title: Determination of critical nitrogen dilution curve based on stem dry matter in rice.
abstract: Plant analysis is a very promising diagnostic tool for assessment of crop nitrogen (N) requirements in perspectives of cost effective and environment friendly agriculture. Diagnosing N nutritional status of rice crop through plant analysis will give insights into optimizing N requirements of future crops. The present study was aimed to develop a new methodology for determining the critical nitrogen (Nc) dilution curve based on stem dry matter (SDM) and to assess its suitability to estimate the level of N nutrition for rice (Oryza sativa L.) in east China. Three field experiments with varied N rates (0-360 kg N ha(-1)) using three Japonica rice hybrids, Lingxiangyou-18, Wuxiangjing-14 and Wuyunjing were conducted in Jiangsu province of east China. SDM and stem N concentration (SNC) were determined during vegetative stage for growth analysis. A Nc dilution curve based on SDM was described by the equation (Nc = 2.17W(-0.27) with W being SDM in t ha(-1)), when SDM ranged from 0.88 to 7.94 t ha(-1). However, for SDM < 0.88 t ha(-1), the constant critical value Nc = 1.76% SDM was applied. The curve was dually validated for N-limiting and non-N-limiting growth conditions. The N nutrition index (NNI) and accumulated N deficit (Nand) of stem ranged from 0.57 to 1.06 and 51.1 to -7.07 kg N ha(-1), respectively, during key growth stages under varied N rates in 2010 and 2011. The values of ΔN derived from either NNI or Nand could be used as references for N dressing management during rice growth. Our results demonstrated that the present curve well differentiated the conditions of limiting and non-limiting N nutrition in rice crop. The SDM based Nc dilution curve can be adopted as an alternate and novel approach for evaluating plant N status to support N fertilization decision during the vegetative growth of Japonica rice in east China.
authors.affiliation: National Engineering and Technology Center for Information Agriculture, Jiangsu Key Laboratory for Information Agriculture, Nanjing Agricultural University, Nanjing, Jiangsu, P. R. China.
authors.forename: Syed Tahir
authors.initials: ST
authors.lastname: Ata-Ul-Karim
authors.affiliation: National Engineering and Technology Center for Information Agriculture, Jiangsu Key Laboratory for Information Agriculture, Nanjing Agricultural University, Nanjing, Jiangsu, P. R. China.
authors.forename: Xia
authors.initials: X
authors.lastname: Yao
authors.affiliation: National Engineering and Technology Center for Information Agriculture, Jiangsu Key Laboratory for Information Agriculture, Nanjing Agricultural University, Nanjing, Jiangsu, P. R. China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Liu
authors.affiliation: National Engineering and Technology Center for Information Agriculture, Jiangsu Key Laboratory for Information Agriculture, Nanjing Agricultural University, Nanjing, Jiangsu, P. R. China.
authors.forename: Weixing
authors.initials: W
authors.lastname: Cao
authors.affiliation: National Engineering and Technology Center for Information Agriculture, Jiangsu Key Laboratory for Information Agriculture, Nanjing Agricultural University, Nanjing, Jiangsu, P. R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000383:Agriculture / Q000379:methods*; D000704:Analysis of Variance; D002681:China; D003433:Crosses, Genetic; D009584:Nitrogen / Q000032:analysis*; D009747:Nutritional Physiological Phenomena / Q000502:physiology*; D012275:Oryza / Q000737:chemistry* / Q000502:physiology; D018547:Plant Stems / Q000737:chemistry*; D013045:Species Specificity
chemical_list: D009584:Nitrogen