Mineral Nutrients Research Articles

Impact of Crop Establishment and Nutrient Management on Wheat Growth under Rice-Wheat System

The rice-wheat system contributes significantly to India's food security. The system's significance is properly handled from time to time, but excessive resource consumption, yield stagnation, environmental deterioration including erosion, and nutrient mining pose the greatest challenges. To address the issue, a research was conducted with objective to see the impact of crop establishment and nutrient management on growth parameters of wheat at Banaras Hindu University's Agricultural Research Farm in Varanasi during the 2019-20 Kharif and 2020-21 Rabi seasons, respectively. The experiment plotted in a split plot statistical design with three replications and four crop establishment methods: CE1: CTPTR-CTW, CE2: CTDSR)-CT wheat, CE3: CTDSR-ZTwheat (rice residue retained), and CE4: ZTDSR-ZT wheat (residue retention in rice and wheat) crop establishment method among the main plot treatments and nutrient management i.e. FP (N1), RFD (N2) and RWCM (N3) based nutrient recommendation among the sub plot treatments. Data recorded on growth parameters i.e. plant height, number of tillers and SPAD value at different stages are presented in this paper. CE4 treatment among main plot and N3 among nutrient management practices produced higher values of plant height, number of tillers at 30, 60, 90 days after sowing and at harvest as well as higher SPAD value at 30, 60 and 90 days after sowing than the other treatments. These results might be due to better nutrient availability, better organic carbon, which leads to improved microbial activity, and better moisture availability under these treatments. It may be concluded that conservation agriculture-based crop establishment i.e. CE4: Zero-till DSR-Zero-till wheat (residue retention in rice and wheat) and RWCM-based nutrient application, may be favourable for improved growth of the wheat crop under the region of eastern Uttar Pradesh.

Abiotic stress alleviation and contribution to resilient crop growth: A trichodermal perspective

Over the past few decades, the use of different biocontrol agents in agricultural methods has resulted in significant improvements in the safety and nutritional quality of food products. Consequently, there has been an increasing interest in finding effective alternative approaches to reduce abiotic stress pressures that also promote plant growth. Trichoderma harzianum is a biocontrol agent that has attracted scientific attention due to its remarkable capacity to combat various abiotic influences. The multifaceted mechanisms of disease prevention and crop growth acceleration exhibited by the filamentous fungus T. harzianum have rendered it a highly useful biocontrol agent. Trichoderma spp. positively influence several physiological cellular processes in plants, such as photosynthesis, stomatal conductance, gas exchange, nutrient absorption and assimilation, and water expenditure efficiency. Trichoderma species promoted optimal root development and improved the absorption of mineral nutrients from the soil. In summary, the fungus Trichoderma shows significant potential as a biocontrol agent for the sustainable protection of crops and the stimulation of plant growth. The varied mechanisms of Trichoderma species make them indispensable for the management of plant diseases. The utilization of Trichoderma potential is a significant avenue for achieving robust and ecologically sound crop production, particularly in challenging circumstances, as the worldwide agricultural sector strives for substitutes to harmful pesticides and excessive use of fertilizers.

Ecotoxicological effects of microplastic types and concentrations in combination with Cd on the bioenergy plant sweet sorghum: Growth and rhizosphere microbiome analysis

Complex interactions occur when microplastics (MPs) and heavy metals cooccur as pollutants, and these interactions have become a popular research topic. However, there is a lack of research examining the impact of concurrent pollution from MPs and heavy metals on the soil microbial community and its roles in nitrogen and phosphorus cycling. Therefore, in this study, we investigated the effects of composite pollution from cadmium (Cd) and different types of MPs (e.g., PVC, PE, and PP) at different concentrations (0.1 % and 0.5 %) on the growth of sweet sorghum, an energy plant, and evaluated Cd accumulation in sweet sorghum and the expression of genes related to soil nitrogen and phosphorus cycling. The results indicated that the growth of sweet sorghum was negatively impacted by combined treatment with the three types of microplastics and Cd, with the composite stress trend being 0.5 % > 0.1 %. The contents of mineral nutrients such as nitrogen, phosphorus, and potassium in the soil decreased due to MP+Cd pollution. Cocontamination with MP and Cd significantly affected the microbial community composition and increased the activity of enzymes such as urease. MP+Cd pollution affected the composition and abundance of functional genes related to nitrogen and phosphorus cycling. The type and concentration of microplastics were identified as the primary factors influencing the composition and abundance of functional genes. Bacteria belonging to Acidobacteria and Actinobacteria are key to soil nitrogen cycling, while Acidobacteria plays crucial roles in soil phosphorus cycling. Metagenomic analysis was performed in this study to determine the impact of microplastic–heavy metal pollution on soil microbial communities and functions and to provide a reference for the environmental assessment of soils contaminated by both microplastics and heavy metals.

