Embed Size (px)
Citation preview
ORIGINAL ARTICLE
Crop and soil nitrogen responses to phosphorusand potassium fertilization and drip irrigationunder processing tomato
K. Liu • T. Q. Zhang • C. S. Tan • T. Astatkie •
G. W. Price
Received: 24 November 2011 / Accepted: 30 April 2012 / Published online: 13 May 2012
� Springer Science+Business Media B.V. 2012
Abstract Shortage of water or nutrient supplies can
restrict the high nitrogen (N) demand of processing
tomato, leaving high residual soil N resulting in
negative environmental impacts. A 4-year field exper-
iment, 2006–2009, was conducted to study the effects
of water management consisting of drip irrigation (DI)
and non-irrigation (NI), fertilizer phosphorus (P) rates
(0, 30, 60, and 90 kg P ha-1), and fertilizer potassium
(K) rates (0, 200, 400, and 600 kg K ha-1) on soil and
plant N when a recommended N rate of 270 kg N ha-1
was applied. Compared with the NI treatment, DI
increased fruit N removal by 101 %, plant total N
uptake by 26 %, and N harvest index by 55 %.
Consequently, DI decreased apparent field N balance
(fertiliser N input minus plant total N uptake) by 28 %
and cumulative post-harvest soil N in the 0–100 cm
depth by 33 %. Post-harvest soil N concentration was
not affected by water management in the 0–20 cm
depth, but was significantly higher in the NI treatment
in the 20–100 cm depth. Fertilizer P input had no
effects on all variables except for decreasing N
concentration in the stems and leaves. Fertilizer K
rates significantly affected plant N utilization, with
highest fruit N removal and plant total N uptake at the
200 kg K ha-1 treatment; therefore, supplementing K
had the potential to decrease gross N losses during
tomato growing seasons. Based on the measured
apparent field N balance and spatial distribution of
soil N, gross N losses during the growing season were
more severe than expected in a region that is highly
susceptible to post-harvest soil N losses.
Keywords Nitrogen balance � Nitrogen harvest
index � Nitrogen uptake � Soil profile nitrogen �Drip irrigation
Abbreviations
DI Drip irrigation
K Potassium
N Nitrogen
Ncum Cumulative soil inorganic nitrogen
Nmin Soil inorganic N concentration
NCSL Nitrogen concentration of stems and
leaves
NHI Nitrogen harvest index
NO3-–N Nitrate nitrogen
NI Non-irrigation
P Phosphorus
K. Liu
Department of Soil Science, University of Manitoba,
Winnipeg, MB R3T 2N2, Canada
T. Q. Zhang (&) � C. S. Tan
Greenhouse and Processing Crops Research Center,
Agriculture and Agri-Food Canada, 2585 County Road 20
E., Harrow, ON N0R 1G0, Canada
e-mail: [email protected]
T. Astatkie � G. W. Price
Department of Engineering, Nova Scotia Agricultural
College, P.O. Box 550, Truro, NS B2N 5E3, Canada
123
Nutr Cycl Agroecosyst (2012) 93:151–162
DOI 10.1007/s10705-012-9506-0
Introduction
Processing tomatoes require adequate supplies of
water and a proper balance of nutrients to achieve
optimum yields (Patane and Cosentino 2010; Zhang
et al. 2010). As described by Hartz and Bottoms (2009),
nitrogen (N) uptake by drip-irrigated (DI) processing
tomatoes varies from 222 to 466 kg N ha-1. The
nutrient uptake ratio of potassium (K) to N for tomato
ranges from 1:1 to 2.5:1 (Tapia and Gutierrez 1997;
Huang and Snapp 2009), suggesting a higher require-
ment for K than N. In Florida, state-wide average rates
of fertilizer N, phosphorus (P), and K used by tomato
growers were 300 kg N ha-1, 87 kg P ha-1, and
461 kg K ha-1, respectively (Florida Agricultural
Statistics Service 1999). Gunes et al. (1998) reported
synergistic effects of N, P, and K on tomato growth,
suggesting that a balance of P and K nutrients enhances
N utilization in plants supplied with adequate N.
In addition to fertilizers P and K, processing tomato
responses to fertilizer N is strongly affected by water
supply (Tilling et al. 2007). In a study of fresh
marketable tomatoes, Santos (2009) reported that
sufficient irrigation reduced N application rates from
336 to 224 kg N ha-1 without significant decline in
yields. A reduced N requirement under sufficient
irrigation is explained by increased N availability from
the soil and fertilizer under conditions of adequate soil
moisture (Kim et al. 2008). Similarly, Gheysari et al.
(2009a) and Santos (2009) reported that some negative
effects of water stress on crop performance are
remedied by an adequate supply of fertilizer N.
However, in regions susceptible to N losses, sub-
stantial increases in N fertilization are associated with
negative environmental effects, such as N induced
water contamination.
South-western Ontario has been identified as a
region with a high risk of N leaching losses (De Jong
et al. 2007). The average annual precipitation at the
study sites from 1991 to 2005 was 780 mm, but only
289 mm occurred during the tomato growing season
between June and September (unpublished data col-
lected at the weather station of Agriculture and Agri-
Food Canada, Harrow, ON), suggesting a water
shortage during the tomato growing season and a
water surplus during the non-growing period. In order
to overcome rainfall deficits, DI is increasingly
practiced with processing tomato in south-western
Ontario. Using DI allows water applications to be
precisely controlled to meet crop demands. During the
non-growing season, water surplus may trigger con-
siderable soil N losses leading to degradation of water
quality in surrounding water systems. De Jong et al.
(2007) estimated that approximately 74 % of soil
inorganic N measured at the end of a crop growing
season is leached into drainage water over the winter
period in the study region. Therefore, it is important to
assess residual soil N after crop harvests to help
develop suitable management practices, such as
irrigation, which potentially mitigate ground water
contamination caused by high residual soil nitrogen.
High residual soil N after processing tomato is
harvested has been reported to be a function of
excessive N fertilizer applications (Florida Agricul-
tural Statistics Service 1999) and low apparent N
recovery by the plants (Scholberg et al. 2000).
Numerous studies have demonstrated N leaching
losses both during crop growing seasons and post-
harvest periods (Gehl et al. 2006; Zotarelli et al. 2007,
2009). In addition to measuring leaching losses of N
from agricultural drainage tiles, N concentration in the
soil profile are also used to evaluate potential leaching
losses (Gehl et al. 2006; Zhang et al. 2011). Hence,
evaluating spatial distribution of N in the soil profile at
the end of a crop growing season, together with plant
N responses, will enhance N management in process-
ing tomatoes production systems.
