e-ifc No. 63, March 2021

Research Findings

Photo 1. Potato experiment field. Photo by the author.

Potential of Polyhalite Fertilizers to Enhance Potato Yield and Quality in the United Kingdom
Garnett, S. (1)*Abstract
Following three decades (1961-1990) of consistent increases,
average potato yields in the UK have plateaued at 36-44 Mg ha–1.
Coincidentally, worldwide atmospheric sulfur (S) deposits havesubstantially declined, resulting in an emerging occurrence of S
deficiencies in many crop species. It was hypothesized that S donor
fertilizers might restart the trend of increasing potato yield in the
UK. Polyhalite, available as a new commercial fertilizer marketed
as Polysulphate® by ICL, is a natural hydrated sulphate of K, Ca,
and Mg with the formula: K2Ca2Mg(SO4)4·2H2O. Polyhalite iscomprised of 48% sulfur trioxide (SO3), 14% potassium oxide

18/37(K2O), 6% magnesium oxide (MgO), and 17% calcium oxide (CaO).
Nevertheless, and due to the very high K requirements of potato crops,
the relatively low proportion of this nutrient in polyhalite does not
permit the use of this fertilizer as a sole K source. ICL PotashpluS®
(ICL UK) is a new granular fertilizer formulated using a combinationof potash (MOP, KCl) and polyhalite, in the formula: 37% K2O, 24%
SO3, 3% MgO and 8% CaO. Both fertilizers contain traces of boron.
IPI Coordinator for UK & Ireland, International Potash Institute, Zug, Switzerland
Corresponding author: Scott.Garnett@icl-group.com(1)*

e-ifc No. 63, March 2021

Sulfur is an essential element for all organisms and has a wide
variety of functions. Methionine, a fundamental brick in protein
biosynthesis, and cysteine, are both sulfur-containing amino acids,
hence the availability of S is essential for normal plant growth anddevelopment. Furthermore, since plants are the primary source of theessential amino acid methionine in the human diet, crops’ S nutritionis particularly important. Several studies have established regulatoryinteractions between N and S assimilation in plants (Kopriva
400

The consistent climb in the UK potato yield during 1960-1990 may
be attributed to the impacts of the ‘Green Revolution’ era, in which
genetic improvements, chemical fertilizers and pesticides wereintensively introduced and disseminated, resulting in significant
increases in the performance of many crop species (Evenson and
Gollin, 2003; Fuglie et al., 2019). The cessation of this processduring the recent decades, which has occurred despite continuing
efforts to enhance agricultural practices, requires explanation. While

8350

Introduction
Potato (Solanum tuberosum L.) is among the five most important
staple crop species cultivated worldwide. With 144,000 ha cultivatedwith potatoes, and production of 5.25 million tonnes in 2019 (FAO,
2021), the United Kingdom is among the 15 leading potato producing
countries in the world.

7

300

6

250

5

200

4

150

3

100

0
1960
50
45

2

Area
Production

50

Average annual yield (Mg ha–1)

Historical analysis of the UK potato industry from 1961 to 2019shows a consistent decline in the potato cultivated area until year
2000, when it stabilized at about 140,000 ha (Fig. 1A). Annual
production slightly decreased, exhibiting substantial fluctuations
until year 2000, from when it consistently dropped from 6.6 to thepresent levels of 5.2 million tonnes (Fig. 1A). The average annual
potato yield doubled from 22-44 Mg ha–1 during the years 1961-2000
but since then it remained stable or even decreased (Fig. 1B).

9

A

B

1970

1980

1990
Year

Annual production (106 tonnes)

Keywords: Calcium; magnesium; polyhalite; Polysulphate; Solanum
tuberosum L.; sulfur; tuber quality.

climate change may provide an ultimate explanation for the recent
fluctuations in the potato yield in the UK (Adesina and Thomas, 2020),
slowly emerging problems of plant nutrition should not be excluded.
Whereas routine examinations of soil nitrogen (N), phosphorus (P),and potassium (K) status are carried out in most commercial potato
producing farms, the availability of secondary macronutrients, suchas calcium (Ca), magnesium (Mg), and sulfur (S), is less addressed.

