Effect of different fertilization on spring cabbage (<i>Brassica oleracea L. var. capitata</i>) production and fertilizer use efficiencies

doi:10.4236/as.2011.23029

Paper Menu >>

Journal Menu >>

Vol.2, No.3, 208-212 (2011)

doi:10.4236/as.2011.23029

Agricultural Scienc es

Effect of different fertilization on spring cabbage

(Brassica oleracea L. var. capitata) production and

fertilizer use efficiencies*

Zhibin Guo1, Chuanlong He1,2#, Youhua Ma3, Hongbin Zhu1,2, Feng Liu1,2, Daozhong Wang1,2,

Li Sun3

1Soil and Fertilizer Research Institute, Anhui Academy of Agricultural Sciences, Hefei, China;

2Key laboratory of Nutrient Cycling and Resources Environment, Anhui Province, Anhui Academy of Agricultural of Agricultural

Sciences, Hefei, China;

3Resources and Environment College of Anhui Agriculture University, Hefei, China; #Corresponding Author:

hcl60128@yahoo.com.cn

Received 23 May 2011; revised 13 July 2011; accepted 27 July 2011.

ABSTRACT

Just after transplanting, the vegetable has dif-

ficulty in nutrients uptake. To explore the effect

of different fertilization on spring cabbage (Bras-

sica oleracea L. var. capitata) production and

fertilizer use efficiencies, this experiment con-

sisting of six treatments was implemented and

divided into three groups: 1) no fertilizer (NF)

and vegetable planting fertilizer (VPF); 2) con-

ventional fertilizer (CF) and conventional fertil-

izer + vegetable planting fertilizer (CVPF); 3)

reduced fertilizer application (RFA) and reduced

fertilizer application + vegetable planting fertil-

izer (RVPF). The results of this experiment in-

dicated that the yi elds of sprin g cabbage treate d

by VPF increased by 38.20% in VPF, 16.00% in

CVPF and 20.40% in RVPF than their controls

respectively. Additionally, the VPF helped im-

prove the total and economic yields of the

spring cabbage in all groups, and the economic

benefits increased by 38.21% in VPF, 15.97% in

CVPF and 20.42% in RVPF than their controls

respectively. Finally, the VPF was of benefit to

spring cabbage to exploit the soil nutrients and

helped improve the chemical fertilizer use effi-

ciencies. Therefore, it is an efficient, economical

and ecological fertilization for vegetable pro-

duction to apply chemical fertilizers in combi-

nation with VPF.

Keywords: Spring Cabbage; Fertilizer Use

Efficiency

1. INTRODUCTION

With an ever-growing population, China has to raise

agricultural productivity in its limited and shrinking

farmland to guarantee food. To increase the grain yield,

a great amount of chemical fertilizers were applied to the

agricultural system. Some study reported that the appli-

cation of chemical fertilizers in China ranged from 225

to 375 kg·ha–1 1. Specially, the applied N fertilizer

ranged from 400 to 600 or more than 600 kg N·ha–1·year–1

in the agricultural regions of intensive farming in the

Northern Plain of China 2,3. For the greenhouse vege-

table, the nitrogen fertilization was as high as 1000 -

1500 kg·ha–1·year–1 2. With the over-application of

fertilizer, the non-point pollution has become seriously

in China and other worldwide regions 4-7. For exam-

ple, over 50% of the wells in Northern Plain of China

have been polluted which were related to the NO3-N

leaching caused by excessive N fertilizer left in the

cropland 6. The coastal regions related about seven

Provinces in China have already suffered seriously en-

vironmental pollution by NPS, which were primarily

caused by the excessive application of synthetic fertilizer

(particular nitrogen) and organic manure 8,9.

It is urgent to strengthen the fertilizer management

and improve the fertilizer use efficiency in agricultural

system. Across the world, only about 30% - 50% of the

nitrogen fertilizer and 45% of the phosphorus fertilizer

were taken up by crops 10,11. Specially, the N and P

fertilizer use efficiencies were much lower and only

about 30% - 35% and 10% - 20% in China (Soil and

fertilizer Institute CAAS, 1994). To secure a maximum

grain yield, excessive fertilizer was applied by farmers

*This research was supported

y National Key Technology R&D

Program (2007BAD87B06) and President Youth Innovation Fund

(11B1021).