Nitrogen application rates are known to affect plant
and soil N in tomato production systems (Hebbar et al.
2004; Vazquez et al. 2006; Zotarelli et al. 2009; Zhang
et al. 2011). A recent study recommended N fertilizer
applications of 271 kg N ha-1 for drip fertigated
processing tomatoes (Zhang et al. 2010), approxi-
mately two times greater than previous N recommen-
dations. In contrast, increased plant N use efficiency in
tomato has been reported at lower fertilizer N rates
with the application of fertilizer K (Fitzpatrick and
Guillard 2004). This suggests that successful process-
ing tomato production relies on an integrated nutrient
management approach where balanced nutrients
rather than any single nutrient supply are required.
At high fertilizer N rates, however, soil and plant N
responses to P and K fertilization, with and without DI,
are unknown.
The objectives of this study were to: (1) determine
plant N responses of processing tomatoes to fertilizers
152 Nutr Cycl Agroecosyst (2012) 93:151–162
123
P and K rates, with and without DI, using a recom-
mended fertilizer N rate, and (2) assess post-harvest
soil profile N responses to water management and
different rates of fertilizers P and K.
Materials and methods
Site description
A 4-year study, 2006–2009, was conducted on the
Research Farm of the Greenhouse and Processing
Crops Research Center, Agriculture and Agri-Food
Canada, Harrow, Ontario (42�020N, 82�930W). The
fields are flat and represent the general topographical
conditions in the study region. Air temperature in the
area averaged over the past 87 years (1917–2004) was
19.1 �C for the growing season (1 May–30 Septem-
ber). Total precipitation was averaged at 789 mm for
the entire year and at 291.8 mm for the growing
season. The preceding crops for the 2006, 2007, 2008,
and 2009 experiments were corn (Zea mays L.), tomato,
corn, and alfalfa (Medicago sative L.), respectively.
The soils at all study sites are classified as Granby
loamy sands (sandy, mixed, mesic Orthic Luvisol).
Selected baseline soil physical and chemical proper-
ties are shown in Table 1.
Experimental design and field management
The experiment was arranged as a split-plot factorial
design with four blocks. The treatments consisted of four
rates of fertilizer P (0, 30, 60, and 90 kg P ha-1), four rates
of fertilizer K (0, 200, 400, and 600 kg K ha-1), and two
water management practices, drip irrigation (DI) and
non-irrigation (NI). Water management was assigned to
the whole plots, with the 16 P and K treatment
combinations assigned to the sub-plots. Triple super-
phosphate was used as the fertilizer P source and
potassium chloride was used as the fertilizer K source.
Prior to tomato transplanting, fertilizer N, as NH4NO3,
was applied at a rate of 270 kg N ha-1 to achieve the
maximum marketable fruit yield (Zhang et al. 2010). All
fertilizers were disked to a soil depth of 15 cm following
hand broadcast.
Greenhouse-grown, 5-week old tomato plants were
transplanted to the fields in late May or early June each
year using a plug transplanter (RJ Equipment, Blen-
heim, Ontario). The plot sizes were 4.5 m by 4.5 m,
composed of three twin rows on a flat 1.5 m by 4.5 m
bed. Plants were spaced 40.6 cm in a row, and the row
spacing was 45 cm within a twin-row, resulting in a
transplanting density of 33,333 plants ha-1. Addi-
tional field management details have been previously
described (Liu et al. 2011b).
The amount and frequency for drip irrigation was
determined using a simplified evapo-transpiration
model which is a product of air temperature and
radiation data, from a nearby weather station. The
model also included a locally determined crop coef-
ficient, dependent on tomato growth stage (ranged
between 0.2 and 1.1), and emitter flow rate, along with
soil moisture retention characteristics (Tan and Fulton
1980; Tan 1990; LeBoeuf et al. 2008). One drip line
Table 1 Selected soil physical and chemical properties in the 0–20 cm soil depth prior to site preparation at the multiple study sites
2006 2007 2008 2009
Sand (g kg-1)a 829 ± 1.0b 821 ± 1.1 771 ± 1.0 823 ± 0.4
Silt (g kg-1) 108 ± 0.4 110 ± 0.8 158 ± 0.6 123 ± 0.2
Clay (g kg-1) 63 ± 0.6 69 ± 0.4 71 ± 0.6 54 ± 0.3
Soil pH 5.8 ± 0.2 6.5 ± 0.1 6.3 ± 0.1 6.8 ± 0.1
Soil total organic carbon (g C kg-1) 7.2 ± 0.3 6.9 ± 0.4 16.7 ± 0.7 8.8 ± 0.2
Soil total N (g N kg-1) 0.61 ± 0.02 0.65 ± 0.05 1.24 ± 0.06 0.77 ± 0.02
2 M KCl extractable N (NO3-–N ? NH4
?–N) (mg N kg-1) 11 ± 2 12 ± 2 13 ± 3 16 ± 2
0.5 M NaHCO3 extractable P (mg P kg-1) 39 ± 3 43 ± 4 65 ± 3 37 ± 4
1 M NH4OAc extractable K (mg K kg-1) 148 ± 10 133 ± 14 179 ± 10 193 ± 12
a Particle size distribution of sand, silt, and clay was determined by soil hydrometer, soil pH was determined using soil:water = 1:1
extract, and soil total carbon and N were determined by combustion using an automatic Leco� analyzerb Values are means ± standard error (SE) with a sample size of 4
Nutr Cycl Agroecosyst (2012) 93:151–162 153
123
was placed on the soil surface in the middle of each
twin-row bed. The emitter spacing was 30 cm to
supply a flow rate of 0.47 L h-1 in order to achieve
uniform soil wetting patterns. During each growing
season, the tomato plants were drip irrigated daily for
1–3 h, depending on the growth stage. Drip irrigation
was suspended whenever there was more than 19 mm
of daily precipitation and was stopped 2 weeks prior to
harvesting. Water supplied through the drip lines was
continuously monitored by a water meter connected to
an irrigation controller.
Plant and soil sampling and laboratory analyses
At the 80 % fruit ripening stage, tomato plants,
including the stems and leaves and tomato fruits, were
hand harvested from a 2 m long central twin row in
each plot. Tomato fruits were separated from the stems
and leaves and graded into marketable and non-
marketable fruits. Fresh tomato fruits and vegetative
parts, including stems and leaves, were sub-sampled,
weighed, and dried at 55 �C for 48 h. After being
ground through a Wiley mill with a 2-mm stainless
steel sieve, fruits and vegetative parts were separately
digested with H2SO4–H2O2 (Thomas et al. 1967).
