Journal of Water Resource and Protection, 2012, 4, 590-596
http://dx.doi.org/10.4236/jwarp.2012.48068 Published Online August 2012 (http://www.SciRP.org/journal/jwarp)
Nitrogen Use Efficiency under Different Field Treatments
on Maize Fields in Central China: A Lysimeter
and 15N Study
Jin Zhang1,2*, Zhao-Hua Li3, Kun Li3, Wei Huang1, Lian-Hai Sang1
1Center for Development Research (ZEF), University of Bonn, Bonn, Germany
2Yangtze River Scientific Research Institute, Wuhan, China
3Faculty of Resource and Environment, Hubei University, Wuhan, China
Received May 7, 2012; revised June 17, 2012; accepted June 23, 2012
ABSTRACT
Nitrogen loss from farmland has caused serious problems all over the world. This field study assessed Nitrogen Use
Efficiency1 (NUE) and biomass yield under four different field treatments in the Hubei Province, in central China. Re-
sults show that 1) in these four treatments, the maize monoculture plots have the highest rate of fertilizer N losses
(69.12%), and the lowest (32.45%) is treated by surface rice straw mulch of maize intercrop with peanut; 2) compared
with monoculture, polyculture plots have 36.9 kg·ha–1 and 26.57 kg·ha–1 more nitrogen absorption in the mulched and
un-mulched plots respectively, however, polyculture has a lesser effect on NUE; 3) surface straw mulch is an effective
way to keep nitrogen in the soil (0 - 100 cm), however it may decrease dry matter yield in monoculture plots; 4) maize
intercrop with peanut and surface mulch can keep 47.63% of the fertilizer N in the soil profiles (0 - 100 cm), which is
the highest among these four treatments.
Keywords: M onoc ulture; Surface Mulch; Nitroge n Us e Efficiency; Leaching; Biomass Yield
1. Introduction
Nitrogen is one of the essen tial elements for plant gro wth,
as it is not only promotes plant growth but also acts as a
building block for protein. In order to increase yield, fer-
tilizer consumption has continued to increase across the
world since the 19th century. The global production of
fertilizer has increased from 27.4 million tons in 1960 to
143.6 million tons in 1990 , and it will rise further to 208
million tons in 2020 [1]. Because of low NUE, the more
fertilizer N applied, the more nitrogen was lost. Only
30% - 35% of the fertilizer N was taken up by p lants and
about 20% - 50% went away through leaching and run-
off [2-4]. Nitrogen lost from farmland is the main source
of non-point source pollution for water systems, causing
problems of groundwater nitrate pollution, surface water
eutrophication, and natural ecological degradation.
Researches into nitrogen losses from agricultural ac-
tivities commenced several decades ago, founding a con-
sensus that nitrogen losses from agricultural land is the
main source of water 3 contamination around the
globe [5]. Nitrogen loss reduction strategies such as ma-
nure fertilizer [6,7], fertilizer application methods [8], en-
vironmental policies [9,10], surface mulching [11], till-
age/irrigation skills [12,13] (Meek, et al., 1995; Turpin,
et al., 1998) and proper intercropping system [14] have
been well documented in existing researches. However,
most of the studies were focused on nitrogen losses or
NUE, with less research being conducted on nitrogen
losses reduction with the yield consideration [15]. Nitro-
gen pollution mitigation strategies without yield consid-
eration cannot be implemented in China, because most
farmers small-scale and therefore pursue high yields to
support their families.
In this paper, we used on-site lysimeters and a stable
isotope 15N urea to compare the nitrogen distribution,
NUE and biomass yield of four different field treatments
in central China. We first analyzed nitrogen distribution
and yield under different treatments, and then examined
the 15N rate in the soil and crops to determine NUE. Fi-
nally, we discussed the field treatments which may im-
prove NUE and reduce nitrogen losses without sacrific-
ing the yield.
NO
2. Materials and Methods
2.1. Site Description
*Corresponding a uthor.
1Nitrogen Use Efficiency in this research is defined as the part of the
applied fertilizer nitrogen whi ch is found in the plant. Lysimeters and a 15N enriched urea were used in this
C
opyright © 2012 SciRes. JWARP

