In this study, several composting strategies such as the use of semipermeable geotextile covers and biochar as an additive were investigated to improve olive mill wastewater (OMW) biodegradability and mitigate greenhouse gas (GHG) emissions during industrial-scale composting. In addition, the final characteristics of the compost obtained and its marketable value were also assessed. For this purpose, four different co-composting mixtures were prepared with OMW as the main ingredient, and two types of manure (cattle and goat manure) and bulking agents (almond pruning and vineyard pruning waste) as N and C sources. The results showed that exothermic behavior and biodegradability were more influenced by the co-composting strategy. The use of biochar as an additive showed a reduction in N losses (−14%) via GHG emissions and a significant improvement in cation exchange capacity (+35%) or the content of humic substances (+10%) in the final product. Lastly, the use of a geotextile cover was shown to be the worst cost-effective strategy, as it did not improve compost quality and showed no effect on GHG emissions.

Cereal crops play a critical role in global food security, but their productivity is increasingly threatened by climate change. This study evaluates the feasibility of using PlanetScope satellite imagery and a UAV equipped with the MicaSense RedEdge multispectral imaging sensor in monitoring winter wheat under various fertilizer treatments in a Mediterranean climate. Eleven fertilizer treatments, including organic-mineral fertilizer (OMF) pellets, were tested. The results show that conventional inorganic fertilization provided the highest yield (8618 kg ha⁻¹), while yields from OMF showed a comparable performance to traditional fertilizers, indicating their potential for sustainable agriculture. PlanetScope data demonstrated moderate accuracy in predicting canopy cover (R² = 0.68), crop yield (R² = 0.54), and grain quality parameters such as protein content (R² = 0.49), starch (R² = 0.56), and hectoliter weight (R² = 0.51). However, its coarser resolution limited its ability to capture finer treatment-induced variability. MicaSense, despite its higher spatial resolution, performed poorly in predicting crop components, with R² values below 0.35 for yield and protein content. This study highlights the complementary use of remote sensing technologies to optimize wheat management and support climate-resilient agriculture through the integration of sustainable fertilization strategies.

Circular economy in the context of municipal organic waste management has boosted the emergence of novel composting scenarios, such as community composting and decentralized urban composting in small installations, which favors localized management and valorization of organic waste streams. However, there is little information about the agronomic use of the composts obtained from these new organic waste management systems as an alternative for inorganic fertilization in crop production. In this work, municipal solid waste-derived composts from two decentralized composting scenarios (CM1 and CM2 from community composting, and CM3 and CM4 from decentralized urban small-scale composting plants) were applied and mixed in the top layer of a calcareous clayey-loam soil to assess their effects as alternative substitutes for conventional soil inorganic fertilization (IN) during two successive cultivation cycles of lettuce (Lactuca sativa L.) grown in pots with the amended soils. These treatments were also compared with an organic waste (goat–rabbit manure, E) and a control treatment without fertilization (B). The effects of the fertilizing treatments on the crop yield and quality, as well as on the properties of the soil considered were studied. In general, the application of the different composts did not produce negative effects on lettuce yield and quality. The compost-derived fertilization showed similar lettuce yields compared to the inorganic and manure-derived fertilizations (IN and E, respectively), and higher yields than the soil without amendment (B), with increases in the initial yield values of B, for the first cycle from 34.2% for CM1 to 53.8% for CM3, and from 20.3% for CM3 to 92.4% for CM1 in the second cycle. Furthermore, the organically amended soils showed a better crop development, obtaining higher values than the control treatment in the parameters studied. In addition, the incorporation of the organic treatments improved the soil characteristics, leading to 1.3 and 1.2 times higher organic matter contents in the soils with CM2 and in the soils with CM1, CM3, and E, respectively, compared to the control soil without fertilizing treatment (B), and 2.0 and 1.8 times greater organic matter contents, respectively, compared to soil with inorganic fertilization (IN). Therefore, the use of municipal solid waste-derived composts from these new organic waste management systems, such as the decentralized composting scenarios studied (community composting and urban decentralized small-scale composting plants), is presented, not only as a sustainable valorization method, but also as an alternative for the use of inorganic fertilizers in lettuce cultivation, while enhancing soil properties, contributing to increasing the circularity of agriculture.

