Low Nutrient Research Articles

Environmental characterization and impact of climatic fluctuations on the diversity of extremophilic bacterial communities of a high-altitude seasonal meltwater pond on Ojos del Salado (Dry Andes, Chile)

Earth has unique environments where only microorganisms adapted to extreme conditions can survive. The focus of this study was a high-altitude seasonal meltwater pond on the Altiplano plateau at 5900 m (Dry Andes). The polyextremophilic bacteria of this habitat must adapt to a range of extremities, including cold and dry climate, high UV radiation, and low nutrient availability. A macro-scale analysis was performed to characterize the environment using satellite imagery. To study the composition of bacterial communities, samples were taken from permafrost, water, and sediment of a meltwater pond during three subsequent expedition years under different weather conditions (average, high precipitation, severe drought). The bacterial diversity of the samples was revealed by Illumina MiSeq 16S rRNA gene amplicon sequencing. The results showed that the relative abundance of dominant phyla, such as Pseudomonadota, Bacteroidota, Acidobacteriota, and Verrucomicrobiota varied according to sample types and weather conditions, supported by the satellite environmental state analysis that showed correlations between the availability of snow, water surfaces, and the corresponding surface temperature values. Strong moisture-dependent quantitative changes were detected in the phyla Cyanobacteriota and Actinomycetota. Predominant sequences were linked to orders Chitinophagales, Burkholderiales, Flavobacteriales, and Sphingomonadales, known for their ability to degrade various organic compounds.

The influence of soil factors on the different vegetation formations of the Dunas Park, Salvador, Bahia, Brazil

This article was conducted in a restinga ecosystem on quaternary sandy deposits of Parque das Dunas, Salvador, Bahia, Brazil; located north of Salvador, this area comprises a landscape formed by different edaphic gradients with varied vegetation formations. An edaphic characterization of the sections of these remnants was carried out to understand the influence of edaphic factors on the distribution of the plant composition of this environment. For this purpose, a transect was delimited perpendicular to the coastline. In this transect, 08 plots of 25x25m were implanted, 100m apart. In the Centre of each plot, a 1m wide and 60 cm deep trench was opened, where soil samples were collected to determine edaphic and granulometric parameters. These samples in each plot followed the distribution of the vegetation formations of this environment. It was found that the different water regimes and topography of the area influence the soil factors, which interferes with the distribution and heterogeneity of the vegetation. The highest levels of fine, very fine and medium sand fractions and calcium and phosphorus were found in the highest portions. These areas, with better drainage, have a higher plant density. There is a lower vegetation density with open sandbanks in lower areas, lower levels of fine, very fine and medium sand fractions, and lower nutrient retention. In these environments, some areas are partially flooded with adapted species. It was also found that most of the plots had a very acidic pH with the presence of exchangeable Al, which could indicate high nutrient unavailability. Thus, the sandbanks' soil conditions influence the vegetation's development, inducing the plant species to develop adaptive mechanisms to maintain their biological organization.