J. ZHANG ET AL. 591
experiment, established in Zhijiang City, in the western
part of Hubei Province (central China) (N43.715635,
E87.251374). The region has a moist monsoon climate
with a mean annual temperature of 16.5˚C, and a mean
annual rainfall of 1032.7 mm. The soil in the exp eriment
field is yellow-brown, and the properties of the surface
soil (0 - 20 cm) are listed in Table 1.
2.2. Treatments
The experiment was a split-plot factorial design with two
factors and three replicates. Three lysimeters are located
in each of the plots, (with the plots being 5 m wide * 8 m
long), and the lysimeter is 1.5 m wide * 1.5 m long * 1.3
m deep, leaving an edge of 0.3 m lysimeter above the soil
surface when put into the field. The four treatments are:
(1) maize monoculture (C); (2) maize intercrop with pea-
nut (C + P); (3) maize with rice straw mulch (C + M); (4)
maize intercrop with peanut and rice straw mulch (C + P
+ M). There are two rows of peanut between two rows of
maize. In the monoculture plots, the plant density is
36,000 maize·ha–1; in the polyculture plots, the plant d en-
sity is 17000 maize·ha–1 and 180000 peanuts·ha–1. Only
urea is applied to the maize, and no nitrogen fertilizer is
applied to peanut. 276 kg N·ha–1, 252 Kg K·ha–1 and 126
kg P·ha–1 were applied in the monoculture plots; 130 Kg
N·ha–1, 252 Kg K·ha–1 and 126 kg P·h a–1 were applied in
the polyculture plots. According to the farmers’ conven-
tional methods, the urea were ap plied twice, with 111 Kg
N·ha–1 (monoculture) and 52 Kg N·ha–1 (polyculture) at
planting as a basic fertilizer, and with 165 Kg N·ha–1
(monoculture) and 78 Kg N·ha–1 (polyculture) as a top-
dressing when the maize plants reach the stage of two
fully expanded leaves. All of the potassium and phos-
phorous was applied at once in the first time. The basic
fertilizer was applied on 5 May, 2008, at the same time
of transplant maize and sowing peanuts; and the top-
dress was applied on 31 May, 2008. All of the crops in
the lysimeter received 15N enriched urea, and ordinary P
and K fertilizers. The abundance of the 15N urea is
5.02%.
2.3. Sample Collection and Lab Analysis
In order to determine the nitrogen assimilated by the
crops, all of the crops were harvested including roots (0 -
20 cm). Crop samples were separated to grain and stem.
Subsequently, all of the samples were dried at 70˚C until
constant weight, and then crushed to powder until pass-
ing a 0.15 mm sieve, waiting for To tal Nitrogen Concen-
tration (TNC) and 15N abundance analysis.
The drainage water sample of each lysimeter was col-
lected whenever drainage occured, stored with dark glass
bottles in the refrigerator at 4˚C, and then return ed to the
laboratory for TNC analysis. Unfortunately, 15N abun-
dance in leached water hadn’t been analyzed; therefore,
fertilizer N deficit in this research includes gaseous and
water losses.
After the crops were harvested in Aug ust, soil samples
in each plot were collected from a depth of 0 - 20, 20 - 40,
40 - 60, 60 - 80 and 80 - 100 cm. The mass of TNC and
fertilizer utilization was calculated after considering the
bulk density of different soil layers.
2.4. Methodology in Lab
1) Water samples: filtered and sent to the lab for TNC
analysis on an Alpkem Flow Solution IV auto-an a lyzer.
2) Plant tissues: TNC in grain and stem of the sub-
samples were determined by the micro-Kjeldahl method
by digesting the sample in H2SO4-H2O2 solution. The
crop samples that waited for 15N were solute as the TNC
method, and the solute samples were analyzed by using
isotope mass spectrometer detector (ANCA-SL/20-20).
3) Soil samples: 10 g of the sub-samples were placed
in a 100 ml 2 N KCl, shaken for 1min and allowed to
equilibrate for 18-24 hrs. Supernatant was removed and
stored at 4˚C. The TNC in the supernatant was measured
colorimetrically on the Lachate auto-analysis system.
The 15N in the supernatan t was determined by an isotope
mass spectrometer detector (ANC A- S L/2 0- 20 ) .
3. Results and Discussion
3.1. Nitrogen in the Soil
TNC in the soil layers were varied among different
treatments. Figure 1 shows that in terms of the TNC
change trend in the soil of 0 - 100 cm, there were steady
decreases in the two plots which were treated by mono-
culture; however, it decreased slowly in the two plots
treated by polyculture, especially in the plot of C + P +
M which increased in the layer of 0 - 60 cm and then de-
creased sharply. The highest TNC in the surface layer (0
- 20 cm) is the plot of C + M which reached up to 1514
kg/ha, the other three plots were approximately in the
range of 900 kg·ha–1.
Straw mulch cannot only keep nitrogen in the surface
Table 1. Soil properties before experiment.
pH Organic Matter
(g·Kg–1) CEC
(mmol·kg–1) Available N (mg·Kg–1) Extractable P (mg·Kg–1) Exchangeable K (mg·Kg–1) Total N (g·Kg–1) Total P (g·Kg–1) Total K (g·Kg–1)
6.27 9.49 10.2 9.67 3.0 72.3 0.21 0.16 8.65

