Impact of repeated fumigant applications on soil properties, crop yield, and microbial communities in a plastic-mulched tomato production system

Pre-plant soil fumigation is widely applied to control nematodes, soil-borne fungal pathogens, and weeds in vegetable crops. However, most of the research evaluating the effect of fumigants on crop yield and soil microbial communities has been done on single compounds despite growers mainly applying fumigant combinations. We studied the effect of different fumigant combinations (chloropicrin, 1,3-dichloropropene, and metam potassium) on soil properties, crop yield, and the soil bacterial and fungal microbiome for two consecutive years in a plastic-mulched tomato production system in Florida (United States). While combinations of fumigants did not improve plant productivity more than the individual application of these products, application of fumigants with >60 % chloropicrin did significantly increase yield. Fumigant combinations had no significant effect on bacterial diversity, but fumigants with >35 % chloropicrin reduced soil fungal diversity and induced temporary changes in the soil bacterial and fungal community composition. These changes included short-term increases in the relative abundance of Firmicutes and Ascomycota, as well as decreases in other bacterial and fungal taxa. Repeated fumigation reduced network complexity and the relative abundance of several predicted bacterial functions and fungal guilds, particularly after fumigation and at end of harvest (3-months post fumigation). A structural equation model (SEM) showed fumigants not only directly impact crop yield, but they can also indirectly determine variations in plant productivity through effects on the soil microbiome. Overall, this study increases our understanding of the environmental and agricultural impacts of fumigants in a plastic-mulched tomato production system.

Uptake, translocation, and nutrient efficiency of nano-bonechar as a plant growth regulator in hydroponics and soil systems

The use of nanotechnology in terms of nanoparticles, carbon nanotubes, and quantum dots, when exposed to the plants, helps increase their productivity. It is worth the effort to comprehend the fate of these nanoparticles in plants. Bonechar derived from bones is a rich source of C, P, Ca2+, and Mg2+ nutrients, which can significantly contribute to the growth of the plants. This study focused on the uptake of nano-bonechar (NBC) in the Syngonium podophyllum plant, and its effects on plant growth under hydroponics and soil systems. The compound microscopy and SEM-EDX results confirmed the presence of NBC in the leaves and roots of the plants in hydroponics and soil systems. The FTIR spectra reflected the presence of functional groups of the NBC in the leaves of the Syngonium podophyllum plant. The plant's growth parameters showed an increase in fresh weight, dry weight, shoot length, chlorophyll content, leaf count, total Ca2+, total PO43-, and total organic carbon of plants in both systems. The NBC not just improved plant physiochemical parameters but also built up the soil quality in terms of bioavailable Ca2+, PO43-, water holding capacity, and soil organic matter. It is concluded that the production of carbon-based NBC not only helps manage bone waste but also their efficient uptake in plants significantly improving plant productivity.

Nitrogen and phosphorus additions alter foliar nutrient concentrations of dominant grass species and regulate primary productivity in an Inner Mongolian meadow steppe

Excessive nitrogen (N) inputs shift grassland productivity from nitrogen (N) to phosphorus (P) limitation. However, how plant nutrient concentrations and stoichiometric dynamics at community and species level responding to variable soil N and P availability, and their roles in regulating net primary productivity in meadow steppe remain unclear. To address this issue, we carried out an experiment with fifteen treatments consisting of factorial combinations of N (0, 1.55, 4.65,13.95, 27.9 g N m-2 yr-1) and P (0, 5.24,10.48 g P m-2 yr-1) for three years in a meadow steppe in Inner Mongolia. We examined concentrations and stoichiometry of C (carbon), N, P in plants and soils, and their associations with plant primary productivity. Results revealed mean community N:P ratios for shoots (12.89 ± 0.98) did not exceed 14 within the control treatment, indicating that plant growth was primarily N-limited in this ecosystem. Shoot N:P ratios were significantly increased by N addition (>16 when N application rate above 4.65 g N m-2 yr-1), shifting the community from N- to P-limited whereas significantly reduced by P addition (N:P ratios <14), further aggravating N limitation. N addition increased leaf-N concentrations whereas decreased leaf C:N ratios of all four species, but only the values for two graminoid species were significantly influenced by P addition. Leaf-P concentrations significantly increased for graminoids but significantly decreased for forbs with the application of N. VPA analysis revealed that aboveground components, especially in grass leaves, explained more variation in aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP) than root and soil components. For grasses, leaf-N concentrations showed high association with ANPP, while leaf-P concentrations were associated with BNPP. These results highlight that N and P depositions could affect the leaf-nutrient concentrations of dominant grasses, and thereby potentially alter net primary productivity in meadow steppe.

