Soil organic carbon dynamics in typical durum wheat-based crop rotations of Southern Italy

Abstract

Mediterranean agriculture commonly combines winter cereals, irrigated summer crops, forage systems and rotations containing bare fallow. Because management and environmental conditions strongly affect soil organic carbon, the study used carbon modelling to compare existing practice with alternative field-management scenarios.

The analysis applied the RothC10N process model with a geographic information system to representative intensive cropping systems in Southern Italy. It evaluated changes in soil organic carbon stocks and associated carbon dioxide emissions over the 1994–2013 study period.

Under the baseline assumptions, existing management did not preserve soil carbon in every rotation. Modelled outcomes improved when crop residues remained in the field and when summer irrigation was managed more efficiently. The findings were presented as evidence that locally adapted residue and water practices may strengthen the environmental performance of intensive rotations.

Introduction

Mediterranean cropping systems have changed through intensification on productive plains and reduced agricultural activity in less fertile areas. These shifts can simplify production systems and affect both environmental pressures and agroecosystem services.

Deep tillage, shortened rotations and removal of crop residues may reduce soil organic carbon. In semi-arid areas of Southern Italy, common systems include continuous durum wheat, wheat with irrigated summer crops, forage systems and mixed successions containing bare fallow. Soil carbon is therefore an important indicator of soil quality, fertility and production potential.

Field experiments remain essential, but long-term and spatially extensive observations are costly. Process-based tools such as RothC can complement them by estimating carbon turnover through time and across different soils. This study set out to predict soil-carbon changes and identify management factors that could improve carbon retention while reducing emissions.

Materials and methods

Study area and data

The research focused on the Manfredonia agricultural area in Apulia, Southern Italy, where durum wheat and processing tomato are important crops. The landscape contains rainfed cereals, irrigated horticulture, forage and pasture, with predominantly clay-rich soils and a warm Mediterranean agricultural setting.

Researchers harmonised monthly weather observations, georeferenced soil information and crop-succession records. Soil properties were normalised to a 0–30 cm layer. Spatial interpolation was then used to assign weather and soil values to each crop-succession record.

Carbon model

RothC10N, a version of the Rothamsted carbon model adapted for dry and Mediterranean conditions, represented the turnover of decomposable plant material, resistant plant material, microbial biomass and humified organic matter. Monthly climate, soil characteristics, plant inputs, land cover and management were used to estimate total carbon storage and carbon dioxide evolution.

Management scenarios

The baseline assumed that 15% of arable-crop residues remained in the field and irrigated crops received water sufficient to refill the modelled soil-water deficit. Three alternatives examined greater residue incorporation, improved pasture management and reduced irrigation in irrigated sequences.

Results and discussion

The crop-succession records were grouped into arable crops and grassland. Continuous durum wheat appeared in 41% of units, while 43% combined wheat with bare fallow, processing tomato or both. Grassland represented the remaining 17%.

Initial soil organic carbon averaged 45.97 Mg C ha⁻¹. In the baseline, rotations containing bare fallow or tomato generally lost carbon, while continuous durum wheat remained close to steady state. All alternative scenarios increased modelled carbon stocks relative to the baseline.

Values are condensed from the study's model outputs. Scenario availability differs by land-use category.

The combined scenario produced the strongest modelled carbon gains in irrigated crop sequences. Residue inputs supplied additional material for humification, while lower summer irrigation moderated conditions associated with rapid decomposition. The study also noted that cover crops could provide another route for increasing carbon inputs between wheat and tomato.

Conclusions

The modelling framework effectively combined crop histories, soil properties and weather information to examine carbon dynamics at a regional scale. For intensive wheat–tomato systems, keeping residues in the field and using irrigation more deliberately produced substantially better soil-carbon outcomes than the baseline assumptions.

These results should be understood as modelled, site-specific evidence rather than a universal prescription. Field conditions, residue quality, crop productivity, soil type and local water constraints all affect outcomes. Even so, the study offers a practical framework for comparing management choices and developing locally appropriate agro-environmental measures.

Selected references

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