil analyses (de Bang et al., 2021; Lilay et al., 2024).
In our published, controlled hydroponic study, wheat was grown with individual macronutrients missing for different lengths of time. Nitrogen, phosphorus and calcium deficiency suppressed biomass accumulation the most. The effect of a shorter deficiency depended on the nutrient, while a long-term deficiency left a marked effect on some traits that did not recover later. This shows why fertiliser decisions depend not only on the rate, but also on how long the deficiency lasts and on the growth stage (Petrauskas et al., 2026).
This does not mean that every day of deficiency cuts yield by the same amount under all conditions. The effect depends on the nutrient, how severe the deficiency is, the growth stage, the variety, the soil and the weather. But a prolonged deficiency increases the risk that part of the lost growth or yield potential can no longer be recovered.
Why do growth stages BBCH 30–37 deserve attention?
In our study, spring wheat was grown hydroponically. The deficiency of a single macronutrient started at BBCH 23 and lasted 21, 28 or 35 days; these periods corresponded roughly to stages BBCH 30, 32 and 37. The effect depended on the nutrient and the duration: for example, a 28-day potassium deficiency reduced the number of productive tillers, while biomass losses grew as nitrogen, phosphorus or calcium deficiency went on.
Important: these day counts should not be transferred directly to soil. In soil, a deficiency develops 3–5 times faster. In soil, plants often also face water shortage, while in hydroponics, where water is never short, the plant can stay longer in a protective state – it is more patient.
BBCH 23
Tillering. Start of deficiency (day 0)
BBCH 30
After 21 days
BBCH 31
First node – a reference point
BBCH 32
After 28 days
BBCH 37
After 35 days
BBCH 30–37 – the warning window in the controlled study
BBCH 31 – the first-node stage. This is an important reference point, because the plant moves into stem elongation, when the future yield structure is being formed. Our data allow us to treat BBCH 30–37 as a practically meaningful warning window, but not as a universal threshold for every field and every nutrient. The study was done in a controlled environment, so under field conditions a deficiency may develop differently.
What does this mean for your fertiliser plan?
If you suspect a nutrient deficiency, it is worth checking and assessing it as early as possible instead of waiting until the symptoms become obvious. BBCH 31 can be a reference point by which it is especially important to check whether the plant is getting the nutrients it needs. A nutrient applied later may improve the plant's further condition, but it will not necessarily bring back lost tillers, damaged growing points or grain primordia that never formed.
From field experience
In the field, time runs several times faster
In hydroponics the plant always has water, so nutrient starvation develops slowly. In soil, according to our agronomists' observations, a similar shortage develops within 5–10 days, and during drought within just 1–3 days. Three weeks of starvation in hydroponics may equal a week in the field, and only a few days in a dry spell.
Hydroponics (controlled study)~28 days
Soil (field experience)5–10 days
Drought (field experience)1–3 days
That is why in the field a few days' delay can already be too late: the plant switches on other processes and may then need different nutrients. A deficiency has to be measured, not waited for until you can see it.
Why can't the eye see a deficiency?
The human eye sees colour with only three types of cones, most sensitive to blue (~440 nm), green (~545 nm) and yellow-red (~565 nm) light, and it boils all light down to three signals (Webvision). It cannot see near-infrared light at all. A plant, meanwhile, absorbs and reflects a great many different wavelengths, and deficiency-related changes show up in its reflectance spectrum earlier than visible symptoms (Petrauskas et al., 2026).
That is why so-called “hidden hunger” can cut yield by 10–35% without any visible symptoms, and growth differences smaller than 20% are hard to spot by eye (GRDC, 2010). You look at the field – it looks great, you expect a good harvest, but in reality it could be bigger.
The field durations are based on observations by agronomists of UAB „Žemdirbių konsultacijos“; they are not a result of the hydroponic study.
A practitioner's conclusions
What to do when SmartAgrometer shows a deficiency
Not every deficiency is worth rescuing in the same way. Sometimes the right decision is to stop investing in a field and give those fertilisers to another, better field. Below are a practising agronomist's conclusions from our research and work in the field.
P
Rescue only early
Only a few kilograms of phosphorus can be applied effectively through the leaves. Phosphorus demand peaks before the end of tillering and well before flowering. Such a sudden, large demand can only be met when the soil has phosphorus at class C or higher.
At early stages it is still worth trying to rescue it through the leaves. If the deficiency appears at the end of stem elongation or later, it no longer pays to invest in nitrogen fertiliser: the plant will wait for phosphorus, start shedding side tillers, the stand will thin out, and the sun will scorch the sparse crop.
A signal to ask: is this field really still worth investing in?
Ca
A signal to stop investing
Calcium deficiency is the worst case. If it shows up, the stand will gradually thin out, and the longer it lasts, the faster it thins.
