Biostimulants (BIOS) are non-mineral substances that, when exogenously applied in very small quantities, stimulate the metabolic activity of plants. Past research with biostimulants has not included differing levels of nitrogen fertility or shade as variables. The research presented was designed to explore some interactions between biostimulants and nitrogen fertility on turfgrass grown under several light conditions. / Master of Science

La protection des vignes contre les maladies cryptogamiques telles que le mildiou est assurée majoritairement par des fongicides de synthèse dont certains posent des problèmes environnementaux et sanitaires. L’induction de résistance de la vigne par des éliciteurs des réactions de défenses pourrait permettre de réduire leur utilisation. Toutefois, l’efficacité de cette stratégie est avérée en conditions de serres, mais reste plus variable au vignoble. L’efficacité des éliciteurs est conditionnée par le niveau de réponse défensif de la plante, et plus globalement, par son état physiologique. Dans ce contexte et dans le cadre de ce travail intégré au projet FUI IRIS+, l’objectif était de vérifier si des biostimulants, via leurs effets sur la physiologie de la plante, étaient susceptibles d’augmenter son niveau de réponse aux éliciteurs. Ce projet impliquait en amont le criblage d’éliciteurs et de biostimulants efficaces sur vigne. L’activation des défenses par des éliciteurs a un coût métabolique et énergétique que la plante doit assumer. Dans un premier temps, nous avons utilisé le modèle « suspensions cellulaires » afin de comparer l’impact de deux éliciteurs oligosaccharidiques sur le métabolisme primaire de la vigne. Des analyses enzymatiques et métaboliques ont permis de montrer que l’oligogalacturonide, qui a eu la plus forte capacité à activer le métabolisme secondaire associé à la défense, comparé à la laminarine, est également celui qui a eu l’impact le plus marqué sur le métabolisme primaire ; notamment sur certains glucides et acides aminés. Ainsi, l’élicitation mobilise des ressources, impacte le métabolisme primaire de la vigne et son efficacité pourrait être conditionnée par l’état physiologique global de la plante. Dans un second temps, un criblage a été réalisé afin d’identifier de nouveaux éliciteurs potentiels parmi sept fournis par le partenaire industriel. Des tests de protection contre Plasmopara viticola (agent du mildiou) réalisés sur boutures herbacées en conditions de serres, ont permis de retenir un extrait de plante codé SDN3. Les autres ont été écartés car déjà utilisés en laboratoire (l’un d’entre eux), insuffisants en terme d’efficacité, instables ou phytotoxiques. Des études in vitro et in planta ont révélé que l’activité biologique de SDN3 est liée à deux modes d’action : par activation des défenses et par effet direct contre l’agent pathogène. Dans un troisième temps, un criblage de cinq biostimulants potentiellement efficaces sur vigne était à réaliser mais aucune méthodologie de test n’était disponible au laboratoire. Ainsi, quatre dispositifs de complexités différentes ont dû être mis au point, permettant le suivi phénotypique des parties aériennes et/ou racinaires (et dans certains cas physiologique) : systèmes « godets », « rhizotron plan », « tubes » et un autre système appelé « X » (non décrit car lié à une protection industrielle). Seuls deux modèles ont montré un intérêt. En effet, le modèle « tube » a permis de montrer une augmentation du poids frais moyen par racine primaire en réponse à un apport par la voie racinaire de l’un des produits testés, codé BS3. Le modèle « X » a également mis en évidence une accélération de l’ouverture du bourgeon, et une augmentation du nombre de racines primaires en réponse à BS3 appliqué par voie racinaire. La mise au point d’applications d’éliciteurs et d’infection par P. viticola est en cours de finalisation afin de vérifier l’hypothèse de départ à l’aide de la combinaison de BS3 avec SDN3. / The protection of vineyards against cryptogamic diseases such as downy mildew is mainly ensured by synthetic fungicides, which cause serious environmental and health problems. The induction of resistance by elicitors could allow to reduce their use. However, even if their efficacy is demonstrated in greenhouse conditions, it remains quite variable in field conditions. Indeed, the efficacy of an elicitor depends on the plant’s ability to respond, or more generally, on the latter’s physiological status. In this context, part of the FUI project IRIS+, the