Nitrogen concentration in the digest was determined
using a Flow Injection Auto-Analyzer (QuikChem
FIA ? 8000 series, Lachat Instruments, Loveland,
CO). Plant N uptake was calculated according to dry
biomass and the corresponding N concentration. Fruit
N removal refers to the N uptake of marketable fruits.
Plant total N uptake is the sum of N uptake of fruits,
stems, and leaves. Apparent field N balance is calcu-
lated as the difference between fertilizer N input and
plant total N uptake.
A Nitrogen Harvest Index (NHI) was calculated as
follows
NHI ð%Þ ¼ Nmfruit
Nfruit þ Nstemsþleaves
� 100 ð1Þ
where Nmfruit is N uptake of marketable fruits, Nfruit is
N uptake of all fruits, Nstem?leaves is N uptake of stems
and leaves.
After the tomato harvest, two soil cores (5 cm
internal diameter) were randomly taken to a depth of
100 cm in each plot. Each core was sectioned into
20 cm depth increments. One soil core was taken in
the middle of the twin rows where the drip lines were
placed, while the other was taken between twin-row
beds. To account for the variability of inorganic N
concentrations (NO3-–N and NH4
?–N) in surface
soils six additional soil cores (1.8 cm internal diam-
eter) per plot were randomly taken to a soil depth of
20 cm. The fresh soil samples were composited by
depth in each plot and extracted with 2 M KCl to
determine soil inorganic N concentration (Nmin). One
additional soil core to a depth of 100 cm was also
taken in 12 randomly selected plots to determine soil
bulk density at each 20 cm soil depth increment.
Cumulative soil inorganic N (Ncum) in the 0–100 cm
depth of each plot was reported on a kg N ha-1 basis,
adjusted on the basis of measured soil bulk density. All
soil response variables were determined in the first
3 years from 2006 to 2008.
Statistical analysis
Soil inorganic N was determined only in the first 3 years
of the study and was analyzed using 12 combinations of
the blocks in the field and the years as blocks for soil
response variables. The plant response variables were
determined throughout the 4-year study period and data
from the split-plot factorial experiment were analyzed
using 16 combinations of blocks for plant variables. For
plant response variables, the three factors with interest
(water management and P and K rates) were considered
as fixed, and block was considered as random. Since
Nmin was measured repeatedly at the depth of 0–20,
20–40, 40–60, 60–80, and 80–100 cm, the data were
analyzed as repeated measures using the most appro-
priate covariance structure. The three factors (i.e. water
management, P rate, and K rate) of interest and soil
depth were considered as fixed, and block was consid-
ered as random. Analysis of variance (ANOVA) was
completed using the Mixed Procedure of SAS (SAS
Institute Inc. 2008), and further multiple means com-
parison was completed for significant (P value \ 0.05)
effects by comparing the least square means of the
corresponding treatment combinations. Letter group-
ings were generated using a 1 % level of significance for
interaction effects and a 5 % level of significance for
main effects. For each response, the validity of model
assumptions was verified by examining the residuals as
described in Montgomery (2009) and appropriate
transformations were applied on responses with violated
assumptions. The results reported in the tables and
figures are back transformed to the original scale.
154 Nutr Cycl Agroecosyst (2012) 93:151–162
123
Results
Fruit N concentration and fruit N removals
Water management had no effect on fruit N concen-
tration, but significantly affected fruit N removal
(Table 2). Fertilizer K rates significantly affected both
fruit N concentration and removal, while effects of
fertilizer P input and any interactions were not
significant for either fruit N concentration or removal.
Fruit N removal was 101 % higher in the DI
treatment than in the NI treatment (Table 3). Fruit N
concentrations did not differ between the 0 and
200 kg K ha-1 treatments or between the 400 and
600 kg K ha-1 treatments. However, K application at
high rates of 400 or 600 kg K ha-1 resulted in a
significant (approximately 4 %) decrease in fruit N
concentration relative to the low rates treatments
receiving 0 or 200 kg K ha-1. Applications of fertil-
izer K (from 200 to 600 kg K ha-1) increased fruit N
removal compared with the K control treatment, with
the highest fruit N removal in the 200 kg K ha-1
treatment (Table 4). Application of K at the rates of
200, 400, and 600 kg K ha-1 increased fruit N
removal by 12, 6, and 8 % relative to the K control
treatment, respectively.
N concentration of stems and leaves
All three main effects of water management, fertilizer
P rates and fertilizer K rate significantly affected N
concentration of stems and leaves (NCSL), but all
interaction effects were not significant (Table 2). Drip
irrigation decreased NCSL by 1.3 g N kg-1, an
equivalent of 8 %, compared with the NI treatment
(Table 3). Both fertilizers P and K inputs had negative
effects on NCSL regardless of water management
(Table 4). The NCSL was significantly (5 %) lower in
the 90 kg P ha-1 treatment than in the control P
treatments receiving 0 kg P ha-1. Compared with the
fertilizer K control treatment, application of K at rates
of 200, 400, and 600 kg K ha-1 significantly decreased
NCSL by 7, 11, and 12 %, respectively.
Plant total N uptake
Water management and fertilizer K rate significantly
affected plant total N uptake, while fertilizer P rate or
all interaction effects were not significant (Table 2).
Similar to the water management effects on the fruit N
removal, plant total N uptake was 37.8 kg N ha-1 (an
equivalent to 26 % increase) higher in the DI
treatment than in the NI treatment (Table 3). Appli-
cation of fertilizer K at 200 kg K ha-1 led to signif-
icantly higher (6–9 %) plant total N uptake than the
other three fertility K treatments, but there was no
difference in plant total N uptake among treatments
receiving 0, 400, and 600 kg K ha-1 (Table 4).