Z. B. Guo et al. / Agricultural Science 2 (2011) 208-212

209209

and contributed to a higher production cost and worse

soil structure through salinization and other forms of

physical, chemical and biological degradation 12-14.

Therefore, a project called decrement and synergism of

chemical fertilizers have been widely proposed for fer-

tilizer management in China 15,16.

It is possible to maintain or increase the grain yield

under limited fertilizer input. The most important step is

to increase the fertilizer use efficiency and implement

the decrement and synergism of chemical fertilizer pro-

ject. Previous studies on limiting N fertilizer demon-

strated that the yield of grain, vegetable and fruit could

be maintained 17-19, and N fertilizer could be saved

by 22% then reduced the runoff N and leaching N by

30% - 40% and 32.3% respectively 20.

In some areas of intensive vegetable production, the

fertilizer use efficiency was low shortly after transplant-

ing 21. Vegetable planting fertilizer (VPF), which con-

sists of Ca(NO3)2, CO(NH2)2, (NH4)2SO4, KH2PO4, etc.,

is a new kind of fertilizer invented by Pro He in 2009

and is beneficial to spring cabbage (Brassica oleracea L.

var. cap ita ta) production and fertilizer use efficiency. To

explore the effects of different fertilization on spring

cabbage production and fertilizer use efficiencies, this

experiment was designed. During the experiment, three

groups consisting of six treatments were implemented: 1)

no fertilizer (NF) and vegetable planting fertilizer (VPF);

2) conventional fertilizer (CF) and conventional fertilizer

+ vegetable planting fertilizer (CVPF); 3) reduced fertil-

izer application (RFA) and reduced fertilizer application

+ vegetable planting fertilizer (RVPF). The aim of this

research was to find a new regime of fertilization to im-

prove the fertilizer use efficiencies and maintain the high

production of vegetable

2. MATERIALS AND METHODS

2.1. Site Description

The experiment was conducted at Jiashen Country in

the Juchao region of Chaohu city, Anhui Province,

China (31˚16′ - 32′ N, 117˚25′ - 58′ E and 105 m above

sea level). The annual mean temperature is 15.7 - 16.1˚C,

ranging from –7.0˚C in January to 40˚C in July. The

annual mean precipitation is about 1200 mm, and 28% -

32%, 38% - 44%, 18% - 19% and 10% - 11% of which

occurred in March-May, June-August, September-Oc-

tober and December-February respectively. The average

annual potential evaporation is about 1500 mm. The soil

is yellow brown earth with 15.0 g·kg–1 soil organic matter,

71.2 mg·kg–1 available phosphorus and 261.2 mg·kg–1

available potassium.

2.2. Experimental Design

The experiment was implemented from 26th February

2009 to 9th May 2009 and divided into three groups con-

sisting of six treatments: 1) no fertilizer (NF); 2) vegeta-

ble planting fertilizer (VPF); 3) conventional fertilizer

(CF); 4) conventional fertilizer + vegetable planting fer-

tilizer (CVPF); 5) reduced fertilizer application (RFA); 6)

reduced fertilizer application + vegetable planting fertil-

izer (RVPF). In CF, 525 kg·ha–1 carbamide and 750

kg·ha–1 NPK (N20-P20-K20) synthetic fertilizer were

applied as base fertilizer and 225 kg·ha–1, 225 kg·ha–1

and 300 kg·ha–1 NH4HCO3 were used for topdressing in

the seedling stage, rosette stage and head formation pe-

riod of spring cabbage respectively. The amount of

chemical fertilizer applied in RFA was 70% of CF

across the spring cabbage growth. In all VPF treatments,

the spring cabbage was treated by 500 ml of 0.112%

vegetable planting fertilizer solution per individual. In

the experimental site, the crop system was spring cab-

bage/corn inter-planting, in which the conventional fer-

tilizer was implemented for spring cabbage growth and

no fertilizer in corn growth. Each plot, about 15 m3, was

replicated three times in a completely randomized design.

2.3. Sampling and Analysis

Plant samples were taken randomly in the head for-

mation period and harvest time of spring cabbage with

three replicates and then divided into two sub-samples:

one was calculated for productivity of spring cabbage

and the other one was dried in an oven at 105˚C for 1 h

and then at 70˚C for a minimum of 72 h for nutrient

testing. Plant nutrient content was analyzed using the

methods outlined by Nanjing Agriculture University

(1996). After a H2O2-H2SO4 digest, the plant nitrogen,

phosphorus and potassium were tested by Kjeldahl di-

gestion method, colorimetric method (using HClO4-

H2SO4) and flame photometry method 22 respectively.