aim of this present work is to evaluate whether biostimulants, through their effect on the plant’s physiology, would be able to increase their responsiveness to elicitors. The activation of defenses implies a metabolic and energetic cost that the plant must get in charge. First of all, we used a cell suspension model in order to compare two oligosaccharidic elicitors on the primary metabolism of grapevine. Enzymatic and metabolic analyses showed that the oligogalacturonide, which had a stronger impact on secondary metabolism related to defense, compared to laminarin, also showed a more notable impact on primary metabolism, particularly on some sugars and amino acids. The elicitation of grapevine defenses effectively turned out to require resources. Secondly, a screening was carried out to select the most effective elicitor among seven products that were provided by the company. Protection assays against Plasmopara viticola on herbaceous cuttings allowed us to identity SDN3 as the most interesting candidate. In vitro and in planta studies revealed that the mode of action of SDN3 relied on both the activation of defenses and a direct effect against the pathogen. Lastly, as no protocol, nor methodology were available in our laboratory to screen biostimulants, four systems were developed, in order to monitor phenotypic traits of aerial and/or root system: the “pot” model, the “rhizotron” model, the “tubes”, and another termed “X” (no description allowed because of an industrial protection). Only the “X” model showed potential interests, since it allowed to display biostimulating effects such as the acceleration of the bud opening, and the increase of the mean number of primary roots, in response to BS3, applied to the roots. The development of the protocol to apply the elicitor and to infect with P. viticola spores are currently in progress, in order to assess the initial hypothesis by using the combination of BS3 and SDN3.

Orientador: Rogério Peres Soratto / Banca: Ciro Antonio Rosolem / Banca: Leandro Borges Lemos / Banca: Orivaldo Arf / Banca: José Fernandes de Melo Filho / Resumo: Em regiões onde as culturas do feijão (Phaseolus vulgaris L.) e trigo (Triticum aestivum L.) atingiram alto nível tecnológico e são obtidas elevadas produtividades, o uso excessivo de nitrogênio (N) é bastante comum. Visando melhorar o desempenho das culturas, muito produtores utilizam bioestimulantes, porém, existem inúmeras dúvidas com relação à eficiência do uso dos mesmos, qual a melhor forma e época de aplicação para as culturas do feijão e trigo, e se existe alguma interação dessa prática com a nutrição nitrogenada das mesmas. Dessa forma, a proposta do presente trabalho foi: a) avaliar o efeito de formas e épocas de aplicação de um bioestimulante na nutrição, crescimento, produtividade e qualidade dos grãos da cultura do feijão; b) avaliar a influência da aplicação do bioestimulante no metabolismo, crescimento e produtividade de grãos na cultura do trigo, e c) avaliar se existe influência da aplicação do bioestimulante na eficiência da adubação nitrogenada das culturas do feijão e do trigo. Foram realizadas duas avaliações, uma no Brasil com a cultura do feijão (Phaseolus vulgaris L.) nomeadas de experimento I e experimento II; e a outra na Inglaterra com a cultura do trigo (Triticum aestivum L.) nomeadas de experimento III, IV e V. No Brasil foram conduzidos dois experimentos: um em casa de vegetação e o outro em campo durante duas safras, em Botucatu, SP, Brasil. Em ambos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In regions where bean and wheat crops reached a high technological level and yields, use of high nitrogen (N) doses is common. In order to improve crops performance many farmers use biostimulants, however, there are many doubts about efficiency of using of biostimulant, the best way and application time for common bean and wheat, and if there is some interaction with the practice of N fertilization. Thus, the aim in this experiment was: a) evaluate the effect of different forms and application time of a plant regulator in nutrition, growth and yield of common bean and wheat, b) evaluate if there is influence of bioestimulant application in metabolism, growth and yield of wheat crop, c) evaluate if there is application influence of bioestimulant in efficiency of N fertilization in common bean and wheat crops. Two evaluations were evaluated, one in Brazil with the bean (Phaseolus vulgaris L.) named experiment I and experiment II, and the other in England with wheat (Triticum aestivum L.) named experiment III, IV and V. In Brazil two experiments were conducted: one at greenhouse and other at field during two seasons in Botucatu, Brazil... