X. Yan H. Zhou Q.H. Zhu X.F. Wang Y.Z. Zhang X.C. Yu X. Peng. Carbon sequestration efficiency in paddy soil and upland soil under long-term fertilization in southern China.Soil and Tillage Research2013 130: 42–51

Abstract

Soil organic carbon (SOC) stock can be improved through the return of crop residues. However the efficiency of C sequestered in soil (i.e. ΔSOC-ΔC input) might differ among crop systems. In this paper we investigated the C input and SOC stabilization in paddy soil and upland soil under different long-term fertilization practices. Our objectives were to determine (i) the response of SOC stock to C input under different fertilization practices and (ii) C sequestration efficiency in the two contrasting agroecosystems. The long-term fertilization experiment in paddy soil started in 1981 while the adjacent upland soil experiment commenced in 1986. Each experiment consists of 9 treatments: CK (no fertilization) N P K NP NK NPK 2NPK (double dose) and NPKOM (NPK plus organic manure). Physical SOC fractions (cPOM silt + clay_f fPOM iPOM_m silt + clay_m) were isolated by sieving dispersion and density flotation. Fertilization increased crop yield and C input but it did not change the quality of SOC as revealed by CPMAS-¹³C NMR spectra. During the period of the experiment SOC stock was improved by 6.7–15.3 Mg ha⁻¹ in paddy soil for all fertilization practices while in upland soil the CK N P K and NP fertilizations reduced the SOC by 1.2–3.8 Mg C ha⁻¹ and the other four fertilizations increased it by 0.5–7.4 Mg C ha⁻¹. The change in SOC was mainly ascribed to the POM fraction whereas the two silt + clay sized fractions were independent of fertilization practice except the NPKOM treatment. At a given C input the C sequestration efficiency was greater in paddy soil than in upland soil which may be attributed to lower microbial activity but greater chemical (i.e. oxalate-soluble Fe) and physical stabilizations (i.e. soil structure) in paddy field. Our results indicate that paddy soil may sequester more SOC with higher efficiency than upland soil does.

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