If a calcium (or also phosphorus or nitrogen) deficiency shows up late, at flowering, not all the grain sites will be used, and the grains will not store enough starch and protein – they will be shrivelled and light.
The earlier calcium deficiency shows up, the stronger the case for giving those fertilisers, at a higher rate, to another good field.
The plant adapts – but calcium is a special case
Our earlier and latest research shows that wheat adapts quite well to a shortage of most macro- and micronutrients. Calcium is a special case. A deficiency is not destructive for the plant – it is adaptive and does not cause chaos.
The plant has a kind of “postal” system that quickly reports upcoming changes. Depending on the role of the missing nutrient, a protective mechanism switches on step by step.
0
Signal
The “postal” system reports the deficiency even before visible symptoms.
1
Internal reserves and waiting
The plant uses its internal reserves – for example, it takes nitrogen from chlorophyll. Some processes stop. When potassium is short, P, Ca, Mg, B, Cu, Fe, Mn, Mo and Zn start to build up in the roots: potassium carries all these nutrients, so the “truck” is missing, and the plant waits and stockpiles.
2
Strong physiological changes
If the deficiency drags on, the plant moves into the second protective stage.
Ca
A special case – calcium
Calcium holds cell walls and membranes together, keeps growing points going and helps cells “talk” to each other. Plants know how to take up calcium and regulate its supply. But if calcium is missing for long, growth is damaged so much that calcium supplied later can no longer fix everything.
In hydroponics we could study calcium deficiency on its own. In soil this is impossible, because there is no soil without calcium – which is why there are few publications on calcium. In our study, a longer calcium deficiency strongly suppressed growth, and after full nutrition was restored the plants recovered poorly: some growth and yield traits never recovered. Perhaps because during evolution plants hardly ever faced calcium deficiency and never learned to adapt to it.
The conclusion is simple: calcium deficiency must be spotted and dealt with in time. This is a result of a controlled study, so in different varieties and fields it may show up differently (Petrauskas et al., 2026).
Calcium is not just a liming material. Calcium is mobile in soil, so a calcium deficiency in the plant is possible even in a non-acidic field.
Conclusions of Ernestas Petrauskas, practising agronomist and VMU PhD candidate, from the research and field work of UAB „Žemdirbių konsultacijos“. Scientific basis: Petrauskas et al., 2026, Plants 15(7), 1094.
Trial photos
12 deficiencies. Could you tell them apart by eye?
The same winter wheat trial: each plant was missing one nutrient. Some differences are obvious, but most are almost invisible to the eye – especially in the field, where all plants look alike. SmartAgrometer shows the deficiency in numbers.
Hydroponic trial in the greenhouse of the VMU Agriculture Academy, December 2025
Everything about the nutrients ↓
12 nutrients
What each nutrient does for wheat, what its deficiency can look like, when it is most dangerous and whether it can be corrected later.
Important: symptoms are only indicative. They can be changed by variety, growing conditions, interactions between nutrients and other stresses. The “most dangerous time” in the cards summarises the nutrient's role and wheat growth stages; science has not set an equally precise field threshold for deficiency duration for every micronutrient.
Foliar feeding: how much actually gets into the plant
Macronutrients
N, P, K, Ca, Mg, S – needed in tens to hundreds of kg/ha
All of them can be applied through the leaves, but the amounts that effectively get into the plant differ and are relatively small. So foliar macronutrients can top up or rescue a deficiency, but the basis has to go into the soil.
Micronutrients
Fe, Mn, Cu, Zn, Mo, B – needed in grams to hundreds of grams/ha
Their requirement can be met almost entirely through the leaves, and problems with them can usually be solved completely. It just has to be done properly and at the right time.
Some nutrients appear in the leaf within a few hours, but getting into the leaf and moving on to other organs are two different things. There is no single efficiency percentage that fits all: it all depends on the nutrient, the fertiliser form, the growth stage and the weather. That is exactly why it matters to know precisely what is missing.
The scientific literature stresses that nutrients needed in large amounts are best applied to the soil, while foliar feeding is an economical and effective way to supplement it – but success requires a correct diagnosis of the deficiency (Fageria et al., 2009). That is exactly what SmartAgrometer is for. In each card you will find a study on foliar feeding of that nutrient.
What does a deficiency cost on your farm?
Enter your own figures. In each card, the yield difference found in the studies will be converted into euros (yield × percentage × price). That is how much you lose when a nutrient is missing and you cannot see it – and how much you can earn when you measure and apply what is missing. For comparison: the first year of SmartAgrometer costs €2,200.
The figures are results of specific trials, not a guarantee for every field: where there is enough of a nutrient, there is no extra yield. In a five-year spring wheat trial in Lithuania, foliar micronutrients and nitrogen did not increase yield every year (Žemdirbystė-Agriculture). So it pays to apply only what is actually missing – and for that you need to measure.