Coordinated influence of Funneliformis mosseae and different plant growth-promoting bacteria on growth, root functional traits, and nutrient acquisition by maize.

Rhizospheric interactions among plant roots, arbuscular mycorrhizal fungi, and plant growth-promoting bacteria (PGPB) can enhance plant health by promoting nutrient acquisition and stimulating the plant immune system. This pot experiment, conducted in autoclaved soil, explored the synergistic impacts of the arbuscular mycorrhizal fungus Funneliformis mosseae with four individual bacterial strains, viz.: Cronobacter sp. Rz-7, Serratia sp. 5-D, Pseudomonas sp. ER-20 and Stenotrophomonas sp. RI-4A on maize growth, root functional traits, root exudates, root colonization, and nutrient uptake. The comprehensive biochemical characterization of these bacterial strains includes assessments of mineral nutrient solubilization, plant hormone production, and drought tolerance. The results showed that all single and interactive treatments of the mycorrhizal fungus and bacterial strains improved maize growth, as compared with the control (no fungus or PGPB). Among single treatments, the application of the mycorrhizal fungus was more effective than the bacterial strains in stimulating maize growth. Within the bacterial treatments, Serratia sp. 5-D and Pseudomonas sp. ER-20 were more effective in enhancing maize growth than Cronobacter sp. Rz-7 and Stenotrophomonas sp. RI-4A. All bacterial strains were compatible with Funneliformis mosseae to improve root colonization and maize growth. However, the interaction of mycorrhiza and Serratia sp. 5-D (M + 5-D) was the most prominent for maize growth improvement comparatively to all other treatments. We observed that bacterial strains directly enhanced maize growth while indirectly promoting biomass accumulation by facilitating increased mycorrhizal colonization, indicating that these bacteria acted as mycorrhizal helper bacteria.

Performance of coal slime-based silicon fertilizer in simulating lead-contaminated soil: Heavy metal solidification and multi-nutrient release characteristics

High-ash coal slime-based silica fertilizer (CSF) has the potential to provide mineral nutrients and passivate lead (Pb) in the soil to ensure the sustainable development of the coal industry and agriculture. This study investigated the performance and passivation mechanism of CSF, which contains potassium tobermorite and potassium silicate as the main components for soil improvement. Leaching experiments showed that low-crystalline muscovite was the only crystalline phase for CSF etching and that the silicon (Si), calcium (Ca), and potassium (K) in CSF had significant citric solubility. Soil cultivation and planting trials confirmed the ability of CSF to neutralize soil acidity, increase available soil Si and K, improve exchangeable Ca content, reduce the bioefficacy of Pb (exchangeable Pb by 19–75 % and carbonate-bound Pb by 6–18 %), and increase residual state Pb content. Compared to untreated Pb-contaminated soil, the 0.4 % CSF treatment reduced Pb in Chinese cabbage (Brassica rapa) by 25 % and increased plant biomass, Ca, and K by 37 %, 36 %, and 4 %, respectively. At the same time, soil pH increased by 0.58, and residual state Pb increased by 5 %. In CSF-treated soils, lead silicate is the dominant form of Pb present in the residual state. First-principle calculations showed that Pb3Si2O7 (cohesion energy −1.98 eV) formed by the passivation of Pb by CSF had greater stability in the soil compared to lead carbonate (PbCO3) (cohesion energy −1.38 eV) and lead sulfate (PbSO4) (cohesion energy −1.41 eV). This work shows the promising application of coal slime mineral fertilizers prepared using hydrothermal methods for soil improvement.