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2014-06-11T19:30:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-11Bitstream added on 2014-06-13T19:19:10Z : No. of bitstreams: 1 almeida_aq_dr_botfca.pdf: 1190491 bytes, checksum: aa845d0bbf37326aabdb89d11ada3476 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Em regiões onde as culturas do feijão (Phaseolus vulgaris L.) e trigo (Triticum aestivum L.) atingiram alto nível tecnológico e são obtidas elevadas produtividades, o uso excessivo de nitrogênio (N) é bastante comum. Visando melhorar o desempenho das culturas, muito produtores utilizam bioestimulantes, porém, existem inúmeras dúvidas com relação à eficiência do uso dos mesmos, qual a melhor forma e época de aplicação para as culturas do feijão e trigo, e se existe alguma interação dessa prática com a nutrição nitrogenada das mesmas. Dessa forma, a proposta do presente trabalho foi: a) avaliar o efeito de formas e épocas de aplicação de um bioestimulante na nutrição, crescimento, produtividade e qualidade dos grãos da cultura do feijão; b) avaliar a influência da aplicação do bioestimulante no metabolismo, crescimento e produtividade de grãos na cultura do trigo, e c) avaliar se existe influência da aplicação do bioestimulante na eficiência da adubação nitrogenada das culturas do feijão e do trigo. Foram realizadas duas avaliações, uma no Brasil com a cultura do feijão (Phaseolus vulgaris L.) nomeadas de experimento I e experimento II; e a outra na Inglaterra com a cultura do trigo (Triticum aestivum L.) nomeadas de experimento III, IV e V. No Brasil foram conduzidos dois experimentos: um em casa de vegetação e o outro em campo durante duas safras, em Botucatu, SP, Brasil. Em ambos... / In regions where bean and wheat crops reached a high technological level and yields, use of high nitrogen (N) doses is common. In order to improve crops performance many farmers use biostimulants, however, there are many doubts about efficiency of using of biostimulant, the best way and application time for common bean and wheat, and if there is some interaction with the practice of N fertilization. Thus, the aim in this experiment was: a) evaluate the effect of different forms and application time of a plant regulator in nutrition, growth and yield of common bean and wheat, b) evaluate if there is influence of bioestimulant application in metabolism, growth and yield of wheat crop, c) evaluate if there is application influence of bioestimulant in efficiency of N fertilization in common bean and wheat crops. Two evaluations were evaluated, one in Brazil with the bean (Phaseolus vulgaris L.) named experiment I and experiment II, and the other in England with wheat (Triticum aestivum L.) named experiment III, IV and V. In Brazil two experiments were conducted: one at greenhouse and other at field during two seasons in Botucatu, Brazil... (Complete abstract click electronic access below)

abstract: Microalgae represent a potential sustainable alternative for the enhancement and protection of agricultural crops. The dry biomass and cellular extracts of Scenedesmus dimorphus were applied as a biofertilizer, a foliar spray, and a seed primer to evaluate seed germination, plant growth, and crop yield of Roma tomato plants. The dry biomass was applied as a biofertilizer at 50 g and 100 g per plant, to evaluate its effects on plant development and crop yield. Biofertilizer treatments enhanced plant growth and led to greater crop (fruit) production. Timing of biofertilizer application proved to be of importance - earlier 50 g biofertilizer application resulted in greater plant growth. Scenedesmus dimorphus culture, growth medium, and different concentrations (1%, 5%, 10%, 25%, 50%, 75%, 100%) of aqueous cell extracts were used as seed primers to determine effects on germination. Seeds treated with Scenedesmus dimorphus culture and with extract concentrations higher than 50 % (0.75 g ml-1) triggered faster germination - 2 days earlier than the control group. Extract foliar sprays of 50 ml and 100 ml, were obtained and applied to tomato plants at various extract concentrations (10%, 25%, 50%, 75% and 100%). Plant height, flower development and number of branches were significantly enhanced with 50 % (7.5 g ml-1) extracts. Higher concentration sprays led to a decrease in growth. The extracts were further screened to assess potential antimicrobial activity against the bacterium Escherichia coli ATCC 25922, the fungi Candida albicans ATCC 90028 and Aspergillus brasiliensis ATCC 16404. No antimicrobial activity was observed from the microalga extracts on the selected microorganisms. / Dissertation/Thesis / Masters Thesis Applied Biological Sciences 2014

