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Pedosphere 25(2): 275–281, 2015
ISSN 1002-0160/CN 32-1315/P
c
°2015 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Zinc Application Affects Tissue Zinc Concentration and Seed Yield
of Pea (Pisum sativum L.)
Ejaz RAFIQUE∗, Munazza YOUSRA, Muhammad MAHMOOD-UL-HASSAN, Sair SARWAR,
Tauseef TABASSAM and Tayyaba K. CHOUDHARY
Land Resources Research Institute, National Agricultural Research Centre, Islamabad 45500 (Pakistan)
(Received June 9, 2014; revised January 7, 2015)
ABSTRACT
A 2-year field experiment was conducted to assess the effect of applied zinc (Zn) on the seed yield of pea (Pisum sativum L.) and
to determine the internal Zn requirement of pea with emphasis on the seed and leaves as index tissues. The experiment was carried
out at two different locations (Talagang, Chakwal district and National Agricultural Research Centre (NARC), Islamabad) in the
Potohar Plateau, Pakistan by growing three pea cultivars (Green feast, Climax, and Meteor). The soils were fertilized with 0, 2, 4, 8,
and 16 kg Zn ha−1along with recommended basal fertilization of nitrogen (N), phosphorus (P), potassium (K), and boron (B). Zinc
application increased seed yield significantly for all the three cultivars. Maximum increase in the pea seed yield (2-year mean) was
21% and 15% for Green feast, 28% and 21% for Climax, and 34% and 26% for Meteor at Talagang and NARC, respectively. In all
cultivars, Zn concentrations in leaves and seed increased to varying extents as a result of Zn application. Fertiliser Zn requirement for
near-maximum seed yield varied from 3.2 to 5.3 kg ha−1for different cultivars. Zinc concentrations of leaves and seeds appeared to be
a good indicator of soil Zn availability. The critical Zn concentration range sufficient for 95% maximum yield (internal Zn requirement)
was 42–53 mg kg−1in the pea leaves and 45–60 mg kg−1in the seeds of the three pea cultivars studied.
Key Words: calcareous soils, diagnostic criteria, vegetable crops, zinc fertiliser, zinc uptake
Citation: Rafique, E., Yousra, M., Mahmood-Ul-Hassan, M., Sarwar, S., Tabassam, T. and Choudhary, T. K. 2015. Zinc application
affects tissue zinc concentration and seed yield of pea (Pisum sativum L.). Pedosphere.25(2): 275–281.
Zinc (Zn) deficiency is a widespread and frequent
micronutrient disorder in crops, predominantly in cal-
careous soils of arid and semi-arid regions worldwide
(Takkar and Walker, 1993; Welch and Graham, 2002)
including Pakistan (Anonymous 1998, Rafique et al.,
2006) because of its low solubility and high fixation
under such soil conditions (Lindsay, 1979). Nearly half
of the agricultural soils contain low levels of plant-
available Zn (Graham and Welch, 1996), thus reducing
crop yield and nutritional quality.
The soils across much of the cultivated areas in
Pakistan are developed from calcareous alluvium and
loess, and low in organic matter as well as many essen-
tial plant nutrients (Rashid and Ahmad, 1994). Mul-
tiple factors like free carbonates, low organic matter,
high pH, and continuous nutrient removal with inten-
sive cultivation coupled with inadequate and imba-
lanced fertiliser use are associated with deficiencies of
nutrient in crops including Zn (Rafique et al., 2006).
Pea (Pisum sativum L.), a cool season vegetable
crop belonging to family Leguminosae, is one of the
leading and popular vegetables in Pakistan. It is a
valuable supplement to cereals and other starchy food
in the human diet due to high contents of lysine and
tryptophan. It is categorized as less sensitive to Zn de-
ficiency (Alloway, 2008). However, Zn deficiency does
occur in peas as Zn has many important roles in plant
growth and a lack of Zn was linked to reduced seed
formation (Bell and Dell, 2008). Zinc deficiency in hu-
man also appears to be a critical nutritional and health
problem in the world. Challenge is being faced to in-
crease seed/grain Zn concentration in crops to over-
come widespread malnutrition especially in developing
countries (Bouis and Welch, 2010). Thus, increasing
Zn levels in seed could deliver more Zn to people who
rely directly or indirectly on pea-derived food. Zinc
application was also an effective strategy of biofortifi-
cation to increase grain Zn concentration in wheat and
rice (Cakmak, 2008; Hossain et al., 2008; Shivay et al.,
2008), but information specific to pea is limited.