Enhancing arbuscular mycorrhiza symbiosis effectiveness through the involvement of the tomato GRAS transcription factor SCL3/SlGRAS18

Arbuscular mycorrhizal (AM) fungi improve plant growth, nutrition, fitness and stress tolerance while AM fungi obtain carbohydrates and lipids from the host. This whole process of mutual benefit requires substantial alterations in the structural and functional aspects of the host root cells. These modifications ultimately culminate in the formation of arbuscules, which are specialized intraradical and highly branched fungal structures. Arbuscule-containing cells undergo massive reprogramming to hosting arbuscule and members of the GRAS transcription factor family have been characterized as AM inducible genes which play a pivotal role in these process. Here, we show a functional analysis for the GRAS transcription factor SCL3/SlGRAS18 in tomato. SlGRAS18 interacts with SlDELLA, a central regulator of AM formation. Silencing of SlGRAS18 positively impacts arbuscule development and the improvement in symbiotic status, favouring flowering and therefore progress in the formation and development of fruits in SlGRAS18 silenced plants which parallel to a discernible pattern of mineral nutrient redistribution in leaves. Our results advance the knowledge of GRAS transcription factors involved in the formation and establishment of AM symbiosis and provide experimental evidence for how specific genetic alterations can lead to more effective AM symbiosis.

Co-hydrothermal carbonization of waste biomass and phosphate rock: promoted carbon sequestration and enhanced phosphorus bioavailability

Co-hydrothermal carbonization (co-HTC) of phosphorus rock (PR) and corn straw (CS) was investigated to prepare hydrochar-based materials as soil conditioners, focusing on the morphological transformation and solid–liquid migration of carbon and phosphorus. Various analytical methods, including elemental analysis, chemical quantification, FT-IR, XRD, 3D-EEM, TG, and XANES, were used to understand the synergistic interactions of PR and CS during co-HTC and determine the properties of the resultant products. The results indicated the acidic solution and humic acid-like substances produced by HTC of CS reduced the crystallinity of the PR and served as the activating agent for PR, allowing the PR to be easily dissolved and reconstituted, producing calcium carbonate and apatite-like materials, and the formation of C–O–PO3, C–PO3, C=O, and O=C–O chemical bonds. At 220 °C, adding 5% PR significantly promoted a 10.3% rise in the yield of CS hydrochar, a 4.3% rise in carbon recovery of CS, and a 4.8% rise in carbon sequestration potential of CS. The formation of Ca–P was notably promoted and the content of AP in co-HTC hydrochar was up to 89.9%, with 39% Hydro-P and 33% CaHPO4. In the case of artificial humic acid (HAa), its content was also remarkably increased by 5.9% in the hydrochar by co-HTC. In addition, the hydrochar produced by co-HTC of CS and PR was composed of carbon with an increased aromatic degree, rich organic matter, and biologically effective mineral nutrient elements and exhibited high stability. The present study provided a promising approach for value-added utilization of waste biomass and low-grade PR towards soil application.Graphical

GmIRT1.1 from soybean (Glycine max L.) is involved in transporting Fe, Mn and Cd

Soybean is one of the most important crops for producing high quality oil and protein. Mineral nutrient deficiencies are frequently observed in soybeans. However, there are few studies to understand the absorption process of mineral nutrients in soybeans. Here, we investigated the functions of soybean (Glycine max L.) IRT1.1 (IRON-REGULATED TRANSPORTER 1.1) in the transportation of mineral elements. Heterologous expression of GmIRT1.1 in yeast mutants revealed that GmIRT1.1 compensated for the growth defects of Δfet3fet4 and Δsmf1 mutants under iron (Fe) and manganese (Mn) deficiency conditions, respectively, and enhanced the sensitivity of the Δycf1 mutant to cadmium (Cd) toxicity. Expression analysis revealed that GmIRT1.1 was only significantly induced by Fe deficiency and was primarily expressed in roots. Furthermore, the GmIRT1.1 overexpression lines enhanced Arabidopsis tolerance to Fe deficiency, leading to increased accumulation of Fe in the roots and shoots. Additionally, the transgenic lines increased the sensitivity to Mn and Cd toxicity. Subcellular localization analysis revealed that GmIRT1.1 was localized on the plasma membrane. Moreover, the results obtained from the soybean hairy roots system indicated that the localization of GmIRT1.1 was dependent on the regulation of Fe homeostasis in plant. Consequently, these results suggested that GmIRT1.1 was responsible for the transportation of Fe, Mn and Cd.