Differences in background environment and fertilization method mediate plant response to nitrogen fertilization in alpine grasslands on the Qinghai-Tibetan Plateau

Grassland degradation threatens ecosystem function and livestock production, partly induced by soil nutrient deficiency due to the lack of nutrient return to soils, which is largely ascribed to the intense grazing activities. Therefore, nitrogen (N) fertilization has been widely adopted to restore degraded Qinghai-Tibetan Plateau (QTP) grasslands. Despite numerous field manipulation studies investigating its effects on alpine grasslands, the patterns and thresholds of plant response to N fertilization remain unclear, thus hindering the prediction of its influences on the regional scale. Here, we established a random forest model to predict N fertilization effects on plant productivity based on a meta-analysis synthesizing 88 publications in QTP grasslands. Our results showed that N fertilization increased the aboveground biomass (AGB) by 46.51 %, varying wildly among plant functional groups. The positive fertilization effects intensified when the N fertilization rate increased to 272 kg ha-1 yr-1, and decreased after three years of continuous fertilization. These effects were more substantial when applying ammonium nitrate compared to urea. Further, a machine learning model was used to predict plant productivity response to N fertilization. The total explained variance and mean squared residuals ranged from 49.41 to 75.13 % and 0.011-0.058, respectively, both being the highest for grasses. The crucial predictors were identified as climatic and geographic factors, background AGB without N fertilization, and fertilization methods (i.e., rate, form, and duration). These predictors with easy access contributed 62.47 % of the prediction power of grasses' response, thus enhancing the generalizability and replicability of our model. Notably, if 30 % of yak dung is returned to soils on the QTP, the grassland productivity and plant carbon pool are predicted to increase by 5.90-6.51 % and 9.35-10.31 g C m-2 yr -1, respectively. Overall, the predictions of this study based on literature synthesis enhance our understanding of plant responses to N fertilization in QTP grasslands, thereby providing helpful information for grassland management policies. Conflict of interest: The authors declare no conflict of interest.

Seasonal precipitation regulates magnitude and direction of the effect of nitrogen addition on net ecosystem CO2 exchange in saline-alkaline grassland of northern China

Increased nitrogen (N) deposition and altered precipitation regimes have profound effects on carbon (C) flux in semi-arid grasslands. However, the interactive effects between N enrichment and precipitation alterations (both increasing and decreasing) on ecosystem CO₂ fluxes and ecosystem resource use efficiency (water use efficiency (WUE) and carbon use efficiency (CUE)) remain unclear, particularly in saline-alkaline grasslands. A four-year (2018-2021) field manipulation experiment was conducted to investigate N enrichment and precipitation alterations (decreased and increased by 50 % of ambient precipitation) and their interactions on ecosystem CO₂ fluxes (gross- ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem CO₂ exchange (NEE)), as well as their underlying regulatory mechanisms under severe salinity stress in northern China. Our results showed that N addition and precipitation alteration alone did not significantly affect the GEP, ER and NEE. While the interaction of N addition and increased precipitation over the four years significantly improved the mean GEP and NEE by 24.9 % and 15.9 %, respectively. The interactive effects of N addition and increased precipitation treatment significantly stimulated the mean value of WUE by 39.1 % compared with control, but had no significant effects on CUE over the four years. Based on the four-year experiment, the magnitude and direction of the effects of N addition on the NEE were related to seasonal precipitation. Nitrogen addition increased the NEE under increased precipitation and decreased it during extreme drought. Soil salinization (pH and base cations) could directly or indirectly affect GEP and NEE via plants productivity, plant communities, as well as ecosystem resource use efficiency (WUE and CUE) based on structural equation model. Our results address lacking investigations of ecosystem C flux in saline-alkaline grasslands, and highlight that precipitation regulates the magnitude and direction of N addition on NEE in saline-alkaline grasslands.

