Vol.2, No.2, 94-103 (2011)
doi:10.4236/as.2011.22014
C opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Sciences
Response of different corn populations to fertigated
nitrogen and certain micronutrients in sandy soil
Ahmed Attia1*, Charles Shapiro2, Mohamed Gomaa1, Ragab Aly1, Abd El-Raham Omar1
1Agronomy Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt; *Corresponding Author:
2Northeast Research and Extension Center Haskell Agricultural Laboratory, University of Nebraska-Lincoln, Concord, USA.
Received 7 November 2010; revised 16 February 2011; accepted 7 March 2011.
ABSTRACT
A field study was conducted during 2008 and
2009 at El-Khattara farm station, Zagazig Uni-
versity, Sharkyia, Egypt (30°36' N, 32°15' E) to
determine the effect of three N rates (214, 273,
and 333 kg·N·ha–1), four micronutrients spray
treatments (Check, Zn, Mn, and Zn + Mn), and
three planting density levels (4.76, 5.7 1, and 6.66
plant·m–2) on growth and grain yield of corn (Zea
mays, L). The soil was sandy (Entisols) and
groundwater was used for irrigation. Response
to N was maximized to 214 kg·ha–1 without a
significant effect on most growth traits and
grain yield. Agronomic efficiency of N use for
grain yield w as negatively related to N rate (r2 =
0.49). Application of micronutrients had no ef-
fect on most gro wth and yield characters excep t
a significant increase by 9.5, 8.7, and 9% in plant
weight (g·plant–1), biomass yield (kg·m–2), and N
agronomic efficiency for biomass yield, respec-
tively. Growth was decreased by increasing
plant density without affecting harvest index,
agronomic efficiency, biomass yield, and grain
yield. The application of Zn to the highest maize
plant density increased grain yield by 16% as
compared to the check. It is recommended, as
predicated by the linear model, that N fertigation
rate should be around 220 kg·ha–1 with plant
density of 6.66 plant·m–2 accompanied by Zn
application for maximum irrigated corn grain
yield in sandy soil. Abbreviations: DAS, days
after sowing; LA, leaf area; LAI, leaf area index;
RPP, relative photosynthetic potential; HI, har-
vest index; BW, plant weight g·plant–1, GYP,
grain yield g·plant–1, BYM, biomass yield kg·m–2,
GYM, grain yield kg·m–2, NAE, nitrogen agro-
nomic efficiency.
Keywords: Fertigation; Micronutrients; Plant
Density; Sandy Soil
1. INTRODUCTION
The increased demand of maize (Zea mays, L.) by
baking and cellulosic biomass industries requires ex-
panding the growing areas to newly reclaimed and sandy
soils. Drip irrigation system has become a popular tech-
nique to reduce the amount of water and fertilizers ap-
plied [1]. Growing corn in rotation with other field and
vegetable crops in sandy soil secures a sustainable agri-
culture to reduce the gap between production and con-
sumption.
Though, sandy soil characterized with low cation ex-
change capacity and soil organic matter [2] it was proved
that fertigation increases fertilizer use efficiency since
nutrients are applied to the active root zone which re-
duces losses of nutrients through leaching or soil fixation
[3]. There are mixed literature reviews on corn response
to different N levels. For instance, under similar condi-
tion to the present study corn grain yield has been sig-
nificantly affected by increasing N rate from 190 to 380
kg N ha–1 [4] while plateaued at 180 kg·ha–1 fertigation
rate in another study [5]. Also, a positive response for
corn grain yield has been recorded for N application up
to 285 kg N ha–1 [6]. These inconsistencies in results
may appear as soil characteristics and other environ-
mental conditions change. As sandy soil has poor water
and nutrients retention while the high N requirement of
corn, adequate level of N must be applied to insure suf-
ficiency. On the other side, there is increased concern
about groundwater pollution by nitrate (NO3-N) which
attributed to excessive N fertilizer application [7]. There
fore, determining crop response to narrow range of N
levels is so important for more understanding to corn N
requirement for these newly developed areas.
