Evaluation of biological and chemical nitrogen indices for predicting nitrogen-supplying capacity of paddy soils in the Taihu Lake region, China

Wenjun Li; Yongqiu Xia; Chaopu Ti; Xiaoyuan Yan

Biology and Fertility of Soils 47(6): 669-678

2011


ISSN/ISBN: 0178-2762
DOI: 10.1007/s00374-011-0577-x
Accession: 036083595

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Abstract
Simple and rapid chemical indices of soil nitrogen (N)-supplying capacity are necessary for fertilizer recommendations. In this study, pot experiment involving rice, anaerobic incubation, and chemical analysis were conducted for paddy soils collected from nine locations in the Taihu Lake region of China. The paddy soils showed large variability in N-supplying capacity as indicated by the total N uptake (TNU) by rice plants in a pot experiment, which ranged from 639.7 to 1,46.2 mg N?pot?1 at maturity stage, representing 5.8% of the total soil N on average. Anaerobic incubation for 3, 14, 28, and 112 days all resulted in a significant (P?<.1) correlation between cumulative mineral NH4+-N and TNU, but generally better correlations were obtained with increasing incubation time. Soil organic C, total soil N, microbial C, and ultraviolet absorbance of NaHCO3 extract at 25 and 26 nm revealed no clear relationship with TNU or cumulative mineral NH4+-N. Soil C/N ratio, acid KMnO4-NH4+-N, alkaline KMnO4-NH4+-N, phosphate borate buffer extractable NH4+-N (PB-NH4+-N), phosphate borate buffer hydrolyzable NH4+-N (PBHYDR-NH4+-N) and hot KCl extractable NH4+-N (HKCl?NH4+-N) were all significantly (P?<.5) related to TNU and cumulative mineral NH4+-N of long-term incubation (>28 days). However, the best chemical index of soil N-supplying capacity was the soil C/N ratio, which showed the highest correlation with TNU at maturity stage (R?=??.929, P?<.1) and cumulative mineral NH4+-N (R?=??.971, P?<.1). Acid KMnO4-NH4+-N plus native soil NH4+-N produced similar, but slightly worse predictions of soil N-supplying capacity than the soil C/N ratio.

Evaluation of biological and chemical nitrogen indices for predicting nitrogen-supplying capacity of paddy soils in the Taihu Lake region, China