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Effects of long-term fertilization on soil organic carbon pool and carbon sequestration under double rice cropping.

SUN Yu-tao1, 2, LIAO Yu-lin1, 2, ZHENG Sheng-xian1, 2, NIE Jun1,2, LU Yan-hong1,2   

  1. (1Soil and Fertilizer Institute of Hunan Province, Changsha 410125, China; 2Scientific Observing and Experimental Station of Arable Land Conservation (Hunan), Ministry of Agriculture, Changsha 410125, China)
  • Online:2013-03-18 Published:2013-03-18

Abstract:

This paper studied the effects of 30 years (1981-2010) fertilization with chemical N, P, and K, pig manure (PM), and rice straw (RS) on the soil organic carbon (SOC) and its components contents under intensive double rice cropping. The experiment was established on a typic Hapli-Stagnic Anthrosols in Hunan in 1981, and the soil samples were collected in November 2010. In treatment NPK, the contents of SOC, particulate organic C (POC), and KMnO4oxidizable C (KMnO4C) were higher than those in treatments NP and NK. The combined application of chemical and organic fertilizers (treatments NK+PM, NP+RS, and NPK+RS) made the contents of SOC, POC, and KMnO4C have a significant increase, as compared with chemical fertilizations. Treatment NK+PM had the highest contents of SOC (84.71 t C·hm-2), POC (8.94 t C·hm-2), and KMnO4C (21.09 t C·hm-2) in top soil (0-45 cm), followed by treatment NPK+RS. Treatment NK+PM had the highest C sequestration (485 kg C·hm-2·a-1), followed by treatment NPK+RS (375 kg C·hm-2·a-1). The C sequestration efficiency (CSE) of SOC in the treatments of chemical fertilizers plus pig manure or rice straw was obviously higher than that in the treatments of chemical fertilizations, and the CSE of the POC in fertilization treatments (ranging from 0.4% and 1.2%) was lower than that of the KMnO4C (ranging from 3.0% to 8.3%). By using the values of humification constant (h) and the decay constant (k) in Jenkinson’s equation, it was possible to predict the SOC storages in different treatments in the year 2010; and by using Jenkinson’s equation, it was possible to calculate the C input required to maintain the SOC storages in the year 1981 (AE). The increase of the SOC in treatments NK+PM, NP+RS, and NPK+RS was due to the annual C input being higher than the AE. It was considered that in the double rice cropping areas in subtropical region of China, long-term application of chemical fertilizers combined with pig manure or rice straw could promote the organic carbon sequestration in paddy soils.