N harvest index
Water management and fertilizer K rate had signifi-
cant effects on NHI (Table 2). Additions of fertilizer P
had no effects on NHI, neither did any treatment
interactions. Drip irrigation increased NHI by 55 %
relative to the NI treatment. Additions of fertilizer K
Table 2 The degree of freedom (df) of treatments and
ANOVA P values for the main and interaction effects of
water management (W), phosphorus (P) rates, and potassium
(K) rates on fruit nitrogen (N) concentration, fruit N removal,
N concentration of stems and leaves (NCSL), plant total N
uptake, N harvest index (NHI), cumulative soil inorganic N in
the 0–100 cm soil profile (Ncum), and apparent field N balance
in processing tomato, 2006–2009
Source of
variation
df Fruit N
concentration
Fruit N
removal
NCSL Plant total
N uptake
NHI Ncum Apparent field
N balance
W 1 0.184 0.001 0.044 0.001 0.001 0.001 0.001
P 3 0.153 0.156 0.025 0.069 0.176 0.520 0.115
W 9 P 3 0.758 0.632 0.753 0.699 0.922 0.581 0.681
K 3 0.001 0.001 0.001 0.001 0.001 0.552 0.001
W 9 K 3 0.187 0.131 0.895 0.233 0.280 0.406 0.133
P 9 K 9 0.137 0.299 0.726 0.116 0.251 0.377 0.096
W 9 P 9 K 9 0.640 0.546 0.647 0.793 0.398 0.552 0.818
Significant effects that need multiple means comparison are italicised
Nutr Cycl Agroecosyst (2012) 93:151–162 155
123
from 200 to 600 kg K ha-1 had no effects on NHI, but
substantially increased NHI compared with the K
control treatments. Application of fertilizer K at the
rates of 200, 400, and 600 kg K ha-1 increased NHI
by 7, 8, and 9 %, respectively.
Post-harvest soil inorganic N
Post-harvest soil inorganic N concentration (Nmin) in
the 0–100 cm soil profile was significantly affected by
the interaction of water management and soil depth
(P \ 0.001). However, neither effects of fertilizers P
and K inputs nor any treatment interactions except for
water management 9 soil depth were significant. In
the 0–20 cm depth, Nmin was comparable between the
DI and NI treatments (Fig. 1). However, Nmin was
significantly lower in the DI treatment than in the NI
treatment at all depths between 20 and 100 cm in the
soil profile. The Nmin in the 20–40, 40–60 cm,
60–80 cm, and 80–100 cm soil depth was 20, 35, 37,
and 38 % lower in the DI treatment than in the NI
treatment, respectively.
The Nmin was significantly higher in the 0–20 cm
soil depth than in any depths of 20–100 cm regardless
of water management. A substantial decrease in Nmin
was found from the 0–20 cm depth to 20–40 cm depth,
with a decrease of 51 % for the DI treatment and 46 %
for the NI treatment. The Nmin in the DI treatment was
significantly higher in the 20–40 cm depth than any
depths from the 40–100 cm depth. The Nmin remained
statistically unchanged in the 40–100 cm depth
(2.1–2.4 mg N kg-1) for the DI treatment and in the
Table 3 Least squares means of fruit N removal, N concen-
tration of stems and leaves (NCSL), plant N uptake, N harvest
index (NHI), cumulative soil inorganic N in the 0–100 cm soil
depth (Ncum), and apparent field N balance at the two levels of
water management in processing tomato, 2006–2009
Water
management
Fruit N removal
(kg N ha-1)
NCSL
(g N kg-1)
Plant total N uptake
(kg N ha-1)
NHI
(%)
Ncum
(kg N ha-1)
Apparent field N
balance (kg N ha-1)
Drip irrigation 122.6 a 15.8 b 184.9 a 66.0a 46.4 b 88.0 b
Non-irrigation 61.1 b 17.1 a 147.1 b 42.5b 69.0 a 122.9 a
Means followed by the same letters within each column are not significantly different at the 5 % level
Table 4 Least squares means of fruit nitrogen (N) concentra-
tion, fruit N removal, N concentration of stems and leaves
(NCSL), plant total N uptake, N harvest index (NHI), and
apparent field N balance at the four rates of potassium (K); and
of NCSL at the four rates of phosphorus (P) in processing
tomato, 2006–2009
K rate
(kg K ha-1)
Fruit N
concentration
(g N kg-1)
Fruit N
removal
(kg N ha-1)
NCSL
(g N kg-1)
Plant total
N uptake
(kg N ha-1)
NHI
(%)
Apparent field
N balance
(kg N ha-1)
P rate
(kg P ha-1)
NCSL
(g N kg-1)
0 19.7 a 86.1 c 17.8 a 165.6 b 51.1b 105.6 a 0 16.8 a
200 20.0 a 96.8 a 16.6 b 174.8 a 54.5a 97.0 b 30 16.3 ab
400 18.9 b 91.6 b 15.8 c 160.7 b 55.4a 110.2 a 60 16.6 ab
600 19.1 b 92.9 b 15.6 c 162.9 b 55.9a 109.1 a 90 15.9 b
Means followed by the same letters within each column are not significantly different at the 5 % level
Post-harvest soil inorganic nitrogen concentration (mg N kg-1)
0 2 4 6 8 10
So
il d
epth
(cm
)
0
20
40
60
80
100
Drip irrigationNon-irrigation
a a
c b
bc
bc
bc
d
d
d
Fig. 1 Least squares means of post-harvest soil inorganic N
concentration in the 0–100 cm soil depth for drip irrigated and
non-irrigated processing tomato receiving an N rate of
270 kg N ha-1, 2006–2008. Means sharing the same letter are
not significantly different at the 1 % significant level
156 Nutr Cycl Agroecosyst (2012) 93:151–162
123
20–100 cm depth (3.4–4.1 mg N kg-1) for the NI
treatment.
When taking soil bulk density into account, cumu-
lative soil inorganic N (Ncum) in the 0–100 cm depth
was calculated and expressed on a kg N ha-1 basis.
The Ncum in the 0–100 cm depth was significantly
affected only by water management among all main
and interaction effects (Table 2). In contrast to the
responses of plant total N uptake to water manage-
ment, Ncum was 33 % lower in the DI treatment than in
the NI treatment. Approximately 37 % of Ncum in the
0–100 cm soil profile was in the 0–20 cm depth for the
DI treatment and 31 % for the NI treatment.
Apparent field N balance
Apparent field N balance, i.e. difference between
fertilizer N input and plant total N uptake, was
significantly affected only by water management and
fertilizer K rate, but not by P rate or by any treatment
interactions (Table 2). Drip irrigation decreased
apparent field N balance by 28 % compared with the
NI treatment. Application of fertilizer K at the rate of
200 kg K ha-1 significantly lowered apparent field N
balance compared with the other three K rates.
Apparent field N balance in the 200 kg K ha-1
treatment decreased by 8, 12, and 11 % when com-
pared with the 0, 400, and 600 kg K ha-1 treatments,
respectively.