N
Nitrogen
Macronutrient · studied in our trial
What it does
Nitrogen is the basis of proteins, chlorophyll and enzymes. Leaf area, the number of tillers and grains, and protein content all depend on it. When nitrogen is short, photosynthesis drops and the plant builds up less biomass.
What a deficiency can look like
The plant grows more slowly, leaves are pale green or yellowing. Older leaves yellow first – the plant “moves” nitrogen to younger ones. Fewer tillers and ears, smaller grains.
When it is most dangerous
A deficiency during tillering reduces the number of productive tillers; during stem elongation and ear formation, the number of grains per ear. A late deficiency reduces grain weight and protein, but cannot bring back tillers and grains that never formed.
What a deficiency can cost
39–50 %
Trials closest to Lithuania
Lithuanian and Latvian wheat trials without nitrogen
Lithuanian and Latvian wheat trials without nitrogen
36 %
Average of 8 studies · used in the calculator
up to 80%
Strong, confirmed deficiency
unfertilised wheat in Germany: 2 t/ha instead of 11 t/ha
unfertilised wheat in Germany: 2 t/ha instead of 11 t/ha
Nitrogen drives yield more than anything else. In Lithuanian and Latvian trials without nitrogen, wheat yield was 39–50% lower, and in southern Germany unfertilised wheat gave only 2.0–2.3 t/ha instead of 10.7–11.4 t/ha. In a Lithuanian barley model, nitrogen stress alone cost up to 54% of yield. After legumes or perennial grasses the difference can be as small as 7–9%.
€ On your farm: about 504 €/ha · about 504,000 € for 1,000 ha
With severe deficiency – up to 1,120 €/ha
Leaf analysis (laboratory reference)
In nitrogen-deficient fields, the flag leaf contained 1.4–2.0% N in dry matter.
Can it be corrected later?
Added nitrogen helps while the plant is still growing actively, but it will not bring back productive tillers already lost or florets that have died. In our study, early nitrogen deficiency hit growth hard, and later supply did not always remove its effects.
Foliar feeding
Wheat takes up nitrogen not only through its roots but also through its leaves. Urea passes through the leaf cuticle into the leaf, where it is broken down and turned into amino acids. Changes in the leaf can be seen after just 3 hours, nitrogen in the leaf peaks after about 12 hours, and within a few hours it moves into the stem and ear. But only 4.5–26.7% of the sprayed nitrogen ends up in the grain. In practice, 10–20 kg N/ha can be applied through the leaves. A meta-analysis of 51 field trials: late foliar nitrogen raises yield by 4% and protein by 6% on average. Solutions that are too strong can reduce yield. So foliar nitrogen can top up soil fertilisation, but not replace it.
Source: Field practice; Yao et al., 2025; Gong et al., 2026; Rawluk et al., 2000; Fernández et al., 2021; Wu et al., 2025; Zhu et al., 2017
Source: Arlauskienė et al., 2020; Staugaitis et al., 2021; Mažvila et al., 2007; Litke et al., 2017, 2019; Hlisnikovský et al., 2023, 2024; Leonte et al., 2026; Asfaw et al., 2025; Wassie et al., 2015; Petrauskas et al., 2026; Žydelis et al., 2025; Mittermayer et al., 2024; Antošovský et al., 2024; Klikocka and Cybulska, 2020
P
Phosphorus
Macronutrient · studied in our trial
What it does
Phosphorus is the plant's energy: it is involved in energy metabolism, root growth, membranes and genetic material. It matters for rooting, tillering and ear development.
What a deficiency can look like
Plants grow more slowly, roots and shoots are smaller, tillering is weaker. Leaves may darken or turn reddish-purple, but this can also be cold or the variety – phosphorus deficiency is hard to judge by eye alone.
When it is most dangerous
An early deficiency limits roots and tillers; during stem elongation and ear formation, the number of ear-bearing tillers and grains.
What a deficiency can cost
7–8 %
Trials closest to Lithuania
Germany's Dikopshof trial, 1906–2018
Germany's Dikopshof trial, 1906–2018
12 %
Average of 9 studies · used in the calculator
up to 23%
Strong, confirmed deficiency
phosphorus-poor or sandy soils
phosphorus-poor or sandy soils
The effect of phosphorus depends mostly on soil reserves. In Germany's century-old Dikopshof trial, wheat yield without phosphorus was 7–8% lower; on poor Finnish soils, up to 19%. Where the soil is rich in phosphorus, there is almost no difference – so there is no single figure for all fields.
€ On your farm: about 168 €/ha · about 168,000 € for 1,000 ha
With severe deficiency – up to 322 €/ha
Leaf analysis (laboratory reference)
In recently matured leaves of spring wheat, the P threshold is 0.27–0.36% in dry matter.
Can it be corrected later?
