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Soil legacy data rescue via GlobalSoilMap and other international and national initiatives The International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture. CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications.

The magnitude of and mechanisms for long-term differences in soil organic matter stocks under no-tillage and conventional tillage are still relatively poorly known. We quantified differences in total C and N stocks after 32 years of no-tillage (NT) and conventional tillage (CT) in plots with a long-term cultivation history before differentiation and the same annual C and N returns to the soil. The role of physical protection of organic matter (OM) in these stock differences was further investigated by examining the changes at different levels of structural complexity, i.e. organic matter fractions, aggregation and pore-size distribution. Four structural zones were sampled: loose and dense soil zones under CT and the 0-5 cm (rich in OM) and 5-20 cm (massive structure) soil layers under NT. The C and N stocks, calculated for an equivalent mass of dry soil, were only 10-15% larger under NT than under CT. Mineral-associated N and particulate organic matter accounted for about 50% of the difference in N stocks. However, 66% of the total difference in C stocks was due to differences in the particulate organic matter (58%) and free residues (8%) fractions. The additional C and N under NT were almost exclusively situated in aggregates larger than 250 mm in diameter. Our results suggest that physical protection of OM under NT contributes significantly to the differences in C and N stocks between NT and CT by (i) enhanced macroaggregate formation in the 0-5 cm layer due to greater microbial activity and OM content and (ii) a better protection of soil organic matter in the 5-20 cm layer due to the presence of small pores and lack of soil disruption by tillage or climate.

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The performance of the PASTIS model was evaluated to simulate soil C and N fluxes under real field conditions with conventional moldboard plowing (CT) and no‐tillage (NT) systems differentiated for 33 yr for a loamy soil in northern France. Afterward, the influences on the C and N fluxes by soil temperature, soil water content, and quantity and localization of soil organic matter (SOM) and crop residues in the soil profile were determined. The model PASTIS was able to provide good simulations for the dynamics of soil water content and temperature, CO2 emissions, residue decomposition, and N mineralization. Simulation showed that the presence of the mulch layer in NT reduced cumulative total water evaporation and increased water drainage at the bottom of the 25‐cm depth. Furthermore, simulation showed that the larger cumulative total CO2 flux in NT resulted from larger CO2 emissions as a product of crop residue decomposition and not as product of SOM decomposition. The larger amount of accumulated residues of previous crops in NT more than compensated for the slower residue decomposition rate of surface compared with incorporated residues. It was the water content of the surface crop residues that largely controlled the magnitude of this difference in decomposition rate of the crop residues between CT and NT. This means that, besides the amount of crop residues in both tillage systems, the distribution of rainfall and potential evaporation have a large influence on the differences in C and N fluxes between the two tillage systems