Discussion
Water management effects
Water management significantly affected NCSL but
had no effects on fruit N concentration. Although fruit
N uptake in the DI treatment was twice as much as in
the NI treatment, fruit N concentration remained
unchanged between DI and NI treatment. The lack of
difference in fruit N concentration could be attributed
to dilution effects by the substantial increase in fruit
yield (Liu et al. 2011b). Such dilution effects did not
exist for NCSL, as water management had no effects
on the dry biomass of stems and leaves (Liu et al.
2011b). Compared with the NI treatment, the signif-
icantly low NCSL in the DI treatment could be a
combined effect of high N translocation to fruits, as
indicated by high NHI, and insufficient N supply at the
late growing season, as demonstrated by low soil
mineral N concentration determined at the harvest
stage.
Critical N concentration is defined as the minimum
N concentration required to maximize plant growth
(Greenwood et al. 1991). The N concentration in
tomato plants, including fruits, stems, and leaves, was
B20 g N kg-1, which was lower than critical N
concentration presented by Tei et al. (2002) and Hartz
and Bottoms (2009) for processing tomato. This
suggests inadequate N supply at this specific sampling
period of harvest stage. The deficient N supply is also
reflected by a corresponding yield reduction, espe-
cially when compared to previous studies (Zhang et al.
2010). At the same N rate of 270 kg N ha-1, the
marketable fruit yield of processing tomato decreased
from 127 Mg ha-1 using a drip fertigation technique
(Zhang et al. 2010) to 100 Mg ha-1 under the DI
approach (Liu et al. 2011b). Despite the same irrigation
schedule, N application timing differed fundamentally
between the drip irrigation and drip fertigation
regimes. Under drip fertigation, N was split and
applied according to crop demand at various growing
stages to maximize N use efficiency, whereas all N was
applied prior to transplanting for drip irrigation.
Therefore, the single application of N at the rate of
270 kg N ha-1 in the present study likely caused
potential N leaching losses by rainfall events during the
tomato growing season, resulting in N deficiency in the
late growing season as indicated by the low NSCL. In
order to maintain adequate N for crop growth, we could
either adjust N application schedule, such as adoption
of drip fertigation, or apply more N prior to transplant-
ing to offset N losses during the growing season which
may in fact exacerbate N losses.
Nitrogen accumulation in the processing tomato
plants was strongly affected by water supply. In a
previous field study of drip fertigated processing
tomato, Zhang et al. (2011) found that plant total N
uptake averaged 256 kg N ha-1 at an N rate of
240 kg N ha-1. In the current study, plant total N
uptake only averaged 185 kg N ha-1 in the DI treat-
ment and 147 kg N ha-1 in the NI treatment using a
higher N fertilizer rate of 270 kg N ha-1. During the
growing seasons in the current study, soil moisture
monitored by a time-domain reflectometer at the 20 cm
depth averaged 25 % (v/v) in the DI treatment and
14 % (v/v) in the NI treatment. High soil moisture in
the DI treatment increases N availability (Ferguson
Nutr Cycl Agroecosyst (2012) 93:151–162 157
123
et al. 2002; Hebbar et al. 2004) and explains the high
plant total N uptake when compared with the NI
treatment. High plant N uptake in the DI treatment left
lower amounts of N exposed to post-harvest N losses.
The positive apparent field N balance (e.g., fertil-
izer N input minus plant total N uptake) demonstrated
that part of fertilizer N was not accounted in the plant
N uptake. We found that apparent field N balance was
42 kg N ha-1 higher than Ncum in the 0–100 cm
depth for the DI treatment, and 54 kg N ha-1 higher
for the NI treatment, suggesting that at least
48 kg N ha-1, averaged across the DI and NI treat-
ments, was lost during the growing season. Water
management not only affected plant total N uptake,
but also influenced N translocation among plant parts.
Wang et al. (2005) found that water stress on wheat
inhibited the translocation of N from vegetative parts
to grains and lowered NHI. Deficient water supply
could cause a depression of stem diameter expansion
of tomato plants and reduced the translocation of
assimilates to fruits (Kanai et al. 2011), consequently
decreasing NHI. Studies have demonstrated that a
smaller proportion of plant total N partitioned to the
fruits when N was applied in excess of crop N
requirements (Stark et al. 1983; Scholberg et al. 2000).
When considering the higher soil inorganic N at
transplanting (13 mg N kg-1) than at harvest
(7 mg N kg-1) in the current study, an additional
14.4 kg inorganic N ha-1 could be provided to crops
at the measured soil bulk density of 1.2 g cm-3. The
combined effects of water stress and excessive N
supplies, with the exception of the late growing
season, substantially lowered NHI in the NI treatment
relative to the DI treatment. Due to the low NHI, more
plant residual N remained in the field in the NI
treatment (86 kg N ha-1) than in the DI treatment
(62 kg N ha-1). High plant residual N in the NI
treatment could compound the off-season N losses as
the decomposition of plant residues can provide
substantial amounts of mineral N in the early fall,
posing challenges for post-harvest N management.
Inorganic N in the soil profile was affected by plant
N uptake and also reflected downward movement of N
during the growing seasons. Even though fertilizer N
supplies were much higher than crop requirements in
the NI treatment compared with the DI treatment,
post-harvest soil N concentration in the 0–20 cm
depth was not different between the two levels of
water management. According to Zotarelli et al.
(2009), 51–78 % of the root of tomato was in the
0–15 cm soil depth with additional 15–28 % in the
15–30 cm soil depth. This suggested that majority of
N uptake by tomato was from surface soil, resulting in
comparable soil N concentration in the 0–20 cm soil
between the two levels of water management.
Soil inorganic N at depths between 20 and 100 cm
was higher in the NI treatment than in the DI
treatment. Higher soil N concentration in the NI
treatment was partially related to the lower plant total
N uptake. In a corn study, Gheysari et al. (2009b)
reported that the decrease in corn N uptake increased
post-harvest soil residual N for the deficit irrigation
system compared with the full rate irrigation system.
Similarly, Wang et al. (2005) found that soil nitrate N
concentration in the post-harvest soil was substantially
(52 %) higher in the water deficit treatment than in the
supplemental irrigation treatment as a result of lower
crop N uptake. In the DI treatment, water is precisely
controlled according to crop needs, ensuring minimal
downward movement of irrigated water to deeper soil
depths. However, movement of nitrate N is strongly
linked with water movement and nitrate accumulation
at the boundary of the wetted area under drip
fertigation circumstances have been reported (Li
et al. 2003). Although the majority of irrigated water
was scheduled to remain in the active root zone in the
0–20 cm soil depth, the wetting front could be down to
the 20–30 cm soil depth, thus higher Nmin could
appear at this lower depth. This might explain the
significantly higher soil inorganic N in the 20–40 cm
depth than the 60–100 cm depths in the DI treatment.
