Soil organic carbon dynamics in a dryland cereal cropping system of the Loess Plateau under long-term nitrogen fertilizer applications
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Concerns over food security and global climate change require an improved understanding of how to achieve optimal crop yields whilst minimizing net greenhouse gas emissions from agriculture. In the semi-arid Loess Plateau region of China, as elsewhere, fertilizer nitrogen (N) inputs are necessary to increase yields and improve local food security.
In a dryland annual cropping system, we evaluated the effects of N fertilizers on crop yield, its long-term impact on soil organic carbon (SOC) concentrations and stock sizes, and the distribution of carbon (C) within various aggregate-size fractions. A current version (RothC) of the Rothamsted model for the turnover of organic C in soil was used to simulate changes in SOC. Five N application rates [0 (N0), 45 (N45), 90 (N90), 135 (N135), and 180 (N180) kg N ha−1] were applied to plots for 25 years (1984–2009) on a loam soil (Cumulic Haplustoll) at the Changwu State Key Agro-Ecological Experimental Station, Shaanxi, China.
Crop yield varied with year, but increased over time in the fertilized plots. Average annual grain yields were 1.15, 2.46, 3.11, 3.49, and 3.55 Mg ha−1 with the increasing N application rates, respectively. Long-term N fertilizer application increased significantly (P = 0.041) SOC concentrations and stocks in the 0–20 cm horizon. Each kilogram of fertilizer N applied increased SOC by 0.51 kg in the top soil from 1984 to 2009. Using RothC, the calculated annual inputs of plant C (in roots, stubble, root exudates, etc.) to the soil were 0.61, 0.74, 0.78, 0.86, and 0.97 Mg C ha−1 year−1 in N0, N45, N90, N135 and N180 treatments, respectively. The modeled turnover time of SOC (excluding inert organic C) in the continuous wheat cropping system was 26 years. The SOC accumulation rate was calculated to be 40.0, 48.0, 68.0, and 100.0 kg C ha−1 year−1 for the N45, N90, N135 and N180 treatments over 25 years, respectively. As aboveground biomass was removed, the increases in SOC stocks with higher N application are attributed to increased inputs of root biomass and root exudates. Increasing N application rates significantly improved C concentrations in the macroaggregate fractions (>1 mm).
Applying N fertilizer is a sustainable practice, especially in carbon sequestration and crop productivity, for the semiarid Loess Plateau region.
KeywordsSoil organic carbon Turnover time C input Soil aggregation Long-term N fertilization RothC
This work was supported by the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau (No.10502-Z11), the "Strategic Priority Research Program—Climate Change: Carbon Budget and Related Issues" of the Chinese Academy of Sciences (No. XDA05050504) and Rothamsted International Fellowship Award. Rothamsted research is an institute of the UK Biotechnology and Biological Sciences Research Council. We thank the two anonymous reviewers for their valuable suggestions to improve the manuscript.
- Barton L, Kiese R, Gatter D, Butterbach-Bahl K, Buck R, Hinz C, Murphy DV (2008) Nitrous oxide emissions from a cropped soil in a semi-arid climate. Glob Change Biol 14:177–192Google Scholar
- Brentrup F, Pallière C (2008) GHG emissions and energy efficiency in European nitrogen fertiliser production and use. In: Proceedings 639, The International Fertilizer Society, York, pp 1–26Google Scholar
- Coleman K, Jenkinson DS (1996) RothC-26.3:a model for the turnover of carbon in soil. In: Powlson DS, Smith P, Smith PJU (eds) Evaluation of soil organic matter models using existing long-term data sets. NATO ASISeries I, vol 38. Springer, Heidelberg, pp 237–246Google Scholar
- Fan TL, Song SY (2000) Grain production and yield-increasing technologies of Loess Highland in North China. In: Proceedings of the Regional Agriculture Development Symposium in China. Gansu Science and Technology Press, LanzhouGoogle Scholar
- Glendining MJ, Powlson DS (1995) The effects of long-continued applications of inorganic nitrogen fertilizer on soil organic nitrogen—a review. In: Lal R, Stewart BA (eds) Soil management: experimental basis for sustainability and environmental quality. Lewis, Boca Raton, pp 385–446Google Scholar
- Herrick JE, Wander MM (1998) Relationships between soil organic carbon and soil quality in cropped and rangeland soils: the importance of distribution, composition and soil biological activity. In: Lal R, Kimble J, Follett R, Stewart BA (eds) Advances in soil science: soil processes and the carbon cycle. CRC, Boca Raton, pp 405–425Google Scholar
- Jenkinson DS (1966) The turnover of organic matter in soil. In: The use of isotopes in soil organic matter studies. Report FAO/IAEA Technical Meeting, Brunsuick, Volkenrode, 1963, Pergamon. pp 187–197Google Scholar
- Lal R, Kimble J, Follet R, Cole C (1998) The potential of US cropland to sequester carbon and mitigate the greenhouse effect. Ann Arbor, ChelseaGoogle Scholar
- Liu G (1999) Soil conservation and sustainable agriculture on the Loess Plateau: challenges and prospects. Ambio 28:663–668Google Scholar
- Nimmo JR, Perkins KS (2002) Aggregate stability and size distribution. In: Dane JH, Topp GC (eds) Methods of soil analysis. Part 4, physical methods. Soil Science Society of America, Madison, pp 317–328Google Scholar
- Nelson DW, Sommers LE (1982) Total carbon, organic carbon, and organic matter. In: Page AL et al (eds) Methods of soil analysis. Part 2, 2nd edn. Agronomy Monographs 9. ASA and SSSA, Madison, WI, pp 539–579Google Scholar
- Paustian K, Collins H, Paul E (1997) Management controls on soil carbon. Soil organic matter in temperate agroecosystems. Long-term experiments in North America. CRC, Boca Raton, pp 15–49Google Scholar
- Powlson DS, Jenkinson DS, Johnston AE, Poulton PR, Glendining MJ, Goulding KWT (2010) Comments on 'Synthetic nitrogen fertilizers deplete soil nitrogen: a global dilemma for sustainable cereal production', by RL Mulvaney, SA Khan and TR Ellsworth in J Environ Qual 2009, 38, 2295–2314. J Environ Qual 39:749–752PubMedCrossRefGoogle Scholar
- SAS Release (6.12) (1998) SAS Institute, Cary, NCGoogle Scholar
- Smith P, Smith JU, Powlson DS, Arah JRM, Chertov OG, Coleman K, Franko U, Frolking S, Gunnewick HK, Jenkinson DS, Jensen LS, Kelly RH, Komarov AS, Li C, Molina JAE, Mueller T, Parton WJ, Thornley JHM, Whitmore AP (1997) A comparison of the performance of nine soil organic matter models using datasets from seven long-term experiments. Geoderma 81:153–225CrossRefGoogle Scholar
- Zhu XA (1989) Soil and agriculture in the Loess Plateau. Agriculture Press, BeijingGoogle Scholar