Distributions of trace elements with Long-term grazing exclusion in a semi-arid grassland of Inner Mongolia.

Trace elements are the essential mineral nutrients in grassland, however, we still know little about the distributions of trace elements in grassland with long-term grazing exclusion. The contents, stocks, and proportions of iron (Fe), aluminum (Al), manganese (Mn), and boron (B) in green plant-litter-root-soil were evaluated by enclosing for 18, and 39 years inside the fence (F18 and F39) and grazing outside the fence (F0) in Inner Mongolia grassland. The results showed that F18 and F39 decreased the stocks of Fe, Al, and Mn in green plant and root compared to F0 (p < .05), while increased the stocks of them in litter (p < .05). The stock of Fe, Al, and Mn in green plant at F39 was 28.6%, 13.9%, and 39.2% higher than that at F18. The stocks of four trace elements in first layer litter at F39 were increased by 12.7%-52.2% compared to F18, whereas the stocks of them in third layer litter were decreased by 32.2%-42.5%. The F18 obviously increased the stocks of Fe and Mn in soil, especially B (p < .05). While the stocks of these trace elements in soil at F39 were 9.1%-28.0% lower than that at F18, especially B (p < .05). In conclusion, the trace elements were mainly shifted from green plant and root to soil and third layer litter with 18-year grazing exclusion. Compared to 18-year grazing exclusion, the trace elements were shifted from third layer litter and soil to root with 39-year grazing exclusion.

Design and Development of Automated Nutrient Regulation System for Hydroponics Unit

Hydroponics is a method of growing plants without soil. Hydroponics, a subset of hydro culture, is a growing plant without soil, using mineral nutrient solutions in a water solvent. In soil less culture especially, hydroponics, the problem of regular maintenance of nutrient solution and required technical knowledge. The automation in hydroponics further helps to boom up the hydroponic cultivation. Automated nutrient regulation in hydroponics environment with automatic nutrient feed technology was developed and tested in the present study. The experiment was carried out an automated controlling and regulation of pH, TDS, temperature in polyhouse hydroponic system using Arduino-Uno controller, solenoid valves containing nutrients, water, pH-up, and pH-down and sensors. In this study, the sensors are connected to Arduino-Uno controller in which liquid crystal display (LCD) of Arduino-Uno circuit controls and regulates the system based on the coding which has been programmed previously. Calibration was done for all the parameters in the automated system. TDS and pH values of nutrient solution were recorded by using TDS and pH sensor probes respectively were fed to Arduino which adjusts the values, if required, through actuators. The prototype model was able to monitor and control the pH and TDS of hydroponic water in the required range with high accuracy.

Improvement in Plant Growth, Yield, and Fruit Quality with Biostimulant Treatment in Organic Strawberry Cultivation

The excessive use of chemical fertilizers in agriculture not only causes a decrease in soil fertility but also has negative effects on the environment, natural resources, and human health. Therefore, environmentally friendly practices, such as the use of organic fertilizers (OFs) and plant biostimulants that increase yield and fruit quality can be effective in solving these problems. In the present research study, we investigated the impact of using an OF alone and in combination with as a biostimulant different doses of humic acid (HA) on plant growth parameters, yield, fruit characteristics, and leaf mineral nutrient concentrations in plants of the Monterey and Albion strawberry varieties. As a result of this study, we determined that the combined application of the OF and HA increased the yield, fruit quality, plant growth, and nutritional elements in the crop compared with using the OF alone. In addition, the Monterey variety plants treated with OF and HA (5.0 L·ha−1) in T3 offered the best results among the different treatment groups and varieties. With this treatment, we obtained the highest total yield (262.42 g/plant), fruit weight, total soluble solids (TSS), and TSS/acid ratio, as well as increased growth parameters, and mineral nutrient concentrations in leaves. These results are hopeful for enhancing organic strawberry production.