2.4. Statistical Analysis

Differences among treatments on the productivity and

nutrients of spring cabbage were analyzed by ANOVA

using SAS 9.1.3. All graphs were plotted by Origin 7.5.

3. RESULTS AND DISCUSSION

3.1. Yields of Spring Cabbage

To secure a maximum yield, a large number of chemi-

cal fertilizers were used by vegetable farmers in the ar-

eas of highly intensive vegetable production, especially

N fertilizer. In this experiment, the yields of spring cab-

bage increased significantly after fertilizing. Compared

to NF, the spring cabbage yields in all fertilizing treat-

ments increased significantly (p < 0.05) both in the head

formation period and harvest time (Ta bl e 1 and Figure

Z. B. Guo et al. / Agricultural Science 2 (2011) 208-212

210

Ta bl e 1. N, P and K fertilizer, total and economic yield of spring cabbage in no fertilizer (NF), vegetable planting fertilizer (VPF),

conventional fertilizer (CF), conventional fertilizer + vegetable planting fertilizer (CVPF), reduced fertilizer application (RFA) and

reduced fertilizer application + vegetable planting fertilizer (RVPF) during the experiment.

Treatments

fertilizer

(kg·ha–1)

fertilizer

(kg·ha–1)

fertilizer

(kg·ha–1)

Total Yield*

(kg·ha–2)

Economic Yield**

(kg·ha–1)

Economic Ratios

(%)

NF 0 0 0 56847 ± 2076d 30306 ± 1107d 53.31c

VPF 4.8 3 2 64824 ± 1555c 41886 ± 1005c 64.62b

CF 481.5 112.5 112.5 81652 ± 2208ab 52854 ± 1429b 64.73b

CVPF 486.3 115.5 114.5 83833 ± 1362a 61293 ± 864a 73.12a

RFA 337.1 78.8 78.8 77715 ± 1732b 49878 ± 1102b 64.18b

RVPF 341.9 81.8 80.8 83347 ± 1854a 60065 ± 1233a 72.07a

1). In all groups, the yields of spring cabbage treated by

VPF were much higher than their controls, especially

CVPF and RVPF (Figure 1) which indicated that the

combination of VPF and chemical fertilizer performed

better than using the chemical fertilizer alone duced fer-

tilizer application and reduced fertilizer application +

vegetable planting fertilizer respectively. Error bars rep-

resent standard errors (n = 3).

the costs of fertilizers were 225.00, 5015.00, 5086.00,

3510.00 and 3582.00 Yuan·hm–2 in VPF, CF,

CVPF, RFA and RVPF respectively (the prices of N, P

and K fertilizers were 6.25 RMB Yuan·kg–1, 7.5 RMB

Yuan·kg–1 and 9.17 RMB Yuan·kg–1 respectively). From

Table 1, it is obviously to find that the economic yield of

spring cabbage treated by VPF increased significantly.

Across the experiment, the output value with different

fertilization was obviously higher than no fertilizing due

to the high vegetable yield (Figure 2). In contrast to NF,

the output value increased by 38.21% in VPF, 74.40% in

CF, 102.25% in CVPF, 64.58% in RFA and 98.20% in

CRFA respectively. Moreover, the output value of spring

cabbage treated by VPF was significantly (p < 0.05)

higher than their controls in each groups.

3.2. Economic Benefit of Spring Cabbage

During the vegetable production, the overuse of fer-

tilizer decreased the income of vegetable farmers by

increasing the production cost and reducing crop yield

caused by soil degradation 12,14,23. In this experiment,

Figure 2. The output values of spring cabbage in the experi-

ment. The NF, VPF, CF, CVPF, RFA and RVPF represented no

fertilizer, vegetable planting fertilizer, conventional fertilizer,

conventional fertilizer + vegetable plant fertilizer, reduced

fertilizer application and reduced fertilizer application + vege-

table planting fertilizer respectively. The price of spring cab-

bage was 1.0 RMB Yuan·kg–1 (the RMB Yuan is the Chinese

Currency unit). Error bars represent standard errors (n = 3).