The importance of foliar fertilization with different
macro and micronutrients on growth, photosynthetic
activity of leaves, and grain yield has been reported by
[8,9]. Deficiency of Mn induces growth inhibition,
chlorosis and necrosis, early leaf fall, and low reutiliza-
tion [10]. Some workers reported a significant increase

A. Attia et al. / Agricultural Sciences 2 (2 011) 94-103
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95
in corn growth and yield parameters by micronutrients
application. Under sandy soil conditions, ear leaf area,
plant height, stem diameter, and HI were increased by
the application of Zn as Zn-EDATA 12%, Mn as
Mn-EDATA 12%, and Fe as Fe-HEEDTA 12%, as solu-
tion spray on maize [11-13]. Also, [14] stated that using
microelements raised plants tolerance for water deficit
stress conditions which increased th e yield. Dry areas of
high pH and low organic matter soils promote Zn defi-
ciencies in corn [15,16] which makes the need for these
micronutrient s bei n g m ore pr o no u nced .
Maize grain is a result of grain yield per plant and
number of plant density per unit area. Therefore, study-
ing the effect of plant density on grain yield is necessary
as hybrids and technology improve. Modern hybrids
have higher radiation use efficiency because of higher
LAI at silking which increases their response to high
plant densities [17]. Results of previous studies indicated
that optimum population of the used cultivar ranged
from 5.0 to 5.6 plant·m–2 when grown in clay soils [18].
Across diverse environments, several studies recorded
different r espons es of corn to plan t den sity. For example ,
corn grain yield was optimized by the combination be-
tween plant density of 69000 plant·ha-1 and 250 kg·N
rate·ha–1 [19]. While [20] reported a positive respon se to
plant density ranged from 82000 to 116000 plant·ha–1.
Thus, investigating the growth of individual maize plant
in sandy soil is important for maximum growth and
grain yield especially with the adop tion of new irrigation
system.
The objectives of this study were to determine the op-
timum combination of N rate and plant density with and
without Mn and Zn application on growth, photosyn-
thetic partitioning parameters, and yield related charac-
teristics in irrigated corn under sandy soil conditions.
2. MATERIAL AND METHODS
2.1. Site Characteristics
A field experiment was conducted for two growing
seasons (2008 and 2009) at the Agricultural Research
Stations of the Faculty of Agriculture, Zagazig Univer-
sity in El-Khattara, Sharkyia Governorate, Egypt (30°36'
N, 32°15' E) and the farm is located at an elevation of 13
m above the sea level. The average minimum and maxi-
mum monthly temperature, precipitation, relative hu-
midity, and wind speed during the summer seasons of
2008 and 2009 are shown in Ta b l e 1 . According to US
soil Taxonomy [21] the sandy high pH soil is an Entisol
with low cation exchange capacity (Table 2).
2.2. Experimental Design and Treatments
The experimental design was split-split p lot with three
replications (Figure 1). The main plot treatments were
three nitrogen rates (N) of 214, 273, and 333 kg·N·ha–1,
the sub plot treatments were four foliar spray micronu-
trients treatments (S) of Zn, Mn, Zn + Mn, and no Zn
and Mn applied (check). The sub-sub treatments were
three plant densities (D) of 4.76 (low), 5.71 (medium),
Table 1. Average maximum and minimum monthly temperature, precipitation, relative humidity, and wind speed
during 2008-2009 summer in El-Khattara, Egypt.
Month
Max Tem. (C˚) Min Tem.( C˚)Percipitation (mm) Relative humidity % Wind speed (km hr–1)
May
June
July
August
September
34.0
37.0
38.8
35.7
32.0
19.0
20.4
22.4
20.8
19.4
0.25
0.10
0.00
0.00
0.00
50
49
56
60
59
14.68
14.68
15.75
13.89
14.48
Table 2. Mechanical and chemical analysis of the experimental field (0 -
0.3 m soil depth) in El-Khattara, Sharkyia, Egypt 2008.
Properties Cation and Anion
Mechanical analysis
Sand
Silt
Clay
Soil Texture
Chemical analysis
N mg kg–1
P mg kg–1
K mg kg–1
Mn mg kg–1
Zn mg kg–1
SOM %
pH
91.87
6.03
2.1
Sandy
4.05
45.5
65.5
1.87
1.05
0.07
8.02
(meq/100 g soil)
Ca+2
Na+2
Mg+2
K+2
(meq/100 g soil)
CO–3
HCO–3
Cl–
SO–4
0.16
0.39
0.18
0.04
0.0
0.18
0.22
0.37

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Figure 1. Layout of one replicate showing the study factors and plant distribution in the blocks.