Cultivation area (103 ha)

The objective of the present preliminary study was to evaluate theinfluences of various polyhalite rates and combinations with MOP
on tuber yield and quality. A set of three separate experiments was
carried out, in which MOP was compared to PotashpluS (Exp. 1),
MOP was progressively replaced by polyhalite (Exp. 2), andPotashpluS was progressively replaced by polyhalite (Exp. 3). In all
three experiments, the application doses of nitrogen (N), phosphorus(P), and potassium (K) were kept equal throughout treatments,
whereas the application doses of calcium (Ca), magnesium (Mg), andS were modified by the polyhalite rates (100, 200, and 300 kg ha–1,
in Exp. 2 and 3). While the differences in crop performance between
MOP and PotashpluS-applied plots were small, replacing MOP or
PotashpluS by polyhalite resulted in significantly enhanced yields
at the higher polyhalite rates. It appears that the combination ofhigh application doses of all three nutrients, Ca, Mg, and S together
promotes higher yields than when each nutrient applied alone. In
addition, high Ca rates increased tuber Ca concentration at harvest,
and reduced tuber weight loss during storage. In conclusion, the setof experiments carried out in the present study demonstrates thepotential of polyhalite fertilizers to enhance potato crop performanceand tuber yield and quality through a more balanced mineral
nutrition. However, further research is necessary to elucidate thecontribution of Ca, Mg, or S to this enhancement, and to establish
precise fertilization strategies for various edaphic conditions.

1
2000

2010

0
2020

40
35
30
25

R² = 0.8593

20
15
10
5
0
1960

1970

1980

1990
Year

2000

2010

2020

Fig. 1. Historical analysis of the potato industry in the UK during 1961-2019.
Potato cultivated area and annual production (A) and, average annual potato
yield (B). Source: FAOstat. 2021.

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e-ifc No. 63, March 2021

deposition in the USA over the last three decades (Fig. 2). Similar
regulations were also introduced in Europe and other regions, giving
rise to comparable environmental impacts.
During the 20th century, industrially-generated atmospheric S
deposition could meet agricultural requirements. Nevertheless, thissituation changed remarkably with the declining S depositions during
the beginning of the 21st century. In Indiana USA, for example,
soil enrichment by S pollution was cut by 45% from 2001 to 2015
(Camberato and Casteel, 2017). Similar processes were reported
in Iowa, USA (Sawyer et al., 2015), as well as in Western Europe(Engardt et al., 2017) and in China (Chen et al., 2019).
Photo 2. Potato root system from polyhalite trial. Photo by the author.

et al., 2002). Sulfur availability regulates N utilization efficiency inplants, and thus affects primary production of crops. Recent studies
have found that interactions between S and other mineral nutrients
may be crucial to normal plant development (Courbet et al., 2019). In
addition, it appears that S-metabolites have essential regulatory roles
in plant cell physiology and, moreover, in plant responses to stress(Chan et al., 2019; Huang et al., 2019; Kaufmann and Sauter, 2019).
Consequently, S deficiency affects the growth, development, disease
resistance, and performance of plants and has a great impact on the
nutritional quality of crops (Kopriva et al., 2019).
Generally, sulfur deficiency problems began occurring in many crop
species in the 1990’s and became increasingly widespread overcountries and continents during the last three decades. The major
reason for this change was the introduction of strict regulation aiming
to diminish the acid rain phenomenon that substantially reduced theindustrial S (and N) emission to the atmosphere. This regulation
resulted in a significant decline in the atmospheric S (SO42-)