<p>Starter fertilizer applied with or near the seed at planting often enhances early season maize growth (<i>Zea mays</i> L.) but does not always result in higher grain yield. Other responses to starter fertilizer, such as reduced thermal time to reach silking, which suggests accelerated plant development, have been documented. The objective of this study was to examine the relationship between dry matter production and accelerated plant development with respect to 5x5 cm starter (ST) and in-furrow popup (PU) fertilizer. A field experiment was conducted in 2016 with three at-planting treatments consisting of one single rate and formulation of ST (53 N and 21 P kg ha^-1) or PU (4 N and 6 P kg ha^-1), and an untreated control. In 2018, the study included four additional site-years with treatments consisting of an intermediate (ST) or high (STH) starter fertilizer rate, and an untreated control. For ST treatments, depending on location, nitrogen (N) and phosphorus (P) fertilizer rates ranged between 26-28 and 6-10 kg ha^-1, respectively, and for STH treatments N and P fertilizer rates ranged between 47-56 and 12-20 kg ha^-1, respectively. In 2016, as new leaf collars appeared, dry matter increased exponentially, but at an equal number of leaf collars ST and PU had similar dry matter as the control. In 2018, dry matter for ST, STH, and control was also similar when normalized for leaf collar number at each site. Overall, these results suggest that enhanced dry matter at a given point in time from ST, STH, or PU was a function of accelerated leaf development as opposed to physically more robust plants of the same leaf collar number. Grain yield was unaffected by ST, STH, or PU treatments at any site-year.</p> <p>Methods used to study roots in crop fields have included extracting soil cores, excavating entire root systems, using radioactive and non-radioactive chemical tracers, or using mini-rhizotrons. However, due to the intensive nature, level of difficulty, and cost associated with these methods, their use in crop fields has been minimal. We developed an alternative method to quantify maize rooting density over time. The method involved perforated cylinders installed vertically into the soil at different distances from the row, which made roots growing into the cylinder voids visible from the soil surface and possible to count [root number density (RND)] at different depths using a video recording device (1m-long borescope). The objective of this study was to determine if the cylinder method could quantify rooting density throughout the growing season (V3, ~V7, and R2-R3) similar to the more intensive soil core method, compared in two starter fertilizer trials [continuous maize (M/M) and maize/soybean (M/S) rotation]. Cylinders were constructed with perforated (49% voids) polypropylene resin to an inside diameter of 2.58 cm and a length of 30 cm. Cylinders were painted with red and green alternating markings (5 cm) on the outside and inside walls to visually aid in identifying depth from the soil surface. After plants emerged, cylinders were inserted vertically into the soil after drilling a 3.5 cm diameter borehole. Ten perforated cylinders were installed in a parallel line 13 or 25 cm away from, and on both sides of, the planted row. Soil cores were also collected at the same relative locations for conducting root extractions and subsequent calculation of length density (RLD). At V3, methods frequently resulted in the same significant (<i>p≤</i>0.10) or insignificant (<i>p></i>0.10) main and interaction effects in both fields, whereas at ~V7 and R2-R3, there were several instances where the cylinder method failed to detect the same effects as the soil core method. At times both the cylinder method and the soil core method detected significant main or interaction effects, but the direction of the effect was opposite.