Copper oxide nanoparticles mitigate cadmium toxicity in rice seedlings through multiple physiological mechanisms.

Heavy metal pollution poses a serious threat to crops growth and yield. Recently, nanoparticles (NPs) have emerged as a promising strategy to mitigate the negative effect of heavy metal on crop growth. This study investigated the beneficial effects of copper oxide nanoparticles (CuO NPs) on the morphological and physiological-biochemical traits of rice seedlings (Oryza sativa L.) under cadmium (Cd) stress. The results demonstrated that the application of CuO NPs increased the contents of nutrition elements in shoots and roots as well as photosynthetic pigments, consequently improving the growth of rice seedlings under Cd stress, especially at low level of Cd stress. Meanwhile, CuO NPs obviously decreased the Cd accumulation in the rice seedlings and immobilized Cd in less toxic chemical forms and subcellular compartments. Moreover, CuO NPs modulated the antioxidant system, ameliorating oxidative damage and membrane injury caused by Cd. Multivariate analysis established correlations between physio-biochemical parameters and further revealed the mitigation of Cd damage to rice seedlings by CuO NPs was associated with inhibition Cd accumulation, altering Cd chemical form and subcellular distribution, increasing the contents of mineral nutrients, photosynthetic pigments and secondary metabolites and antioxidant enzyme activities, and reducing oxidative damage. Overall, the present study indicated that CuO NPs could effectively reduce the Cd toxicity to rice seedlings, demonstrating their potential application in agricultural production.

Rethinking environmental sustainability in rainfed cropping systems

Activity data from a 30-year on-farm experiment with six soil-management treatments were used to develop inventory data for environmental partial life-cycle assessment (LCA). The purpose was to compare the treatments based on environmental outcomes and evaluate conservation agriculture (CA) in Australia's dryland cropping zone. Multiple trade-offs were revealed that highlight the need for a nuanced approach to sustainable intensification and show that rules-based CA is not sufficient to guarantee low greenhouse gas (GHG) emissions, nor low overall environmental impact. Nutrient mining in dryland cropping even under CA can lead to losses in soil carbon that can double GHG intensity. In these systems, additional nutrient inputs can reduce the loss of soil carbon as well as net GHG emissions, demonstrating the critical need to include the effects of soil carbon change in LCA to prevent perverse outcomes.The treatment involving strategic tillage and nutrient balancing, along with stubble retention, had the lowest GHG intensity, but there was a trade-off with the higher embedded impacts across several other environmental categories. Higher fertiliser input could lead to toxicity impacts, due to heavy-metal content, that contribute significantly to the Human health endpoint. However, limitations in modelling such local, site-specific impacts were considerable and more research is needed to address this.In general, trade-offs were found to exist between impacts from on-farm activities versus upstream manufacture of inputs; between GHG emissions and land use (yield) versus other environmental categories; and between different on-farm GHG emission sources. Despite these trade-offs, the treatments all had similar overall scores in the Human health and Ecosystems damage categories. There was no single treatment with low, or high, impact scores across all environmental indicators, indicating that trade-offs need to be carefully considered when making farm-management decisions in the context of net-zero or carbon-neutral farming.