A

Optimum management of crop nutrition supports high tuber yield(Koch et al., 2019a), however, it is also significant to primary tuber
quality traits including dry matter and starch contents; skin integrity;and tolerance to various diseases (Zhang et al., 2018; Koch et al.,2019b; Naumann et al., 2020). While efficient potato crop nutrition
management is well established in the UK with regard to N, P, and K,
less attention has been paid to other essential macronutrients such as
Ca, Mg, and S.
The significance of Ca nutrition to the development and yield ofpotatoes has been investigated in the last two decades, and the numberof studies demonstrating Ca effects on tuber number and size is
steadily increasing (Ozgen et al., 2003; Palta, 2010; Seifu and Deneke,2017; Singh, 2018; Potarzycki and Grzebisz, 2020). In addition, Ca
is pivotal to the process of tuber skin development and maturation,
being a key element in periderm cell wall integrity (Ginzberg et al.,2012), which explains the contribution of Ca to the generally enhanced
postharvest tuber quality (Palta, 2010; Murayama et al., 2016; KerenKeiserman et al., 2019; Koch et al., 2019b; Naumann et al., 2020).
Magnesium is part of chlorophyll in all green plants and is essential
for photosynthesis and carbohydrate partitioning (Cakmak and Yazici,

B

Fig. 2. The amount of annual sulfur (SO 4 2- ) atmospheric deposition in the USA in 1990 (A), and in 2019 (B). Source: ht tps: //w w w3.epa.gov/castnet /airconc.html

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e-ifc No. 63, March 2021

2010; Farhat et al., 2016). The importanceof adequate Mg nutrition for potato plantdevelopment, carbohydrate partitioning(Koch et al., 2019a), as well as tuber yieldand disease tolerance (Singh, 2018) has
recently been demonstrated. Potato crops
exhibit no special S requirement comparedto other crop species. Typically, 1 tonneof potato tubers will remove 4.5 kg of S
(Burke, 2016). However, S-deficient plants
develop short and spindly stems, smallersize, pale yellow foliage, and bright yellow
young leaves. As a result, tuber yield andquality may decline, resembling N deficiency
consequences (Burke, 2016).
Polyhalite, a new commercial fertilizer
marketed as Polysulphate® by ICL, is anatural hydrated sulphate of K, Ca, and Mg
with the formula: K2Ca2Mg(SO4)4·2H2O.
The purity of the product is very high (95%polyhalite) with <5% sodium chloride(NaCl) and traces of boron (B) and iron (Fe)at 300 and 100 ppm, respectively. Polyhalite
is comprised of 48% sulfur trioxide (SO3),
14% potassium oxide (K2O), 6% magnesiumoxide (MgO), and 17% calcium oxide(CaO). Calcium, the least soluble nutrientin polyhalite (Yermiyahu et al., 2019), canprovide available Ca at rates equivalent tothose of gypsum. Polyhalite fertilizer, tested
as an alternative source of Ca in potato, had
a positive effect on tuber skin appearance
and skin-related gene expression (KerenKeiserman et al., 2019). When examined

Table 1. Soil properties at the three different experiment sites.
Exp. 1
Exp. 2pH
6.9
6.8
Phosphorus (ppm)
14
10
Potassium (ppm)
9458
Magnesium (ppm)57
87
Calcium (ppm)
2013
2432
Sulfur (ppm)2
1Manganese (ppm)
33
28
Copper (ppm)
4.3
5.0
Boron (ppm)
1.3
1.48
Zinc (ppm)
2.8
4.8
Molybdenum (ppm)
0.01
0.02
Iron (ppm)693
830
Sodium (ppm)
27
34
C.E.C. (meq 100 g–1)
12.6
15.7

as a substitute K donor fertilizer in Brazil,
polyhalite enhanced potato yield with apositive influence on various quality traits(da Costa Mello et al., 2018).
Nevertheless, and due to the very high K
requirements of potato crops, the relatively
low proportion of this nutrient in polyhalite
does not permit the use of this fertilizer
as a sole K source. ICL PotashpluS® is a
new granular fertilizer formulated using
a combination of potash (MOP, KCl) andpolyhalite. While primarily a potash andsulphate fertilizer, PotashpluS also contains
essential Mg and Ca, and supplies all K andS crop requirements in a single application.
The formula is 37% K2O, 9% S (24%SO3), 3% MgO and 8% CaO. In addition,
PotashpluS contains boron.