NATIVE MYCORRHIZAE FROM ETHIOPIA IMPROVE TREE GROWTH AND SEEDLINGS SURVIVAL CONTRIBUTING TO THE GREEN LEGACY PROGRAM

<p><strong>Background</strong>: A rapid production of tree seedlings in nurseries with a high survival rate after transplanting is important to respond to the current demand for programs of restoration of arid environments by forestation. The low level of seedlings’ survival and establishment, caused by low moisture and nutrient content of soils, has been a bottleneck to reaching the target of the forest national restoration in Ethiopia of last years. It is suggested that, inoculation with root-associated plant growth promoting microorganisms could help to ameliorate this scenario and also respond to the Ethiopia's Green Legacy Program. <strong>Objective</strong>: To assess the potential of inoculation with arbuscular mycorrhizal fungi (AMF) native to Ethiopia to improve the survival and growth of trees that could be used in afforestation programs in Ethiopia. <strong>Methodology</strong>: The study was carried out in three stages: (1) soil samples associated with roots of selected acacia species (T<sub>1</sub>-AMF of<em> A. abyssinica</em>, T<sub>2</sub>-AMF of<em> A. seyal</em>, T<sub>3</sub>-AMF<em> </em>of <em>A. tortilis </em>and<em> </em>T<sub>4</sub>-Control) were collected of highland and lowland areas from Ethiopia, (2) Sorghum (<a href="https://www.researchgate.net/publication/342429051_Evaluation_of_sorghum_Sorghum_bicolor_L_Moench_variety_performance_in_the_lowlands_area_of_wag_lasta_north_eastern_Ethiopia"><em>Sorghum bicolor</em> (L.), provided by the Melkasa Agricultural Research Center-(MARC) served as a trap plant for </a>the AMF consortium multiplication and (3) plant growth promotion by AMF was assessed throughout inoculations of seedlings of<em> </em><em>Delonix regia</em> (Hook.) Raf.,<em> Sesbania grandiflora </em>(L.)<em>, Cassia fistula </em>L<em>., </em>and<em> Azadirachta indica </em>A. Juss., trees<em>. </em><strong>Results</strong>: All inoculated seedlings showed significantly greater responses in all growth and mycorrhizal parameters over the non-inoculated trees. Consortium T<sub>2</sub>-AMF associated to roots of<em> A. seyal </em>from lowlands of Batu, showed significantly greater responses in all plant growth and mycorrhizal parameters over the AMF inoculums associated to other tree species evaluated. Significant and positive correlations were found between mycorrhizae and plant-growth parameters<em>. </em><strong>Implications:</strong> Our results suggest that inoculation with native arbuscular mycorrhizal fungi indigenous from Ethiopia has the potential to significantly enhance survival and growth rates of tree seedlings. This could thereby advance national reforestation goals and addressing challenges in seedling establishment in arid environments. <strong>Conclusion</strong>: The potential for growth promotion and establishment of tree seedlings evidenced, implies that further efforts should be directed towards the in-mass production of AMF-based inoculants, particularly associated with <em>A. seyal</em> roots.</p>

Recycling steel slag as fertiliser proxy in agriculture is good circular economy but disrupts plant microbial symbioses in the soil

Modern agriculture depends on synthetic fertilisers to ensure food security but their manufacture and use accounts for ~5 % of the global greenhouse gas emissions. Achieving climate change targets therefore requires alternatives, that while maintaining crop productivity, reduce emissions across the lifecycle of fertiliser utilisation. Steel slag, a nutrient-rich by-product of steel manufacture, offers a viable alternative. Being substantially cheaper than fertilisers, it is economically attractive for farmers, particularly in low-middle income countries of the Global South. However, slag application in agriculture poses risk of pollutant transfer to the human food chain and disruption of key plant-microbe symbioses like the arbuscular mycorrhizal fungi (AMF). Here, using barley as a model crop, we tested the suitability of slag as a fertiliser proxy. Mycorrhizal and non-mycorrhizal barley were grown in soils ameliorated with slag in concentrations of 0, 2, 5 and 10 t ha−1. We analysed slag-mycorrhiza interaction and their combined effects on crop yield and risks to human nourishment. Slag increased grain yield by respective 32 and 21 % in mycorrhizal and non-mycorrhizal barley. Grain concentration of metal pollutants in mycorrhizal and non-mycorrhizal barley fertilised with slag were within the WHO recommended limits. But slag reduced mycorrhizal colonisation in barley roots and extraradical hyphal spread in the soil. The consequent decline in symbiont function lowered AMF-mediated plant nutrient uptake and increased mineral losses in leachates. AMF are keystone species of the soil microbiome. Loss of AMF function presents long-term ecological consequences for agriculture and necessitates a careful evaluation of slag application to soil.

Influence of Acetylene Concentration on N2O and N2 Emissions from an Intensive Vegetable Soil under Anoxic and Oxic Conditions