Intraspecific responses of plant productivity and crop yield to experimental warming: A global synthesis

Maintaining plant productivity and crop yield in a warming world requires local adaptation to new environment and selection of high-yield cultivars, which both depend on the genetically-based intraspecific differences in the plant response to warming (referred to as "genetically-based intraspecific responses"). However, how the genetically-based intraspecific responses mediate warming effects on plants remains unclear, especially at the global scale. Here, a dataset was compiled from 118 common-garden experiments to examine the responses of plant growth, productivity, and crop yield to warming among different ecotypes/genotypes/cultivars. Our results showed that the genetically-based intraspecific responses on average accounted for 34.7 % of the total variance in the warming responses across all the studies but with large variability (2 %-77 %). The intraspecific responses of plant productivity and crop yield were larger than those of organ level traits and biomass allocation, suggesting that plant growth was mainly achieved by iterating the relatively invariant terminal modules (e.g., leaves). The warming-induced changes in intraspecific variability of aboveground biomass were larger in woody plants, non-leguminous herbs, perennial herbs and noncrops than those in nonwoody, leguminous, annual and crop ones, respectively, indicating the potential important role of plant longevity in mediating the change in intraspecific variability. Moreover, larger intraspecific responses reduced the consistence of relative performance between control and warming treatments for both plant productivity and crop yield. These results highlight the unneglectable role of genetically-based intraspecific differences in plant responses to warming, indicating the difficulty of maintaining high crop yield and tree productivity under global climate change, and posing a grave threat to the food security and wood supply in the near future.

Night warming at the vegetative stage improves pre-anthesis photosynthesis and plant productivity involved in grain yield of winter wheat

We conducted pot experiments during the 2018-2020 growing seasons to study the effects of night warming at different growth stages of wheat on the photosynthetic performance; accumulation, transportation, and distribution of dry matter; and grain yield of winter wheat. Night warming at all the different growth stages resulted in an elevation of wheat yield by increasing the 1000-grain weight and the number of grains per ear. Night warming during the period from jointing to booting stage resulted in the greatest increase in wheat yield. It also increased the amount of overall dry matter and transferrable amount of dry matter in plants and increased the distribution of dry matter to grains to increase grain weight. Night warming treatments at three different growth stages enhanced pre-anthesis photosynthetic capacity by increasing flag leaf net photosynthetic rate, chlorophyll content, and photochemical efficiency of winter wheat at the early stage of grain filling, especially in the night warming treatment from jointing to booting stage. Night warming not only increased the stomatal density and stomatal index of wheat leaves but also increased stomatal conductance and transpiration rate in the early stage of grain filling, thus being conducive to the smooth progress of photosynthesis. In conclusion, night warming treatment at different growth stages increased the photosynthesis of flag leaves at the early stage of grain filling, and promoted the accumulation of dry matter in plants after anthesis, which was conducive to the grain yield of winter wheat.

Mitigation of lead toxicity in Vigna radiata genotypes by silver nanoparticles

Heavy metal (HM) contamination of the soil through anthropogenic activities influences the living systems and drastically impacts food chain. This study examined the application of silver nanoparticles (AgNPs) in two genotypes (G1 and G2) of Mung bean (Vigna radiata) for ameliorating the Pb toxicity. Different doses of Pb (0, 25, 50 μM) were differentially tackled by AgNPs with the aim of ameliorating the plant attributes. Both genotypes displayed statistically significant quantitative and qualitative modulations for Pb tolerance. In G2, the most prominent increase in plant height (43.79%), fresh biomass (49.56%) and total chlorophyll (20%) was observed at L2 (AgNPs 10 mg/L) in comparison with the control. Overall, photosynthetic rate was increased by 26% in G2 at L6 (AgNPs 25 mg/L + Pb 25 μM). In addition, the results presented 78.5% increase in water use efficiency of G2 while G1 experienced a maximum internal CO₂ concentration (209.8%) at L8 (Pb 50 μM). AgNPs triggered balanced uptake of minerals and improved growth of Vigna genotypes. 50 μM Pb was most hazardous and caused maximum reduction in growth of Vigna plants along with a significant suppression in photosynthetic activity, increase in MDA (199.7%) in G1 and H₂O₂ (292.8%) in G2. In comparison to control, maximum superoxide dismutase (376%), peroxidase (659.8%) and catalase (9.3%) activity was observed in G2 at L11. The application of AgNPs substantially enhanced plant growth and helped them in surviving well in absence as well as presence of Pb. G2 genotype exhibited substantial tolerance capability and revealed less impairment in the studied attributes than G1 and treatment of AgNPs i.e. 25 mg/L was the best level that yielded best results in both genotypes. The results demonstrate that AgNPs mediate response(s) of plants under Pb stress and particularly contributed to HM tolerance of plants and thus showing great promise for use in phytoremediation.