Exp. 3
6.2
88
89
75
1293
3
30
21.3
0.76
17.5
<0.01
1249
29
8.5

In the context of the diminishing atmospheric
S deposits and the recently expanding
occurrence of S deficiency in various crop
species, it was hypothesized that S donor
fertilizers would restart the trend of theincreasing potato yield in the UK. The
objective of this preliminary study was toevaluate the influences of various polyhalite
rates and combinations with MOP on tuber
yield and quality.
Materials and methods
Three preliminary experiments were carriedout at three locations in the UK. The soil
properties of the experiment sites aredetailed in Table 1.
The first experiment (Exp. 1) aimed
to compare the effects of the fertilizer

Table 2. Detailed description of the fertilizer treatments that were evaluated in the three different experiments carried out in the present study.
Nutrients
Treatment
N
P
K
Ca
Mg
S
Supplementary fertilizers----------------------kg ha–1---------------------Exp. 1
Farmers’ practice
180
170
330
30
60
MOP, MgSO4(cv. Brooke)
PotashpluS
180
170
333
72
25
207
Farmers’ practice
180
170
330
30
60
MOP, MgSO4
Poly100
180
170
330
17
36
108
MOP, polyhalite
Exp. 2(cv. Brooke)
Poly200
180
170
330
34
42
154
MOP, polyhalite
Poly300
180
170
330
51
48
204
MOP, polyhalite
PotashpluS
Polyhalite
Composite NPK-------------------kg ha–1---------------------PotashpluS
222
185
333
32
11
199
400
0
1235
Poly100
222
185
334
46
16
239
365
100
1235
Exp. 3(cv. Shelford)
Poly200
222
185
335
60
21
279
330
200
1235
Poly300
222
185
341
76
26
322
310
300
1235

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e-ifc No. 63, March 2021

Seed tubers were sown in April in all threeexperiments. Aerial NDVI screening of the
fields was conducted in June, when the crop
reached full coverage. At harvest, sample
2 m digs were taken from each treatment(5 replicates) for the determination of plantand stem counts, tuber yield, and tuber size
distribution.
In Exp. 1 and 2, tubers were sampled forthe determination of N, K, Ca, Mg, and B
concentration. In Exp. 3, tuber samplesof 10 kg from each polyhalite treatment(5 replicates) were stored under commercial
conditions for 4 months, and weight loss
was determined.
Statistical analyses were made separately
for each experiment using ANOVA and JMP
software.

A

B

Potas
hpluS

PotashpluS vs. MOP (usual farmers’
practice) with regard to crop performance,yield, and tuber size. The second experiment(Exp. 2) tested polyhalite at three different
rates (100, 200, and 300 kg ha–1) as a partial
replacement of MOP as the K source,compared to the farmers’ practice of 100%
MOP. In the third experiment (Exp. 3), threepolyhalite rates were tested in combination
with declining PotashpluS rates, from 400 to
310 kg ha–1. About half of the K applicationdose in Exp. 3, 185 kg ha–1, was applied
through a composite NPK fertilizer. In
each experiment, the rates of N, P, and K
application were equal in all treatments,
while the differences were focused on the
K source, and on the rates of Ca, Mg, and S
application, as described in details in Table 2.

Fig. 3. Experiment 1 field. The PotashpluS-applied plot is marked with a blue border, surrounded by the MOPapplied area (A); NDVI image of the field in June (B).

Results
Experiment 1 – PotashpluS vs. MOP
In Exp. 1, the area treated with PotashpluS
showed a darker color in NDVI images
recorded in June (Fig. 3), which is usuallyassociated with a better status of crop
nutrition. However, no differences could beobserved from visual assessments at groundlevel between the two treatments during site
visits.
No significant differences between thefertilizer treatments were detected in theplants and stems counts at harvest (Table 3).
Total and marketable tuber yields wereslightly but not significantly higher under
the PotashpluS treatment. The proportionof larger size (65-85 mm) tubers was
significantly greater under the PotashpluS
treatment. Tuber nutrient concentrations
were unaffected by the fertilizer treatmentsin this experiment (Table 3).
Experiment 2 – polyhalite vs. MOP
In Experiment 2, the plots treated withpolyhalite showed slightly darker colors in
NDVI images made in June (Fig. 4). The
polyhalite-applied strips looked greener
throughout the season.