Acetylene (C2H2) is often employed to assess soil total denitrification (N2O + N2) due to its ease of implementation. However, this technique underestimates soil denitrification in soils with low nutrient contents, particularly those supporting grain yields. To our knowledge, there are limited studies that have specifically investigated the impact of C2H2 on nutrient-rich vegetable soils, especially concerning the emissions of N2 and N2O and the nitrogenous gas product ratio (i.e., N2O/(N2O + N2)). In this study, we conducted both anoxic and oxic incubations at various C2H2 concentrations (0%, 0.01%, and 10%, v/v) and utilized a robotized sampling and analysis system to quantify soil N2, N2O, and CO2 emissions. Our findings revealed that the cumulative N2O production in soil treated with 10%C2H2 was significantly lower than that in soil treated with 0.01%C2H2 and soil without C2H2. Contrarily, high concentrations of C2H2 (10%, v/v) led to increased N2 production. Similar trends were observed under oxic conditions, where 10%C2H2 concentration did not enhance N2O production but markedly increased N2 and CO2 emissions. Moreover, the N2O/(N2O + N2) product ratio was notably higher in soils treated with 0%C2H2 compared to the 10%C2H2 treatment under anoxic conditions. These findings indicate that high concentrations of acetylene could facilitate the reduction of N2O to N2 and lead to underestimated soil total denitrification in vegetable soil, regardless of anoxic or oxic conditions. This discovery underscores the drawbacks when employing high concentrations of acetylene to evaluate actual total denitrification in intensive greenhouse vegetable soils, highlighting the necessity for further investigation into alternative methodologies.

Farmland Degradation in the Czech Republic: Drivers and Barriers of Mitigation Strategies in Agricultural Soils

ABSTRACTIn line with Sustainable Development Goal (SDG) 15.3, which aims to restore degraded land and soil, and the priorities of the Common Agriculture Policy (CAP) to mitigate environmental issues caused by intensive agriculture, understanding the factors influencing farmers' adoption of soil conservation practices (SCPs) is crucial. However, there is still a limited understanding of these specific factors, particularly in the context of the Czech Republic. This study investigates the perceptions and determinants influencing the adoption of SCPs among farmers in the Czech Republic. We analyzed 358 randomly selected farm households using probit and multivariate probit models. Our results show that a significant number of farmers perceive soil degradation as an important problem, attributing it to factors such as low soil nutrient content, declining soil humus, water and wind erosion. The results of our analysis showed positive associations for perceived effectiveness and profitability, indicating that farmers tend to adopt practices such as minimum tillage, mulching, mixed cropping, cover cropping, and continuous soil cover when these methods are perceived to be effective and profitable. Conversely, negative associations are found for perceptions of soil degradation and education, suggesting potential barriers to adoption with higher levels of perceived soil degradation and education. The study also highlights the complex interplay of information sources on adoption, with both positive and negative trends. In light of these findings, we propose recommendations, including that awareness campaigns should be tailored to address perceptions of soil degradation, and that the use of peer networks and information dissemination from research institutions can bridge the gap between scientific recommendations and on‐farm practices. Policy makers and agricultural extension services should work together to develop targeted strategies that take into account regional differences in the factors influencing adoption and ultimately promote widespread adoption of SCPs.

Exotic mangrove Laguncularia racemosa litter input accelerates nutrient cycling in mangrove ecosystems.

Exotic plant litter presents different chemical and physical properties relative to native plant litter and alters ecosystem processes and functions that may facilitate exotic plant dispersal. However, these effects are largely unknown, especially within wetland ecosystems. This study examines whether introducing litter from theexotic mangrove Laguncularia racemosa could result in (1) accelerated community litter decomposition rates and increased nutrient cycling rates and (2)microbial community structure changes in the invaded areas. A single decomposition experiment using litterbags was conducted to examine the short-term effects of L. racemosa litter in the native mangrove forest ecosystem. The soil nutrients and microbial communities of Rhizophora stylosa, L. racemosa, and mixed forests were also compared to explore the long-term cumulative effects of L. racemosa litter in native ecosystems. The results indicated that L. racemosa has lower-quality leaf litter than R. stylosa and a significantly faster decomposition rate. This may result from changes in the soil microbial community structure caused by L. racemosa leaf litter input, which favors the decomposition of its own litter. Both the short-term and cumulative effect experiments demonstrated that L. racemosa leaf litter significantly increased the relative abundance of microbes related to litter decomposition, such as Proteobacteria and Bdellovibrionota, and enhanced the alpha diversity of soil fungi, thus creating a microbial environment conducive to L. racemosa leaf litter decomposition. Moreover, the accumulation of soil nutrients was lower under L. racemosa than under R. stylosa over several years. This may be related to the more rapid growth of L. racemosa, which causes soil nutrient absorption and storage within the plant tissues, thereby reducing the soil nutrient content. Inputting exotic mangrove L. racemosa leaf litter reduced the soil blue carbon content, potentially adversely affecting global climate change. L. racemosa may employ a unique strategy to lower soil nutrient levels in native mangroves based on its low-quality leaf litter, thereby weakening the competitive ability of native plants that are intolerant to low-nutrient conditions and enhancing its own competitive advantage to further spread into these areas. In summary, the input of exotic L. racemosa leaf litter accelerates nutrient cycling in local mangroves.