Possible risks for the functioning of cyclic processes in the experimental model of a closed ecosystem

The purpose of the present study is to consider a number of possible risks that may emerge when processed human wastes are involved into mass exchange processes as fertilizers for plants cultivated in the experimental model of the closed ecosystem (CEEM). The problems relating to the disruption of cycling processes in closed ecosystems can be tentatively divided into two groups: the problems that can be rather easily overcome and the chronic problems. Addition of plant inedible biomass to the soil-like substrate (SLS) can result in a decrease in plant productivity because of allelopathic interactions and enhanced growth of microorganisms. The 30% decrease in wheat productivity by the end of long-duration experiments in the CEEM, with plants grown on quasi-non-renewed solutions based on liquid products prepared by physicochemical mineralization of human wastes, was caused by lower resistance of the plants affected by toxicants accumulated in the solution because of incomplete mineralization of the wastes. The reason for the differences between the macronutrient inflows and outflows was that the donor of human wastes followed a European-type diet while the system produced only part of the plant-based diet. Moreover, macronutrients were partly sorbed in rooting substrates and became unavailable to plants: the substrates in the system retained about 50% of the Ca and 20% ÷ 25% of the Mg, Na, and P inflows over one cycle. These problems are temporary and can be minimized in the foreseeable future.

Adjustments of carbon allocation and stomatal dynamics by target localized strategies to increase crop productivity under changing climates

Increasing crop productivity to ensure food security for future generations is one of the greatest challenges in current plant research. This challenge is even greater due to global climate changes, as enhancing crop yields must occur against the backdrop of increasingly changing environments, particularly rising temperatures and water constraints. Global crop yield growth depends on an improved dynamic balance between carbon and water usage. Here we discuss different approaches that highlight the role of vascular tissue and guard cells in attempting to mitigate the carbon-water trade-off. We argue that crop engineering in the future will require the incorporation of a combination of improved traits. Since targeted gene modifications generally produce fewer undesirable pleiotropic effects than constitutive modifications, we envision that modifications of specific cell types, such as phloem companion cells and guard cells, represent an effective approach for adding beneficial gene modifications in the same plant. This approach will enable trait stacking to design future crops with both high yield and resilience to various climate change stresses.

Nonlinear spatial and temporal decomposition provides insight for climate change effects on sub-Arctic herbivore populations

Global temperatures are increasing, affecting timing and availability of vegetation along with relationships between plants and their consumers. We examined the effect of population density, herd body condition in the previous year, elevation, plant productivity and phenology, snow, and winter onset on juvenile body mass in 63 semi-domesticated populations of Rangifer tarandus throughout Norway using spatiotemporal generalized additive models (GAMs) and varying coefficient models (VCMs). Optimal climate windows were calculated at both the regional and national level using a novel nonlinear climate window algorithm optimized for prediction. Spatial and temporal variation in effects of population and environmental predictors were considered using a model including covariates decomposed into spatial, temporal, and residual components. The performance of this decomposed model was compared to spatiotemporal GAMs and VCMs. The decomposed model provided the best fit and lowest prediction errors. A positive effect of herd body condition in the previous year explained most of the deviance in calf body mass, followed by a more complex effect of population density. A negative effect of timing of spring and positive effect of winter onset on juvenile body mass suggested that a snow free season was positive for juvenile body mass growth. Our findings suggest early spring onset and later winter permanent snow cover as reinforcers of early-life conditions which support more robust reindeer populations. Our methodological improvements for climate window analyses and effect size measures for decomposed variables provide important contributions to account for, measure, and interpret nonlinear relationships between climate and animal populations at large scales.