6.66 (high) plant·m–2. Nitrogen was applied as ammo-
nium sulfate (20.5% N and 24% S) through the irrigation
system in five equal doses from 21 DAS (V3) to 50 DAS
(V9) [22].The solution spray of micronutrients treatment
was applied in two applications the 1st was at 30 DAS
(V4) and the 2nd was at 45 DAS (V8). Tank volume 20
L water were used for each treatment since Zn and Mn
sprayed on plant foliage at a rate of 150 g·ha–1 in the
form of EDATA. Plant densities were given by reducing
hill spacing form 42, 35, to 30 cm for low, medium, and
high densities, respectively.
The sub-sub plot size was 3 m by 4 m. All plots were
fertilized with 240 kg·ha–1 calcium superphosphate
(15.5% P) and 129 kg·ha–1 potassium sulfate (48% K
and 19% S). The phosphorous and potassium were
broadcast applied at seeding around the drip lines.
Each plot has three drip lines space one m apart with
drippers spaced 0.35 m apart within the line and each
dripper had a flow rate of 4 L·ha–1. Irrigation was initi-
ated two days before sowing with a rate of 1.1 cm·day–1
until tasseling, 2.3 cm·day–1 from tasseling to R3, and
1.1 cm·day–1 from R3 to R5. Ground water was pumped
from 30 m soil depth and had an SAR of 11.7 (Table
3).The soil and ground water were analyzed by the cen-
tral laboratory of the faculty of Agriculture, Zagazig
University.
A three way cross corn hybrid (TWC 321 from Gem-
meza Research Station, Cairo, Egypt) was manually
planted in May 22 on both sides of the drip line with row
spacing of one m apart. The preceding crops were fallow
and garlic in the 1st and 2nd seasons, respectively. Three
weeks after planting (V3) seedling were thinned to one
plant per hill. Weed control consisted of hand weeding
throughout the season to control any weeds. Agrinate
90% SP (Methomy l) insecticide was applied at V3 at a
rate of 715 g·ha–1 for Aphids control.
2.3. Field and Plant Measurements
At silking stage (R3) five contiguous plants plot–1
were used for measurements; Leaf area plant–1 (LA/plant
dm2), such trait was computed as Leaf area = 0.75 × (L ×
W) where L is the blade length (cm) and W is the maxi-
mum width of the blade (cm) [23]. Leaf area index was
determined as: leaf area plant–1 (dm2)/land area plant–1
(dm2).
Plants were cut at the surface from the two rows on
either side of the middle irrigation line on September 25
in both seasons. Ears were manually harvested, shelled,
and weighed. Subsamples of grain were oven dried at
60˚C for adjusting grain yield to 155 g·Kg–1 water con-
tent. Stover sample were air dried for three weeks after
harvest at 25.7˚C mean temperature. Biomass yield was
calculated from stover and grain weights. Then the fol-
lowing characters were determined ;
Grain yield·dm–2 LA (g·dm–2), it was determined as:
GY at 15.5% moist (g plant–1)/dm2 of LA.
Relative photosynthetic potential (RPP) for: a) grain
yield was determined as; RPPgrain = Ygrain/plant/LAI
(g/LAI), b) biomass yield was determined as; RPPbio =
RPPbio/plant/LAI (g/LAI), this parameter were computed
3 N × 4 S × 3 D = 36 treatments
kg N/ha
Sub-plot
Fertilizer tank
Sub-sub plot
1.5 m
space
Sub
irrigation
line
3 m
4 m
Main irrigation line
Double rows of corn
p
er irrigation line
0.5 m space
214.2 333.2 273.7

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Table 3. Ground water analysis in the experimental field site, El-Khattara, Sharkyia, Egypt 2008.
