Martin A. Bolinder

Strategies for carbon sequestration in agricultural soils in northern Europe

Abstract We present new and synthesize published results from long-term field studies exploring management options for carbon sequestration in cropland and grassland. Agricultural practices were evaluated within the framework set by global food demand and limited area available for agricultural production. Among options for higher C sequestration, we found minimizing the time with bare soil, improving recycling of organic materials and increasing yields through N fertilization to be efficient. Indeed, our results suggest that C stocks can increase with 1–2 kg C for each kg of mineral N fertilizer applied. Possibilities to decrease C emissions by reduced tillage were found to be limited under Nordic conditions. Options for reducing C emissions from drained cultivated organic soils are limited when used as cropland. Extensive production leads to lower soil C stocks and requires more land. Increasing photosynthesis at the global scale by intensification of crop production was found to be the most effective mitigation option and is a prerequisite for preventing further areal expansion of agriculture.

Soil organic carbon sequestration potential for Canadian agricultural ecoregions calculated using the Introductory Carbon Balance Model

The potential for storage of atmospheric CO2-C as soil organic C (SOC) in agroecosystems depends largely on soil biological activity and the quantity and quality of annual C inputs to soil. In this study we used the Introductory Carbon Balance Model (ICBM) approach driven by daily standard weather station data, specific soil properties and crop characteristics at the scale of Canadian agricultural ecoregions. The objectives were to calculate a climate-dependent soil biological activity parameter representative for annual agricultural crop production systems (re_crop) and to estimate the effect of fallow (re_fallow). These parameters are based on the daily product of soil temperature and stored water that influence biological activity in the arable layer, and are used to adjust the decomposition rates of the ICBM SOC pools. We also tested re_crop and re_fallow on SOC stock change data for different site and treatment combinations from long-term field experiments located in some of the ecoregions. An re_cro...

Biological Stability of Carbon and Nitrogen in Organic Products and Crop Residues using Fourier-Transform Near-Infrared Reflectance Spectroscopy

Lignin plus cutin (LIC) content and biological stability index (BSI) are well-recognized indexes of potentially recalcitrant carbon (C) in organic products, and C / nitrogen (N) and lignin/N ratios have been related to potentially mineralizable N (PMN). Our objective was to use Fourier-transform near-infrared (FT-NIR) spectroscopy to estimate PMN and BSI of plant residues, composts, and manures. We also evaluated FT-NIR for determining the C/N, LIC/N, and BSI/N ratios as indexes of N mineralization in selected organic products. We analyzed 148 organic products for biochemical composition and total C and N. A subset of 10 products was incubated in a sandy soil to determine PMN. The FT-NIR successfully determined lignin and cutin (LIC) and BSI from r2, the ratio of prediction to standard deviation, and the ratio error range criteria. The PMN was less closely related to the C/N ratio (r2 = 0.64) than the BSI/N (r2 = 0.84) and LIC/N (r2 = 0.87) ratios. There was some N immobilization at an early stage of incubation when C/N, LIC/N, and BSI/N ratios exceeded 14, 10, and 15, respectively. There is a need to characterize a larger number of organic compounds in the soluble and LIC fractions to improve the BSI equation.

Contribution of Régis R. Simard to phosphorus research in agroecosystems and future prospects.

In this paper we present the soil test P saturation, budget, and fractionation procedures used in R. R. Simard’s laboratory. We expand that work to: (1) Mehlich-III P saturation index using a weighting factor for Fe accumulation in soils; (2) P budget including below-ground biomass; and (3) compositional data analysis of P fractions to describe changing patterns of soil P fractions that differ in their availability to plants and risk to the environment. The Mehlich III P and Al two-way classification applied to forage crops by Simard and co-workers was replaced by the P/Al ratio test for P fertilizer recommendation in Quebec. The concept was further expanded to (P/[Al + γFe), where γ is 0 or 1 in mineral soils and 5 in organic soils. To provide a more complete picture of the P budget and risk index in agroecosystems, it would be advantageous to consider root P, despite limited data. Using compositional analysis for a closed information space or simplex, a perturbation vector describing relative increase o...