Pedosphere 28(1): 135--143, 2018
ISSN 1002-0160/CN 32-1315/P
©2018 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Fate of Basal N Under Split Fertilization in Rice with 15N Isotope Tracer
LI Ganghua1, LIN Jingjing1,3, XUE Lihong2, DING Yanfeng1, WANG Shaohua1, YANG Linzhang2
1National Engineering and Technology Center for Information Agriculture, Key Laboratory of Crop Physiology and Ecology in Southern China, Nanjing Agricultural University, Nanjing 210095 (China)
2Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014 (China)
3Yancheng Biological Engineering Higher Vocational Technology School, Yancheng 224051 (China)
      Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen (N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understanding of the basal N fate under split fertilization is crucial for determining rational basal N split ratio to improve the yield and reduce the loss to environment. A two-year field experiment with two N rates of 150 and 300 kg N ha-1, two split ratios of basal N, 40% and 25%, and two rice varieties, Wuyunjing 23 (japonica) and Y-liangyou 2 (super hybrid indica), was conducted. Labelled 15N urea was supplied in micro-plots as basal fertilizer to determine the plant uptake, translocation, soil residual, and loss of basal N fertilizer. The results showed that basal N absorbed by rice was only 1.6%-11.5% before tillering fertilization (8-10 d after transplanting), 6.5%-21.4% from tillering fertilization to panicle fertilization, and little (0.1%-4.4%) after panicle fertilization. The recovery efficiency of basal N for the entire rice growth stage was low and ranged from 18.7% to 24.8%, not significantly affected by cultivars or N treatments. Soil residual basal N accounted for 10.3%-36.4% and decreased with increasing total N rate and basal N ratio, regardless of variety and year. 43.8%-70.4% of basal N was lost into the environment based on the N balance. Basal N loss was significantly linearly positive related with the basal N rate and obviously enhanced by the increasing basal N ratio for both varieties in both 2012 and 2013. The N use efficiency and yield was significantly improved when decreasing the basal N ratio from 40% to 25%. The results indicated that the basal N ratio should be reduced, especially with limited N inputs, to improve the yield and reduce the N loss to the environment.
Key Words:  N balance,N loss,N split ratio,N use efficiency,plant uptake,rice variety,soil residual N,yield
Citation: Li G H, Lin J J, Xue L H, Ding Y F, Wang S H, Yang L Z. 2018. Fate of basal N under split fertilization in rice with 15N isotope tracer. Pedosphere. 28(1):135-143.
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