Research Review: Pharmacological and non-pharmacological treatments for adolescents with attention deficit/hyperactivity disorder - a systematic review of the literature.

Attention Deficit/Hyperactivity Disorder (ADHD) demonstrates unique developmental manifestations in adolescence with implications for optimized, age-appropriate treatment. This 10-year update is the third in a series of systematic reviews examining the efficacy and safety of adolescent ADHD treatments. We broadly examined efficacy on ADHD symptoms, impairments, and other reported outcomes. Acute and long-term efficacy, and treatment moderators, were considered. We performed PubMed, EMBASE, and PsycINFO searches for articles published or in press from 2013 to 2024, integrated with hand search and randomized controlled trials (RCTs) identified in this series' earlier reviews. RCTs examining the safety or efficacy of interventions delivered to adolescents (ages 10.0-19.9) with a diagnosis of ADHD were included. Study characteristics were extracted and reviewed, quality of evidence was assessed using GRADE, and effect sizes were calculated for individual studies and illustrated using forest plots. Sixty-three RCTs were identified. Quality of evidence ranged from high (medication; k = 29) to very low (nutrient supplementation, neurofeedback, occupational therapy; k = 1 each). Medications demonstrated consistent strong impact on ADHD symptoms and inconsistent impact on impairment. Diverse cognitive/behavioral treatments (C/BTs) demonstrated inconsistent impact on ADHD symptoms but strong and consistent impact on impairment and executive function skills, plus moderate benefits on internalizing symptoms. No interventions demonstrated significant safety concerns. Long-term maintenance (up to 3 years post-treatment) was demonstrated for C/BTs, though moderate quality of evidence was noted because participants cannot be fully blinded to receipt of treatment. The effects of C/BTs and medication appear complementary, not duplicative. Combining medication and C/BT is advised at treatment outset to maximize engagement, maintenance, and response breadth (i.e. improving both ADHD symptoms/cognitive performance and coping skills/functional impairments). Engagement strategies (e.g. motivational interviewing) may facilitate uptake. Novel treatments do not yet demonstrate effects on ADHD symptoms or impairments in adolescents but remain a promising area for research.

Post-harvest loss assessment of Hilsa (Tenualosa ilisha) along the value chain in Bangladesh

Hilsa, the national fish of Bangladesh, contributes more than 12 % of the country's total fish production. Considering the species' importance, this study assessed the post-harvest loss (PHL) of Hilsa across the value chain. Data were collected at the landing and distribution chain from 200 fisherman, 40 aratdars (Aratdar-I), 40 wholesalers at landing sites of the Chandpur district, 40 aratdars (Aratdar-II), and 70 retailers at the distribution sites of the Jamalpur district. The results revealed 12.56 % post-harvest losses in the value chains, most of which were caused by quality losses (8.41 %). Along the value chain, fishermen faced the highest losses 5.291 %, followed by 3.813 % in the retailers. These findings suggest fishermen and retail markets are hotspots of spoilage and fish loss. The OLS regression model indicated that inappropriate age and lack of experience of stakeholders, prolonged harvesting time, inadequate washing facilities, fishermen small size group, longer distances between fishing locations and landing sites, lack of proper education and training, delaying auctioning, insufficient infrastructure facilities, longer selling time, and insufficient cooling facilities were the significant factors causing PHL in the value chain. Nutritional analysis revealed substantial changes across the value chain. Moisture content increased steadily, which accelerated the spoilage. A significant decrease in protein, lipid and ash indicated the substantial loss of nutrients after harvesting up to the retail market. Principal Component Analysis (PCA) for nutritional composition analyses demonstrated that after the catch, aratdar-I, and boat had higher nutrient levels, while aratdar-II, local wholesaler, and post-transportation had higher moisture and lower nutrient levels. The PC1 accounted 95.92 % of the variation, indicating that handling and storage had significant influences in maintaining nutritional quality. To reduce post-harvest losses, the government must implement standardized practices throughout the Hilsa value chain to ensure food security and sustainability in the Hilsa fishery and boost the economy.