Recycling Selected Wetlands’ Sediments for a Vegetable Crop Cultivation in Terrestrial Ecosystem of a Humid Region

This study aimed to evaluate the selected wetlands' sediments regarding physicochemical attributes including heavy metals (HMs), and their potentiality to be used in crop cultivation with or without mixing with different generic farmers' field soils in the upland. Forty geo-referenced sediment samples were collected from each study site (n=3), and mixed to get three separate composite samples for mineral nutrients, HMs analyses and experimentation. Two pot experiments were conducted following Completely Randomized Design (CRD) with three replicates using farmers’ field soils (FFS) Gleysols and Cambisols to grow amaranth. The treatments were: T0: FFS; T1: FFS + wetland sediment of hilly area I (1:1); T2: FFS + wetland sediment of hilly area II (1:1); T3: FFS + wetland sediment of a floodplain area (1:1); T4: wetland sediment of hilly area I; T5: wetland sediment of hilly area II; T6: wetland sediment of a floodplain area. Regarding nutrient elements, exchangeable K, extractable P, Ca, and Zn were observed higher in wetland sediment of hilly area II except organic carbon (OC). Only Cd, Pb, and Ni were individually found higher than the maximum permissible addition for all wetland sediments, but all HMs collectively posed no “ecological risk”. The highest values of the plant growth index of amaranth were observed for T5 treatment. Moreover, the highest total fresh and dry biomasses were found in T5 treatment. The highest nutrient uptake was observed in T5 treatment for the most of nutrients. Studied wetlands’ soil materials, OC, and nutrients could be used to benefit upland crop cultivation.

Ecophysiological responses of native and introduced coastal tree species parasitized by Cassytha filiformis in Brunei.

Hemiparasitic Cassytha filiformis commonly infects native host (Dillenia suffruticosa and Melastoma malabathricum) and introduced host (Acacia auriculiformis and Acacia mangium) species in threatened heath forests in Brunei. This study aims to investigate the impact of parasitism on the ecophysiology of these host species. This study addresses the research gap in understanding the ecophysiology of C. filiformis-host associations, particularly when native and introduced hosts were infected. We generated CO2 and light response curves to examine the effects of increasing CO2 and light levels of infected and uninfected hosts and examined gaseous exchange, mineral nutrients, and secondary bioactive compounds of host-parasite associations. Infected hosts were negatively impacted by C. filiformis as exhibited in the CO2 and light response curves, with C. filiformis-native host association performing better than introduced species. There were no significant differences in photosynthetic parameters between infected and uninfected hosts, except in D. suffruticosa. Certain nutrient contents showed significant differences, but total N, Ca, and K in uninfected hosts were similar to infected hosts. Total phenols and tannins were significantly higher in introduced hosts than native hosts. Our findings asserted that this hemiparasitic vine relies on both its photosynthetic efficiency and nutrient acquisition from its hosts. The parasitism did not significantly hinder the ecophysiological performance of infected hosts, suggesting a plausible co-existence between the hosts and C. filiformis. This study provides essential ecophysiological information for future research on how C. filiformis can establish itself without negatively impacting the co-habitating native hosts.

Foliar Application of Mineral Nutrients after Non-traditional Removing of Flowers Improved The Yield and Fruit Quality of Pomegranate Trees

Foliar Application of Mineral Nutrients after Non-traditional Removing of Flowers Improved The Yield and Fruit Quality of Pomegranate Trees

Thermal stability and digestibility of a biopolymer system for the delivery of minor nutrients in enriched meat products

Thermal stability and digestibility of a biopolymer system for the delivery of minor nutrients in enriched meat products

Genome-wide association study reveals genetic loci for ten trace elements in foxtail millet (Setaria italica).