</p> <p>In-furrow biological (BIO) and plant growth regulator (PGR) products, otherwise known as biostimulants, are becoming increasingly available in the commercial maize market. The objective of this study was to compare the effects of several commercially available in-furrow biostimulant products on maize growth and development, nutrient uptake, and grain yield to starter fertilizer in large-plot field trials. The study was conducted across five locations in 2016, and three locations each in 2017 and 2018 at Purdue University research farms. At each location, treatments consisted of four different BIO or PGR products plus starter fertilizer, starter fertilizer only, and an untreated control. Compared to the control, starter-only increased grain yield at 7 of 8 site-years in 2016 and 2018 ranging from 125 to 753 kg ha^-1, depending on location, but no increase was found at any of the 3 locations in 2017. Grain yield was increased (3 of 11 site-years) or decreased (2 of 11 site-years) by some of the BIO or PGR products, but in 6 of 11 site-years none of the products affected yield compared to starter-only.</p>

Studies on plant growth-promoting rhizobacteria (PGPR) and fungi (PGPF) as biostimulants have shown significant positive effects on plant health, fruit yield, or pest management. However, very few published studies to date have been specific regarding their effects on strawberries (Fragaria × ananassa), particularly on soilborne disease prevalence in organically grown strawberries. Empirical data on the results of using these products in commercial growing applications under various conditions would be highly valuable, especially for organic growers who have limited synthetic chemical pesticides, herbicides and fertilizers registered for use. The objective of this study is to evaluate the efficacy of biostimulant supplementation on strawberries for improving fruit yield, fruit quality, and plant health in both high-tunnel, open-sided ‘hoophouse’ and field conditions. This study consisted of two research projects. The first project investigated the effects of commercially available PGPR-based biostimulant products on strawberry plant health. The three products contained differing proprietary combinations of PGPR, primarily from the Bacillus and Lactobacillus genera. Plants were grown in two different soil types: sandy and clay, in order to investigate the effects of biostimulant supplementation in different soil conditions. In fall of 2018, 160 ‘Monterey’ strawberry plants were grown in an outdoor hoophouse in 3-gallon pots. Plants were either treated monthly with a single bacterial biostimulant product (EM-1, Accomplish LM, or Armory), or left untreated as a control. Plants were grouped into 20 blocks, each block comprised of 8 plants (each of the four treatments replicated in both soil types). Fruit yield (g), fruit sugar content (Brix), and leaf SPAD absorbance levels were measured weekly from January 27 to June 26, 2019. The treatments tested had no significant effects on fruit yield, leaf SPAD absorbance or Brix; soil type, however, did significantly impact fruit yield, with higher yields in sandy soil. The second project was a field trial beginning in spring of 2020, in collaboration with Rutiz Farms in Arroyo Grande, CA, involving a total of 480 ‘Chandler’ strawberry plants. The farm is organically managed and has a history of soilborne diseases, including Verticillium dahliae. These plants were either treated monthly with one of three microbial biostimulant products: a product containing a proprietary strain of Trichoderma harzianum biocontrol fungus (TrichoSym), and two of the same PGPR-based products used the previous year (Accomplish LM and Armory); or left untreated as a control. The experiment was laid out in a randomized complete block design with four blocks, with each block consisting of 4 plots for each of the 4 treatments; each plot contained 30 plants. Fruit yield (g) per plot was measured weekly throughout the 2020 growing season and phenotypic disease incidence was measured biweekly. Soil samples were taken at three different points throughout the season, cultured on selective media, and analyzed to obtain estimates of V. dahliae colony-forming units (CFU) per gram soil. The treatments tested had no significant effect on fruit yield, phenotypic disease incidence, or V. dahliae CFU/g soil. The results are inconclusive as to whether this lack of effect is due to viability of the products themselves, ineffective application techniques resulting in lack of rhizosphere colonization, or some combination of these. Further research is needed to determine whether or not supplementation with microbial biostimulants can produce reliable, beneficial results in strawberries.