Phosphorus moves little in soil, so later on the plant struggles to reach the fertiliser – an early shortage is harder to correct. In our study, when phosphorus supply was restored, lost growth and yield components did not fully recover.
Foliar feeding
Only a few kilograms of phosphorus can be applied effectively through the leaves. How much gets in depends on the solution, additives and spraying time: with a surfactant, leaves absorb about 80% of the phosphorus, but only about 40% moves on into the plant, and spraying at tillering can scorch the leaves. In the field, the effect also depended on how strongly the soil holds phosphorus. In field trials, 2 kg P/ha through the leaves did not raise yield, while phosphorus in the soil at sowing raised it by 38–45%. Conclusion: the basis is phosphorus in the soil; through the leaves you can only try to rescue.
Source: Field practice; Peirce et al., 2019; Malik et al., 2024; McBeath et al., 2020
Source: Janušauskaitė and Lazauskas, 2007; Saarela et al., 2006; Valkama et al., 2011; von Tucher et al., 2018; Márton, 2008; Leonte et al., 2026; Sun et al., 2024; Asfaw et al., 2025; Jones et al., 2003; Shi et al., 2019; Petrauskas et al., 2026; Seidel et al., 2021
K
Potassium
Macronutrient · studied in our trial
What it does
Potassium controls water balance, stomata, enzymes and sugar transport. It keeps up cell “pressure”, helps the plant withstand drought and strengthens the stem.
What a deficiency can look like
The edges of older leaves turn yellow or brown, and the damage later spreads inwards. Stems weaken, the plant copes worse with drought, and grain filling is shortened. Drought or damaged roots can look similar.
When it is most dangerous
From rapid growth to grain filling, especially when water is short. Potassium deficiency also increases the risk of lodging.
What a deficiency can cost
11–15 %
Trials closest to Lithuania
Lithuanian trials (Skėmiai, barley)
Lithuanian trials (Skėmiai, barley)
13 %
Average of 7 studies · used in the calculator
up to 24%
Strong, confirmed deficiency
potassium-deficient soils, global meta-analysis
potassium-deficient soils, global meta-analysis
In Lithuanian trials without potassium, yield was 11–15% lower. A 2026 global meta-analysis shows that potassium raises wheat yield by 24% on average and barley by 16.5%, but these are mostly potassium-deficient soils. Where there is enough potassium, there may be no extra yield.
€ On your farm: about 182 €/ha · about 182,000 € for 1,000 ha
With severe deficiency – up to 336 €/ha
Leaf analysis (laboratory reference)
In potassium-deficient fields, the flag leaf contained 0.8–1.4% K in dry matter.
Can it be corrected later?
An early or moderate potassium shortage can be reduced while the plant is still growing. In our study, plants recovered better after a shorter deficiency than after a long one.
Foliar feeding
Foliar potassium improves leaf gas exchange and photosynthesis. In a study on wheat and maize, it also made the plant take up more potassium through the roots – the leaf spray seems to “kick-start” the roots. In field trials, foliar potassium (potassium chloride) raised the yield of one variety but not another. One spray gets only a few kilograms of potassium into the plant, so the basis is in the soil.
Source: Ishfaq et al., 2023; Gu et al., 2021
Source: Arbačauskas et al., 2023; Mikšytė, 2009; Andrzejewska et al., 2025; Sun et al., 2024; He et al., 2022; Liang and Schlesinger, 2026; Engel, MSU Fertilizer Facts 18; Asfaw et al., 2025; Wassie et al., 2015; Petrauskas et al., 2026
Ca
Calcium
Macronutrient · studied in our trial
What it does
Calcium holds cell walls and membranes together and is needed for cell division and growth signals. It hardly moves from old tissues to new ones, so it is especially important for growing leaves and roots.
What a deficiency can look like
Young leaves and growing points suffer first: leaf tips or edges become deformed, tissues may die, root growth slows. In wheat this is hard to tell apart from other disorders.
When it is most dangerous
Throughout active growth, especially while new leaves, roots and the ear are forming. Because calcium moves little, a deficiency in young tissue is hard to make up later.
What a deficiency can cost
none
Trials closest to Lithuania
no field trials with calcium alone were found in Lithuania
no field trials with calcium alone were found in Lithuania
14 %
Average of 3 studies – indicative · used in the calculator
11–20 %
Strong, confirmed deficiency
calcium and gypsum trials elsewhere – a reference only
calcium and gypsum trials elsewhere – a reference only
There are almost no field trials on calcium deficiency alone: there is no soil without calcium, and in liming trials pH and aluminium toxicity change at the same time. Calcium and gypsum trials elsewhere show an 11–20% difference, but this is only a reference. In our study, calcium deficiency was one of the hardest to correct – if a measurement shows it, it is a serious signal.
€ On your farm: about 196 €/ha · about 196,000 € for 1,000 ha
With severe deficiency – up to 280 €/ha
Leaf analysis (laboratory reference)
In one field study, 0.3–0.5% Ca in the flag leaf was considered sufficient.