Properties Concentration Properties Concentration
EC
pH
HCO3–1
Mg+2
K+
(dsm–1)
(mol./L)
(mol./L)
(mol./L)
(mol./L)
1.53
8.31
7.61
1.09
0.15
SO4–2
Cl–1
Ca+2
Na+2
SAR
(mol./L)
(mol./L)
(mol./L)
(mol./L)
(mol./L)
1.59
6.07
1.27
12.87
11.73
using the procedure outlined by [24]. Both RPP traits are
describing the contribution of leaf area index into bio-
logical and grain yield.
Harvest index (HI) was determined as; grain yield
(g·plant–1)/biomass yield (g·plant–1). HI determines the
total dry matter partitioned into grain yield.
Grain yield (g·plant–1) at 15.5% moist. Plant weight
(g·plant–1) was calculated from cob, stover, and grain
weight per plant. Biomass yield (kg·m–1). Grain yield
(kg·m–1). Nitrogen agronomic efficiency (NAE) for: a)
Grain yield was determined as: Kg grain Kg–1 added N,
b) Biomass yield was determined as: Kg biomass Kg–1
added N.
2.4. Data Analysis
Crop performance parameters were analyzed using the
SAS PROC GLM procedure to develop the ANOVA for
a split-split plot design over years. The PROC MIXED
procedure was used to make tests of simple effects [25]
with N rates as the main factor, micronutrients spray as
the split factor, and plant density as the split-split factor.
Mean separation of treatment effects was measured us-
ing Fisher’s protested least significant difference (LSD)
test. Nitrogen fertilization and plant d ensity were treated
as a quantitative variab les and solution spray was treated
as a qualitative variables. The study factors were treated
as fixed effects, and year and replicates were treated as
random effects.
3. RESULTS AND DIS CUS SIONS
3.1. Growth Parameters
Linear decrease in LA plant–1 (Figure 2(a)) and linear
increase in LAI (Figure 2(b)) were recorded by increas-
ing the plant density since the dense planting had the
lowest LA plant–1 with the highest LAI values. These
results could be attributed to the intra-plant competition
for the elements essential for production such as light,
water and nutrients. This in agreement with the results
obtained by [26] who reported that linear increase in
LAI with increasing corn population from 60 up to 90
thousand plant·ha–1.
Neither N rate nor applying foliar fertilization influ-
enced LA plant–1 and LAI (Ta b l e 4 ) while [27] found a
differences in LAI by changing N rate. As shown in the
chemical analysis, the soil has 1.05 and 1.87 mg·kg–1
available Zn and Mn, respectively. This might account
for the insignificant effect of added both microelements
on plant LA and LAI observed herein.
According to the combined analysis, the N × D inter-
action significantly affected LA plant–1 (Table 5). Under
both low and medium densities, N rate did not affect LA
plant–1 but was significantly smaller by 12.7% for the
dense plants fertilized with the lowest nitrogen rate.
These results emphasize the importance of considering
both nitrogen and planting density effect on the variable.
In the pooled data, plant growth factors; RPPgrain, RPPdry
mass, and GY dm–2 LA (g·dm–2) were not affected by N
rate and micronutrients application either alone or their
interaction (Table 4). Increasing planting density sig-
nificantly decreased these parameters where, a gradual
decrease in both GY dm–2 LA (g·dm–2) and RPP traits by
increasing the planting density from the low to the high
density. The decreases in such potentials could be ex-
plained through the increase in harmfu l effect of shading
with the increase in LAI as the population of corn was
increased.
The first order interactions were without significant
effect on HI over years but HI was affected by YR × S
interaction (Table 6). The parameter was increased by
6.5% and 6.6 % due to Zn + Mn treatment compared to
check in 2008 and 2009, respectively (Figure 3). The
high available residual soil P may be restricted absorp-
tion and assimilation of both these micronutrients which
has caused unbalanced nutrition. This was more pro-
nounced in the 1s t season bu t plan ting after garlic in the
2nd season can help in solubility of fixed soil P through
its association with Mycorrhizae. These findings sus-
tained those outlined by [28]. Meantime, there was also
a significant interaction between N × S since the HI had
a gradual increase with increasing N rate for plants
sprayed with Zn (Table 7).
3.2. Yield Determination Parameters
A slight increase was noticed in both BW and GYP
due to the application of the 273 kg·ha–1 N rate but not
enough to be statistically significant (Table 6). These
results are in agreement with the results obtained by [26]
where grain DM of maize response for raising N rate
from 75 to 225 kg·N·ha–1 was similar. There was a sig-
nificant effect for the foliar fertilizatio n on BW (Table 6)

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Table 4. Analysis of variance for the effect of nitrogen (N), foliar fertilization (S), and plant density (D) over two years (YR).
