2016 SWAT Conference Reporter: Chengchun Sun Co-worker: Shufeng Chen; Wenliang Wu

Transcription

1 Nitrate leaching characteristics in a typical high-yield production area under different irrigation and fertilization management practices in the North China Plain 2016 SWAT Conference Reporter: Chengchun Sun Co-worker: Shufeng Chen; Wenliang Wu sunspringer@gmail.com Shandong.baozi@163.com 1

2 Contents Purpose Methodology Results Discussion Conclusions 2

3 Purpose Background Review 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 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 District Effects of improving nitrogen management on nitrogen utilization, nitrogen balance, and reactive nitrogen losses in a Mollisol with maize monoculture in Northeast China 3

4 Purpose Nitrogen N management alternative:(the optimized one) N fertilization based on soil testing provide ideas for us to optimize N management Irrigation Irrigation management alternative:(the optimized one) Irrigation based on real-time soil moisture monitoring Purpose Purpose: To analyze nitrate leaching characteristics of different fertilization and irrigation managements in the typical wheatmaize rotation system put up a proper BMP to reduce nitrate leaching 4

5 Purpose I 2, optimized irrigation is based on real-time soil moisture monitoring N 2, optimized N fertilization is based on soil testing I 1 N 1 traditional N fertilization & Irrigation management I 2 N 1 optimized N fertilization & traditional irrigation management Irrigation & Fertilization I 1 N 2 traditional N fertilization & optimized irrigation management I 2 N 2 optimized N fertilizer & optimized irrigation 5

6 Methodology Nitrate Pollution Level Study Area Site and elevation Huantai County, Shandong province in the NCP This picture showed us the groundwater nitrate pollution level. 6

7 Methodology Field Monitoring Experiment The Darcy s Law The 2.0m soil layer Depth at 2.0m of soil layer Water moisture; Nitrate concentrations; Water drainage amount Nitrate leaching amount Precipitation Fertilization Irrigation 7

8 Methodology Crop Two tensiometers Neutron tube Determining drainage amounts Extractor of soil solution Settings of monitoring equipments 8

9 Methodology Irrigation events of the four managements for wheat cropping season Winter wheat Winter wheat Items I 1 /mm I 2 /mm Date N 1 I 1 N 2 I 1 N 1 I 2 N 2 I Total Total Precipitation: relatively high & temporally uneven 9 Irrigation:67.5 mm for all managements at heading stage of maize.

10 Methodology N fertilization of the four managements Items Fertilizer application rate/ kg N ha -1 Season Date N 1 I 1 N 2 I 1 N 1 I 2 N 2 I , Summer maize , Winter wheat 2007, Summer maize , Winter wheat Subtotal Subtotal Subtotal Subtotal Total

11 Results Fig. 1 Rainfall from June, 2005 to May, 2008 in Huantai County (2005) , Drier in summer , wetter in winter 11

12 nitrate concentrations:n 2 (optimized) lower than N 1 ;(Triangle<rectangle ) I 2 (optimized) higher than I 1 ;(white>black) Effects of two practices on con.(gaps of con. Changes): N is higher than I 12 nitrate concentrations of both N 2 I 1 and N 2 I 2 management had a decreasing trend from 2006 to 2008, while the two under N 1 managements were inclined to increase.

13 N1 input N1 input High at first, stable then. Less precipitation and only minor water drainage Rise under I 1 ; Correspondingly, water drainage under I 1, but not I 2 N con. increased sharply, heavy water drainage No obvious changes, though slight water drainage occurred. 13

14 N 2 input are much less than N 1 Even heavy water drainage in summer of 2007, No obvious N con. increasing 14

15 N amount= sum(c N *Water drainage) N leaching characteristic is similar to water 2006,summer maize wheat 2007, summer maize wheat 15 Almost no leaching Nitrate leaching occurred only under N 1 I 1 and N 2 I and kg N ha -1, respectively Irrigation and P Serious nitrate leaching Excessive rainfall occurred Same N 1, NLA of I 2 higher than I 1 Same I, NLA of N 2 half of N 1 NLA under I 1 heavier than I 2 Same I 1,NLA of N 2 1/2 of N 1 Same I 2, NLA of N 2 1/3 of N 1

16 Discussion N first or I first? Nitrate con. gaps caused by nitrogen input is obvious than irrigation I 2 worked in wet winter season. N first Irr. manag. can be considered. Results Convincing? 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 What is proposed? 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. 16

17 Conclusion 01 The experiment showed that elevated nitrate con. were found in the relative wet season, especially under the traditional N management. Soil nitrate movement to deeper soil layer should be considered an important pathway of N losses in the wheat-maize fields. 02 N input play a great role in decreasing nitrate concentrations in the soil solutions. N 2 effectively decrease N leaching. timely N supplement are need when P is high 03 Less water inputs of I 2 increase N con. in the extracted soil solutions reduce N leaching amounts I 2 should also be proposed 17

18 18 Thank you for your attention!