Modelling the Organic Evolution of a Mediterranean Limestone Soil under Usual Cropping of Durum Wheat and Faba Bean

Hatem Ibrahim,Marc Pansu,Karel Van Den Meersche,Didier Blavet,Nadhem Brahim,Sinda Gaieb

doi:10.3390/agronomy11091688

Abstract

The modeling of carbon (C) and nitrogen (N) fluxes between microorganisms and plants in pure and associated cultures of durum wheat and faba bean demonstrated a close link between the C and N cycles in agroecosystems. The MOMOS (microorganisms and organic matter of soils) model integrates simplified descriptions of photosynthesis (origin of organic C in soil), N microbial exchange (soil origin for N), N fixation (atmospheric origin for N), and plant growth with an organic matter decomposition core that has the soil microbial community at its center. This work provides estimates of the exchange parameters between plant organs and microbes, which were compared to literature data when available. In a connection with photosynthesized C, the root demand for inorganic N can be adjusted by its microbial production. Our approach is a new methodology for improving plant production, by optimizing the interactions with soil microorganisms. Additionally, the coupling of plant growth and microbial processes enabled determining changes of the organic compartments of soil. In the unfertilized limestone soil of this study, sequestration was found to be located in the labile microbial metabolites for one year, then significantly transferred to stable humus during 6-year intercropping. Thus, we propose the MOMOS mathematical tool, not only for guiding ecological intensification, but also related to the management of agroecosystems for climate change mitigation.

Highlights

Models that link more accurately the carbon (C) and nitrogen (N) cycles have long been sought after to predict the transfers between the organic and inorganic compartments of plants and soils [1,2,3]
One main result, which was demonstrated previously [23,24,25], was that the parameters of the pink rectangle in Figure 1 defined and calibrated in tropical rainy conditions and acidic soil could be preserved in this study in semi-arid Mediterranean conditions on calcareous soils. This is a proof of the robustness and transferability of the MOMOS core method
The model was able to decompose the total flow of respiration into microbial respiration regulated by the MOMOS microbial core and plausible values of root respiration for each plant, depending on the balance between photosynthesis and the C content of plant organs (Figure 2a)

Summary

Introduction

Models that link more accurately the carbon (C) and nitrogen (N) cycles have long been sought after to predict the transfers between the organic and inorganic compartments of plants and soils [1,2,3]. Many recent research works have focused on modeling the long term evolution of OC stocks connected with different variables and practices: the effects of crop rotation [4,5], afforestation [6], soil temperature [7], farming systems [8,9], bioenergy crops [10], fire and drought [11], tillage and N fertilization [12], organic amendments, and forest systems [13]. Some other models have focused on plant production, nitrogen (N) cycle, and N fixation over shorter periods [15,16,17]. Proposed for a comparative prediction of 14 C flows in tropical soils [18], it

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