Ocean warming enhances the competitive advantage of Ulva prolifera over a golden tide alga, Sargassum horneri under eutrophication

Recent years have seen the Ulva green tide and Sargassum golden tide become commonplace in the coastal waters of China. However, little is known on how the combination of ocean warming and eutrophication would affect the interaction of green and golden tides. In this study, we cultured the green tide alga Ulva prolifera and the golden tide alga Sargassum horneri under different temperatures (5, 10, 15, 20, 25, and 30°C) and two nutrient concentrations (Low nutrient, LN: 5 μM-nitrate and 0.5 μM-phosphate; High nutrient, HN: 500 μM-N and 50 μM-P) in both monoculture and coculture systems to investigate the physiological responses and their competitive relationships. In monocultures, the growth of U. prolifera and S. horneri, along with pigment concentrations and photosynthesis, increased with rising temperature, reaching a plateau at 15 - 25°C. However, when the temperature increased to 30°C, the growth of U. prolifera and S. horneri decreased abruptly, with S. horneri even suffering death. In coculture, the growth of both U. prolifera and S. horneri was inhibited compared to the monoculture, with the greatest decline observed in S. horneri at 25°C under two nutrient conditions. Our results show that U. prolifera would outcompete S. horneri under high temperature in coculture, suggesting that ocean warming would enhance the competitive advantage of green tide over golden tide under eutrophication in the future.

Application of oil palm and cacao waste biochar to improve the chemical properties of an Ultisol of Langsa, Aceh

Ultisols, including those of Langsa, Aceh, are known to have low fertility due to low pH, low available nutrients, low base saturation, high pH and exchangeable Al, and low cation exchange capacity. These problems can be alleviated by applying organic amendments to the soil. One of the soil amendments is biochar. This study aimed to elucidate the potential of oil palm and cacao waste biochar for improving the chemical properties of an Ultisol of Langsa, Aceh. Biochars generated from oil palm kernel shell (PKS), oil palm empty fruit bunch (PEFB), and cacao pod husk (CPH) were applied to the soil and incubated in the laboratory for 16 weeks. At 4, 8, 12, and 16 weeks after incubation, the changes in soil chemical properties were measured. The results showed that applying different types of biochar significantly improved the chemical properties of the Ultisol of Langsa. Specifically, PEFB biochar caused significant increases in soil pH (H2O and KCl), total phosphorus, available phosphorus, organic C, and cation exchange capacity. These increases became more pronounced with longer incubation times. In addition, using PEFB biochar resulted in the lowest levels of exchangeable Al and Fe in the soil. These levels decreased further with longer incubation times. In general, PEFB biochar produced at a pyrolysis temperature of 450oC for 4 hours is the most effective biochar for improving the chemical properties of the Ultisol of Langsa.

Local sediment amendment can potentially increase barley yield and reduce the need for phosphorus fertilizer on acidic soils in Kenya

Soil acidification and low nutrient availability are two major challenges facing agriculture in most regions of East Africa, resulting in aluminum toxicity and poor crop yields. The amendment of local sediments to cropland can potentially alleviate these challenges, but responses are variable. In this study, we investigated the potential of two different local sediments influenced by volcanic deposits to increase soil pH, Si and P availability and reduce Al toxicity, thereby improve barley yield. Hence, a field experiment was established in Eldoret, Western Kenya, using 1% and 3% addition by weight of two sediments in barley cultivated plots. The Baringo 3% amendment significantly increased soil pH (from 4.7 to 7.0), the available P content (from 0.01 mg g−1 to 0.02 mg g−1) and decreased the Al availability (from 3.03 mg g−1–2.17 mg g−1). This resulted in a barley yield of 4.7 t/ha (+1061%). The Nakuru 3% and Baringo 1% amendments increased yield to 2–3 t/ha, while the Nakuru 1% did not significantly increase yield. These results highlight that, from a biophysical perspective, there are natural and local opportunities to reduce soil acidification and to partly replace mineral fertilizer, but its magnitude depends on the sediment and the amendment rate.