Can it be corrected later?
In our study, calcium shortage was one of the hardest to recover from: growth processes damaged during the deficiency did not always recover.
Foliar feeding
Calcium gets into the sprayed leaf, but moves on from it with difficulty – it hardly travels through the plant's “pipelines” (the phloem). So calcium landing on an old leaf will not necessarily reach newly growing leaves and the ear. In a field study, calcium with boron, sprayed twice, increased the number of grains per ear by 24% and yield by 30%.
Source: Peirce et al., 2019; Zoz et al., 2016
Source: Abbas et al., 2023; Michalovicz et al., 2014; Roy Chowdhury et al., 2019; de Bang et al., 2021; Wassie et al., 2015; Petrauskas et al., 2026
Mg
Magnesium
Macronutrient · studied in our trial
What it does
Magnesium is the heart of chlorophyll: without it there is no photosynthesis. It is needed for enzymes and for moving sugars into the grain.
What a deficiency can look like
Older leaves change first – chlorosis appears between the veins, and as the deficiency worsens the tissues dry out. Photosynthesis weakens, leaving less “building material” for the grain.
When it is most dangerous
During the season it limits leaf function, and at flag leaf and grain filling it limits photosynthesis just when the plant is filling the grain.
What a deficiency can cost
4–9 %
Trials closest to Lithuania
Polish winter wheat: +0.5–0.9 t/ha
Polish winter wheat: +0.5–0.9 t/ha
9 %
Average of 5 studies · used in the calculator
up to 17%
Strong, confirmed deficiency
magnesium-deficient soils
magnesium-deficient soils
A meta-analysis of 99 field studies and 570 comparisons shows an average 8.5% higher yield after magnesium fertilisation. In Polish winter wheat trials, magnesium raised yield by 0.5–0.9 t/ha. How much you lose depends on soil Mg, pH and the K and Ca ratio.
€ On your farm: about 126 €/ha · about 126,000 € for 1,000 ha
With severe deficiency – up to 238 €/ha
Leaf analysis (laboratory reference)
In one field study, 0.25–0.83% Mg in the leaves was rated as sufficient – a wide range, so the growth stage and the plant part sampled matter.
Can it be corrected later?
In our study, plants recovered better after a short magnesium deficiency than after a long one, and the effects of a long shortage remained.
Foliar feeding
Magnesium is taken up through the leaf, but how much depends on the form of the magnesium salt and the leaf surface. In a wheat study, magnesium spraying significantly reduced yield losses from magnesium deficiency – the grains grew larger.
Source: Barlas et al., 2023; Ceylan et al., 2016
Source: Grzebisz and Potarzycki, 2022; Andrzejewska et al., 2025; Wang et al., 2020; Wang et al., 2025; Niaz et al., 2020; de Bang et al., 2021; Wassie et al., 2015; Petrauskas et al., 2026
S
Sulphur
Macronutrient · studied in our trial
What it does
Sulphur is needed for amino acids, proteins, enzymes and nitrogen metabolism. Nitrogen and sulphur work as a pair: when sulphur is short, the plant uses nitrogen less well, even if there is nitrogen in the soil.
What a deficiency can look like
The plant turns pale and grows more slowly. Unlike nitrogen deficiency, sulphur deficiency more often shows first in younger leaves. The symptoms resemble nitrogen shortage, so it is worth testing both together.
When it is most dangerous
In early spring it holds back regrowth, later protein synthesis, grain filling and quality. A lot of nitrogen can bring out a sulphur deficiency.
What a deficiency can cost
19–23 %
Trials closest to Lithuania
Estonian winter wheat trials
Estonian winter wheat trials
10 %
Average of 6 studies · used in the calculator
up to 33%
Strong, confirmed deficiency
Estonian calcareous soils, unfavourable years
Estonian calcareous soils, unfavourable years
In Estonian winter wheat trials, sulphur raised yield by 22–23% on average, and in some years on calcareous soils the deficiency cost a third of the yield. A global meta-analysis of 55 studies shows a more modest average – about 4%. Where there is enough sulphur, there is no extra yield.
€ On your farm: about 140 €/ha · about 140,000 € for 1,000 ha
With severe deficiency – up to 462 €/ha
Leaf analysis (laboratory reference)
A commonly used N:S ratio in plant tissue is about 17. But on its own it can be misleading, so N and S need to be looked at separately too.
Can it be corrected later?
In our study, plants recovered more after a shorter sulphur deficiency than after a long one. But later supply does not necessarily restore a number of tillers or grains that has already dropped.
Foliar feeding
How much sulphur gets in through the leaves and where it ends up depends on the fertiliser composition and spraying conditions. Foliar sulphur can also improve grain protein quality. In Estonian field trials, foliar sulphur (3+3 kg S/ha, at tillering and stem elongation) raised winter wheat yield by 30–55% on calcareous soil, while on slightly acidic soil there was almost no effect.
