Residue decomposition dynamics under different cropping systems in dryland cereal systems.

 

Efficient management of crop residues is crucial for soil conservation and efficient nutrient dynamics in semi-arid agroecosystems. This study aims to evaluate decomposition dynamics and release of carbon (C) and nitrogen (N) from cover-crop residues in barley (Hordeum vulgare L.) cropping systems in Mediterranean semi-arid conditions. During one year a litterbag experiment is being conducted to examine cover crops decomposition dynamics.

The field experiment consists in two cover crop termination management strategies: chopped (residues left on soil surface) and tilled (incorporated into soil) and three cover crops species: cereal (oat - Avena sativa L.), legume (vetch - Vicia sativa L.) and mix (70:30) of both species. The experiment started at May 2025 and will be monitored 10 samplings times during 48 weeks of litter decomposition simultaneously with the following soil quality parameters: residue decomposition rate, soil mineral nitrogen (NO₃⁻ and NH₄⁺), soil permanganate oxidizable carbon (POxC), soil basal respiration, microbial biomass, and soil enzymatic activities (β-glucosaminidase and dehydrogenase).

Here we present results from the litter decomposition across the first 16 weeks. Plots under chopped termination showed 30% of residue decomposition while plots under tilled termination showed 70% of residue decomposition. In tilled termination, the mixed species had lower decomposition rate compared to cereal and legume, while in chopped termination there were no differences among species in residue decomposition. Most of the decomposition (50 to 70% of total decomposition; in chopped and tilled managements respectively) occurred during the first four weeks. During these weeks, legume residue decomposed more rapidly than cereal and mix species under both terminations, which related with higher soil microbial biomass levels, soil enzymatic activities (dehydrogenase, β-glucosaminidase) and soil nitrates. From the fourth week, there was a decrease in soil microbial biomass and activity for both terminations, which was associated with the summer period (low soil moisture and high temperature).

In our study, the first four weeks after residue incorporation were critical for decomposition, accounting for more than 50% of total decomposition and coinciding with highest soil enzymatic and microbial activity. Whether residues were left on the surface or incorporated into soil, the release of C and N contributed to the stimulation of biological activity and, consequently, to soil health. By week 16, decomposition trends converged across practices, yet legumes consistently accelerated litter decomposition and enhanced nitrogen availability. Cover crops are a key sustainable management practice in semi-arid Mediterranean regions, and understanding their decomposition dynamics is essential to ensure more sustainable agroecosystems in semi-arid Mediterranean regions.

ACKNOWLEDGEMENTS: This research was supported by the Spanish State Agency for Research (AEI) (Grant PID2021–126343OB-C31).