Data Sheet 1_Introduction of summer cover crops in soft wheat (Triticum aestivum spp. aestivum) monoculture rotation: effects on agronomic traits and soil properties after three years.pdf

ContextContinuous wheat systems are common across Mediterranean Europe, yet management strategies that simultaneously sustain yield and improve soil health remain poorly defined.
ObjectiveThis study aimed to assess the short-term effects of introducing summer cover crops and different nitrogen rates in a soft wheat monoculture during the system’s initial transition toward a new equilibrium.
MethodsA three-year field experiment in northern Italy evaluated the combined effects of summer cover crop species and N fertilization rates on wheat yield, grain protein concentration, nitrogen use efficiency (NUE), and soil organic carbon (SOC) dynamics. Five ground-cover treatments (bare fallow, natural grassing, sorghum, sorghum + cowpea, cowpea + niger) were tested under three nitrogen (N) fertilizer rates (0, 90, 150 kg N ha−¹).
ResultsWheat yield and protein were primarily determined by N rate and cover crop residue quality. Legume-based covers (cowpea + niger and sorghum + cowpea) maintained yields comparable to the fertilized fallow at 90 kg N ha−¹, while pure sorghum residue required 150 kg N ha−¹ to partially offset yield reductions associated with its high C/N ratio. Across all years, NUE declined at 150 kg N ha−¹, indicating limited efficiency gains from higher fertilization. Grain protein concentration followed a similar pattern, increasing with N rate but constrained under sorghum cover. Soil analyses showed that cover crops increased total SOC by approximately 6 Mg C ha−¹ compared to fallow, with 74% of the additional C stabilized in the mineral-associated organic matter (MAOM) fraction. SOC gains were greatest under sorghum residues but required higher N inputs to sustain yield and grain quality.
ConclusionsThese results demonstrate that adjusting N fertilization according to cover crop residue quality is critical to balancing productivity and soil C sequestration in continuous wheat systems. Legume-based summer covers combined with moderate N inputs (90 kg N ha−¹) optimized NUE while maintaining yield and enhancing SOC.
ImplicationsThis research provides practical, field-based guidance for integrating cover crops into Mediterranean cereal systems to improve both agronomic performance and soil resource sustainability.