Source: Zang et al., 2024; Järvan, 2012
Source: Järvan et al., 2008; Järvan, 2012; Staugaitienė et al., 2013; Tabak et al., 2020; Kulig et al., 2025; Roa et al., 2024; Gülüt et al., 2021; Zhao et al., 2018; Asfaw et al., 2025; Petrauskas et al., 2026
Fe
Iron
Micronutrient
What it does
Iron is involved in electron transport, chlorophyll formation and photosynthesis. Little is needed, but a shortage seriously disrupts leaf function.
What a deficiency can look like
Interveinal chlorosis of young leaves: veins stay greener, the tissue between them is pale; with severe deficiency the leaves turn almost white. More common on alkaline or calcareous soils.
When it is most dangerous
When the deficiency starts while young leaves are growing, the photosynthetic area shrinks; if it lasts into stem elongation and ear formation, further growth is disrupted.
What a deficiency can cost
≈4 %
Trials closest to Lithuania
Polish spring barley trial
Polish spring barley trial
14 %
Average of 10 studies – indicative · used in the calculator
up to 20%
Strong, confirmed deficiency
iron chlorosis on calcareous, high-pH soils
iron chlorosis on calcareous, high-pH soils
Iron deficiency is most dangerous on calcareous, high-pH soils – there chlorosis can cost up to 20% of yield. A meta-analysis of 107 publications shows an average 12% gain, but in Kansas trials iron helped in only 4 fields out of 7. In a Polish barley trial the gain was about 4%. Severe iron deficiency is rare in Lithuanian soils.
€ On your farm: about 196 €/ha · about 196,000 € for 1,000 ha
With severe deficiency – up to 280 €/ha
Leaf analysis (laboratory reference)
In one field study, 71–97 mg/kg Fe in the leaves was considered sufficient.
Can it be corrected later?
Foliar iron improves the condition of the sprayed tissue, but soil reaction matters in the long run. A late spray will not bring back lost leaf area or yield components that never formed.
Foliar feeding
Iron gets into the leaf with difficulty, and into the grain with even more difficulty. In three-year field trials, iron sulphate raised grain iron content only slightly, because iron enters the leaf to a limited extent and moves little into the grain. In another study, iron spraying increased yield and grain iron content. Iron in the leaf does not mean it will reach the grain, so it is worth spraying while new leaves are growing actively.
Source: Singh et al., 2024; Razmjoo and Ghafari, 2015
Source: Zhou et al., 2024; Taskin and Gunes, 2022; Bhatti et al., 2024; Stewart et al., 2021; Zulfiqar et al., 2020; Khatun et al., 2024; Hao et al., 2021; Singh et al., 2026; Ali et al., 2021; Niyigaba et al., 2019; Lilay et al., 2024; Liszewski and Błażewicz, 2018; Godsey et al., 2003
Mn
Manganese
Micronutrient
What it does
Manganese is needed for photosynthesis, enzymes and protection against oxidative stress. It also matters for pollen viability and grain formation.
What a deficiency can look like
Pale spots or stripes appear between the leaf veins, later dead patches. More common where manganese is poorly available in the soil.
When it is most dangerous
It limits early growth, later photosynthesis and pollen viability. In a field trial, spraying about 26 days after sowing was more effective than at about 32 days.
What a deficiency can cost
6–10 %
Trials closest to Lithuania
Polish spring barley trials
Polish spring barley trials
13 %
Average of 10 studies · used in the calculator
up to 36%
Strong, confirmed deficiency
Swedish winter barley; up to 33% more plants survived the winter
Swedish winter barley; up to 33% more plants survived the winter
In Swedish winter barley trials, manganese raised yield by up to 36%, and up to 33% more plants survived the winter. In Polish barley trials the gain reached 6–10%, but in another Polish wheat trial there was no clear effect. Varieties differ a lot: in a manganese-deficient field, the yield of 24 wheat varieties was 6–25% lower.
€ On your farm: about 182 €/ha · about 182,000 € for 1,000 ha
With severe deficiency – up to 504 €/ha
Leaf analysis (laboratory reference)
In the youngest fully expanded leaf, the critical level is about 11 mg/kg Mn.
Can it be corrected later?
Foliar manganese improves supply, especially if sprayed before the florets suffer. If pollen viability has already dropped, yield may not recover.
Foliar feeding
Manganese is taken up well through the leaves and moves from the sprayed leaf into growing tissues and the grain; the effect depends on the fertiliser form. In a two-year field study, spraying with manganese sulphate (0.5%) raised wheat yield by about 8–20% compared with fertilisation without manganese.