Plant productivity and microbial composition drive soil carbon and nitrogen sequestrations following cropland abandonment

Understanding the variations in soil organic carbon (SOC) and total nitrogen (STN) stocks in the different ages of abandoned cropland ecosystems of different ages is essential for land use decisions to maximize C sinks or improve ecosystem services. However, knowledge of the dynamics of SOC and STN stocks and their controlling factors after cropland abandonment is limited. Thus, this study investigated the changes in the SOC and STN stocks of loessal soil (Calcaric Regosols) with a chronosequence of 3, 8, 13, 18, 23 and 30 years following cropland abandonment on the Loess Plateau. As a whole, we examined 42 field plots and implemented multivariable linear regression analysis (MLRA) and structural equation modeling (SEM) using 22 influencing variables related to plant, soil and microbial properties to quantify the controls of SOC and STN stocks. The results revealed that SOC and STN stocks significantly increased after cropland abandonment for 30 years, and there were minor decreases in C and N sequestrations in the early restoration stage (<18 years). The SOC and STN changes had significant positive correlations, in which that exhibited STN stocks shifted concurrently with the rate of relative SOC stock changes. The MLRA models demonstrated that the SOC stocks were primarily controlled by aboveground biomass, STN, fungi, and the ratio of fungi to bacteria, while STN stocks were mainly driven by root biomass, above-ground biomass, STN, fungi and the ratio of fungi to bacteria after cropland abandonment. The SEM models further demonstrated that plant productivity not only directly determined the variations in SOC and STN stocks but also changed the microbial community following post-cropland restoration. These results suggest that long-term (>18 years) cropland abandonment can be a successful approach for reinstating SOC and STN stocks, while plants and microbes together mediate microbial C and N stocks during vegetation succession in a semiarid region.

Trophic interactions as determinants of the arbuscular mycorrhizal fungal community with cascading plant-promoting consequences

BACKGROUND

The soil mycobiome is composed of a complex and diverse fungal community, which includes functionally diverse species ranging from plant pathogens to mutualists. Among the latter are arbuscular mycorrhizal fungi (AMF) that provide phosphorous (P) to plants. While plant hosts and abiotic parameters are known to structure AMF communities, it remains largely unknown how higher trophic level organisms, including protists and nematodes, affect AMF abundance and community composition.

RESULTS

Here, we explored the connections between AMF, fungivorous protists and nematodes that could partly reflect trophic interactions, and linked those to rhizosphere P dynamics and plant performance in a long-term manure application setting. Our results revealed that manure addition increased AMF biomass and the density of fungivorous nematodes, and tailored the community structures of AMF, fungivorous protists, and nematodes. We detected a higher abundance of AMF digested by the dominant fungivorous nematodes Aphelenchoides and Aphelenchus in high manure treatments compared to no manure and low manure treatments. Structural equation modeling combined with network analysis suggested that predation by fungivorous protists and nematodes stimulated AMF biomass and modified the AMF community composition. The mycorrhizal-fungivore interactions catalyzed AMF colonization and expression levels of the P transporter gene ZMPht1;6 in maize roots, which resulted in enhanced plant productivity.

CONCLUSIONS

Our study highlights the importance of predation as a key element in shaping the composition and enhancing the biomass of AMF, leading to increased plant performance. As such, we clarify novel biological mechanism of the complex interactions between AMF, fungivorous protists, and nematodes in driving P absorption and plant performance. Video Abstract.

Exploring the potentialities of beneficial endophytes for improved plant growth

Pathogen affects plant growth, host health and productivity. Endophytes, presumed to live inside the plant tissues, might be helpful in sustaining the future of agriculture. Although recent studies have proven that endophytes can be pathogenic, commensal, non-pathogenic, and/or beneficial, this review will focus on the beneficial category only. Beneficial endophytes produce a number of compounds which are useful for protecting plants from environmental conditions, enhancing plant growth and sustainability, while living conveniently inside the hosts. The population of endophytes is majorly controlled by location, and climatic conditions where the host plant grows. Often the most frequently isolated endophytes from the tissues of the plant are fungi, but sometimes greater numbers of bacteria are isolated. Beneficial endophytes stand a chance to replace the synthetic chemicals currently being used for plant growth promotion if carefully explored by researchers and embraced by policymakers. However, the roles of endophytes in plant growth improvement and their behavior in the host plant have not been fully understood. This review presents the current development of research into beneficial endophytes and their effect in improving plant growth.