J. ZHANG ET AL. 592
80-100
60-80
40-60
20-40
0-20
-- 600 700 800 9001000110012001300
Total Nitrogen Content (kg.ha-1)
Soil Depth ( cm)
CPM
CM
CP
C
There are two reasons which might explain this phe-
no
as applied (30
Ju
3.3. Biomass Yield and Nitrogen Absorption
were
6 June19 June30 June4 August
3
4
5
6
7
8
9
Figure 1. Total nitrogen retention in the soil (0 - 100 cm)
after harvest.
layer of the soil, but also can improve the yield and water
use efficiency [16]. Alexandra found that a mulch-based
cropping system could increase TNC in the surface soil
layer (0 - 30 cm) in the long-term. Similar results were
found in this experiment, with the TNC of the surface
soil layer (0 - 60 cm) in the mulched plots being higher
than the un-mulched ones. However, there were no sig-
nificant differences in the deeper soil layer (80 - 100 cm)
among these four treatments. Conversely, the plots treat-
ed by C + M had higher TNC in the soil layer of 0 - 20
cm. This may be due to the straw being decomposed 3
months after mulching; however, maize cannot utilize
surface nitrogen because of its deeper root and less rain-
fall at that time.
In summary, mulch and polyculture are the two treat-
ments keeping nitrogen in the surface soil layer (0 - 60
cm) which provide more nutrients for the crops of next
season. However, nitrogen accumulation in the soil is
regarded as a potential danger for the water system, be-
cause it is leached out when the rainy season arrives. Its
termed as a “memory effect” in [17]. Therefore, C + P +
M is suitable for intensive agriculture, because it can
provide more nutrients for the following season with less
fertilizer N consumption.
3.2. Nitrogen in the Leachate
With regards to TNC in the leachate, there were no ob-
vious differences between the four treatments, Figure 2.
After basic fertilizer was applied, there was no drainage
water in the lysimeter until 6 June. At beginning, the
TNC in the leachate from the two plots treated by mulch
were a little lower than the o ther two plots.
During the whole cropping period, the peak of the
TNC in the leachate occurred three months after the basic
fertilizer was applied, and reached up to more than 7
kg·ha–1.
menon. Firstly, plants do not consume too much ni-
trogen after the growing period, therefore the nitrogen in
the root zone will be leached. Secondly, as [18] described,
the period which is most prone to leaching is autumn,
because during that time evaporation decreases and soil
moisture increases, soil microbial activities increase, and
there is an increased mineralization of organic nitrogen,
which cause more nitrogen to be leached.
Two months after the basic fertilizer w
ne), the TNC in the leachate was at the bottom. We
consider this to be because two months after maize being
planted is the fast growing period, with nitrogen being
rapidly taken up by the crops, and the amount of the fer-
tilizer nitrogen leached during this season is normally
low [19].
The crops’ nitrogen absorption in the plots which
treated by polyculture was much higher than in the
monoculture plots. The highest nitrogen absorption by
the crops was the treatment of C + P + M, reaching up to
124 kg/ha; the lowest was C + M, which only recorded
87.6 kg/ha. As for monoculture, un-mulched plots had
higher nitrogen absorption than mulched plots, which is
similar to the results of other research (Wang Wei-Ming,
1986). The main reason is that straw has a high C/N con-
tent which may cause nitrogen immobilizati on. Th erefor e
available nitrogen in the plots of C + M is not sufficient
for the crops’ growth. However, the intercropping plots
had the opposite results; with the reason being that the
nitrogen fixed by the peanut is not Figure 3 shows that
the crops’ nitrogen absorption in the plots which were
treated by polyculture were much higher than in the
monoculture plots. The highest nitrogen absorption by
the crops was the treatment of C + P + M, reaching up to
10
Total Nitrogen Content in Leachate ( kg.ha-1)
Time
C
CP
CM
CPM
Figure 2. Nitrogen leaching from farmland during gro
season. w