Source: Zulfiqar et al., 2023; Dhaliwal et al., 2023
Source: Tobiasz-Salach et al., 2018; Stadnik et al., 2024; Sobolewska et al., 2020; Zulfiqar et al., 2021; Yang et al., 2025; Jaidka et al., 2026; Bansal and Nayyar, 1998; Shahrajabian et al., 2020; Dhaliwal et al., 2023; Reuter, 1972; Lilay et al., 2024; Stoltz and Wallenhammar, 2014; Jhanji et al., 2013; Stępień and Wojtkowiak, 2019
Cu
Copper
Micronutrient
What it does
Copper is involved in enzyme activity, photosynthesis, respiration, the formation of lignin (stem strength) and reproduction. A shortage harms pollen and ear fertility.
What a deficiency can look like
Young leaves twist, tips dry out, stems weaken. The ear has trouble emerging from the sheath, and grains may not form or may be empty. Symptoms appear late.
When it is most dangerous
Copper matters while the ear and pollen are forming. Pollen viability, once lost, cannot be restored later.
What a deficiency can cost
5–9 %
Trials closest to Lithuania
Polish winter wheat, 3 varieties out of 5
Polish winter wheat, 3 varieties out of 5
7 %
Average of 10 studies · used in the calculator
up to 22%
Strong, confirmed deficiency
Canadian copper-deficient soils
Canadian copper-deficient soils
In Polish winter wheat trials, copper raised yield by 5–9% in three of five varieties. A summary of 115 Canadian field trials is clear: when soil copper was below 0.4 mg/kg, yield responded in 87% of trials; at 0.4–0.8 mg/kg in 16%; and above 0.8 mg/kg in none. Copper shortage disrupts pollen, so fewer grains set in the ear, even though the plant looks lush.
€ On your farm: about 98 €/ha · about 98,000 € for 1,000 ha
With severe deficiency – up to 308 €/ha
Leaf analysis (laboratory reference)
In the whole above-ground plant at tillering, less than about 2 mg/kg Cu indicates a possible shortage.
Can it be corrected later?
An early copper shortage can be corrected, but timing matters: if pollen or the ear has been damaged, lost grains will not come back. Varieties respond differently.
Foliar feeding
Foliar copper corrects copper deficiency well – in the field it was sprayed at early stem elongation. But be careful with concentration: a solution stronger than 0.03% can already damage leaves. In four-year trials in Western Australia, the highest yield was reached with 0.8–1.8 kg/ha of copper product; chelated copper was the most effective.
Source: Fouad et al., 2020; Brennan, 1990
Source: Korzeniowska and Stanisławska-Glubiak, 2009, 2011; Tobiasz-Salach et al., 2018; Liszewski and Błażewicz, 2018; Rahman and Schoenau, 2022; WARC, 2022; Franzen et al., 2008; Karamanos et al., 2004; Hoess and Heard, 2002; Alberta Agriculture, 1999; Lilay et al., 2024; Karamanos, Goh and Harapiak, 2003
Zn
Zinc
Micronutrient
What it does
Zinc is needed for many enzymes, protein synthesis, growth regulation and normal development of roots and shoots.
What a deficiency can look like
The plant is shorter, tillers less, leaves are shorter or narrower, sometimes with pale patches. More common on alkaline, calcareous soils and where there is a lot of phosphorus.
When it is most dangerous
An early deficiency limits roots, leaves and tillers; if it lasts into stem elongation and ear formation, there are fewer productive tillers and grains.
What a deficiency can cost
≈10 %
Trials closest to Lithuania
Poland: 74 spring wheat trials, response in 34
Poland: 74 spring wheat trials, response in 34
5 %
Average of 10 studies · used in the calculator
10–30 %
Strong, confirmed deficiency
confirmed zinc deficiency
confirmed zinc deficiency
In 74 spring wheat field trials in Poland, zinc raised yield in 34 – by about 10% on average. When a deficiency is confirmed, cereal yield usually drops by 10–30% and barley by 16–29%, and drought makes the effect stronger. Where there is enough zinc, there is no extra yield.
€ On your farm: about 70 €/ha · about 70,000 € for 1,000 ha
With severe deficiency – up to 420 €/ha
Leaf analysis (laboratory reference)
The deficiency threshold is about 14 mg/kg Zn for young leaves and 12–16 mg/kg for flag leaves.
Can it be corrected later?
Zinc deficiency can be corrected while leaves and stems are forming. Late zinc can raise its content in the grain, but it will not bring back lost tillers or grains.
Foliar feeding
Zinc starts entering the leaf within a few hours, but moves very little within the leaf itself – less than 2.5 cm from the droplet in a day. So it matters that the solution covers the leaves well. In 23 trials in seven countries (including Kazakhstan), foliar zinc raised its content in the grain by 84% without reducing yield.
