Labile Organic Matter, Aggregates, and Stratification Ratios in a Semiarid Vineyard with Cover Crops

Under semiarid Mediterranean climatic conditions, scarce attention has been given to the utilization of permanent cover crops (PCCs) in vineyard agroecosystems to increase soil organic C (SOC) and to improve the soil quality. We evaluated the feasibility of two permanent cover crops (resident vegetation, RV, and ‘Aurora gold’ blue fescue [Festuca longifolia Thuill.] vegetation, FV) to increase SOC and to improve the soil quality with respect to conventional tillage in a semiarid vineyard. We studied the influence of these management practices on the labile organic matter fractions (particulate organic C [POC], potentially mineralizable N [PMN], and water-soluble C [WSC]), on the water aggregate stability (WAS) and on the stratification ratios (SRs) of these soil attributes. The field experiment was conducted on a fine-loamy, mixed, thermic Typic Haploxerept soil in a vineyard located in the La Rioja region (northeast Spain). Soil samples were collected from four soil layers (at depths of 0–2.5, 2.5–5, 5–15, and 15–25 cm) during June 2008, 4 yr after cover crop establishment. The SOC content, POC, WSC, PMN, and WAS were measured. At a depth of 0 to 2.5 cm, the cover crops increased SOC, POC, WSC, PMN, and WAS. The C sequestration rates for RV and FV were 1.34 ± 0.31 and 1.52 ± 0.70 Mg ha−1 yr−1, respectively. Regression analyses indicated positive strong correlations among all parameters monitored. The SRs of the SOC, POC, and PMN were >2 in all depth ratios calculated and therefore were efficient indicators of the soil quality improvement caused by the PCCs. In a semiarid Mediterranean vineyard, a PCC has proven to be an effective strategy to enhance the SOC and to improve the soil quality in the short term.Peer reviewe