Nitrate leaching characteristicsin a typical high-yield production area under different irrigation and fertilization management practices in the North China Plain

2016 SWAT ConferenceReporter: Chengchun SunCo-worker: Shufeng Chen;

Wenliang WuEmail：sunspringer@gmail.comShandong.baozi@163.com

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Contents

Purpose

Methodology

Results

Discussion

Conclusions

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Purpose

Background:Nitrate contamination has been a common problem in groundwater of the North China Plain (NCP),owing to irrigation and overuse of fertilizers.Best management practices (BMPs) guideline for famers is a kind of mission of SWAT modeling.

Review :Improved water and nitrogen management practices are alternative BMP to decrease nitrate leaching into groundwater.

Articles Related(Mahvi et al. 2013; Zhang et al. 1996，Hu et al. 2010; Sun et al. 2010；Yan et al. 2016) etc.Agricultural activities impact on groundwater nitrate pollution；Agricultural water-saving and sustainable groundwater management in Shijiazhuang Irrigation DistrictEffects of improving nitrogen management on nitrogen utilization, nitrogen balance, and reactive nitrogen losses in a Mollisol with maize monoculture in Northeast China

Background

Review

articles

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Purpose

N management alternative:(the optimized one)N fertilization based on soil testingprovide ideas for us to optimize N management

Irrigation management alternative:(the optimized one)Irrigation based on real-time soil moisture monitoring

Purpose:To analyze nitrate leaching characteristics of different fertilization and irrigation managements in the typical wheat-maize rotation systemput up a proper BMP to reduce nitrate leaching

Nitrogen

Irrigation

Purpose

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I1N1

I2N1

I1N2

I2N2

traditional N fertilization&Irrigation management

traditional N fertilization&

optimized irrigation management

optimized N fertilization

&

traditional irrigation management

optimized N fertilizer

&

optimized irrigation

Irrigation

&

Fertilization

Purpose

I2, optimized irrigation is based on real-time soil moisture monitoringN2, optimized N fertilization is based on soil testing

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Methodology

Study AreaSite and elevation

Nitrate Pollution Level

Huantai County, Shandong province in the NCPThis picture showed us the groundwater nitrate pollution level.

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Water drainage amountNitrate leaching amount

Water moisture; Nitrate concentrations;

PrecipitationFertilization

Irrigation

Field Monitoring Experiment

The Darcy’s

Law

Methodology

The 2.0m soil layer

Depth at 2.0m of soil layer

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Methodology

Two tensiometers

Neutron tube

Extractor of soil solution

Crop

Determining drainage amounts

Settings of monitoring equipments

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MethodologyIrrigation events of the four managements for wheat

Items I1/mm I2/mmcropping season Date N1I1 N2I1 N1I2 N2I2

06-07Winter wheat

10-05 67.5 67.5 40 40

11-27 67.5 67.5 42 4103-23 67.5 67.504-03 43 4104-26 67.5 67.5 46 4005-13 48 4105-25 58 5806-07 67.5 67.5 50 52Total 337.5 337.5 327 313

07-08Winter wheat

10-18 67.5 67.5

12-08 67.5 67.5 40 4003-25 67.5 67.504-03 55 4004-26 67.5 67.505-29 48 4006-06 67.5 67.5Total 337.5 337.5 143 120

Precipitation: relatively high & temporally unevenIrrigation:67.5 mm for all managements at heading stage of maize.9

MethodologyN fertilization of the four managements

Items Fertilizer application rate/ kg N·ha-1

Season Date N1I1 N2I1 N1I2 N2I2

2006,Summer maize

06-02 100 100 3806-1606-28 100 35 10007-23 100 100 38

Subtotal 300 35 300 38

2006-2007,Winter wheat

10-05 150 15003-20 150 40 150 3504-0204-16 22 18

Subtotal 300 62 300 53

2007,Summer maize

05-26 100 10006-09 63 5706-26 100 10007-28 100 100

Subtotal 300 63 300 57

2007-2008,Winter wheat

10-16 150 15003-20 150 44 150 3604-0204-16 30 31

Subtotal 300 74 300 67Total 1200 234 1200 215

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Results

Fig. 1 Rainfallfrom June, 2005to May, 2008in Huantai County(2005)

2006-2007, Drier in summer

2007-2008, wetter in winter

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nitrate concentrations：N2 (optimized) lower than N1;(Triangle<rectangle ) I2 (optimized) higher than I1;(white>black)

Effects of two practices on con.(Gaps of con. Changes): N is higher than I

nitrate concentrations of both N2I1 and N2I2 management had a decreasing trend from 2006 to 2008, while the two under N1 managements were inclined to increase.

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High at first, stable then. Less precipitation and only minor water drainage

Rise under I1; Correspondingly, water drainage under I1, but not I2

N con. increased sharply, heavy water drainage

No obvious changes, though slight water drainage occurred.

N1 input

N1 input

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Even heavy water drainage in summer of 2007,No obvious N con. increasing

N2 input are much less than N1

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2006-2007wheat

2006,summer maize

2007, summer maize

2007-2008wheat

•Almost no leaching

• Nitrate leachingoccurred only underN1I1 and N2I1•23.00 and 23.99 kgN·ha-1, respectively•Irrigation and P

• Serious nitrate leaching•Excessive rainfall occurred•Same N1, NLA of I2higher than I1•Same I, NLA of N2half of N1

• NLA under I1heavier than I2•Same I1,NLA of N2 1/2 of N1

•Same I2, NLA of N2 1/3 of N1

N amount= sum(CN*Water drainage)N leaching characteristic is similar to water

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Discussion

What is proposed?Results Convincing?N first or I first?

• Nitrate con. gaps caused by nitrogen input is obvious than irrigation

• I2 worked in wet winter season.

N firstIrr. manag. can be considered.

• The leaching amounts were close to those reported by in this region (Zhang et al. 2005; Zhu et al. 2005)

•Report:N leaching did occurr in low-rainfall regions, episodically during extraordinarily wet periods; just as ours in summer of 2007

• Less nitrogen input is quite important for nitrate reduction

• Customs to obtain high grain yield though high N input should be conducted and reduced reasonably

•Economic incentive measures might be tried.

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Conclusion

030201

• The experiment showed that elevated nitrate con. were found in the relative wet season, especially under the traditional Nmanagement.

•Soil nitrate movement to deeper soil layer should be considered an important pathway of N losses in the wheat-maize fields.

• N input play a great role in decreasing nitrate concentrations in the soil solutions.

• N2 effectively decrease N leaching.

• timely N supplement are need when P is high

• Less water inputs of I2•increase N con. in the extracted soil solutions

•reduce N leachingamounts

•I2 should also be proposed

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Thank youfor your attention!

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