Application of organic mulches has repeatedly been shown to reduce infestation with Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), the Colorado potato beetle (CPB). In order to determine if the nutritional status of potatoes as affected by mulch could explain the mulch effects in potatoes against CPB, we determined potato leaf nutrient composition in unmulched control plots and plots mulched with grass-clover or triticale-vetch and assessed mulch effects on CPB damage and development in the field during 3 years and under controlled conditions. In mulched plots, foliar Mo, Cl, and K contents were consistently higher than those without mulch, and leaf damage by CPB was reduced significantly. In addition, increased B contents were associated with undamaged plant material, while higher Zn contents were associated with leaves damaged by CPB. Under controlled conditions, CPB fitness was not affected by mulch application. Overall, reduced CPB damage could not be clearly attributed to altered foliar nutrient contents due to mulching. It is thus more likely that CPB reductions in mulched systems are due to mechanisms other than an altered nutrient balance.

From 2016 to 2019, 128 organic and conventional spring and winter pea fields in Germany were surveyed to determine the effects of cropping history and pedo-climatic conditions on pea root health, the diversity of Fusarium and Didymella communities and their collective effect on pea yield. Roots generally appeared healthy or showed minor disease symptoms despite the frequent occurrence of 4 Didymella and 14 Fusarium species. Soil pH interacted with the occurrence of the Fusarium oxysporum species complex (FOSC) and F. tricinctum that correlated with reduced or increased soil pH values, respectively. While legumes in the cropping history or reduced time between legumes correlated with occurrence of D. pinodella and to a lesser degree with the members of the F. solani species complex (FSSC), the reverse was true at least in organic spring peas for F. redolens. Only in conventional systems increased root infections with F. redolens and the FSSC were linked to root rot incidence whereas yields negatively correlated with the FOSC and positively with F. tricinctum isolation frequencies. Overall, this study shows that pea root rot pathobiome is rather stable and that the damage caused is mostly due to the interaction with environmental conditions.

In New York, organic production of muskmelon (Cucumis melo) and other cucurbits is limited by pests, diseases, and weeds. Among the most important pests are striped (Acalymma vittatum) and spotted (Diabrotica undecimpunctata howardi) cucumber beetles that cause damage through feeding. Cucumber beetles also transmit the bacterium, Erwinia tracheiphila, the causal agent of bacterial wilt. Mesotunnels are a modified row cover system consisting of nylon mesh netting supported by hoops approximately 1-m high, which have potential for incorporation into organic muskmelon production systems. The netting is an effective barrier for pests and insect-vectored diseases and also prevents insect-mediated pollination and in-season weed management in inter-bed areas. Two separate experiments were conducted in 2021 and 2022 to: (a) evaluate mesotunnels for organic muskmelon production and methods to control weeds in inter-bed areas (experiment 1), and (b) evaluate selected pollination treatments for integration into a mesotunnel production system (experiment 2). In experiment 1, there were four treatments: (i) landscape fabric in the inter-bed area with a mesotunnel, (ii) landscape fabric in the inter-bed area without a mesotunnel, and a (iii) ryegrass/white clover in the inter-bed area with a mesotunnel; or (iv) ryegrass cover crop in the inter-bed area with a mesotunnel. In experiment 1, mesotunnels significantly reduced cucumber beetle populations and bacterial wilt epidemic progress but did not affect the incidence of the foliar diseases, powdery mildew, or Alternaria leaf spot. In the mesotunnel and non-covered treatments, landscape fabric, applied for weed control between beds, resulted in greater fruit weight and more marketable fruit compared to mesotunnels with cover crops in the inter-bed area. In experiment 2, treatments were on/off/on (removal of netting during flowering followed by replacement), open ends (open ends during flowering), and a closed mesotunnel (with the insertion of a commercial bumblebee hive). Although the on/off/on treatment increased cucumber beetle populations and bacterial wilt epidemic progress compared to the open ends and closed treatments, it conferred significant yield benefits in both years. These findings emphasize the importance of systems-level analysis for evaluating the suitability of mesotunnels in organic muskmelon production.