One hundred and fifty-five QTL for trace element concentrations in foxtail millet were identified using a genome-wide association study, and a candidate gene associated with Ni-Co-Cr concentrations was detected. Foxtail millet (Setaria italica) is an important regional crop known for its rich mineral nutrient content, which has beneficial effects on human health. We assessed the concentrations of ten trace elements (Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn) in the grain of 408 foxtail millet accessions. Significant differences in the concentrations of five elements (Ba, Co, Ni, Sr, and Zn) were observed between two subpopulations of spring- and summer-sown foxtail millet varieties. Moreover, 84.4% of the element pairs exhibited significant correlations. To identify the genetic factors influencing trace element accumulation, a comprehensive genome-wide association study was conducted, identifying 155 quantitative trait locus (QTL) for the ten trace elements across three different environments. Among them, ten QTL were consistently detected in multiple environments, including qZn2.1, qZn4.4, qCr4.1, qFe6.3, qFe6.5, qCo6.1, qPb7.3, qPb7.5, qBa9.1, and qNi9.1. Thirteen QTL clusters were detected for multiple elements, which partially explained the correlations between elements. Additionally, the different concentrations of five elements between foxtail millet subpopulations were caused by the different frequencies of high-concentration alleles associated with important marker-trait associations. Haplotype analysis identified a candidate gene SETIT_036676mg associated with Ni accumulation, with the GG haplotype significantly increasing Ni-Co-Cr concentrations in foxtail millet. A cleaved amplified polymorphic sequence marker (cNi6676) based on the two haplotypes of SETIT_036676mg was developed and validated. Results of this study provide valuable reference information for the genetic research and improvement of trace element content in foxtail millet.

Foliar applications of zinc oxide nanoparticles and boric acid affect leaf oxidative metabolism and productivity in young pecan trees

Zinc and boron are nutrients that often suffer low bioavailability to pecan trees grown in calcareous soils whereas adequate supplies of these two elements is essential for commercial pecan production. Working with young pecan trees, we evaluated changes in oxidative metabolism, levels of bioactive compounds, yield components and foliar nutrient concentrations in response to foliar sprays (50 or 100 mg L−1) of zinc oxide nanoparticles (ZnO NPs) and boron (H3BO3). Four different treatment solutions were applied in a completely randomised design with six replications per treatment (24 trees in total). Zinc and B treatments were applied before pistil receptivity (3 weeks before anthesis) and at stem elongation stage 31, 39/60; flowering stage 69; fruit stages 7–75 and continued for a total of five applications at 14-day intervals. We evaluated enzyme activities (SOD, H2O2, CAT and GPx), AC, phenols, flavonoids, leaf area, chlorophyll, total anthocyanins and nut yield and quality (nut weight and % kernel). The mineral concentrations in the leaflets were also determined. The mineral concentrations (N, P, K, Ca, Mg, Fe, Cu, Mn, Ni, Zn and B) in the leaflets were also determined. Spraying ZnO NPs and B increased SOD activity, CA, chlorophyll concentration, mineral nutrients (N, K, Ca, Zn and B) and yield. However, reductions were observed for CAT activity, nut quality and concentrations of phenol, flavonoid, anthocyanin and Fe. Boron increased GPx activity and P concentration. These results demonstrate that spraying low doses (50 mg L−1) of ZnO NPs and B can help reduce oxidative stress and increase yield, nut quality and leaf concentrations of Zn and B in young cv. Wichita pecan trees established on a calcareous soil.

SPATIAL DISTRIBUTION OF PHOMA LEAF SPOT OF COFFEE AND RELATIONSHIP WITH ENVIRONMENTAL AND HOST VARIABLES

The objective of this study was to evaluate the spatial distribution of Phoma leaf spot of coffee and its relationship with the environmental variables altitude, soil texture, and mineral nutrients. In addition, the relationship between disease and foliar nutrients, leafing, and plant production was evaluated. The study was carried out in a 7.65 ha coffee plantation for two years. A total of 86 points were georeferenced in this area. The incidence and severity of the disease were assessed monthly, and the data were transformed into annual values of “Area Under the Incidence Progress Curve” (AUIPC) and “Area Under the Severity Progress Curve” (AUSPC) of the disease. Likewise, the monthly data for the leafing were transformed into annual values of “Area Under the Leafing Progress Curve” (AULPC). Environmental and host variables significantly correlated with the AUIPC were subjected to geostatistical modeling. Higher AUIPC and AUSPC were observed in the second year of the study. The altitude, P-rem and Ca present in the soil, as well as the P and N present in the leaves, showed a positive correlation with the AUIPC. The K, Cu, and Mn present in the leaves, the AULPC and the production were negatively correlated with this variable. The exponential semivariogram model was the most appropriate to model the spatial autocorrelation of the variables analyzed, except for altitude.