Table 3. Effects of PotashpluS application on potato crop performance, yield, tuber size distribution, and on tuber N, K, Ca, Mg, and B concentration,compared to MOP-applied control plants, in Exp. 1.
Treatment

Plant count Stem count Total yield Field loss1
Plants m–2 Stems m–2-------Mg ha–1------PotashpluS
4.03
11.77
48.4
7.1
MOP
3.6
11.88
45.2
6.3
* Significant difference at 0.05%.
1
Field loss: small tubers

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Marketable yield
Mg ha–1
%
41.3
85.4
38.9
86.0

Tuber size (mm)< 45 45-65 65-85 > 85----------------%---------------14.6 46.8 38.50
14.0 58.1* 27.9*0Tuber concentration
N
K
Ca
Mg
B
--------------mg 100 g–1-------------320.4 426.6 21.61 23.49 0.12
320.5 427.7 21.41 21.54 0.11

e-ifc No. 63, March 2021

Crop establishment was unaffected by thefertilizer treatments. Plant and stem counts
ranged from 6.4-6.6 m–2 and 12.4-13.3 m–2,
respectively, excluding the Poly300
treatment, which was somewhat lower, with
6.0 plants m–2 and 12.2 stems m–2.

BPol
Pol y100
Pol y200y30
0A

Total tuber yield (Mg ha –1)

The total tuber yield of the Poly200
treatment, 57.2 Mg ha–1, was significantly
higher than those of the MOP-applied
control and the Poly100 treatment, with 50.8
and 44.9 Mg ha–1, respectively, and slightly
but insignificantly higher than that of the
Poly300 treatment (Fig. 5A). Interestingly,
the polyhalite treatments increased the rate
Fig. 4. Experiment 2 field. The polyhalite-applied plots are marked with blue borders, while the surroundingof the marketable yield from 86% to 88-92%,
area was farmers’ usual practice, MOP-applied control (A); NDVI image of the field in June (B).
mainly through significant reduction of field
losses due to too small tubers. Although the
response pattern of the marketable yield to the fertilizer treatment
remained similar to that of the total yield (Fig. 5B), the polyhalite
65
A
treatments displayed remarkable effects on the tuber size distribution,
60
with a clear reduction in the proportions of small and medium size
tubers, and a consequent increase in that of the large tubers (Fig. 5C).
55
Polyhalite treatments resulted in progressive increases of tuber N,
Ca, Mg, and B concentrations that also were significantly higher
than under MOP (Table 4). Similarly, tuber K concentration
was significantly lower under MOP application compared to thepolyhalite-applied plants, however no differences occurred between
the treatments with different polyhalite rates.

50
45
40
35
30
60

Control

B

Poly100

Poly200

Poly300

70

Treatment

Control

60
Tuber size distribution (%)

55
Marketable yield (Mg ha –1)

C

50
45
40
35

Poly100
Poly200

50

Poly300
40
30
20
10

30

0
Control

Poly100

Poly200

Poly300

Treatment

<45

45-65

65-85

>85

Tuber size (mm)Fig. 5. Effects of increasing polyhalite application rates on potato tuber yield and qualit y, compared to farmer’s usual practice or MOP-applied control. Total (A), andmarketable (B) tuber yields, and tuber size distribution (C). Bars indicate SE.