Source of variance df LA plant–1 LAI GY dm–2 LA
(gm·dm–2) RPPgrain (g·LAI–1) RPPdry mass (g·LAI–1)
P > F
YR
N
YR × N
S
YR × S
N × S
YR × N × S
D
YR × D
N × D
YR × N × D
S × D
YR × S × D
N × S × D
YR × N × S × D
1
2
2
3
3
6
6
2
2
4
4
6
6
12
12
0.006
0.531
0.121
0.294
0.457
0.333
0.268
0.002
0.133
0.020
0.810
0.755
0.931
0.110
0.495
0.109
0.740
0.176
0.270
0.666
0.385
0.069
< 0.0001
0.051
0.061
0.631
0.970
0.398
0.529
0.132
0.015
0.393
0.293
0.574
0.634
0.308
0.625
0.001
0.259
0.209
0.597
0.067
0.841
0.178
0.720
0.012
0.417
0.437
0.731
0.798
0.212
0.716
< 0.0001
0.149
0.193
0.712
0.205
0.413
0.156
0.657
0.005
0.203
0.594
0.385
0.223
0.378
0.951
< 0.0001
0.052
0.658
0.333
0.340
0.321
0.101
0.963
Ta ble 5. Leaf area plant–1 (dm2) as affected by nitrogen levels and plant density interac-
tion over years.
N levels Plant density
(kg ha–1) low medium high
214 93.6 Aa 91.9 Aa 8 3.5 Bb
274 95.7 Aa 89.3 Ba 90.9 ABa
333 90.9 ABa 94.3 Aa 86.3 Bab
Treatments means are av eraged ov er micronut rients spr ay. Means in ro w within N level followed b y the same
capital letter are not significantly different at P = 0.05 according to Fisher ’s protested LSD test. Means in col-
umn withi n pl ant dens it y fol lowed by t he sa me sm all l ett er ar e no t s ign ifi cant ly differen t at P = 0.05 accordi ng
to Fisher’s LSD test.
Table 6. Analysis of variance for the effect of nitrogen (N), foliar fertilization (S), and plant density (D) over two years.
Source of df Harvest
Index GYP BW BYM GYM
NAE for
BYM NAE for GYM
variation (g·plant–1) (g·plant–1) (kg·m–2) (kg·m–2) (kg bio. Kg–1 N) (kg grain kg–1 N)
P > F
YR
N
YR × N
S
YR × S
N × S
YR × N × S
D
YR × D
N × D
YR × N × D
S × D
YR × S × D
N × S × D
YR × N × S × D
1
2
2
3
3
6
6
2
4
4
4
6
6
12
12
0.008
0.534
0.169
0.623
0.004
0.020
0.011
0.612
0.388
0.467
0.140
0.213
0.935
0.549
0.685
0.128
0.238
0.719
0.207
0.946
0.520
0.554
< 0.0001
0.639
0.118
0.397
0.131
0.778
0.024
0.466
0.039
0.250
0.234
0.058
0.254
0.578
0.954
< 0.0001
0.842
0.407
0.254
0.390
0.839
0.016
0.835
0.004
0.136
0.106
0.038
0.401
0.365
0.957
0.291
0.052
0.366
0.401
0.243
0.404
0.164
0.723
0.234
0.359
0.525
0.146
0.732
0.147
0.776
0.351
0.068
0.368
0.101
0.724
0.311
0.013
0.143
0.004
< 0.0001
0.687
0.037
0.480
0.452
0.982
0.268
0.050
0.486
0.333
0.235
0.489
0.137
0.857
0.294
< 0.0001
0.707
0.184
0.886
0.244
0.851
0.316
0.062
0.458
0.051
0.594
0.471
0.005
0.191
since Zn treatment was higher by 8.72% than check
treatment. Meanwhile, others have reported significant
increase in maize grain yield and its attributes by foliar
spray of microelements [13,29]. The results of both sea-
-sons and their combined analysis clearly represented a
significant decrease in both BW and GYP regarding
varying the plant density (Table 6). It was found a lin ear
decrease in BW as a result of increasing plant density
(Figure 4(a)). Whereas, [30] stated that the planting
density of 6.6 and 8.3 plants·m–2 recorded 23.5 and

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(a) (b)
Figure 2. LA plant–1 (dm2) (a) as a negative linear function in the pooled data and LAI (b) as a positive linear function
in the pooled data.