Figure 1. Effect of different fertilization on the biomass in the

head formation period of spring cabbage. The NF, VPF, CF,

CVPF, RFA and RVPF represented no fertilizer, vegetable

planting fertilizer, conventional fertilizer, conventional fertil-

izer + vegetable plant fertilizer, reduced fertilizer application

and reduced fertilizer application + vegetable planting fertilizer

respectively. Error bars represent standard errors (n = 3).

Openly accessible at

Z. B. Guo et al. / Agricultural Science 2 (2011) 208-212

211211

3.3. Nutrient Content of Spring Cabbage

and the Fertilizer Use Efficiency

During the past decades, the land area for vegetable

production in China has increased significantly, ranging

from 3.2 to 17.6 million hectares from 1984 to 2004

(China Statistical Year book, 2005). To maximize the

yield and output value of vegetable production, the fer-

tilizer input increased significantly. For example, the

nitrogen and phosphorus fertilizers using globally in-

creased 7- and 3.5-fold from 1960 to 1995 and both were

expected to increase another 3-fold by 2050 if the fertil-

izer use efficiency was constant 24,25. Past study in-

dicated that the N, P and K fertilizer use efficiencies

were only about 30% - 35%, 10% - 20% and 40% - 50%

respectively in China (Soil and fertilizer Institute CAAS,

1994). Therefore, a great amount of NPS fertilizers was

lost and then caused seriously environmental damage

20,26,27. In this experiment, it helped improve the

fertilizer use efficiency and maintain the quality of

spring cabbage that combination of chemical fertilizer

and VPF (Tables 2 and 3). During the spring cabbage

production, the VPF helped decrease the chemical fertil-

izer and increase the economic income of vegetable

farmers. In CF, the ratio of spring cabbage output value:

fertilizer cost was 10.54; Compared to CF, the ratio of

output value to fertilizer cost increased significantly (p <

0.05) and reached to 12.05 in CVPF, 14.21 in RFA and

16.77 in RVPF respectively.

In agricultural system, nitrogen is an essential, limited

nutrient for crop growth. However, over-application of N

fertilizer could contribute to agricultural non-point

source pollution 6,7. In some areas of intensive vege-

table production, the level of applied nitrogen fertilizer

was commonly double the recommended level 28 then

over half of the nitrogen fertilizer was lost from the

Table 2. N, P and K of spring cabbage in no fertilizer (NF),

vegetable planting fertilizer (VPF), conventional fertilizer (CF),

conventional fertilizer + vegetable planting fertilizer (CVPF),

reduced fertilizer application (RFA) and reduced fertilizer ap-

plication + vegetable planting fertilizer (RVPF) during the

experiment.

Treatments N

(g kg–1)

NF 32.6 ± 1.8a 4.6 ± 0.2a 13.9 ± 0.4ab

VPF 30.6 ± 2.1a 4.6 ± 0.3a 13.0 ± 0.4b

CF 32.5 ± 0.9a 4.6 ± 0.2a 14.8 ± 0.3a

CVPF 32.3 ± 1.2a 4.6 ± 0.3a 15.0 ± 0.2a

RFA 32.3 ± 1.2a 4.5 ± 0.1a 14.3 ± 0.4ab

RVPF 31.8 ± 1.8a 4.5 ± 0.2a 14.4 ± 0.3a

Table 3. Fertilizer use efficiencies of spring cabbage treated by

different fertilization.

Fertilizer using efficiency

Treatments N (%) P (%) K (%)

VPF 148.6 ± 1.7a 153.5 ± 2.7a 180.5 ± 3.1a

CF 9.3 ± 0.3c 12.7 ± 0.5c 24.9 ± 0.6 c

CVPF 9.8 ± 0.1c 13.2 ± 0.4c 27.3 ± 1.2c

RFA 10.8 ± 0.6c 13.9 ± 0.4c 27.2 ± 1.3c

RVPF 12.9 ± 0.4b 17.8 ± 0.3b 34.0 ± 1.3b

VPF = vegetable planting fertilizer, CF = conventional fertilizer, CVPF =

conventional fertilizer + vegetable planting fertilizer, RFA = reduced fertil-

izer application and RVPF = reduced fertilizer application + vegetable

planting fertilizer. Values within a column followed by the same lower case

did not differ at p < 0.05 for the specific variable. Error bars represent

standard errors (n = 3).

cropland as gases or in drainage or runoff water before it

could benefit crop growth 2. To reduce NO3-N leach-

ing and increase N use efficiency, it is important to

strengthen the management of N inputs 12,13. From

Ta b le 3, it’s easy to find that the nitrogen fertilizer use

efficiency increased significantly after combination of

VPF and chemical fertilizer or VPF applied alone.

