Oribatid mites in different Mediterranean crop rotations fertilized with animal droppings.

Unsustainable soil management is one of the drivers of soil degradation, but impact assessment requires the development of indicators. Oribatids might be considered as early indicators of disturbances due to the stability of their community. The aim of this study was to investigate the feasibility of oribatids as bioindicators of sustainable agricultural practices. Under a dry Mediterranean climate, three fertilization experiments - two under a two-crop rotation system and one under maize monoculture and established 12 years earlier - were sampled 3× for oribatid identification during the last annual cropping cycle. The hypothesis was that different nutrient and crop managements affect the number of oribatid species and individuals present, and these parameters could be used as indicators of soil degradation. In total, 18 oribatid species were identified, and 1974 adult individuals were recovered. Maximum abundance was found prior to sowing. Pig slurry (PS) vs. control, and dairy cattle manure (CM) vs. mineral fertilization increased oribatid abundance. This increase was evident when the average applied rates with PS were ca. 2 Mg of organic matter (OM) ha- 1 yr- 1, or higher than ca. 4 Mg OM ha- 1 yr- 1 for CM. When the preceding crop was wheat and PS or CM were used, Oribatula (Zygoribatula) excavata (which reproduces sexually) predominated. In maize monoculture fertilized with CM, Tectocepheus sarekensis and Acrotritia ardua americana (which can reproduce through parthenogenesis) prevailed vs. Oribatula, which indicated a heavily disturbed soil. Under this specific Mediterranean environment, the predominance of certain parthenogenic oribatid species and the number of individuals provide advanced warning on soil degradation.

Dairy cattle slurry fertilization management in an intensive Mediterranean agricultural system to sustain soil quality while enhancing rapeseed nutritional value.

Animal excreta are commonly recycled as fertilizers, although attention should be given to environmental impacts. Legislation must also be adapted to new research findings. The framework of this study is an intensive fodder Mediterranean agricultural system affected by EU legislation on the protection of waters against nitrate pollution. This paper studies the effect of two N based dairy cattle slurry (DCS) rates (170 vs. 250 kg N ha-1 yr-1) plus additional mineral N (up to 450 kg N ha-1 divided between two crops), on different soil quality parameters. A control (no N applied) was included. The experiment, which lasted for 8 years, included forage maize followed by ryegrass, grain maize and rapeseed. In the whole period, the organic carbon inputs from the DCS treatments comprised C slurry inputs (14.8 or 21.9 Mg ha-1) plus the C input difference in crop residues (8.3 Mg ha-1) between DCS and the control treatment. In the 0-0.3 m soil depth, slurries significantly increased soil organic carbon (SOC) from by 2.3 or 2.7% yearly (c. 2.8 Mg C with 10 Mg C ha-1 input) mainly in its light fraction. The size of the microbial biomass increased by 5.1% yearly (c. 0.12 Mg C with 10 Mg C ha-1 input). A higher aggregate stability against slaking disruption was observed. Soil pH slightly decreased, P (Olsen) fertility increased (up to 10 mg P kg-1) as did K availability (up to 140 mg K kg-1) and Mn and Ni bioavailability. In rapeseed plants, seed Ca, S, Cu and Mn content increased as did K, S, Fe, Mn and Zn in the rest of the plant biomass. These changes were within acceptable concentration ranges. The higher N rate from DCS has proved useful for the circular nutrient economy, while improving soil physical and chemical quality and the sustainability of the agricultural system as a whole.