Drip irrigation was conceived as an ideal technol-
ogy to enhance water and nutrient use efficiency while
reducing N leaching losses (Hebbar et al. 2004);
however, heavy N application at the beginning of crop
growing season and uncontrollable rainfall events
during the growing season might cause large amounts
of N losses, thereby decreasing N use efficiency. The
current study was conducted on a loam sandy soil in a
region classified as a high risk area of N leaching
losses (De Jong et al. 2007). Our results showed that
post-harvest soil N concentration was 7 mg N kg-1 in
the 0–20 cm depth and ranged from 2 to 4 mg kg-1 in
the 20–100 cm depth, and was much lower than
13 mg N kg-1 determined prior to the pre-transplant-
ing. The low post-harvest soil N concentration
suggested that N leaching losses during the following
non-growing season might be minimal compared with
158 Nutr Cycl Agroecosyst (2012) 93:151–162
123
the growing season losses. By contrast, in a commer-
cial field with drip irrigated processing tomato, Stork
et al. (2003) reported higher N losses in the post-
harvest season than during the growing season in a
clay soil. Differences in results between our study and
Stork et al. (2003) can be due mainly to the soil texture
affecting water and associated N movement in soil.
Substantial amounts of N losses during the growing
season in our study led to reduced N losses during the
non-growing season. Therefore, more attention needs
to be paid to reduce N losses during the growing
season rather than in the post-harvest season on highly
permeable soils.
Water management effects on Nmin were mostly
apparent in the subsurface soil compared with the
surface soil, with significantly lower Nmin in the DI
treatment than in the NI treatment. No difference in
Nmin at the 20–100 cm depth for the NI treatment
could be a result of N downward movement during the
growing season with extreme rainfall induced water
percolation (Gehl et al. 2006). A study conducted in
the same region showed that N concentration in the tile
drainage was occasionally higher than 10 mg N L-1
during the growing season in a clay soil, demonstrat-
ing intensive rainfall during the growing season in the
study region causes heavy N leaching losses (Drury
et al. 2009). Furthermore, no deep accumulation of N
in the examined soil depths, along with the positive
apparent field N balance, confirmed that N downward
moved beyond the depth (0–100 cm) we examined.
Such deep movement of N during the crop growing
season has been well documented. For example, Stork
et al. (2003) found that soil N decreased with soil
depths down to 100 cm but accumulated at depths
between 150 and 200 cm at the harvest time in a clay
soil. Gehl et al. (2006) also reported that N could move
below 2 m in a coarse textured soil during the growing
season in an irrigated corn production system. During
the growing season of processing tomato receiving
200 kg N ha-1 of fertilizer N, Vazquez et al. (2006)
found that 18–188 kg N ha-1 was leached below 1 m
soil depth as a result of occasional rainfall events. The
N leaching losses determined at a depth of 75 cm
averaged 40 kg N ha-1 during the tomato growing
season at the N rate varied from 176 to 330 kg N ha-1
(Zotarelli et al. 2009). The rainfall averaged 310 mm
during the growing seasons in the current 4-year study,
making deep downward movement of N during the
growing season a very likely N loss pathway.
Fertilizer P effects
Wright (2004) reported a strong positive correlation
between N and P concentrations in leaves across
various species, suggesting plant N uptake was
affected by P supplies. The negative P effects on
NCSL in the present study could be attributed to
dilution effects, since fertilizer P input increased the
biomass of stems and leaves (Liu et al. 2011b).
However, plant total N uptake was not affected by
fertilizer P input as evidenced by the opposite effects
of P on N concentration and biomass. In a recent field
study of fertilizer N and P effects on high yielding drip
fertigated processing tomato, Zhang et al. (2011)
reported that fertilizer P rates, ranging from 0 to
87.3 kg P ha-1, had no effects on plant N uptake,
apparent N recovery, or post-harvest soil N. The soil P
fertility in the current study ranged from medium to
high levels for processing tomato according to
provincial guidelines (OMAFRA 2008). The medium
to high background soil P fertility might provide
sufficient P required for healthy tomato growth, thus
having no effects on tomato N uptake and soil N.
Although soil N was not affected by fertilizer P input,
post-harvest water extractable soil P and Olsen P
increased linearly in response to P application (Liu
et al. 2011a), suggesting high fertilizer P input
exacerbated the adverse P effects on surrounding
water systems. Therefore, fertilizer P application in
the processing tomato production systems in the study
region skewed the nutrient balance potentially causing
adverse environmental effects.
Fertilizer K effects
Nitrogen concentration in the processing tomato
production system was responsive to fertilizer K
application. The decreased NSCL at the high fertilizer
K input treatments might be related to K-induced
enhancement of assimilate translocation to fruits. With
medium or high N supplies, water use increased in
response to increasing fertilizer K application (Ebdon
et al. 1999). Similarly, Huang and Snapp (2009) found
that increasing K to N ratio from 0.8:1 to over 1.7:1
significantly increased water uptake of tomato fruits.
The K:N ratios for the treatment receiving 200, 400,
and 600 kg K ha-1 are 0.7:1, 1.5:1, and 2.2:1, respec-
tively. The increased water uptake at high K:N ratio
might explain the decrease in fruit N concentration in
Nutr Cycl Agroecosyst (2012) 93:151–162 159
123
the 400 and 600 kg K ha-1 treatments compared with
K control or the 200 kg K ha-1 treatment.
Fertilizer K input affected plant N responses with
the highest N uptake when K rate was 200 kg K ha-1.
The soil K fertility in the current study ranged from
medium to high levels for processing tomato according
to the provincial guidelines (OMAFRA 2008). The N
response to external fertilizer K input in the present
study demonstrated high K requirements for processing
tomato supplied with a high N rate (270 kg N ha-1) and
suggested K deficiencies in the K control treatment.
Similarly, Liu et al. (2008) found that, under a relatively
high background soil K fertility circumstance, applying
fertilizer K significantly increased yield of tomato
supplied with high N. Without fertilizer K input, high
yield potential driven by high N input might deplete soil
K supply. The deficient K in the control treatment
substantially decreased photosynthesis (Kanai et al.