Improving sugarcane productivity on marginal soil in Takalar, Indonesia, through the application of sugarcane factory waste

Marginal soil with low nutrient content is a crucial problem in reducing crop productivity, including sugarcane. This study aimed to elucidate the possible improvement of the physical and chemical properties of marginal soil through the application of organic waste from sugar factories, namely kettle ash and press mud. Nine treatment combinations of 0, 10, and 20 t ha-1 of each kettle ash and press mud were arranged in a two-factor randomized factorial design with three replications. Soil organic matter, N, P, and K, soil aggregate stability, and sugarcane productivity were measured after planting sugarcane for five months. The results showed that the application of kettle ash and press mud, especially with a ratio of 20 t ha-1 kettle ash and 10 t ha-1 press mud, was able to reduce the leaching of organic matter and improve sugarcane growth, particularly increasing the number of tillers by 16%, stem height by 14%, and diameter by 16%. The sugarcane productivity obtained was 58.02 t ha-1. Other portions of kettle ash and press mud did not have a favorable effect on sugarcane productivity. This study provided practical insights for increasing agricultural productivity, especially in sugarcane plantations.

Pedoclimatic conditions impact the mycorrhizal potential of the rhizospheric soil, essential oil yield, chemical profile, and biological activities in Lavandula dentata

Lavandula dentata produces a wide range of products, essential oils (EO) and bioactive molecules, extensively used for their various cosmetic and medicinal properties. However, in Morocco, L. dentata has been classified among vulnerable species experiencing a noticeable decline due to several biotic and abiotic stresses. This study aims to better understand the relationship between the ability of L. dentata, to produce bioactive molecules and pedoclimatic conditions. The study was carried out in two semi-arid regions: Asni (altitude: 1400 m) and Had Draa (altitude: 120 m). The results showed that the pedoclimatic conditions did not affect significantly the natural mycorrhization of Lavender expressed in terms of mycorrhizal frequency and colonization intensity. However, the mycorrhizal potential of the soil was 3 to 4 times higher in Asni than in Had Draa. Asni pedoclimatic conditions favored higher EO yield (14 μL/g DM) which was 2 times higher than in Had Draa. However, EO of Had Draa exhibited greater effectiveness in terms of antimicrobial, and herbicidal activities. While the EO of Had Draa was characterized by a high abundance of endo-borneol (36%) and fenchol (20%), the EO chemical profile of the EO of Asni showed high abundance of camphor (28%) and terpinene-4-ol (12%). Taken together, the findings pointed out that the pedoclimatic conditions prevailing in Asni such as high altitude, high precipitation, low nutrient levels, and low organic matter could improve the mycorrhizal potential of the soil, increase L. dentata EO yield, but have a negative impact on its biological activities.

Performance of the edible halophyte Cakile maritima under critical magnesium and potassium thresholds

In their natural biotope, plants are challenged with low nutrient availability which is one of the most important limiting factors for plant production. Nutrient limitation causes disruption in several metabolic pathways resulting in a decrease in plant growth and establishment. Such responses were mostly studied in glycophytes while in halophytes the data remained scare. In the present investigation, using Cakile maritima as a plant model for halophytes, we attempt to elucidate the behavior of this species under critical magnesium and potassium thresholds. Our data showed that low K or Mg supply (0.01 mM) reduced leaf number and biomass production in leaves, stems and roots while both parameters were improved at 0.05 mM Mg and K concentration before reaching an optimum at 0.25 mM Mg and 1 mM K, respectively. Several indices of K and Mg stress tolerance were reduced upon deficiency in both elements and were significantly improved by moderate K and Mg supply. Photosynthetic pigment content was reduced upon both deficiencies with the highest reductions recorded in plants suffering from severe Mg and K starvation. Increasing Mg and K supply resulted in better chlorophyll synthesis as reflected by the increase in chlorophyll stability index parameter (CSI). Furthermore, both deficiencies triggered oxidative damages as malondialdehyde content (MDA) and electrolyte leakage (EL) increased while membrane stability index (MSI) decreased under both deficiencies. Such results suggested that the cell redox homeostasis was altered when Mg and K were omitted from the nutrient solution. Interestingly, moderate and high Mg and K concentrations promoted C. maritima growth and reduced the oxidative damage caused by the lack of both elements in the external medium. Overall, C. maritima exhibited a typical halophytic behaviour, requiring less macroelements to express its growth performance when cultivated under critical magnesium and potassium thresholds.