In this study several phosphorus fertilizers were evaluated under controlled production conditions using Lactuca sativa var. baby leaf and a clay-loam soil of pH 6.5 as a plant–soil model system. Various inorganic (phosphate rock, monoammonium phosphate, struvite), organic (bone meal and bone meal pelletized with compost) and organomineral fertilizers (phosphate rock, monoammonium phosphate, struvite pelletized with compost) were compared. The soil properties, crop yield, morphological aspects and metabolomics of the plants were analyzed. After 45 days of the growing cycle, the organomineral fertilizers (OMFs) composed of compost and monoammonium phosphate (OMF₂(MAP+C)) or struvite (OMF₃(STR+C)) exhibited the best yield results: 101.37 g and 83.21 g, respectively. These treatments also exhibited the best phosphorus use efficiency (PUE) results: 7.40% and 8.33%, respectively. The yield of plants treated with MAP was 56.01 g, and its PUE was 5.33%. The yield of plants treated with STR was 62.10 g and the PUE was 4.67%. Accordingly, the development of OMFs with compost had a positive effect regarding MAP and STR fertilization. Lettuce fertilized with organic bone meal fertilizers had the lowest yield and nutrient use efficiency. The non-targeted metabolic study of green tissue revealed an overactivation of the TriCarboxylic Acids-TCA cycle and amino acid biosynthesis in plants fertilized with bone meal and phosphate rock treatments, likely as a plant stress response. The overall conclusion of this work is that the development of OMFs with compost is a good strategy to increase soil P availability and, accordingly, plant P uptake and %PUE.

Olive mill wastewater is a polluting residue generated from the olive oil industry and is one which constitutes an environmental concern in Mediterranean countries. Composting has been reported as a viable valorization alternative, as it reduces the volume and the phytotoxic characteristics of OMW. In this study, several composts derived from OMW were evaluated under controlled conditions over two growing season pot experiments using Lactuca sativa as a test crop. The analysis focused on soil quality changes, crop yield, and plant development. Additionally, potential phytotoxicity was also evaluated through a direct acute toxicity plant growth test. Application of OMW composts improved soil fertility indicators, including oxidizable carbon, Kjeldahl total nitrogen, Olsen phosphorous, and plant availability. Crop yields were comparable to those obtained with other organic amendments such as vermicompost and fresh cattle manure in both growing seasons and plant development (in terms of chlorophyll content and canopy cover) was not negatively affected. Nutrient uptake (NPK) was consistent during both growing seasons, with similar nitrogen use efficiency to that achieved in other organic treatments. Regarding the potential toxic effect, the OMW composts tested enhanced seed germination when mixed with coconut fiber at weight ratios below 29.2%. No half-maximal effective concentration (EC50) values were detected, even at 100% compost concentration, while half-maximal inhibitory concentration (LC50) values ranged between 65–75%. These results indicate that OMW composts can serve as an effective short-term source of plant-available nitrogen and a medium-term source of phosphorus, without risk of finding inhibitory or phytotoxic effects on crops.

This study evaluates the agronomic and environmental performance of pelletized compost derived from olive mill waste as a sustainable alternative to mineral fertilizers for cultivating wheat (Triticum turgidum L.) under conventional tillage methods. A field experiment was conducted in semi-arid Spain, employing three fertilization strategies: inorganic (MAP + Urea), sewage sludge (SS), and organic compost pellets (OCP), each providing 150 kg N ha⁻¹. The parameters analyzed included wheat yield, grain quality, soil properties, and greenhouse gas (GHG) emissions. Inorganic fertilization yielded the highest productivity and nutrient uptake. However, the OCP treatment reduced grain yield by only 15%, while improving soil microbial activity and enzymatic responses. The SS and OCP treatments showed increased CO₂ and N₂O emissions compared to the control and inorganic plots. However, the OCP treatment also acted as a CH₄ sink. Nutrient use efficiency was greatest under mineral fertilization, though the OCP treatment outperformed the SS treatment. These results highlight the potential of OCP as a circular bio-based fertilizer that can enhance soil function and partially replace mineral inputs. Optimizing application timing is critical to aligning nutrient release with crop demand. Further long-term trials are necessary to evaluate their impact on the soil and improve environmental outcomes.