Foliar analysis at a particular crop growth stage
is widely used as a diagnostic guide for fertilization.
Whole shoots or recently matured leaves at early flowe-
ring are the tissues usually recommended for analysis
∗Corresponding author. E-mail: ej.rafique@gmail.com.
276 E. RAFIQUE et al.
(Jones et al., 1991). According to Jones et al. (1991),
seed usually is not a better index tissue for estimating
the nutrient status of plants. Nevertheless, seed ana-
lyses have also been used for determining Zn supply
to young plants (Rashid and Fox, 1992). Zinc concen-
tration of seeds reflects differences among soils in their
ability to supply Zn and the ability of plants to ac-
cumulate Zn (Rashid and Fox, 1992; Rafique et al.,
2011).
Much of the information regarding sensitivity of
pea species to Zn deficiency is based on field obser-
vations, whereas corresponding experimental work is
rarely reported in literature. Moreover, information
concerning Zn requirement and critical concentration
in plant parts of the crop is limited. Further, plant
analysis diagnosing Zn concentration values published
in the literature may not be appropriate for various
crop genotypes grown in different agro ecological zones.
Even the cultivars of the same plant species demon-
strate a variable response to a specific nutrient sup-
ply/deficiency (Rengel and Romheld, 2000; Hacisali-
hoglu et al., 2004). The objective of this study was
to assess the effect of Zn application on the yield and
internal Zn requirement of pea with emphasis on the
seed and leaves as index tissues for determining the Zn
status of crop under field conditions.
MATERIALS AND METHODS
Sites description
A 2-year (2010–2012) field experiment was con-
ducted at two locations, i.e., Talagang, Chakwal dis-
trict (32◦560N, 72◦250E), a sandy loam Balkassar soil
(coarse loamy mixed, hyper thermic Udic Haplustalf)
and National Agricultural Research Centre (NARC),
Islamabad (33◦430N, 73◦50E), a loam Nabipur soil
(fine loamy mixed, hyper thermic Udic Ustochrept) in
the Potohar Plateau, Pakistan. The Balkassar soil is
relatively coarse-textured with lesser soil organic mat-
ter (OM), compared with Nabipur soil (Table I).
Nutrient treatments, experimental design and crop
management
The experiment consisted of 45 plots, each com-
prised of three raised beds of 1.25-m width and 9.0-m
length, arranged in split-plot design with three replica-
tions. Three pea cultivars, i.e., Green feast, Climax,
and Meteor were in main-plots and Zn doses, i.e., 0, 2,
4, 8, and 16 kg Zn ha−1as ZnSO4·7H2O were applied
in sub-plots. Additionally, 60 kg N ha−1as urea, 100
kg P2O5ha−1as single super phosphate, 60 kg K2O
ha−1as sulphate of potash, and 1 kg B ha−1as boric
acid were applied as basal dose to produce normal ma-
ture plants, plus extra nutrient to provide a margin of
safety in the soil until harvest. Full doses of P, K, B, Zn
and one-third of N were applied at the time of sowing.
Remaining amount of N was applied in two splits, i.e.,
at apparent flowering and pod formation stages. The
pea seeds were sown on both sides of beds 5 cm apart
in mid October. Irrigation, weeding, and other cultural
practices were done according to regular recommenda-
TABLE I
Selected initial physico-chemical characteristics of soils at two field experimental sites in the Potohar Plateau of Pakistan
Soil characteristic Experimental site
Talagang NARCa)
Soil series Balkassar Nabipur
Soil family Coarse-loamy mixed hyper thermic Udic Haplustalf Fine-loamy mixed hyper thermic Udic Ustochrept
Clay (%) 10 15
Silt (%) 22 45
Texture Sandy loam Loam
pH (1:1) 8.1 8.3
ECb) (1:1) (dS m−1) 0.40 0.54
Organic matter (g kg−1) 3.4 4.9
CaCO3(g kg−1) 24 31
NO−
3-N (mg kg−1)c) 2.2 3.0
P (mg kg−1)c) 1.3 1.9
K (mg kg−1)c) 90 120
Zn (mg kg−1)c) 0.28 0.42
B (mg kg−1)d) 0.17 0.25
a)National Agricultural Research Centre.
b)Electric conductivity.
c)Ammonium bicarbonate-DTPA-extractable.
d)Hot water-extractable.