J. ZHANG ET AL. 593
140
120
100
80
60
40
20
0 C C+P C+M C+P+M
Peanut
Maize
Treatments
Kg/ha) Nitrogen Absorption by Crops(
Figure 3. Nitrogen absorption by crops after harvest.
24ed 1
8 kg/ha; the lowest was C + M, which only record 7.6 kg/ha. As for monoculture, un-mulched plots had a
higher nitrogen absorption than mulched plots, which is
similar to the results of other research (Wang Wei-Ming,
1986). The main reason is that straw has a high C/N con-
tent which may cause nitrogen immobilization, therefore
available nitrogen in the plots of C + M is not sufficient
for the crops’ growth. However, the intercropping plots
had the opposite results; with the reason being that the
nitrogen fixed by the peanut is not only used by the crops
but also by the microorganism. Therefore the number of
microorganisms in the soil explodes in a short time, and
the microorganism can decompose the mulched straw
which will provide more nitro gen resources for the crops
that may contribute to the yield enhancement by inter-
cropping [20].
Compared to monoculture, the intercropping system
contributes greatly to crop production through its effec-
tive utilization of resources [21,22]. This research pro-
duced the same results, with crops absorbing more ni-
trogen in plo ts which were treated by polycultu re. This is
because legumes can fix nitrogen from the air and pass it
to the cereals which are intercropped with them [23-25].
However, if it is not handled properly, polyculture will
fail to work better than monoculture. For exa mple, when
maize is intercropped with ryegrass, they not only sho w-
ed weaker growth but also took up smaller amounts of
nitrogen than plant maize alone [26].
4. Nitrogen Recovery
Fertilizer N utilization by crops and retention in the soil
were calculated as Equations (1)-(6):
Amount ofn
% utilizationofaddedfertiliser =utrient inthe plant derived from the fertiliser100
Amountofnutrientapplied a sfertiliser (1)


15 plant/soil/water
15 Fertilizer
atom % N excess
%Ndff 100
atom % N excess
  (2)
 





2
2
10000 mhaSDW kg
DM yieldkg/haFW kgSFW kg
area harvested m
 (3)
 
%N
N yield = DM kg/ha kg/hayield 100  (4)
 
%Ndff
Fertilizer N yiel d kg/ha kg/= N yiedhal100  (5)
Fertilizer N yield
% fertilizer N utilization= 100
Rate of N application (6)
where: ction of N in the plant derived from the 15N
ple dry weight.
4.
s, C + P had
the highest NUE (reaching up to 24.38%), while maize
are planted together, the intercropping system has effi-
ciency more efficient use of natural resources [27-29].
by monoculture,
, however the plots
e opposite trend. In the
polyculture plots, mulched plots had a higher nitrogen
absorption yet lower NUE. This may be because peanuts
Ndff—Fra
labeled fertilizer.
FW—Fresh wei ght per area ha rvest e d.
SDW—Subsam
SFW—Subsample fresh weight.
DM—Dry matter Yield.
1. Fertilizer N Utilized by Crops
Considering fertilizer N utilization by crop
monoculture had the lowest NUE of only 18.36%. Be-
cause competition exists between the two crops which
In the two plots which were treated
straw mulch increased the NUE
treated by polyculture displayed th

J. ZHANG ET AL. 594
can fix the nitrogen, therefore the system has enough
nitrogen resources, and mulched straw can be decom-
posed fast and provides more nitrogen resources for the
crops (which can cause lower NUE). In the monoculture
plots, surface mulch can reduce the fertilizer nitrogen
pe
NO
rcolation and volatilization , which may improve NUE;
therefore, mulched crops have higher NUE.
4.2. Fertilizer N Retention in the Soil
When maize is intercropped with legume crops, nitrogen
content in the soil p rofiles will improve significantly [30].
In our experiment, 47.63% of the fertilizer N remained in
the soil (0 - 100 cm) after harvest in the plots of C + P +
M, which was the high est amongst these four treatments.
However, maize monoculture plots have the lowest fer-
tilizer N soil retention (only 12.52%). This is because
legume crops can improve soil fertility through biologi-
cal nitrogen (N) fixation [31].
Straw mulch can increase the soil fertilizer N retention,
3