Among all the treatments, the N fertilizer use efficiency

of VPF was the highest and reached to 148.6%, which

suggested more nitrogen stored in the soil was exploited

by spring cabbage beside vegetable planting fertilizer.

Additionally, VPF also helped improve the chemical

fertilizer use efficiency. In each group, the fertilizer use

efficiencies of CVPF and RVPF were much higher than

their controls. Similarly, the VPF helped improve the P

and K fertilizer use efficiencies across the vegetable

production.

4. CONCLUSIONS

In the experiment, the vegetable planting fertilizer

performed better than the traditional fertilizers. In the

head formation period and harvest time of spring cab-

bage, it helped the vegetable exploit more soil nutrients

for its growth. Moreover, the vegetable planting fertilizer

combined with chemical fertilizers was beneficial to

improve the chemical fertilizer use efficiencies with

maintenance of vegetable yield, which contributed to

low fertilizer cost and increase the income of farmers.

Therefore, the vegetable planting fertilizer is an efficient,

economic and ecological fertilizer for vegetable produc-

tion after combination with chemical fertilizer. More

research needed to be done to learn how the vegetable

planting fertilizer improved the spring cabbage ability to

exploit soil nutrients during its growth.

5. ACKNOWLEDGEMENTS

The authors thank bachelors Jing Zhao, Dan Ma and Zhengfei Feng

Z. B. Guo et al. / Agricultural Science 2 (2011) 208-212

212

for their helps during the experiment.

Openly accessible at

REFERENCES

[1] Zeng, X.B. and Li, J.M. (2004) Fertilizer application and

its effect on grain production in different counties of

China. Scientia Agr icultura Sinica, 37, 387-392.

[2] Zhu, Z.L. and Chen, D.L. (2002) Nitrogen fertilizer use

in China—contributions to food production, impacts on

the environment and best management strategies. Nutri-

ent Cycling in Agroecosystems, 63, 117-127.

doi:10.1023/A:1021107026067

[3] Liu, X. and Ju, X. (2003) Nitrogen dynamics and budgets

in a winter wheat-maize cropping system in the North

China Plain. Field Crops Research, 83, 111-124.

doi:10.1016/S0378-4290(03)00068-6

[4] Newbould, P. (1989) The use of nitrogen fertilizer in

agriculture. Where do we go practically and ecologically?

Plant and Soil, 11, 297-311.

doi:10.1007/BF02202596

[5] Follett, R.F. (1989) Nitrogen management and ground

water protection. Elsevier Science Publishers, Amster-

dam.

[6] Zhang, W.L., Tian, Z.X., Zhang, N. and Li, X.Q. (1996)

Nitrate pollution of groundwater in Northern China. Ag-

riculture. Ecosystems and Environment, 59, 223-231.

doi:10.1016/0167-8809(96)01052-3

[7] Delgado, J.A. (2002) Quantifying the loss mechanisms of

nitrogen. Journal of soil water conservation, 57, 389-

398.

[8] Ju, X.T., Liu, X.J., Zhang, F.S. and Roelcke, M. (2004)

Nitrogen fertilization, soil nitrate accumulation, and pol-

icy recommendations in several agricultural regions of

China. Ambio: A Journal of the Human Environment, 33,

300-305.

[9] Shen, R.P., Sun, B. and Zhao, Q.G. (2005) Spatial and

temporal variability of N, P and K balances for agroeco-

systems in China. Pedosphere, 15, 347-355.

[10] Cassman, K.G., Dobermann, A. and Walters, D. (2002)

Agroecosystems, nitrogen-use efficiency, and nitrogen

management. AMBIO, 31, 132-140.

[11] Smil, V. (2000) Phosphorus in the environment: natural

flows and human interferences. Annual Review of Energy

Environment, 25, 53-88.

doi:10.1146/annurev.energy.25.1.53

[12] Khosla, R., Fleming, K., Delgado, J.A., Shaver, T. and

Westfall, D. (2002) Use of site specific management

zones to improve nitrogen management for precision ag-

riculture. Journal of Soil Water Conservation, 57, 513-

518.