ZINC APPLICATION AFFECTS PEA ZINC AND YIELD 277
tions for the region. Nutrient treatments were same at
both locations for 2 years.
Composite diagnostic plant tissue, i.e., recently
matured leaves at flower initiations, were collected
(Jones et al., 1991). Picking was started when pods
were well filled with young and tender seeds, and three
pickings were taken. Seed and stalk yield was recorded
and representative samples were kept for Zn analysis.
Zinc analysis
Diagnostic plant parts, i.e., leaf, stalks, and seeds,
were digested in a double acid mixture (2:1), i.e.,
nitric acid and perchloric acid. Zinc in the digests
was determined by atomic absorption spectrophotom-
etry (AAnalyst 800, Perkin Elmer, USA) (Wright and
Stuczynski, 1996). Internal Zn requirement, the con-
centration of Zn in specific tissue sufficient for 95%
maximum yield (Rashid and Fox, 1992), was deter-
mined from relative yield versus Zn concentration us-
ing a boundary line technique (Webb, 1972).
Statistical analysis
Analysis of variance (ANOVA) of the measured pa-
rameters was performed using MSTAT-C and the Zn
doses and cultivars means were compared using Dun-
can’s multiple range test at 5% probability level.
RESULTS AND DISCUSSION
Seed yield
There were no significant differences in pea seed
yield and change pattern across the years at both lo-
cations, so data of 2 years were pooled in this study.
Analysis of variance showed significant effects of Zn
and cultivar on pea seed yield at both locations (Ta-
ble II, P < 0.05). However, interaction effect (Zn rates
×cultivars) was non-significant. Zinc application in-
creased seed yield of all pea cultivars. Increasing Zn
application rate to 8 kg Zn ha−1increased seed yield
of Green feast at both locations. However, increased
seed yields of Meteor was observed at 16 kg Zn ha−1
application. The yield differences between 0 and 8 kg
Zn ha−1were significant, while no significant diffe-
rence was found between 8 and 16 kg ha−1. Among
cultivars, increase in seed yield with Zn fertilization
over control, was highest for Meteor and lowest for
Green feast. Maximum increase in pea seed yield (2-
year mean) at Talagang and NARC was 21% and 15%
for Green feast, 28% and 21% for Climax, and 34% and
26% for Meteor. Better impact of applied Zn over con-
trol was more in coarse-textured Balkassar soil at Ta-
lagang compared with that in Nabipur soil at NARC.
It was probably related to lesser native OM content in
the former soil than in Nabipur soil at NARC (Table
I). In this study, seed yield increased up to 8 kg Zn
ha−1application. No toxicity symptom was observed
at this rate. In a pot study conducted by Shukla and
Raj (1980) on a calcareous Zn-deficient soil using pi-
geon pea as test crop, 93% increase in seed yield was
observed with 5 mg Zn kg−1soil application. However,
50 mg Zn kg−1soil did not increase seed yield sig-
nificantly over 5 mg Zn kg−1soil application. As Zn
has many important roles in plant growth, i.e., photo-
synthesis, enzyme activity such as carbonic anhydrase
(Rengel, 1995), chlorophyll concentration, and stom-
atal conductance (Hu and Sparks, 1991), a continuous
supply of Zn is necessary for optimum plant growth
and yield.
TABLE II
Effect of Zn fertilization on the seed yields of three pea cultivars at two field experimental sites in the Potohar Plateau of Pakistan
Zn applied Seed yield
Talagang NARCa)
Green feast Climax Meteor Mean Green feast Climax Meteor Mean
kg ha−1t ha−1
0 1.676 1.498 1.375 1.516Db) 1.945 1.670 1.538 1.718D
2 1.868 1.758 1.635 1.754C 2.121 1.861 1.713 1.898C
4 1.935 1.848 1.732 1.838B 2.169 1.979 1.798 1.982B
8 2.027 1.915 1.821 1.921A 2.237 2.021 1.907 2.055A
16 2.002 1.909 1.841 1.917A 2.228 2.029 1.938 2.065A
Mean 1.901ac) 1.785b 1.681c 2.140a 1.912b 1.779c
a)National Agricultural Research Centre.
b)For each Zn application rate, means in a column followed by the same uppercase letter are not significantly different at P≤0.05.
