Pedosphere 28(5): 814--822, 2018
ISSN 1002-0160/CN 32-1315/P
©2018 Soil Science Society of China
Published by Elsevier B.V. and Science Press
A New Critical Nitrogen Dilution Curve for Rice Nitrogen Status Diagnosis in Northeast China
HUANG Shanyu1,2, MIAO Yuxin1,3, CAO Qiang4, YAO Yinkun1, ZHAO Guangming5, YU Weifeng1, SHEN Jianning1, YU Kang1,2, and Georg BARETH2
1International Center for Agro-Informatics and Sustainable Development, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193(China)
2Institute of Geography, University of Cologne, Köln 50923(Germany)
3Precision Agriculture Center, Department of Soil, Water and Climate, University of Minnesota, St. Paul 55108(USA)
4National Engineering and Technology Center for Information Agriculture, Nanjing Agricultural University, Nanjing 210095(China)
5Qixing Farm, Jiansanjiang, Jiamusi 156399(China)
      In-season diagnosis of crop nitrogen (N) status is crucial for precision N management. Critical N (Nc) dilution curve and N nutrition index (NNI) have been proposed as effective methods to diagnose N status of different crops. The Nc dilution curves have been developed for indica rice in the tropical and temperate zones and japonica rice in the subtropical-temperate zone, but they have not been evaluated for short-season japonica rice in Northeast China. The objectives of this study were to evaluate the previously developed Nc dilution curves for rice in Northeast China and to develop a more suitable Nc dilution curve in this region. A total of 17 N rate experiments were conducted in Sanjiang Plain, Heilongjiang Province in Northeast China from 2008 to 2013. The results indicated that none of the two previously developed Nc dilution curves was suitable to diagnose N status of the short-season japonica rice in Northeast China. A new Nc dilution curve was developed and can be described by the equation Nc=27.7W-0.34 if W ≥ 1 Mg dry matter (DM) ha-1 or Nc=27.7 g kg-1 DM if W < 1 Mg DM ha-1, where W is the aboveground biomass. This new curve was lower than the previous curves. It was validated using a separate dataset, and it could discriminate non-N-limiting and N-limiting nutritional conditions. Additional studies are needed to further evaluate it for diagnosing N status of different rice cultivars in Northeast China and develop efficient non-destructive methods to estimate NNI for practical applications.
Key Words:  japonica rice,nitrogen nutrition index,nitrogen use efficiency,plant nitrogen concentration,precision nitrogen management
Citation: Huang S Y, Miao Y X, Cao Q, Yao Y K, Zhao G M, Yu W F, Shen J N, Yu K, Bareth G. 2018. A new critical nitrogen dilution curve for rice nitrogen status diagnosis in Northeast China. Pedosphere. 28(5):814-822.
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