2008 2009
Year
HI
0.00.1 0.2 0.3 0.40.5
Check
Mn
Zn
Zn + Mn
Figure 3. Effect of YR × S interaction on harvest index in both seasons. P > F = 0.035 and 0.020
in 2008 and 2009, respectively. Error bars represtent the standard error.
40.0% higher GY of pop corn compared with 5.55 plants
m–2.
It is evident from the results in (Table 6) that none of
the first order interactions affected significantly both
BW and GYP in both seasons and their combined analy-
sis. These results clearly indicate that the main effect of
plant density on both traits masked and dominated any
other interacting effects between each two of the factors
under study.
Varying N rate from 214 up to 333 kg·ha–1 did not af-
fect BYM and GYM (Table 6) however, there was a
slight increase of 6.83% and 3.2% in favor of 273 kg N
ha–1 rate compared to 2 14 kg N ha–1 for BYM and GYM,
respectively. Similar findings have been found by [31]
where irrigated corn in sandy soils did not response for
N application more than 185 kg·ha–1 while others re-
ported significant increase in grain yield as a result of
raising N rate from 190 to 380 kg·ha–1 [4].
Biomass yield m–2 has been affected by foliar fertili-
zation of micronutrients (Table 6) and there was 7.0%
HI
2008 2009
Year

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increase in GYM due to Zn application compared with
the check (P > F, 0.146). The beneficial effects of Zn
addition can be achieved partially through its activation
of carbonic anhydrase as a catalytic enzyme, conse-
quently CO2 fixation in carbohydrate metabolism. In
addition, Zn deficiency may have a more dramatic effect
on the rate of photosynthesis in C4 compared with C3
plants.
Biomass yield m–2 and GYM were not affected by
plant density (Table 6). Though, analysis separates by
year showed a significant effect for GYM in 2008 with
the following respon se equ ation; y = – 20.864 + 7.80 x –
0.686 x2 this equation indicated that GYM could have
been maximized at 1.307 kg·m–2 with a planting density
of 5.71 plants·m–2 (Figure 4(b)). This possibly could be
attributed to the increased po llen to silk ing interv als and
the increased barrenness at the high planting density.
These results disagree with [20] since they reported
maximum maize grain yield at plant density of 8.2 to
11.6 p lants·m–2. There was YR × D interaction effects on
BYM showed greater response due to the medium or
high plant density in 2008 (Table 8).
There was N × S × D interaction effects on grain yield
showed differences in N response depending on spray
and densities but, generally there was a negative or con-
stant slope of the line by increasing N rate (Figure 5).
Across N rates and densities, Zn treatment produced
greater grain yield of 11.6 Mg·ha–1 compared to 10.0
Mg·ha–1 by check treatment. It is noteworthy that apply-
ing 214 kg N ha–1 and Zn to the highest plant density
prouced the greatest grain yield of 12.5 Mg·ha–1.These
results suggest a beneficial effect of Zn application on
corn grain yield as sandy high pH soil promotes Zn defi-
ciency. Zinc has an important role on basic plant life
process such as N metabolism, photosynthesis, carbon
anhydrase activity, and resistance to abiotic and biotic
stress. The results agree with the finding of [32] since
corn grain yield has increased by 18 % as a result of ap-
plying 1.0 to 1.5 kg·ha–1 of Zn. Increasing N rate did not
result in greater grain yield which might be related to
nitrogen losses by leaching. Similar results have been
reported by [33] where changing N rate from 128 to 278
kg·ha–1 did not affect either biomass or grain yield.
