Organic farming is a holistic production management system that promotes and enhances agroecosystem health, including biodiversity, biological cycles and soil biological activity, and consequently, it is an efficient and promising approach for sustainable agriculture within a circular and green economy. There has been a rise in the consumption of organic vegetables in the last years because of their organoleptic properties, higher nutritive value and lower risk of chemical residues harmful to health. The recent scientific evidence regarding the use of the major elements responsible for organic vegetable crop production indicates plant material, soil management and crop nutrition, soil disinfection, crop management and pest, disease and weed management. These techniques are the focus of this study. In general, the main outcomes of this review demonstrate that a great effort of innovation and research has been carried out by industry, researchers and farmers in order to reduce the environmental impact of the established and innovative horticultural practices while satisfying the requirements of consumers. However, research-specific studies should be carried out in different farming systems and pedoclimatic conditions to achieve the highest efficiency of these horticultural practices.

Organic solid wastes are rarely considered when planning for rural production in Argentina. Onion production in the low valley of Río Colorado (Buenos Aires) generates between 12,000 and 20,000 Mg year⁻¹ of vegetal wastes (i.e., leaves, stems, skins, roots) from harvesting, cleaning and classification of bulbs, causing many problems with their management. The aim of this work is to study the effect of different doses of onion residue-bovine manure compost and onion residue-bovine manure compost tea on the soil physicochemical properties, microbial activity and agroecological onion production in sandy soil. Results showed that the highest dose of compost caused the highest effects on soil pH, electrical conductivity and nutrient content. Soil enzymatic activities were already high in the soil before the compost was applied, which may have contributed to the small effect caused by any dose on soil activity. A significant positive effect on bulb weight and organic onion yield were found as a result of the amendment and growing season. In conclusion, agroecological production of onion with the addition of a 300 kg N ha⁻¹ compost and compost tea guarantee yields comparable to those of conventional fertilization, as occurred during the two growing seasons of this study.

Composted manure is the greatest nitrogen (N) source in organic agriculture, where the use of chemical fertilizers, except the use of rock phosphate as P source, is not allowed. The aim of this study was to evaluate the effect of the soil type and compost characteristics on the potential rates of mineralization and on the kinetics of the nitrogen (N), phosphorus (P), and carbon (C) release patterns. For this, an aerobic incubation study was conducted over the course of 119 days at 25 °C using two different composts as amendments: a compost from biosolids and wood shavings (CRUB), and a compost from poultry manure with wheat straw (CSP). The composts were incorporated into two different soils of contrasting texture, sandy loam (S1) and silty clay loam (S2), at the dose of 160 kg N ha⁻¹. Samples were collected eight times during the incubation period. The N and C dynamics were studied separately according to the different soil type. In both soils, a predominance of the nitrification process immediately after compost application was observed, showing a higher mineralization in the sandy loam soil, this trend being followed by a decrease and even an immobilization process, associated with stable organic materials such as compost. Moreover, both composts presented high contents of available P, but without exceeding 50 mg P kg⁻¹, due to the slow release from the stable organic P fractions present in compost. The results obtained showed that despite the initial mineralization, both composts showed a significant period of N immobilization after their application into the pampean soils, which makes it necessary to anticipate their incorporation to avoid this lack period for crops. Furthermore, the application of these composts to the pampean soils implied an incorporation of available P, but with a slow release that avoided overfertilization, but also reducing N:P ratio and producing a relative deficit of N. Therefore, the results obtained suggested that it is necessary to study nutrient mineralization processes of the amendments prior to their use, according to the edaphoclimatic condition of each crop, in order to predict the release dynamics on soils and the fertilization potential to minimize potential environmental impacts.

This review highlights the importance of olive trees growing in the southwest of Buenos Aires, Argentina. It also discusses the importance (1) of the different fertilizations forms in the determination of the various soil physicochemical and leaf chemical properties, olives yield, oil yield and quality, and (2) oil quality parameters. Cover crops can be beneficial to soil properties. The incorporation of organic manures is also beneficial to improve plant and soil physical and biological properties, which allows a better root development and longevity, and nutrient absorption. Additionally, organic crops can increase the oil yield and quality in comparison to non-organic treatments. Foliar fertilization can be a very efficient system for supplying N, P and K to olive trees. However, several applications are required to meet the needs of the crop. Olive yield decreases significantly when soil fertilization with N is eliminated for several consecutive years in comparison to the fertilization that is carried out annually. Nutrient overfertilizationcan lead to several negative effects from the environmental point of view. Fertilization with P might be unnecessary due to the extensive root system of the olive trees. Olive have a high K requirement since large amounts of K are removed each year at harvest. However, fertilization with different levels of K had negligible effects on oil quality. Oil quality parameters were first associated with N concentrations in leaves and fruits. The phenolic content of the oil decreased linearly in relation to the increase of N in the leaves, which indicates a competition between the synthesis of proteins and the phenolic compounds.

Our objective was to study the effect of fertilization on soil chemical traits on an olive orchard (artificially irrigated), considering areas with or without a cover crop, in southwestern Buenos Aires, Argentina, during the period 2020/2021. Fertilization treatments were (1) organic manure applied to the soil near the tree trunk; inorganic fertilization applied to the (2) soil or (3) to the leaves of Olea europaea L. trees; and (4) unfertilized control. Seeding of Vicia benghalensis L. and Avena sativa L. around subplots (one per each of the four studied treatments) constituted the areas with a cover crop. Subplots which were not seeded corresponded to the control areas. Soil pH was lower (p<0.05) under organic and inorganic soil fertilization. In areas without a cover crop in April 2021, soil nitrate concentrations were greater (p<0.05) under organic soil fertilization than in the control. At 0-20 cm soil depth, P concentrations were greater (p<0.05) under organic and inorganic soil fertilizations than in the other treatments. The greatest (p<0.05) K concentrations were found in the organic fertilization treatment. Organic soil fertilization on areas without a cover crop showed greater values for the soil chemical studied traits.

There is a scarcity of information on the effects of fertilization combined with cover crops on the soil physicochemical properties in olive orchards. We assess the effects of fertilization, cover crop, and harvest time on various soil characteristics in an olive (Olea europaea) orchard. Studies were conducted during the growing seasons of 2021/2022 and 2022/2023 in southwestern Buenos Aires, Argentina. The general experimental design in 2021/2022 and 2022/2023 was split plots. Fertilization treatments included an organic manure applied to the soil, inorganic fertilization applied to the soil or leaves of olive trees, and an unfertilized control. Additionally, a mixture of Vicia benghalensis with Avena sativa was either planted or not (control) as a cover crop. The study demonstrated that soil pH increased on average from mid-spring to mid-autumn during both studied growing periods. Soil organic matter, available phosphorus (P), and extractable potassium (K) were greater at 0-20 cm than at 20-40 cm soil depth. In 2022/2023, the percentage of soil organic matter appeared to be higher in areas with a cover crop than in those without, from early summer to early winter. Soil concentrations of ammonium, nitrate, P, and K were either similar or most often higher never lower in soils with organic and inorganic fertilizations compared to the inorganic foliar fertilization. These three types of fertilization showed greater nutrient concentrations than the unfertilized control. Finally, soil available P concentrations appeared to be higher in areas without vegetation cover than in those with a cover crop at 0-20 cm soil depth.