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e-ifc No. 63, March 2021

Table 4. Effects of polyhalite application rate on the nutrient concentrations in potato tubers at harvest, compared to MOP-applied control.
Treatment
Nutrient
N
K
Ca
Mg
B
--------------------------------------------------------------------mg 100g–1-------------------------------------------------------------------MOP
320.5
427.7
21.41
21.54
0.11
Poly100
346.3
456.6
26.17
23.19
0.14
Poly200
355.7
448.4
30.81
24.78
0.16
Poly300
374.7*
445.7*
33.10*
24.16*
0.16** Indicates significant differences at 0.05%

Experiment 3 – PotashpluS vs. polyhalite
In experiment 3, the polyhalite-applied plots were much darker
than the PotashpluS-applied area in the NDVI image made in June
(Fig. 6), and exhibited a slightly greener color during most of theseason.
Crop establishment was similar under the higher polyhalite rates aswell as under PotashpluS, with counts ranging at 3.8-4.0 plants m–2
and 23.5-24.9 stems m–2, respectively. At the lower polyhalite rate,
counts were smaller, with 3.6 plants m–2 and 19.7 stems m–2.
In this experiment, both total and marketable tuber yields displayed asignificant positive response to increasing polyhalite application rates.
While Poly100 treatment gave rise to significantly lower yields than
Poly300, Poly200 and PotashpluS obtained intermediate, comparable
yields (Fig. 7A and B). No influence on the marketable yield rate,
which was very close to 90% in all treatments, could be observed inthis experiment. In addition, the proportion of small tubers (<45 mm)
was similar, about 10% in all treatments. The proportion of mediumsize tubers (45-65 mm) increased from 55 to 65% with the rising
polyhalite application rate, which was probably at the expense of thelarge-size tubers (65-85 mm). Under the Poly100 treatment, about
2% of the tubers were too large, bigger than 85 mm (Fig. 7C).

Table 5. Relationships between the ascending marketable yield and the
input of secondary macronutrients Ca, Mg, and S across the threeexperiments.
Marketable yield
Nutrient application doseCa
Mg
S
Mg ha–1----------kg ha–1---------38.9
0
30
60
39.9
17
36
108
41.3
72
25
207
43.0
46
16
239
43.7
0
30
60
47.5
60
21
279
48.6
32
11
199
50.2
51
48
204
50.3
34
42
154
51.6
76
26
322

A four-month storage test revealed a consistent reduction of tuber
weight loss along with the rising polyhalite application rate in thefield (Fig. 8). Unfortunately, there was no data available on weightloss of tubers from the PotashpluS treatment.

Pol
Pol y100y2Pol
y30 000Discussion
In the light of plateaued potato yields during the last two decades, theimpact of various polyhalite fertilizers that enrich the crop rhizospherewith four essential macronutrients (K, Ca,
Mg, and predominantly S) was preliminarily
evaluated. The diminishing atmosphericA
B
S deposits since the 1990’s have led to
an increasing occurrence of S deficiency
symptoms in numerous crop species(Camberato and Casteel, 2017). Accordingly,
awareness of crop S requirements is steadilyrising (Engardt et al., 2017; Chan et al.,2019; Chen et al., 2019; Courbet et al.,2019; Huang et al., 2019). The synergistic
relationships between N and S in plant
metabolism gave rise to the assumption thatsoils with poor available S might restrict N
uptake and subsequently, inhibit potato crop
establishment. No significant differences in
the number of plants or stems were observed
Fig. 6. Experiment 3 field. The polyhalite-applied plots are marked with blue borders, while the surroundingthat could be related to the fertilizer
area was applied with PotashpluS (A); NDVI image of the field in June (B).

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e-ifc No. 63, March 2021

65

-3

A

-3.5

55

Tuber weight loss (%)

Total tuber yield (Mg ha –1)

60

50
45
40

30
PotashpluS

B

Poly100

Poly200

Poly300

Treatment

Marketable yield (Mg ha –1)

-5.5
0

100

200

300

400

Polyhalite rate (kg ha –1)

55

Fig. 8. Water loss from tubers during storage from June to September as a50function of polyhalite application rate in the field. Bars indicate SE.

45

type – MOP, PotashpluS, or polyhalite. Establishment differences
observed in response to polyhalite application rate were inconsistent.