Least significant difference (LSD, P < 0.05) was 0.06 and 0.04 for Talagang and NARC, respectively.
c)For each pea cultivar, means in a row followed by the same lowercase letter are not significantly different at P≤0.05.
Least significant difference (LSD, P < 0.05) was 0.05 and 0.03 for Talagang and NARC, respectively.
278 E. RAFIQUE et al.
Genotypic variation
In the present study, the term “Zn efficiency” is em-
ployed as the ability of a plant to grow and yield well
in a Zn-deficient soil (Graham, 1984). Based on the
reduction in seed yield, Zn efficiency of the cultivars,
i.e., ratio of seed produced under Zn deficiency to Zn
fertilization was: 86%–89% for Green feast, 81%–85%
for Climax, and 78%–84% for Meteor (Table III). Thus,
under given conditions, efficiency of the grown pea cul-
tivars declined in the order of Green feast >Climax >
Meteor. It is most likely that the Zn taken up by more
efficient cultivars is used for dry matter production un-
der Zn deficient condition and thus diluted to similar
concentrations as in the inefficient cultivars, and not
accumulated in seeds. The reason for higher sensiti-
vity of Meteor to Zn deficiency as compared to Green
feast is not known. These differences among the culti-
vars might be related to the higher Zn accumulating
capacity of Meteor. The observed variation in Zn ac-
cumulation among the genotypes supported earlier re-
sults of Rafique et al. (2011) who reported that the Zn
accumulation was related to the genotypic variation
in onion. Differential susceptibility to Zn deficiency
among onion and wheat genotypes is attributed to the
differential capacity of genotypes in acquisition of Zn
from soils (Graham et al., 1992; Cakmak et al., 1996a;
Rafique et al., 2011). Cakmak et al. (1994, 1996b) also
reported that differences in Zn efficiency among wheat
genotypes might be related to their efficiency to release
Zn mobilizing phytosiderophores (phytometallophores)
from their roots to the rhizosphere and absorption and
translocation of Zn from roots to shoot meristem. Phy-
tosiderophores are known to be effective in mobilizing
Zn by chelating sparingly soluble Zn compounds in cal-
careous soils (Treeby et al., 1989).
Fertiliser Zn requirement
The observed fertiliser Zn requirement for 95%
maximum yield of pea cultivars was 3.2 kg Zn ha−1
for Green feast, 3.4 kg Zn ha−1for Climax, and 5.3
kg Zn ha−1for Meteor (Fig. 1). The field study re-
vealed that despite low sensitivity of peas to Zn de-
ficiency, this nutrition disorder caused a considerable
yield loss. Anonymous (1998) reported that a dose of
about 4 kg Zn ha−1can help ameliorate the deficiency
not only in the current crop but also in subsequent
crop grown in the same field. Thus, a nominal invest-
ment on Zn fertiliser, in soil-deficient situation, can
improve crop productivity, increase plant Zn concen-
tration, enhance growers’ income, and help sustain the
soil resource base.
Leaf Zn composition
Pea leaf Zn concentration increased significantly
Fig. 1 Relationships between Zn fertiliser rates and relative
seed yields of three pea cultivars (Green feast, Climax, and Me-
teor). Maximum yields of the pea cultivars were 2.132 t ha−1
for Green feast, 1.972 t ha−1for Climax, and 1.900 t ha−1for
Meteor.
TABLE III
Effect of Zn application on seed yield and Zn efficiency of three pea cultivars grown in two Zn-deficient soils at two field experimental
sites in the Potohar Plateau of Pakistan
Cultivar Talagang NARCa)
Seed yield Increase Zn Seed yield Increase Zn
over control efficiencyd) over control efficiency
Controlb) Zn applied treatmentsc) Control Zn applied treatments
t ha−1% t ha−1%
Green feast 1.676 1.958 17 86 1.945 2.179 12 89
Climax 1.498 1.857 24 81 1.670 1.960 17 85
Meteor 1.375 1.757 28 78 1.538 1.827 19 84
Mean 1.516 1.857 22 82 1.718 1.989 16 86
a)National Agricultural Research Centre.
b)0 kg Zn ha−1.
c)Zn applied at 2, 4, 8, and 16 kg ha−1.
d)Zinc efficiency was calculated as the ratio of dry seed yield at 0 kg Zn ha−1to the mean dry seed yield at 2, 4, 8, and 16 kg Zn
ha−1.
