Reliable models predicting soil organic carbon (SOC) evolution are required to better manage cropping systems with the objectives of mitigating climate change and improving soil quality.In this study, data from 60 selected long-term field trials conducted in arable systems in France were used to evaluate a revised version of AMG model integrating a new mineralization submodel. The drivers of SOC evolution identified using Random Forest analysis were consistent with those considered in AMG. The model with its default parameterization simulated accurately the changes in SOC stocks over time, the relative model error (RRMSE = 5.3%) being comparable to the measurement error (CV = 4.3%). Model performance was little affected by the choice of plant C input estimation method, but was improved by a site specific optimization of SOC pool partitioning. AMG shows a good potential for predicting SOC evolution in scenarios varying in climate, soil properties and crop management. Highlights:• SOC evolution in 60 long-term French trials was analyzed and simulated • On average, SOC stocks declined between 1970 and 2015 at a rate of -0.20 t C/ha/yr • Drivers of SOC evolution were similar in Random Forest analysis and AMG model • Implementing a new mineralization module in AMG improved SOC evolution predictions • Optimizing site-specific stable C pool could further improve model performance

We thank the Lawes Agricultural Trust and Rothamsted Research for data from the e-RA database. The Rothamsted Long-term Experiments National Capability (LTE-NC) is supported by the UK BBSRC (Biotechnology and Biological Sciences Research Council, BBS/E/C/000J0300) and the Lawes Agricultural Trust. We thank the Station d'Expérimentation Rhône-Alpes Information Légumes for providing data from the SERAIL experiment.

Because climatic conditions conducive to natural lodging of maize (Zea mays L.) are sporadic and unreliable, a need exists for methods of evaluating the resistance of genotypes to root lodging. A portable electronic device was built for horizontal pushing resistance measurements on individual plants. The apparatus simultaneously records the angle of inclination and the resistance torque of the plant during an artificial pushing test. The device consists of a support, a force sensor, an angle sensor, and a control head. Data logging is possible by using a microprocessor‐based system. Data may be transferred to a computer using an RS232 serial transfer protocol. The time required for the test in field conditions is approximately 1 min per plant. Preliminary results obtained on 14 maize genotypes grown in three field environments showed that genotypes susceptible to root lodging were characterized by low average values of their maximum resistance torque.

fig 5). These results emphasize the role of the roots of the upper internodes on stem stability. The date of appearance of these roots, and their mechanical properties, must also be taken into account.

CT3 ; EnjS3 ; Département EAIn France, agronomists have studied the effects of cropping systems on soil structure using a field method that is based on a visual description of the soil structure. This “profil cultural” method was designed as a field diagnostic tool to identify the effects of tillage and compaction on soil structure dynamics. It is of great benefit to agronomists seeking to improve crop management and preserve soil structure and fertility. However, the “profil cultural” method was developed and has mainly been used in conventional tillage systems with regular ploughing. As there has been an increase in the use of various forms of reduced, minimum and no-tillage systems in many parts of the world, it is necessary to re-evaluate this method’s ability to describe and interpret soil structure dynamics in no-till or reduced tillage. In these situations, changes in soil structure over time are mainly driven by compaction and by regeneration through natural agents (climatic conditions, root growth and macrofauna), therefore it is important to evaluate the effects of these natural processes on soil structure dynamics. These concerns have led to adaptations and amendments to the initial method based on field observations and experimental work in different cropping systems, soil types and climatic conditions. The description of crack types has been improved and a criterion of biological activity based on the visual examination of clods has been introduced. To test this modified method, a comparison with the initial method was undertaken and its ability to make diagnoses tested in five experiments in France, Brazil and Argentina. The adapted method allowed an improved assessment of the impact of cropping systems on soil functioning when natural processes were integrated into the description