2011), and limited growth of crops even supplied with
adequate N (Fofana et al. 2008), resulting in signifi-
cantly lower N uptake in the K control treatment. The K
deficiency was also reported to depress stem diameter
expansion and then limited the translocation of assim-
ilates to fruits (Kanai et al. 2011), lowering NHI in the K
control treatment.
Plant N response to fertilizer K depended on soil
N fertility level. Under the conditions of low soil N
fertility, application of K was reported to increase N
use efficiency (Fitzpatrick and Guillard 2004). When
N supplies were high, appropriate amounts of fertilizer
K application were required to increase plant N uptake
while reducing N contamination to environment (Niu
et al. 2011). In the current study, K application at the
rate of 200 kg K ha-1 increased N concentration and
uptake compared with the K control treatment and had
potentials for decreasing N losses as indicated by the
lowest apparent field N balance. Although tomato
requires large amounts of K for profitable production,
over applied K input had no effects on yield (Liu et al.
2011b) and plant N uptake. Similarly, studies on corn
(Bruns and Ebelhar 2006) demonstrated that supple-
menting extra K had minimal effects on crop when K
supplies was adequate for healthy crop growth.
However, over applications of K decreases farmers’
net economic returns. Considering the economic and
N utilization effects, we suggest that application of K
at the rate of 200 kg K ha-1 were required for
processing tomatoes supplied with adequate N in the
study region.
Conclusions
Water management (DI vs. NI) had larger effects on soil
and plant N response variables, especially soil N, than
fertilizers P and K in processing tomato. As indicated by
the difference between apparent field N balance (e.g.,
fertilizer N input minus plant total N uptake) and Ncum,
more N was lost beyond the 0–100 cm soil depth in the
NI treatment (53.9 kg N ha-1) than in the DI treatment
(41.6 kg N ha-1) during tomato growing seasons. Due
to such considerable N losses, N applied at the rate
required to maximize fruit yield appeared insufficient at
the late tomato growing seasons as indicated by the low
NSCL. Although the study area was located in a region
with high risks of post-harvest soil N losses, post-harvest
soil N losses in this study might be minimal when
considering the low post-harvest soil N concentration
ranging from 2 to 4 mg N kg-1 in the 20–100 cm soil
depth. Therefore, more attention needs to be paid to
reduce N losses during the growing season rather than
after harvesting, particularly for the processing toma-
toes receiving a high N rate on a sandy loam soil. The
application schedule of N in drip irrigation needs to be
evaluated further to reduce potential environmental
contamination if used for drip irrigated tomatoes. Plant
and soil N variables, except for N concentration of stems
and leaves, did not respond to fertilizer P input due to
existing high soil P fertility. Application of K at the rate
of 200 kg N ha-1 increased plant N utilization which
has implications for reducing N losses. Consequently,
the 4-year field study indicated that water management
and fertilizer K rates should be incorporated into N
management in a sustainable processing tomato pro-
duction, with the goal of achieving high yields while
decreasing N losses.
Acknowledgments We thank M. Reeb, D. Pohlman, K. Rinas,
and B. Hohner for technical assistance and the Ontario Agri-
Business Association, International Plant Nutrient Institute, Cana-
dian Fertilizer Institution, Ontario Tomato Research Institute,
Ontario Processing Vegetable Growers, A & L Canada Labo-
ratories Inc., and Agriculture and Agri-Food Canada Matching
Initiative Investment (MII) program for financial assistance.
References
Bruns HA, Ebelhar MW (2006) Nutrient uptake of maize
affected by nitrogen and potassium fertility in a humid
subtropical environment. Commun Soil Sci Plant Anal
37:275–293
160 Nutr Cycl Agroecosyst (2012) 93:151–162
123
De Jong R, Yang JY, Drury CF, Huffman EC, Kirkwood V,
Yang XM (2007) The indicator of risk of water contami-
nation by nitrate-nitrogen. Can J Soil Sci 87:179–188
Drury CF, Tan CS, Reynolds WD, Welacky TW, Oloya TO,
Gaynor JD (2009) Managing tile drainage, subirrigation,
and nitrogen fertilization to enhance crop yields and reduce
nitrate loss. J Environ Qual 38:1193–1204
Ebdon JS, Petrovic AM, White RA (1999) Interaction of nitrogen,
phosphorus, and potassium on evapotranspiration rate and
growth of Kentucky bluegrass. Crop Sci 39:209–218
Ferguson RB, Hergert GW, Schepers JS, Gotway CA, Cahoon
JE, Peterson TA (2002) Site-specific nitrogen management
of irrigated maize: yield and soil residual nitrate effects.
Soil Sci Soc Am J 66:544–553
Fitzpatrick RJM, Guillard K (2004) Kentucky bluegrass
response to potassium and nitrogen fertilization. Crop Sci
44:1721–1728
Florida Agricultural Statistics Service (1999) Vegetabel chem-
ical use. Florida Agricultural Statistics Service, Orlando
Fofana B, Wopereis MCS, Bationo A, Breman H, Mando A
(2008) Millet nutrient use efficiency as affected by natural
soil fertility, mineral fertilizer use and rainfall in the West
African Sahel. Nutr Cycl Agroecosys 81:25–36
Gehl RJ, Schmidt JP, Godsey CB, Maddux LD, Gordon WB
(2006) Post-harvest soil nitrate in irrigated corn: variability
among eight field sites and multiple nitrogen rates. Soil Sci
Soc Am J 70:1922–1931
Gheysari M, Mirlatifi SM, Bannayan M, Homaee M, Hoogen-
boom G (2009a) Interaction of water and nitrogen on maize
grown for silage. Agr Water Manage 96:809–821
Gheysari M, Mirlatifi SM, Homaee M, Asadi ME, Hoogenboom
G (2009b) Nitrate leaching in a silage maize field under
different irrigation and nitrogen fertilizer rates. Agr Water
Manage 96:946–954
Greenwood DJ, Gastal F, Lemaire G, Draycott A, Millard P,
Neeteson JJ (1991) Growth rate and %N of field grown
crops: theory and experiments. Ann Bot 67:181–190
Gunes A, Alpaslan M, Inal A (1998) Critical nutrient concen-
trations and antagonistic and synergistic relationships
among the nutrients of NFT-grown young tomato plants.