ZINC APPLICATION AFFECTS PEA ZINC AND YIELD 279
with Zn fertiliser rates at both locations (Table IV).
However, the magnitude of increase varied among cul-
tivars. Leaf Zn concentration increase was relatively
higher at Talagang than NARC for all the culti-
vars. Extent of increase was 65% in Green feast, 74%
in Climax and 76% in Meteor with applied Zn at Tala-
gang. Similar trend was observed at NARC but the Zn
concentration was relatively low at NARC, i.e., 44% in
Green feast, 58% in Climax and 63% in Meteor. The
largest range of Zn concentration among Zn rates oc-
curred in Meteor and the smallest in Green Feast, that
might be attributed partially to a dilution effect as the
result of greater seed production of Green feast (Table
II). The data of 2 years at both locations were pooled
in this study for determining internal Zn requirement
of leaves (plotting leaf Zn concentration versus relative
seed yield of peas) and estimated internal Zn require-
ment was 42 mg kg−1for Green feast, 46 mg kg−1for
Climax and 53 mg kg−1for Meteor (Fig. 2).
Total Zn uptake
Zinc application increased total Zn uptake (seeds +
stalks) at both locations (Table IV). Total Zn uptake
differed significantly among the Zn rates and cultivars,
while interaction effect (Zn rate ×cultivar) was non-
significant. Increase in total Zn uptake over control was
high at Talagang, i.e., 94% in Green feast, 119% in Cli-
max, and 147% in Meteor. While this increase was less
at NARC probably due to greater yield potential; i.e.,
75% in Green feast, 84% in Climax, and 111% in Me-
teor. Obviously higher uptake by Meteor at both sites
was due to its larger internal Zn requirement of leaves
compared with the other cultivars. The total Zn uptake
was positively related with seed yields and the correla-
tion coefficient (r) values were 0.95, 0.96, and 0.96 for
Green feast, Climax, and Meteor, respectively. Even
strong correlation (r= 0.998) between total uptake
and leaf Zn concentration was observed.
Seed Zn composition
Zinc concentration in seeds differed widely among
cultivars and influenced by Zn application to the soils
in which the plants grew (Table IV). The Zn concen-
trations in seeds, attributable to Zn fertilization, were
TABLE IV
Zinc concentration in tissues and total Zn uptake by three pea cultivars (Green feast, Climax and Meteor) (mean of 2 years) as affected
by Zn fertilization at two field experimental sites in the Potohar Plateau of Pakistan
Zn Talagang NARCa)
applied Green feast Climax Meteor Mean Green feast Climax Meteor Mean
kg ha−1
Zn concentration in leaves (mg kg−1)
0 32 35 37 35Eb) 34 36 36 35E
2 37 44 45 42D 39 42 43 41D
4 44 50 54 49C 44 47 50 47C
8 49 56 59 55B 47 51 54 51B
16 53 61 65 60A 49 57 59 55A
Mean 43cc) 49b 52a 42a 47b 49a
Zn concentration in seeds (mg kg−1)
0 34 39 42 38E 35 41 44 40E
2 42 49 52 48D 42 46 51 46E
4 48 57 59 55C 45 51 58 51E
8 52 62 65 60B 48 58 65 57B
16 57 66 72 65A 52 61 70 61A
Mean 47c 54b 58a 44c 51b 57a
Total Zn uptake (mg kg−1)
0 113 108 102 108E 130 126 124 127E
2 153 158 151 154D 166 157 165 163D
4 179 190 187 186C 191 188 194 191C
8 201 218 220 213B 211 213 230 218B
16 219 237 252 236A 228 233 262 241A
Mean 173b 182a 183a 185b 183b 195a
a)National Agricultural Research Centre.
b)For each Zn application rate, means in a column followed by the same uppercase letter are not significantly different at P≤0.05.
Least significant difference (LSD, P < 0.05) was 1.28 and 1.00 for Zn concentration in leaves, 1.34 and 1.35 for Zn concentration in
seeds, and 5.78 and 3.96 for total Zn uptake for Talagang and NARC, respectively.
c)For each pea cultivar, means in a row followed by the same lowercase letter are not significantly different at P≤0.05. LSD (P < 0.05)
was 1.26 and 0.58 for Zn concentration in leaves, 0.67 and 1.11 for Zn concentration in seeds, and 2.85 and 4.91 for total Zn uptake
for Talagang and NARC, respectively.