[13] Delgado, J.A., Khosla, R., Bausch, W.C., Westfall, D.G.,

and Inman, D. (2005) Nitrogen fertilizer management

based on site specific management zones reduce potential

for nitrate leaching. Journal of Soil Water Conservation,

60, 402-410.

[14] Li, X.X., Hu, C.S., Delgado, J.A., Zhang, Y.M. and Ouy-

ang, Z.Y. (2007) Increased nitrogen use efficiences as a

key mitigation alternative to reduce nitrate leaching in

North China Plain. Agricultural Water Management, 89,

137-147. doi:10.1016/j.agwat.2006.12.012

[15] Xie, W.F. and Ye, H.H. (2007) Field experiment on dec-

rement and synergism of Chemical fertilizer. Journal of

Anhui Agriculture Science, 35, 6868-6875.

[16] Zhang, Y. Zh., Wang, K.R., Liu, J.P., Huang, Zh.N., Zeng,

X. and Zhou, Sh.Q. (2006) Demonstrations and studies

on techniques for rice quality security control. Crop Re-

search, 4, 287-296 (in Chinese).

[17] Xiao, G.X., Li, C.J., Wang, L. and Cheng, G.H. (2003)

Study of reducing the amount of using fertilizer in corn

growth. Soils and Fertilizers, 6, 37-40 (in Chinese).

[18] Yao, C.X., Chen, Z.L., Qiu, Q., Huang, Y.H., Yin, J.,

Zhang, J.X., Li, C.H. and Mao, G.F. (2005) Influence of

nitrogen fertilizer reduction amount on watermelon yield

and quality under canopy cultivation. Acta Agriculturae

Boreali-Sinica, 20, 76-79 (in Chinese).

[19] Jiang, Q., Yu, H.J. and Shi, Z.Y. (2006) Effective ways of

reducing chemical N fertilizer application in rice growth.

Journal of Shanghai Jiaotong University (Agricultural

Science), 24, 452-455 (in Chinese).

[20] Zhang, G., Wang, D.J. and Chen, X.M. (2008) Efffects of

reduced fertilizer application on environmental of paddy

field. Chinese Journal of Ecoagriculture, 16, 327-330 (in

Chinese). doi:10.3724/SP.J.1011.2008.00327

[21] Wang, G.H., Dobermann, A., Witt, C., Sun, Q.Z. and Fu,

R.X. (2001) Performance of site-specific nutrient man-

agement for irrigated rice in southeast China. Agronomy

Journal, 90, 178-185.

[22] Parkinson, J.A. and Allen, S.E. (1975) A wet oxidation

process suitable for the determination of nitrogen and

mineral nutrients in biological material. Communications

in Soil Science and Plant Analysis, 6, 1-11.

doi:10.1080/00103627509366539

[23] Buresh, R., Peng, S., Huang, J., Yang, J., Wang, G.,

Zhong, X. and Zou, Y. (2004) Rice systems in China with

high nitrogen inputs. In: Mosier, A.R., Syers, J.K. and

Freney, J.R., Eds., Agriculture and the Nitrogen Cycle:

Assessing the Impacts of Fertilizer use on Food Produc-

tion and the Environment, Island Press, Washington, 143-

153.

[24] Tilman, D., Reich, P.B., Knops, J., Wedin, D., Mielke, T.

and Lehman, C. (2001) Diversity and productivity in a

long-term grassland experiment. Science, 294, 843-845.

doi:10.1126/science.1060391

[25] Cassman, K.G. and Pingali, P.L. (1995) Intensification of

irrigated rice systems: Learning from the past to meet

future challenges. GeoJournal, 35, 299-305.

doi:10.1007/BF00989137

[26] Tong, Y.N. (2001) Nitrogen fertilizer and environment. In:

Feng, F., Ed., Study on Plant Nutrition-Progress and

Prospect, China Agricultural University Press, Beijing,

207-215 (in Chinese).

[27] Mosier, A.R. and Zhu, Z.L. (2000) Changes in patterns of

fertilizer nitrogen use in Asia and its consequences for

N2O emissions from agricultural systems. Nutrient Cy-

cling in Agroecosystems, 57, 107-117.

doi:10.1023/A:1009716505244

[28] Zhang, W.L., Wu, S.X., Ji, H.J. and Kolbe, H. (2004)

Estimation of agricultural non-point source pollution in

China and the alleviating strategies I Estimation of agri-

cultural non-point source pollution in China in early 21

century. Scientia Agricu tura Sinica, 36, 1008-1017.