Replication Data for: DISOSMED Decomposition study data

Observational dataset for the scientific article "Residue
decomposition and topsoil organic carbon dynamics under contrasting
management in irrigated Mediterranean systems" by Gonçalo Nascimento,
Carlos Cantero-Martínez and Jesús Fernández-Ortega.

Data originates from a long-term field experiment in Agramunt, NE Spain
(41º48' N, 1º07' E, 330 m asl), on a Typic Xerofluvent silt loam soil
(pH 8.5) under a cold semi-arid steppe climate (440 mm yr⁻¹, 14.6 °C).
The experiment (established 1996, converted to irrigated maize in 2015)
compares monocropping long-cycle maize (MC) with double cropping
short-cycle vetch-maize (DC), under three tillage systems (conventional
tillage – CT, reduced tillage, and no-till – NT) and three N fertilization
rates, in a randomized block design (3 blocks, 54 plots of 3 × 48 m).
Full experimental details are reported in Fernández-Ortega et al. (2024).

This dataset corresponds to a residue decomposition study conducted between
the 2020 and 2021 maize harvests. To isolate rotation and tillage effects,
only plots under high N fertilization (400 kg N ha⁻¹ in MC; 300 kg N ha⁻¹
in DC) and two tillage levels (CT and NT) were included; reduced tillage
was excluded.

Maize residue decomposition was monitored using litterbags (40 × 25 cm,
1 mm mesh) containing ~20 g of dried maize straw. Eight replicates per
plot were installed one week after maize chopping (surface-placed in NT;
buried at ~10 cm in CT). Two replicates per plot were retrieved at four
sampling dates over one year, and residues were analysed for dry weight,
ash content, and C and N concentration (Dumas combustion). Ash correction and
non-degraded straw (NDS) weight was calculated following OECD (2006). C and N
release was calculated as fraction of initial C and N content.
Sampling dates are expressed as cumulative decomposition degree-days (DDD,
base temperature 0 °C).

Topsoil (0–10 cm) was sampled concurrently at each date for bulk density,
soil mineral N (KCl extraction + segmented flow analysis), microbial
biomass C (substrate-induced respiration), and organic C fractions: total
SOC and mineral-associated organic C (MAOC) by Walkley-Black after size
fractionation at 53 µm, with particulate organic C (POC) obtained by
difference. Dehydrogenase and β-glucosidase activities were measured only
at litterbag installation and at the final sampling.

C and N inputs from maize and vetch aboveground and belowground biomass
are also reported; belowground biomass was estimated using literature-based
shoot:root ratios (see Fernández-Ortega et al., 2024).