Anthropogenic activities have resulted in land desertification in various regions of the world, leading to the degradation of critical soil characteristics such as organic matter (OM) content, nutrient stock, and prevailing biodiversity. Restoring such degraded soils through organic matter amendments and diversified crop rotations is thus an intrinsic part of organic farming. This review discusses a wide range of organic farming impacts on soil health and crop productivity by focusing on organic fertilizers and crop diversification. Conventional fertilizers were considered vital for agricultural production to harvest high crop yields. Nevertheless, they are now deemed as environmentally hazardous and an obstacle to sustainable agroecosystems due to intensive chemical inputs that damage the soil over time and have long-lasting impacts. Conventional fertilization results in nutrient depletion, loss of microbial diversity, organic matter reduction, and deterioration of physical characteristics of the soil. Conversely, organic fertilization makes use of naturally existing resources to improve soil health. Organic amendments such as biochar, manure, and fermented grass improve soil's physical, chemical, and biological properties and promote the growth and diversity of beneficial soil microorganisms-important in nutrient cycling and soil stability. They facilitate the uptake of nutrients, hinder crop pathogen growth, mitigate heavy metals, and decompose xenobiotic organic substances. Moreover, growing cover crops is also a major strategy to improve soil health. Diversified crop rotation with combinatorial use of organic fertilizers may improve soil health and agricultural yields without any detrimental impacts on the environment and soil, ensuring sustainable food production, safety, and security. This integrated approach contributes to minimizing the use of chemical fertilizers and their effects on environmental health. It also contributes to reducing agricultural inputs along with enhancing OM, soil microbial diversity and biomass, nitrogen fixation, and carbon sequestration. Therefore, cover crops and organic fertilization may offer sustainable agroecosystems and climate change mitigation.

The production gap between current and attainable yields is highest on Africa's smallholder farms, and some studies indicate that they might not benefit from the yield gains offered by conventional farming. Simultaneously, alternative farming systems like organic provide biodiversity and soil fertility advantages, but their ability to produce sufficient food is still under debate. Additionally, comparative data on the productivity of organic versus conventional in tropical regions are scarce or short-term. We investigated the crop productivity of organic and conventional farming systems using 15 years in two long-term systems comparison trials in Kenya. The trials were established in 2007 at two sites in the Central Highlands of Kenya. At each site, conventional and organic systems were compared at high input levels. The trial involved a three-year crop rotation cycle of maize, vegetables, legumes, and potatoes, repeated five times since its establishment. Management practices were kept similar in the first four rotations and revised in the fifth to improve systems representing best practices. Our results showed that while maize and baby corn had relatively low yield gaps (-13 to +12 %) between organic and conventional systems, cabbage, French beans, and potato had high yield gaps (-50 to-30 %). We attributed this to nutrient limitations and higher pest and disease damage. The yield gap could partially be closed by adopting best practices in the organic system, including system diversification and effective soil fertility, nutrient, and integrated pest management.

The increasing global population has raised concerns about meeting growing food demand. Consequently, the agricultural sector relies heavily on chemical fertilizers to enhance crop production. However, the extensive use of chemical fertilizers can disrupt the natural balance of the soil, causing structural damage and changes in the soil microbiota, as well as affecting crop yield and quality. Biofertilizers and biostimulants derived from microalgae and cyanobacteria are promising sustainable alternatives that significantly influence plant growth and soil health owing to the production of diverse biomolecules, such as N-fixing enzymes, phytohormones, polysaccharides, and soluble amino acids. Despite these benefits, naturally producing high-quality microalgal biomass is challenging owing to various environmental factors. Controlled settings, such as artificial lighting and photobioreactors, allow continuous biomass production, but high capital and energy costs impede large-scale production of microalgal biomass. Sustainable methods, such as wastewater bioremediation and biorefinery strategies, are potential opportunities to overcome these challenges. This review comprehensively summarizes the plant growth-promoting activities of microalgae and elucidates the mechanisms by which various microalgal metabolites serve as biostimulants and their effects on plants, using distinct application methods. Furthermore, it addresses the challenges of biomass production in wastewater and explores biorefinery strategies for enhancing the sustainability of biofertilizers.