content and improve soil fertility after harvest [32 ].
Results show that the fertilizer N soil retention in the
polyculture plots which were treated by mulch and un-
mulch were 47.634% and 30.69% respectively; in the
monoculture plots, the figures were 23.06% and 12.52%
respectively.
Table 2. Dry matter yield and nitrogen absor
Fertilization (kg/ha) Dry M
ption by crops under different field treatments.
atter (kg/ha)
Treatments N P K Biomass Grain Nitrogen Absorption (kg N/ha)
C
Maize 276 126 252 16253.3 ± 150.3 6540 ± 62.3 90.3 ± 7.5
1951.11 ± 13.5 48.5 ± 3.6
1680.88 ± 19.1 62.9 ± 5.8
C + M
Maize
Maize 5.2 2048.3 47.5 ± 3.6
Pt 126 252 4786.± 37.4 1344.± 15.9 77.1 ± 5.4
C + P
Maize 130 4933.3 ± 73.4
Peanut 0
126 252 6997.0 ± 38.1
276 126 252 15573.3 ± 128.8 5720 ± 41.6 87.6 ± 5.2
C + P + M
130 195.6 ± 614.44 ± 1
eanu0 6 3
Table 3. Nitrogen fertilization utilization among different treatments.
ments ertilizer NFertilizeTreatTotal N (kg/ha) F (kg/ha) r utiliz a ti on (%)
C
Crop 90.3 ± 7.5 50.67 ± 6.2 18.
il 44.41.5 34.55 ±
22.93 ± 8.1 - -
87.61 ± 5.2 65.2 ±
Soil 23.06
Water -
C+P
1
C+P+M
36
So368 ± 164.8 12.52
Water
Deficit
C+M
69.12
Crop 4.5 23.62
4804.8 ± 159.6 63.64 ± 8.7
22.25 ± 5.2 -
Deficit 53.32
Crop 11.5 3 ± 9.4 31.7 ± 2.1 24.38
Soil 4058.88 ± 173.8 39.9 ± 5.7 30.69
Water 22.01 ± 4.5 - -
Deficit 44.93
Crop 124.51 ± 9.0 25.9 ± 1 .9 19.92
Soil 4878.72 ± 168.2 61.92 ± 7.1 47.63
Water 22.33 ± 3.2 - -
Deficit 32.45

J. ZHANG ET AL. 595
4.3. Fer
Results shohat polyculture is omost effective
ways to e fertilizer N lolizer losses in
the plotsd by C + P + MP were 32.45%
and 44.spectively. However, in the plots treated
by C an they were 69.12% an d 53.32%.
Surface straw mulch can re
effectivelnd in our resed 15.8% and
12.48% rtilize N lossesonoculture and
olycultpectively. This is because s
evaporation and retain soil
the yield and reduce
- 100 cm), however, it should be
systems because it may sacrifice
in the first season when used in
6.
, B. Wolff, C. D’Antonio, A. Dob-
indler, W. H. Schelsinger, D.
er, “Forecasting Agriculturally
tilizer N Losses
w
educ
tn e of the
sses. The fertir
treate and C +
93% re
d C + Mduce the fertilizer N losses
y, aarch it reduce
of fe in the m
pure plots resurface
straw mulch can reduce soil
moisture, which may increase nu-
trient losses [33-35].
5. Conclusions
According to the results and discussions above, we can
confidently draw the fo llowing conclusions:
Maize intercrop with peanut is an effective way to re-
duce fertilizer N losses, increasing the nitrogen absorp-
tion by crops and fertilizer N retention in the soil profiles
(0 - 100 cm); however, it has a lesser effect on NUE.
Compared with un-mulched plots, surface rice straw
mulch can reduce nitrogen losses and keep nitrogen in
the root zone area (0
used in intercropping
the crop dry matter yield
maize monoculture.
Acknowledgements
This study was supported by Key Project of Nation Spark
Program of China (201176GA0009) and National Peo-
ple’s Livelihood Science and Technology Plan of China
(2011MSB05007).
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