The results of both seasons and their combined analy-
sis for NAE for GYM and NAE for BYM indicated that
there was a consistent reduction in NAE when N rate
increased from 214 up to 333 kg·ha–1 (Tabl e 6 ). Since,
as in the pooled data, increasing N rate from 214 to 273
and to 333 kg·ha–1 gradually decreased the NAE from
32.03 to 26.78 and to 20.90 kg·bio. ·kg–1 N applied and
form 11.80 to 9.89 and to 7.67 kg grain kg–1 N, in re-
spective order. This agrees with the results obtained by
[34] and [35].
The main effect of S significantly affected NAE for
BYM (Ta b le 6 ) where Zn treatment increased the vari-
able by 9.04% compared to the check. This matches the
results obtained by [36] that NAE has significantly in-
creased by Zn application. Nitrogen agronomic effi-
ciency significantly affected by YR × D interaction but
the analysis separates by year did not show a significant
effect (Ta bl e 8 ). In addition, N × S × D interaction sig-
nificantly affected NAE for GYM (Table 6) being in-
Table 7. Harvest index as affected by nitrogen and spray interaction in 2009.
N levels Micronutrients Treatment
(kg·ha–1) Check Zn Mn Zn + Mn
214 0.401 Aa 0.381 Cc 0.402 Aa 0.388 Bc
273 0.349 Dc 0.390 Bb 0.379 Cc 0.420 Aa
333 0.392 Cb 0.434 Aa 0.388 Db 0. 40 8 Bb
Treatments means are averaged over plant density. Means in row within N levels followed by the same capital letter are not sig-
nificantly different at P = 0.05 according to Fisher’s protest LSD test. Means in column within micronutrients treatments fol-
lowed by the same letter are not significantly different at P = 0.05 according to Fisher’s protest.
Table 8. Effect of plant density on BYM and NAE for GYM in 2008 and 2009.
Variable Plant density P > F
BYM low Medium Kg·m–2 high
2008
2009 3.44 2.34 3.71 2.25 3.70 2.32 0.054 0.533
NAE for BYM Kg m –2
2008 30.71 33.13 33.09 0.058
2009 21.19 20.18 21.13 0.394

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101
(a) (b)
Figure 4. Plant weight (g·plant–1) (a) as a negative linear function of plant density in the pooled data and GYM (kg·m–2) (b) as a
quadratic function of plant density in 2008.
Figure 5. Effect of N × S × D interaction on grain yield (Mg·ha–1) over seasons.
Shaded areas are 95% confidence intervals of the response curve.
favor of applying 214 kg N ha–1 and Zn with the low
density.
4. CONCLUSIONS
Expanding corn cultivatio n through sandy arid soils of
Egypt based on drip irrigation system can help in; di-
minishing the ga p between consumption and productio n,
saving water, and better efficient use for the other agro-
nomic inputs. Corn is so vulnerable to N deficiency and
its grain yield greatly affected by the population. In the
meantime, crops grown in sandy soils with high pH lev-
els suffer from malnutrition with certain micronutrients.
y = 809.20 – 47.29 x
r2 = 0.38 y = – 20.864 + 7.80 x – 0.686 x
2
r2 = 0.97
Predicted
Predicted

A. Attia et al. / Agricultural Sciences 2 (2 011) 94-103
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102
Accordingly, these three agronomic aspects are of prior-
ity for studying.
The results of this study showed a maximum yield re-
sponse for N application up to 214 kg·ha–1 since there
was no significant effect due to any extra addition of N
on all the studied traits, except for both NAE traits
which gradually reduced as the N rate increased.
Co-application of the lowest fertigated N rate with Zn to
the highest plant density produced the greatest grain
yield of 14.4 Mg·ha–1, along with irrig ation frequency as
described in the material. Thus, splitting 214 kg N ha–1
considers the best rate and there is no need for further
addition of N under the study conditio ns especially when
it could result in ground water contamination by nitrate
N [37].
Micronutrients spray significantly affected BW, BYM,
NAE for BYM, and GYM in favor of Zn treatment
without response for the rest of the study characteristics.
Most of the study parameters have been affected by in-
creasing the plant density from 4.76 to 6.66 plant·m–2
except biomass and grain yield per m2 which may indi-
cate that a higher plant density might produce more
biomass and grain yield per unit area. These results arise
that more investigation is required in order to fully un-
derstanding the interaction between production factors
and optimum plant density for maximizing corn biomass
and grain yield under sandy so il conditions.
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