J Plant Nutr 21:2035–2047
Hartz TK, Bottoms TG (2009) Nitrogen requirements of drip-
irrigated processing tomatoes. HortScience 44:1988–1993
Hebbar SS, Ramachandrappa BK, Nanjappa HV, Prabhakar M
(2004) Studies on NPK drip fertigation in field grown tomato
(Lycopersicon esculentum Mill.). Eur J Agron 21:117–127
Huang J, Snapp SS (2009) Potassium and boron nutrition
enhance fruit quality in Midwest fresh market tomatoes.
Commun Soil Sci Plant Anal 40:1937–1952
Kanai S, Moghaieb RE, El-Shemy HA, Panigrahi R, Mohapatra
PK, Ito J, Nguyen NT, Saneoka H, Fujita K (2011) Potas-
sium deficiency affects water status and photosynthetic rate
of the vegetative sink in green house tomato prior to its
effects on source activity. Plant Sci 180:368–374
Kim K, Clay DE, Carlson CG, Clay SA, Trooien T (2008) Do
synergistic relationships between nitrogen and water
influence the ability of corn to use nitrogen derived from
fertilizer and soil? Agron J 100:551–556
LeBoeuf J, Shortt R, Tan CS, Verhalen A (2008) Irrigation
scheduling for tomatoes—an introduction. Factsheet order
no. 08-011
Li J, Zhang J, Ren L (2003) Water and nitrogen distribution as
affected by fertigation of ammonium nitrate from a point
source. Irrig Sci 22:19–30
Liu Z, Jiang L, Li X, Hardter R, Zhang W, Zhang Y, Zheng D
(2008) Effect of N and K fertilizers on yield and quality of
greenhouse vegetable crops. Pedosphere 18:496–502
Liu K, Zhang TQ, Tan CS (2011a) Processing tomato phos-
phorus utilization and post-harvest soil profile phosphorus
as affected by phosphorus and potassium additions and drip
irrigation. Can J Soil Sci 91:417–425
Liu K, Zhang TQ, Tan CS, Astatkie T (2011b) Responses of fruit
yield and quality of processing tomato to drip irrigation and
fertilizers phosphorus and potassium. Agron J 103:1339–1345
Montgomery DC (2009) Design and analysis of experiments,
7th edn. Wiley, New York
Niu J, Zhang W, Chen X, Li C, Zhang F, Jiang L, Liu Z, Xiao K,
Assaraf M, Imas P (2011) Potassium fertilization on maize
under different production practices in the North China
Plain. Agron J 103:822–829
Ontario Ministry of Agriculture, Food, Rural Affairs (OMAFRA)
(2008) Vegetable production recommendations 2008–2009.
Publication 363. Queen’s Printer for Ontario. Toronto
Patane C, Cosentino SL (2010) Effects of soil water deficit on
yield and quality of processing tomato under a Mediterra-
nean climate. Agr Water Manage 97:131–138
Santos BM (2009) Combinations of nitrogen rates and irrigation
programs for tomato production in spodosols. HortTech-
nology 19:781–785
SAS Institute Inc (2008) SAS OnlineDoc� 9.2. SAS Institute
Inc., Cary, NC
Scholberg J, McNeal BL, Boote KJ, Jones JW, Locascio SJ,
Olson SM (2000) Nitrogen stress effects on growth and
nitrogen accumulation by field-grown tomato. Agron J 92:
159–167
Stark JC, Jarrell WM, Letey J, Valoras N (1983) Nitrogen use
efficiency of trickle-irrigated tomatoes receiving continu-
ous injection of N. Agron J 75:672–676
Stork PR, Jerie PH, Callinan APL (2003) Subsurface drip irri-
gation in raised bed tomato production. I. Nitrogen and
phosphate losses under current commercial practice. Aust J
Soil Res 41:1283–1304
Tan CS (1990) Irrigation scheduling for tomatoes-water budget
approach. OMAF, Toronto, ON, Factsheet order no.
90-049
Tan CS, Fulton JM (1980) Ratio between evapotranspiration of
irrigated crops from floating lysimeters and class A pan
evaporation. Can J Plant Sci 60:197–201
Tapia ML, Gutierrez V (1997) Distribution pattern of dry
weight, nitrogen, phosphorus, and potassium through
tomato ontogenesis. J Plant Nutr 20:783–791
Tei F, Benincasa P, Guiducci M (2002) Critical nitrogen con-
centration in processing tomato. Eur J Agron 18:45–55
Thomas RL, Sheard RW, Moyer JR (1967) Comparison of
conventional and automated procedures for N, P and K
analysis of plant material using a single digestion. Agron J
59:240–243
Tilling AK, O’Leary GJ, Ferwerda JG, Jones SD, Fitzgerald GJ,
Rodriguez D, Belford R (2007) Remote sensing of nitrogen
and water stress in wheat. Field Crops Res 104:77–85
Vazquez N, Pardo A, Suso ML, Quemada M (2006) Drainage
and nitrate leaching under processing tomato growth with
Nutr Cycl Agroecosyst (2012) 93:151–162 161
123
drip irrigation and plastic mulching. Agr Ecosyst Environ
112:313–323
Wang Z, Li S, Vera CL, Malhi SS (2005) Effects of water deficit
and supplemental irrigation on winter wheat growth, grain
yield and quality, nutrient uptake, and residual mineral
nitrogen in soil. Commun Soil Sci Plant Anal 36:1405–1419
Wright JJ (2004) The worldwide leaf economics spectrum.
Nature 428:821–827
Zhang TQ, Tan CS, Liu K, Drury CF, Papadopoulos AP, Warner
J (2010) Yield and economic assessments of fertilizer
nitrogen and phosphorus for processing tomato (lycopers-
icon esculentum Mill.) with drip fertigation. Agron J 102:
774–780
Zhang TQ, Liu K, Tan CS, Warner J, Wang YT (2011) Pro-
cessing tomato nitrogen utilization and soil residual
nitrogen as influenced by nitrogen and phosphorus addi-
tions with drip-fertigation. Soil Sci Soc Am J 75:738–745
Zotarelli L, Scholberg JM, Dukes MD, Munoz-Carpena R
(2007) Monitoring of nitrate leaching in sandy soils:
comparison of three methods. J Environ Qual 36:953–962
Zotarelli L, Dukes MD, Scholberg JMS, Munoz-Carpena R,
Icerman J (2009) Tomato nitrogen accumulation and fer-
tilizer use efficiency on a sandy soil, as affected by nitrogen
rate and irrigation scheduling. Agr Water Manage
96:1247–1258
162 Nutr Cycl Agroecosyst (2012) 93:151–162
123