Source: Doolette et al., 2018; Zou et al., 2012; Singh et al., 2024
Source: Sobolewska et al., 2020; Irmes et al., 2023; Rahman and Schoenau, 2022; Zou et al., 2012; Ram et al., 2016, 2024; Sordi et al., 2021; Hui et al., 2025; Huang et al., 2024; Rashid et al., 2005; Lilay et al., 2024; Korzeniowska, 2004; Bağcı et al., 2007
Mo
Molybdenum
Micronutrient
What it does
Molybdenum is needed for the enzymes that turn nitrate into nitrogen the plant can use. That is why its shortage looks like nitrogen deficiency.
What a deficiency can look like
Growth slows, leaves turn pale, chlorosis or dead patches may appear. The risk is highest on acidic soils.
When it is most dangerous
In a study on acidic Australian soils, leaf molybdenum content was linked to yield both at tillering (GS24) and at heading (GS59).
What a deficiency can cost
≈6 %
Trials closest to Lithuania
Belarusian pea trial
Belarusian pea trial
15 %
Average of 10 studies · used in the calculator
15–59 %
Strong, confirmed deficiency
wheat on very acidic Australian soils
wheat on very acidic Australian soils
Molybdenum shortage is rare in cereals – legumes and brassicas are more sensitive. On very acidic Australian soils, the wheat yield response reached 15–59%, in a Belarusian pea trial about 6%, and in a recent Polish wheat trial no separate molybdenum gain was found. The risk is highest on acidic soils.
€ On your farm: about 210 €/ha · about 210,000 € for 1,000 ha
With severe deficiency – up to 826 €/ha
Leaf analysis (laboratory reference)
In the youngest leaf, about 0.08–0.09 mg/kg Mo is associated with roughly 90% of maximum yield.
Can it be corrected later?
Whether it can be corrected depends on soil pH and the plant's condition. On acidic soil, a prolonged shortage is harder to correct, and a late top-up will not bring back lost yield components.
Foliar feeding
Molybdenum is needed in mere grams. In a field study, molybdenum sprayed twice – at the end of tillering and stem elongation – at up to 35 g/ha increased the number of ears and yield. Exactly how much is taken up has not been determined – the effect depends on the deficiency and conditions.
Source: Zoz et al., 2012
Source: Tsyganov and Vildflush, 2004; Vasin et al., 2021; Kabylbekova et al., 2024; Zoz et al., 2012; Oliveira et al., 2022; Saquee et al., 2023; Brennan and Bolland, 2007; Guanzon and Tuazon, 2026; Marcondes and Caires, 2005; Gris et al., 2005; Jarecki, 2026
B
Boron
Micronutrient
What it does
Boron matters for cell walls and growing tissues. In wheat it is especially important for pollen: when boron is short, pollen develops poorly and grains set badly.
What a deficiency can look like
Young leaves and ears may become deformed, and empty spikelets may remain. At the reproductive stage, anthers may be poorly developed and pollen less viable.
When it is most dangerous
Most sensitive around flag leaf emergence and unfolding (BBCH 37–39). In a study, about 7 days of deficiency at this time did the greatest and irreversible damage to floret fertility.
What a deficiency can cost
9–15 %
Trials closest to Lithuania
Polish winter wheat, 4 varieties out of 10
Polish winter wheat, 4 varieties out of 10
12 %
Average of 10 studies · used in the calculator
15–50 %
Strong, confirmed deficiency
confirmed severe boron deficiency
confirmed severe boron deficiency
In Polish winter wheat trials, boron raised yield by 9–15% in four of ten varieties; the others did not respond. In Belarusian oilseed rape and sunflower trials the gain reached 10–23%. With severe deficiency, wheat yield fell by 15–50% – the ear forms, but part of the grains do not set.
€ On your farm: about 168 €/ha · about 168,000 € for 1,000 ha
With severe deficiency – up to 700 €/ha
Leaf analysis (laboratory reference)
In the flag leaf, the critical level is about 5–7 mg/kg B.
Can it be corrected later?
If boron is added while the plant is still in the sensitive period, grain set can recover. But if the deficiency has already damaged the pollen, later boron will not bring back grains that did not set.
Foliar feeding
Foliar boron can help, but boron reaching the developing ear comes mostly from the roots, not from leaves sprayed earlier. So boron in the leaves does not guarantee there will be enough for the ear. In Polish field trials, spraying boron (175 g/ha of boric acid) raised the yield of four out of ten winter wheat varieties by 9–15% on average.
Source: Stangoulis et al., 2001; Korzeniowska, 2008
Source: Apresyan and Bulavin, 2011–2013; Grodno SAU trials, 2007–2008; Goncharuk, 2013; Korzeniowska, 2008; Rahman and Schoenau, 2022; Stewart et al., 2021; Soylu et al., 2005; Rashid et al., 2011; Ahmad and Irshad, 2011; Rerkasem et al., 1989; Güneş et al., 2003; Wróbel, 2008
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