Unraveling the Relationship between Soil Nutrients and Maize Leaf Disease Occurrences in Mopani District Municipality, Limpopo Province, South Africa

Maize is a staple crop important for food security that millions globally depend upon as an energy source, primarily due to its high starch and fat content. For growth and disease resistance, maize production requires a balanced intake of essential nutrients, including nitrogen (N), phosphorus (P) and potassium (K). This study investigated the relationship between soil nutrient levels and maize disease occurrences in the Mopani District Municipality, Limpopo Province, South Africa. Soil and maize leaves were collected using a systematic sampling approach. Grids of 10 × 10 m were created, covering a maize field. Forty soil samples were collected a day before the planting date and sent to the laboratory for analysis of N, P and K. During the tasseling stage of the maize plant, 40 maize leaf samples were collected and sent to the laboratory for disease identification. Maize leaves were classified as healthy, southern corn leaf blight (Bipolaris maydis), northern corn leaf blight (Exserohilum turcicum), maize streak disease (Maize streak virus), nitrogen-deficient or phosphorus-deficient. Generalized Linear Models (GLMs) with a corrected Akaike Information Criterion (AICc) showed a significant relationship between low soil nutrient levels of N, P and K and maize disease occurrence (p < 0.0001). The interaction of the N*P*K model had the lowest AIC value (AICc = 28.53), indicating the necessity of considering synergistic effects in maize disease management. All the model performances had a delta AICc = 0. These findings highlight the significance of comprehensive soil management strategies in enhancing the disease resistance, well-being and yields of maize crops.

Optimizing Biochemical and Phytochemical Attributes in Peaches through Foliar Applications of Silicon and Zinc

Peach production faces significant pre-harvest challenges, including low moisture, nutrient deficiencies, flower drop, physical damage, and surface discoloration, which can limit yield and fruit quality. To mitigate these issues, the present study hypothesized that foliar applications of silicon and zinc could enhance peach growth, yield, and quality due to their known roles in improving stress tolerance, nutrient uptake, and antioxidant activity. Therefore, this research aimed to identify optimal concentrations of silicon and zinc for quality peach production. Ten-year-old peach trees of uniform size were sprayed with four levels of silicon (0%, 0.1%, 0.2%, and 0.3%) and zinc (0%, 0.25%, 0.50%, and 0.75%) for two consecutive growing seasons, at the berry and pit hardening stages, using a Randomized Complete Block Design (RCBD) with three replications. The averaged data from the two years showed that the pre-harvest foliar application of silicon significantly improved all yield and quality attributes of peaches. The foliar application of silicon at 0.3% notably enhanced fruit growth, yield, and biochemical attributes. Additionally, the highest fruit growth, yield, and quality of peach fruits were observed at the 0.75% zinc concentration. Maximum antioxidant activity, flavonoid content, proline content, and catalase activity were observed in fruits from plants treated with 0.3% silicon, which were statistically on par with 0.2% silicon. However, peroxidase activity was highest at 0.2% silicon. Regarding zinc levels, antioxidant activity, flavonoid content, proline content, and peroxidase activity were highest in fruits treated with 0.75% zinc, while catalase activity was superior when fruits were sprayed with 0.50% zinc. The interaction between silicon and zinc concentrations was found to be non-significant for most parameters, except for titratable acidity, TSS–acid ratio, ascorbic acid content, antioxidant activity, flavonoid content, and peroxidase activity. In conclusion, the foliar application of 0.3% silicon and 0.75% zinc independently enhanced all yield and quality characteristics of peaches. For the agro-climatic conditions of Peshawar, 0.2% silicon and 0.50% zinc are recommended for optimal peach production.

