In dryland Mediterranean semi‐arid areas, the use of slurries and no‐till are encouraged to reduce costs. This paper evaluates the effect of such practices in terms of morphological changes of the topsoil porosity. The experiment had seven fertilization strategies (five of them including pig slurries applied at cereal sowing or at tillering) combined with no‐till or tillage by disc‐harrowing at sowing. Soil was classified as a Typic Xerofluvent. Texture was silt loam. Pores in the apparent pore diameter (APD) intervals higher than >15 μm and at intervals up to 400 μm were studied with a micromorphological approach plus image analysis. Fifty‐four undisturbed and surface soil samples (0.06 m deep) were analysed. Samples were collected in the third year after the establishment of tillage treatments and throughout the cereal growing season: just before tillage, at cereal tillering and at grain maturity. The incorporation of slurry at pre‐sowing (~2 Mg ha ⁻¹ of organic matter ha ⁻¹ ) enhanced porosity (>15 μm) by 33% in the cropping season but mainly in the 200–400‐μm class. Similar behaviour was observed in plots without topdressing fertilization, when till was compared with no‐till. Thus, the potential movement of water and nutrients due to bypass flow was increased. When slurries were only applied at cereal tillering, only the tillage treatment increased topsoil porosity at grain maturity in the 15–100‐μm class by 22% and, thus, increased those pores responsible for soil and water storage. Temporary changes in pore shape after tillage can be explained by microstructure collapse and compaction followed by a partial porosity recovery by faunal activity at grain maturity. Highlights: Slurry at pre‐sowing, combined with tillage, increases topsoil coarse pores Tillage increases mesoporosity at grain maturity regardless of the slurry fertilization strategy Pore shape changes after tillage are not further visible at grain maturity No‐till tends to compact silty topsoils, creating platy structures later counteracted by fauna

Intensive pig farming produces large amounts of slurry, which is applied to agricultural soils as fertilizer. A 7-year field study was performed to check the effect of pig slurry on soil properties and on the accumulation of some essential nutrients and heavy metals in a calcareous silty-loam soil (0–0.3 m) and in barley (Hordeum vulgare L.) plants in two cropping seasons with contrasting amounts of rainfall. Five fertilization treatments, control (no N applied), mineral fertilizer (90 kg N ha⁻¹), and different N doses of pig slurry (146, 281, 534 kg N ha⁻¹), were applied at sowing of a barley crop. Organic carbon, available P and K, and total P in soil increased with slurry dose. No differences were found in Co, Cr, Fe, Mn, Ni, and Pb soil concentrations. Slurries increased Cu, Mn, and Zn extractions and plant concentrations of P in straw and Zn in grain. However, the lowest slurry rate was able to maintain the highest grain yields while improving fertility. The results of this research study support the sustainability of pig slurry fertilization at appropriate rates in relation to soil chemical quality.

The aim of this study was to evaluate the effects of sludge compost (SC) in two rates and pig slurry (PS) on soil quality, in the framework of a field experiment (19-year-old) in a Mediterranean rainfed system. The treatments were compared with mineral fertilization (MF) plus a control treatment (no N fertilization). Soil microstructure and types of voids, earthworm community and its bioturbation were studied using micromorphological methods. Two earthworm species, Koinodrilus roseus and Nicodrilus trapezoides were identified; the latter was not present in the SC treatments. Earthworm abundance and biomass were not affected by fertilization. Pig slurry increased bioturbation associated with earthworm activity, improved soil microstructure (crumb type) and increased the biopore presence (compound packing voids). The control and MF plots showed a platy to massive microstructure with an absence of faunal chambers. In SC plots, non-mixed soil-organic materials were observed and soil vughs were not visible. Composition differences between SC and PS and the total amount of OM applied may have had an impact on the activity and species of earthworms; such changes can be an early indicator of further potential impacts on soil quality however, further contaminant studies are needed to validate this initial assessment.

Effects of applications of pig slurry on soil aggregate stability are not well understood in dryland agriculture. This research aims to (i) identify aggregate stability tests that give a reliable description of the soil's behaviour when pig slurry ( PS ) is applied to calcareous soil and (ii) interpret them in terms of chemical, biological, morphological and physical soil properties for soil quality assessments. Soil samples from eight fertilizer treatments (mineral fertilizers and PS ), applied over seven growing seasons were analysed. We applied five methodologies to examine different mechanisms of aggregate breakdown. Porosity was characterized by image analyses. There was minimum resistance to the mechanical breakdown of aggregates when slurries had been applied 12 months before analysis. Recent applications of slurry (3 months before the analysis) improved resistance to implosion caused by the penetration of water into dry aggregates (slaking), although the opposite result can occur if the method of evaluation is not chosen properly. Recent applications of PS also enhanced soil respiration and increased soil porosity in the 25–100‐µm size range (packing pores between aggregates) and in the 100–400‐µm size range (interaggregate or faunal pores). In dryland systems and in the winter cereal cropping season, the resistance of dry aggregates to slaking is improved temporarily if PS is applied at N rates equivalent to around 1.7 Mg OM ha ⁻¹ year ⁻¹ . Highlights: How does soil aggregate strength change in response to pig slurry ( PS ) applications? Improve understanding of PS as a fertilizer and its effect on soil quality assessments Changes in aggregate stability are controlled by time since pig slurry application The effects of PS on the increase in packing pores between aggregates are transient