Agroecosystem and cycling loops are open when considering the reutilization of inputs in farming areas. Non-renewable resources have been transformed or relocated from the air, water and land into the system and are flowing out as wastes rather than reusable, recyclable resources. Therefore, current trends in agriculture have moved towards more sustainable cultivation systems with higher efficiency of input use, since mineral nutrient losses due to runoff, leaching, erosion and gas emissions are leading to environmental degradation. A huge variety of materials can serve as a crop nutrient supply and they can be derived from different resources. The integrated plant nutrition system (IPNS) thrives tailoring plant nutrition and soil fertility management, taking advantage of the conjunctive and harmonious use of inorganic, organic and biological resources. We hypothesize that the synergetic effects of the combination of humic acid HA + biofertilizer will improve plant agronomic outcomes when comparing the application of each product alone. We initiated this project conducting a greenhouse study and field experiments evaluating the effects of an IPNS on corn. Posteriorly, the positive results in terms of corn biomass increasing, led to another greenhouse study addressing cannabis (Cannabis sativa L.) due its valuable biomass as an end/selling product. The greenhouse studies evaluated the effects of commercial synthetic fertilizer, HA, compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively, and their synergy on corn and cannabis early development under a period of water deficit stress. Generally, for both studies, when compared to the control values, the use of HA, biofertilizers and the integration of both substances generated significantly greater early season plant height, chlorophyll content and photosynthetic efficiency. The three-year field trial investigated the effects of nitrogen (N) fertilizer, HA, compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively and their synergy on corn growth. The individual and integrated application of HA and biofertilizer generally influenced corn development, to varying degrees. In 2017, corn height, NDVI, greenness and vigor were sensitive to the application of these biostimulants in different magnitudes and growth stages, however grain yield and nutrient content were not affected. In combined studies from 2018 and 2019 corn height was not impacted by biostimulant application but NDVI, photosynthetic efficiency, greenness and vigor were affected at different doses and corn growth stages. Only one treatment integrating HA + biofertilizer led to increased grain yield. In sum, these studies provided evidence that the individual and combined application of HA and biofertilizer can positively influence corn and cannabis growth most likely due to their plant biostimulant effects. However, the current study cannot conclusively affirm that the integrated use of HA and biofertilizers following the IPNS is a superior practice than the application of each compound individually and further studies should be conducted to validate these findings. / Doctor of Philosophy / The status of the corn (Zea mays L.) demand in Virginia and the Mid-Atlantic region is currently in deficit regarding the production in this area. This demand is exceeding supply by approximately 150%, then increasing feed grain yield and consequently production in the region can be simultaneously beneficial to crop farmers, end-users and the entire food supply chain. Furthermore, the consumer market is becoming more aware about sustainable practices for food production, which encourages producers to adopt agricultural practices that can minimize negative environmental impacts. This scenario enforces the scientific community's responsibility to test and develop environmental-friendly methods able to increase fertilization efficiency, decreasing the use in synthetic inputs but maintaining yield. The integrated plant nutrition system (IPNS) implements the combined and harmonious use of inorganic, organic and biological resources to take advantage of the potential synergetic effects. We conducted greenhouse studies and field experiments evaluating the effects of an IPNS on corn, and posteriorly based on the preliminary results obtained with corn, a greenhouse study addressing cannabis (Cannabis sativa L.) was also carried out. The greenhouse studies evaluated the effects of commercial synthetic fertilizer, humic acid (HA), compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively, and their synergy on corn and cannabis growth under a period of drought. Generally, for both studies, when comparing to the control values, the use of HA, biofertilizers and the integration of both compounds generated significantly greater early season plant height and photosynthesis measurements. The three-year field trial investigated the effects of nitrogen (N) fertilizer, HA, compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively and their synergy on corn growth. The individual and combined application of HA and biofertilizer generally influenced corn development, to varying degrees. In 2017, corn height, vegetation index, greenness and vigor were sensitive to the application of these biostimulants in different magnitudes and growth stages, however grain yield and nutrient content were not affected. In combined studies from 2018 and 2019 corn height was not impacted by biostimulant application but vegetation index, photosynthetic efficiency, greenness and vigor were affected at different doses and corn growth stages. Only one treatment combining HA + biofertilizer led to increased grain yield. In sum, these studies provided evidence that the individual and combined application of HA and biofertilizer can positively influence corn and cannabis growth most likely due their plant biostimulant effects. Even though, the current study cannot affirm that the combined use of HA and biofertilizers following the IPNS is a better practice than the application of each compound individually, this practice can be a more sustainable alternative to fit in the conventional farming scene.

