Organic mulching is a promising technique for sustainable weed control and soil management, as it enhances crop growth, soil quality, water retention, and erosion control. This research evaluated the effects of organic mulches—wheat straw, wood chips, spray cellulose pulp, compost, and a cover crop mixture—on the physical–mechanical properties of organic garden soil transitioning to natural farming. The controlled soil received no mulch. The soil was fertilized with mature bovine manure prior to a three-year crop rotation of tomato, lettuce, and savoy cabbage. Mulching occurred after the second harrowing and before transplanting. Soil analyses were conducted to assess changes after three years. Soil organic carbon levels increased significantly in soils treated with compost, cover crops, or chipped wood mulching (6.81, 3.17, and 2.07%, respectively) compared to other treatments (1.24% in the control plot). Different kinds of mulch had a significant impact on soil’s physical–mechanical parameters. Compost, compared to the control, decreased the bulk density (from 1.22 to 0.89 Mg m⁻³), increased the infiltration rate (from 8.53 to 21.07 L m⁻²), and reduced compressive deformation (from 37.08 to 18.23%). The composition of mulch materials, specifically their nitrogen and carbon concentrations, C/N ratio, and moisture content, plays a significant role in influencing changes in soil properties.

The organic fraction of sewage sludge administered to agricultural soil can contribute to slowing down the loss of soil’s organic carbon and, in some cases, can improve the physical and mechanical properties of the soil. One of the main constraints to the agricultural use of sewage sludge is its heavy metals content. In the long term, agricultural administration of sewage sludge to soil could enhance the concentration of soil heavy metals (as total and bioavailable fractions). The aim of this research was to evaluate the effects of medium-term fertilization with diversely processed sewage sludge on the soil’s organic carbon content and humification–mineralization processes, on the physical–mechanical properties of soil and their influence on the pool of potentially bioavailable heavy metals, in order to assess their effectiveness as soil organic amendments. After eight years of sludge administration; an increase in the concentrations of bioavailable form was evidenced in all the heavy metals analyzed; independently of the type of sludge administered. The form of sludge administration (liquid, dehydrated, composted) has differently influenced the soil humification–mineralization processes and the physical–mechanical properties of soil. The prolonged amendment with composted sewage sludge contributed to keeping the soil humification–mineralization process in equilibrium and to improving the physical and mechanical qualities of the treated soil.

The current guidelines of waste management are aimed at the recovery and recycling of biowaste while respecting the protection of human health and the environment. The recent European legislation on fertilizers provides for the use of digestates derived from the organic fraction of municipal solid waste (OFMSW). The objectives of this study were to verify the fertilizing effect of three types of OFMSW digestates on the ryegrass culture comparing mineral fertilization and to evaluate the nitrogen lost to leaching in soil diversely fertilized following simulated rainfall. The ryegrass was grown in pots. The soil was fertilized with mineral fertilizer or OFMSW digestates. For each treatment, five mowing procedures were performed on the crop, and the ryegrass biomass production and nitrogen concentration were determined from the ryegrass samples. During the experiment, six rains were simulated, and the leached nitrogen was analyzed. The results showed that: (i) the fertilizing effect of OFMSW digestates on nitrogen nutrition of ryegrass was similar to ammonium sulphate fertilization, confirming the agronomic validity of these by-products to reduce the use of synthetic fertilizers; (ii) soil fertilization with OFMSW digestates had a positive effect limiting nitrogen loss due to leaching compared to mineral fertilization, highlighting the soil-improving properties of these by-products, in particular of the composted digestate.