280 E. RAFIQUE et al.
Fig. 2 Relationships between the Zn concentrations of leaves
(a) and seeds (b) and the relative seed yields of three pea culti-
vars (Green feast, Climax and Meteor).
higher in Meteor compared with the other two culti-
vars, i.e., Green feast and Climax. Seed Zn concen-
trations ranged from 34 to 57 mg kg−1in Green feast,
from 39 to 66 mg kg−1in Climax, and from 42 to 72 mg
kg−1in Meteor at Talagang. The extent of variation
in Zn concentration was relatively lower at NARC as it
ranged from 35 to 52 mg kg−1in Green feast, from 41
to 61 mg kg−1in Climax, and from 44 to 70 mg kg−1in
Meteor. Seeds of pea may be taken as a diagnostic tis-
sue like other crops because of a range of Zn concentra-
tion and better analytical precision (Rashid and Fox,
1992). Internal Zn requirement of seed was estimated
by plotting seed Zn concentration versus relative seed
yield (Fig. 2). Data of 2 years at both locations were
pooled in the present study. Estimated internal Zn re-
quirement associated with the 95% of maximum seed
yield was 45 mg kg−1for Green feast, 51 mg kg−1for
Climax, and 60 mg kg−1for Meteor, respectively.
The use of seed as diagnostic tissue has several ad-
vantages like easy collection, cleaning, and processing.
Moreover, date of seed sampling is not critical, analy-
zing mature seeds may minimize differences in Zn con-
centration due to stage of development, and seed use
may increase analytical precision because seeds con-
tain little silica and are well suited to dry ashing. A
probable disadvantage for seed use is that while leaf
analysis might be useful for current crop, seed analy-
sis can only be used to diagnose former problems and
apply for future strategy.
Critical level of Zn in diagnostic plant parts es-
pecially in seed is not well documented in literature.
However, Huett et al. (1997) reported 61 mg Zn kg−1
as the adequate concentration in pea seed and 53 mg
Zn kg−1in leaflets at early flowering stage. A relatively
wide range, i.e., 25–100 mg Zn kg−1, has been reported
by Jones et al. (1991) as the sufficient concentration in
recent fully developed leaflets at first bloom. The re-
sult of this study indicates that critical concentration
varies with cultivars and was not the same in all culti-
vars even grown under the same conditions. Variation
in critical levels of nutrients can occur most proba-
bly due to differences in crop genotypes and plant age
(Jones et al., 1991). It is obvious that no single critical
Zn concentration can be used to predict Zn deficiency.
Further, plant’s internal requirement of a nutrient may
also vary because of plant growth interaction with the
supply of other nutrients and with environmental fac-
tors such as temperature, CO2concentration, diseases
and pests, and errors involved in derivations (Munson
and Nelson, 1990; Smith and Loneragan, 1997). Criti-
cal values can also vary with environmental factors af-
fecting Zn uptake, such as water, soil texture, and soil
pH (Sims and Johnson, 1991). It is not only the exter-
nal factors but also the plant species differing in their
abilities to absorb Zn from the same soil that affect the
plant in accumulating Zn (Cakmak et al., 1997).
CONCLUSIONS
Despite the general perception regarding pea’s less
sensitivity to Zn deficiency, Zn use enhanced pea’s pro-
ductivity in alkaline calcareous soils. Zinc centrations
of pea leaves as well as mature seeds appeared to be
a good indicator of soil Zn availability status. Exten-
sive research work has established the utility of Zn ap-
plication in agronomic crops. However, application of
micronutrients such as Zn, B, and Fe is not commonly
being practiced for vegetable crops. The results of this
study clearly demonstrated the beneficial effect of Zn
application on vegetable yields and plant tissue Zn con-
centrations.
ACKNOWLEDGEMENTS
This research is supported by the project of Mi-
cronutrient Management for Sustaining Major Crop-
ping Systems and Fruit Orchards, which was funded
by Ministry of Food, Agriculture and Livestock, Go-
ZINC APPLICATION AFFECTS PEA ZINC AND YIELD 281
vernment of Pakistan, Islamabad. We are grateful to
Mr. Muhammad Hayat of Land Resources Research
Institute, National Agricultural Research Centre, Is-
lamabad for assistance in analytical work and Mr.
Shamas-Ud-Din Sial of Land Resources Research In-
stitute, National Agricultural Research Centre, Isla-
mabad for assistance in analytical and field work.
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