A field study was conducted in 2022 and 2023 at two different locations in Mississippi (MS) implementing a split-plot design. Nitrogen (N) rates as the main plot including 0 (control), 90, 180, 269 kg N ha-1 at Starkville and 224 kg N ha-1 at Stoneville. The subplot was seven treatments, including a no biostimulant (check) and six commercially available microbial biostimulants (Source Corn®, Envita®, iNvigorate®, Blue N®, Micro AZTM, and Bio level phosN®) applied either as foliar at V4-V5 growth stages or in-furrow at planting. Only N rates positively affected grain yield and nitrogen use efficiency at all site years. The agronomic optimum N rate (AONR) differed across all site years, ranging from 202, 128, and 166 kg N ha-1 at Starkville 2023 and Stoneville 2022 and 2023. In summary, microbial biostimulants within this study showed minimal to no effect on corn grain yield and all other tested parameters.

Disease management in organic apple orchards in Vermont is focused on controlling diseases with sulfur fungicides. The objective of this two year study was to evaluate the target and non-target effects of an organic disease management system containing agricultural biostimulants compared to two sulfur-based systems on foliar and fruit diseases, pest and beneficial arthropods, tree growth, yield and fruit quality on four cultivars, `Ginger Gold', `Honeycrisp' and `Liberty' and `Zestar!'. Trees were arranged in a complete randomized design of five three-tree replications in a certified organic orchard. The two sulfur-based systems differed in the number of applications; in the third system, sulfur was replaced with biostimulants including pure neem oil, liquid fish, an activated microbial inoculant plus equisetum and stinging nettle teas. Each biostimulant application also included kelp meal, unsulfured organic molasses and yucca extract emulsifier. The biostimulant system did not successfully manage apple scab and rust diseases as well as the sulfur-based fungicide systems, and had variable results with other diseases. No differences were observed among the three systems in tree growth parameters; however, the length of the study may not have been sufficient to determine effects. Differences in the incidence of disease among the three systems were reflected in extrapolated figures for gross income per hectare which takes into account fruit yield and quality. In the higher fruit-bearing year of the study, it was estimated that the gross income per hectare of the biostimulant system would be significantly lower than the reduced-sulfur system and the full-sulfur system by at least $5,800 and $12,000, respectively. In that same year, it is estimated that the full-sulfur system would have generated approximately $6,500 more gross income per hectare than the reduced-sulfur system suggesting the number of sulfur sprays can influence fruit quality and income. The use of the agricultural biostimulants had very limited non-target effects and when present, they were beneficial in suppressing insect pest incidence and/or damage on foliage compared to one or both of the sulfur-based fungicide systems. However, many insect pests or their damage were not observed on the foliage or had incidence of less than 1% in any of the systems. The biostimulant system did appear to suppress European red mites in both years compared to both sulfur-based systems when data were averaged across cultivars. On fruit, no differences in non-target impacts on arthropod pests were observed among the three systems except for surface-feeding Lepidoptera and San Jose scale damage. In a separate phytophagous mite study on the cultivar `Zestar!' leaf samples were evaluated for the number of motile phytophagous mites every 14 days from 1 July through 26 August each year. When there were differences, the biostimulant system had less mite incidence per leaf than one or both of the sulfur-based systems in both years. The difference in the number of sulfur sprays did not have a major effect on the mite populations. In summary, the use of the biostimulant system resulted in insufficient disease management which led to lower estimated gross income compared to the sulfur-based systems. These results show more research and further evaluation of new organic disease management tools, including the use of agricultural biostimulants, are necessary before growers consider replacing the use of standard sulfur fungicides for disease management in Vermont orchards.