40
35
30
PotashpluS

Poly100

Poly200

Poly300

Treatment
70

C

PotashpluS

60
Tuber size distribution (%)

y = 0.0056x - 5.2733
R² = 0.9996

-4.5

-5

35

60

-4

Poly100
Poly200

50

Poly300
40
30
20
10
0
<45

45-65

65-85

>85

Tuber size (mm)Fig. 7. Effects of increasing polyhalite application rates on potato tuber yieldand qualit y, compared to a PotashpluS-applied control. Total yield (A), andmarketable (B) tuber yields, and tuber size distribution (C). Bars indicate SE.

Tuber yield was positively influenced by the polyhalite fertilizers
commensurate with rate of application. While the advantage ofPotashpluS comparing to MOP with regard to tuber yield was small
and insignificant statistically (Table 3), the progressive replacementof MOP by polyhalite was responded to by a clear increase of the tuber
yield under the higher polyhalite rates (Fig. 5). In a similar way, thehigher the polyhalite rate the higher tuber yield under a progressive
replacement of PotashpluS by polyhalite (Fig. 7). In each experiment,
the rates of N, P, and K application were kept equal between
treatments and hence, the differences in crop performance could be
attributed solely to the rates of the secondary macronutrients – Ca,
Mg, and S. At this early stage of the present study, it would be
difficult to elucidate the precise nutrient responsible. Nevertheless,a rough analysis of the results indicates a minimum threshold for
Ca input of about 30 kg ha–1, which would be required for achieving
marketable yield levels higher than 50 Mg ha–1 (Table 5), comparedwith the current 10-year range of marketable tuber yields in the UKof 36-44 Mg ha–1 (Fig. 1C).
Increasing Ca input resulted in greater Ca concentration in the tubers(Tables 1 and 3). Recent studies have pointed to the key role Ca playsin the tuber development (Ozgen et al., 2003; Palta, 2010; Seifu andDeneke, 2017; Singh, 2018; Potarzycki and Grzebisz, 2020), andparticularly in the periderm maturation and integrity (Ginzberg et al.,2012; Keren-Keiserman et al., 2019), and its subsequent positive

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e-ifc No. 63, March 2021

effects on the duration and safety of potato tuber storage (Murayama
et al., 2016; Koch et al., 2019b; Naumann et al., 2020). An indication
for these positive influences is the clear reduction of water loss fromtubers during long storage (Fig. 8).
However, high Ca inputs do not guarantee high marketable yields.
High yields also coincided with high S inputs, but not always, and
Mg inputs displayed no correlation with tuber yield at all. It appears
that the combination of high application doses of all three nutrients
together promotes higher yields rather than each nutrient alone(Table 5). Such combinations are made easily available to the cropusing various polyhalite fertilizers and application rates that shouldbe thoroughly adjusted to the properties of the local soil and to crop
rotation.
In conclusion, the set of experiments carried out in the present study
demonstrates, in agreement with several recent studies (da Costa
Mello et al., 2018; Keren-Keiserman et al., 2019), the potentialof polyhalite fertilizers to enhance potato crop performance andtuber yield and quality through a more balanced mineral nutrition.
However, further research is necessary to elucidate the contributionof Ca, Mg, or S to this enhancement, and to establish precise
fertilization strategies for various edaphic conditions.

References
Adesina, O., and B. Thomas. 2020. Potential Impacts of Climate
Change on UK Potato Production. International Journal ofEnvironment and Climate Change 10(4):39-52.
Burke, J.J. 2017. Growing the Potato Crop. Vita, Equity house,
Upper Ormond Quay, Dublin 7, Ireland.
Cakmak, I., and A.M. Yazici. 2010. Magnesium: a Forgotten
Element in Crop Production. Better Crops 94:23-25.
Camberato, J., and S. Casteel. 2017. Sulfur Deficiency. Purdue Univ.
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Photo 3. Comparing root system and potato tuber yield from polyhalite potato trial. Photo by the author.

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The paper “Potential of Polyhalite Fertilizers to Enhance
Potato Yield and Quality in the United Kingdom” also appearson the IPI website.

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