Two neglected contributors to water biosafety risks: The impacts of microbial co-existence and light on viral inactivation

Virus-induced risks to water quality persist, with the viability of viruses in complex aquatic environments impacted by various factors, including coexisting bacteria and exposure to light. This study investigated the disinfection efficacy of UV254 irradiation and free chlorine (FC) on Bacteriophage phiX174 in the presence of coexisting bacteria, specifically Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). To elucidate the underlying mechanisms, this study examined the effects of bacterial compounds (i.e., E. coli lipopolysaccharide (LPS) and B. subtilis peptidoglycan (PGN)) on viral inactivation, thermal stability, and environmental persistence. The research results demonstrated that bacterial presence and their associated compounds significantly impaired viral inactivation, with greater concentrations of coexisting bacteria and their compounds exacerbating this effect. Additionally, the photoreactivation of phiX174 was explored following UV254 irradiation, indicating that high-dose UV254, coupled with low nutrient availability and minimal host bacteria levels, effectively suppressed viral photoreactivation. This study is the first to investigate the multifactorial effects on viral photoreactivation. The results offer novel insights into the challenges associated with virus-related pressures in water treatment, with potential implications for optimizing disinfection processes.

An evaluation of cyanobacterial occurrence and bloom development in Adirondack lakes

Cyanobacterial harmful algal blooms (cyanoHABs) have occurred in many low nutrient (oligotrophic) lakes in the northeastern United States. The Adirondack Park in New York is a large, mountainous region with many low nutrient lakes. There is a gap in understanding regarding whether cyanoHAB reporting data are truly reflective of the susceptibility of lakes to develop bloom conditions. We evaluated lakes with and without documented cyanoHABs for cyanotoxin synthetase gene quantification, phytoplankton community composition, and akinete abundance to identify conditions associated with the observation of cyanoHABs. We analyzed (1) contributions of cyanobacteria to the overall phytoplankton community, (2) differences in cyanobacterial communities and the presence of cyanotoxin synthetase genes, and (3) lake physical and geomorphological attributes as drivers of differences in cyanobacteria occurrence. Two sample types (water and sediment) were collected from 2 sample locations (nearshore and open water) in 5 lakes in 2021. We found cyanobacteria in all lakes and sample locations. Phytoplankton biovolume and cyanotoxin synthetase genes differed among lakes and by cyanoHAB history. Samples from lakes with documented blooms were associated with marginally higher total phosphorus. Nonmetric multidimensional scaling was used to identify which environmental factors influenced community structure. Our study demonstrates the importance of multifaceted approaches to detect cyanobacteria that may only be apparent during ephemeral bloom events and the similarities among lakes with and without a history of bloom reports. This work contributes to a better understanding of cyanoHAB occurrence in Adirondack lakes, and of conditions that may cause low nutrient lakes to be susceptible to cyanoHABs.

The microbiome of continuous wheat rotations: minor shifts in bacterial and archaeal communities but a source for functionally active plant-beneficial bacteria

Continuous wheat cropping often leads to yield decline, with suspected causes including increased pathogen susceptibility, decreased root growth, or low nutrient use efficiency, though the exact causes remain unknown. Here, we investigated soil and root-associated bacterial and archaeal communities in wheat under rotation versus continuous cultivation, monitored fungal pathogen presence, and used beneficial bacteria to mitigate Gaeumannomyces tritici (Ggt) symptoms in greenhouse experiments. Sampling was conducted at two field sites with different soil textures over two years and at two plant developmental stages, capturing site-specific and seasonal fluctuations. By cultivation, 767 bacterial isolates were screened for plant-beneficial traits. Amplicon sequencing revealed minor effects on community structure due to wheat rotational position but pronounced effects related to site, year, and microhabitat. Rhizoplane isolates with plant-beneficial traits were mainly Flavobacterium, Microbacterium, Pedobacter, Pseudomonas, Stenotrophomonas, and Variovorax. Continuous wheat rotations showed the highest proportion of bacteria with fungal antagonistic potential, indicating plant roots’ recruitment of beneficial bacteria. Introducing Ggt in the greenhouse experiment altered the bacterial and archaeal community, confirming field study results and demonstrating that applying beneficial bacteria early in the season at the seedling stage can control Ggt and improve plant growth. This study highlights the dynamic nature of wheat's below-ground bacterial and archaeal community, influenced by soil type, season, and microhabitat, with wheat rotation playing a minor role. In addition, it confirms the potential of selected Bacillus and Pseudomonas isolates, whether used individually or in consortia, for microbe-assisted mitigation of yield decline in intensive wheat production.