Estimating net primary production and annual plant carbon inputs, and modelling future changes in soil carbon stocks in arable farmlands of northern Japan

Nobuhisa Koga, Pete Smith, Jagadeesh B. Yeluripati, Yasuhito Shirato, Sonoko D. Kimura, Manabu Nemoto

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Abstract

Soil C sequestration in croplands is deemed to be one of the most promising greenhouse gas mitigation options for Japan's agriculture. In this context, changes in soil C stocks in northern Japan's arable farming area over the period of 1971-2010, specifically in the region's typical Andosol (volcanic ash-derived) and non-Andosol soils, were simulated using soil-type-specific versions of the Rothamsted carbon model (RothC). The models were then used to predict the effects, over the period of 2011-2050, of three potential management scenarios: (i) baseline: maintenance of present crop residue returns and green manure crops, as well as composted cattle manure C inputs (24-34 Mg ha(-1) yr(-1) applied on 3-55% of arable land according to crop), (ii) cattle manure: all arable fields receive 20 Mg ha(-1) yr(-1) of composted cattle manure, increased C inputs from crop residues and present C inputs from green manure are assumed, and (iii) minimum input: all above-ground crop residues removed, no green manure crop, no cattle manure applied. Above- and below-ground residue biomass C inputs contributed by 8 major crops, and oats employed as a green manure crop, were drawn from yield statistics recorded at the township level and crop-specific allometric relationships (e.g. ratio of above-ground residue biomass to harvested biomass on a dry weight basis). Estimated crop net primary production (NPP) ranged from 1.60 Mg C ha(-1) yr(-1) for adzuki bean to 8.75 Mg C ha(-1) yr(-1) for silage corn. For the whole region (143 x 10(3) ha), overall NPP was estimated at 952 +/- 60 Gg C yr(-1) (6.66 +/- 0.42 Mg C ha(-1) yr(-1)). Plant C inputs to the soil also varied widely amongst the crops, ranging from 0.50 Mg C ha(-1) yr(-1) for potato to 3.26 Mg C ha(-1) yr(-1) for winter wheat. Annual plant C inputs to the soil were estimated at 360 +/- 45 Gg C yr(-1) (2.52 +/- 0.32 Mg C ha(-1) yr(-1)), representing 38% of the cropland NPP. The RothC simulations suggest that the region's soil C stock (0-30 cm horizon), across all soils, has decreased from 13.96 Tg C (107.5 Mg C ha(-1) yr(-1)) in 1970 to 12.46 Tg C (96.0 Mg C ha(-1) yr(-1)) in 2010. For the baseline, cattle manure and minimum input scenarios, soil C stocks of 12.13, 13.27 and 9.82 Tg C, respectively, were projected for 2050. Over the period of 2011-2050, compared to the baseline scenario, soil C was sequestered (+0.219 Mg C ha(-1) yr(-1)) by enhanced cattle manure application, but was lost (-0.445 Mg C ha(-1) yr(-1)) under the minimum input scenario. The effect of variations of input data (monthly mean temperature, monthly precipitation, plant C inputs and cattle manure C inputs) on the uncertainty of model outputs for each scenario was assessed using a Monte Carlo approach. Taking into account the uncertainty (standard deviation as % of the mean) for the model's outputs for 2050 (5.1-6.1%), it is clear that the minimum input scenario would lead to a rapid decrease in soil C stocks for arable farmlands in northern Japan. (C) 2011 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)51-60
Number of pages10
JournalAgriculture Ecosystems & Environment
Volume144
Issue number1
DOIs
Publication statusPublished - Nov 2011

Keywords

  • Allometric relationship
  • Net primary production
  • Plant carbon input
  • RothC
  • Soil carbon stock
  • Yield statistics
  • Long-term experiments
  • Organic-carbon
  • Management
  • Emissions
  • Croplands
  • Residues
  • Manure
  • Sequestration
  • Uncertainties
  • Tillage

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