Impact of spring phenology variation on GPP and its lag feedback for winter wheat over the North China Plain

Spring green-up date (GUD) is a sensitive indicator of climate change, and of great significance to winter wheat production. However, our knowledge of the chain relationships among them is relatively weak. In this study, based on 8-day Enhanced Vegetation Index (EVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS) from 2001 to 2015, we first assessed the performance of four algorithms for extracting winter wheat GUD in the North China Plain (NCP). A multiple linear regression model was then established to quantitatively determine the contributions of the time lag effects of hydrothermal variation on GUD. We further investigated the interactions between GUD and gross primary production (GPP) comprehensively. Our results showed that the rate of change in curvature algorithm (RCCmax) had better performance in capturing the spatiotemporal variation of winter wheat GUD relative to the other three methods (Kmax, CRmax, and cumCRmax). Regarding the non-identical lag time effects of hydrothermal factors, hydrothermal variations could explain winter wheat GUD variations for 82.05% of all pixels, 36.78% higher than that without considering the time lag effects. Variation in GUD negatively correlated with winter wheat GPP after green up in most parts of the NCP, significantly in 35.75% of all pixels with a mean rate of 1.89 g C m^-2 yr^-1 day^-1. Meanwhile, winter wheat GPP exerted a strongly positive feedback on GUD in >82.42% of all pixels (significant in 28.01% of all pixels), characterized by a humped-shape pattern along the long-term average plant productivity. This finding highlights the complex interaction between spring phenology and plant productivity, and also suggests the importance of preseason climate factors on spring phenology.

Soil bacterial taxonomic diversity is critical to maintaining the plant productivity

Soil microbial communities play a central role in driving multiple ecosystem functions and ecological processes that are key to maintaining the plant productivity. However, we lack sound evidence for the linkage between soil microbial diversity and plant productivity, which hinders our ability to predict the consequences of microbial diversity loss for food security under the context of global environmental change. Here, we used the dilution-to-extinction approach to test the consequences of soil microbial diversity loss for the aboveground plant biomass in a glasshouse experiment. Compared with original soils, the bacterial alpha-diversity (Observed operational taxonomic units and Shannon index) significantly decreased in treatments with serially diluted inoculum. Principal coordinates analysis showed that the overall bacterial community compositions (beta-diversity) in original soils were clearly separated from the treatments with serially diluted inoculum. The aboveground biomass of lettuce harvested from the original soils was significantly higher than that from the sterilized soils regardless of the inoculation. The ordinary least squares regression model showed a significant linear relationship between the plant biomass and bacterial alpha-diversity, indicating that reduction in soil microbial diversity could result in a significant decline in the biomass of lettuce. No significant correlation was observed between plant biomass and soil processes including soil basal respiration and denitrification rates. Structural equation models suggested that the effects of soil microbial diversity on the plant biomass were maintained even when simultaneously accounting for other drivers (soil properties and biological processes). Our study provides experimental evidence that soil microbial diversity is important to the maintenance of the plant productivity and suggests that the functional redundancy in soil microbial communities may be overestimated especially in the agroecological system.

Effect of walnut shell biochars on soil quality, crop yields, and weed dynamics in a 4-year field experiment

The introduction of biochar has been extensively tested under short-term greenhouse or field studies mainly in sandy or acidic soils, while its effects on soil properties, crop plants, and weed species especially in neutral or alkaline soils are still not well understood. Therefore, this study focused on relatively long effects of two walnut shell biochars (5 t ha^-1) on soil nutrient dynamics, two crop plants (wheat and lentil) growth and developments, and weed growth dynamics over 4 years (2014-2017). Applied biochar added once at the beginning of the experiment while planted crops were supplied with macro-nutrients and sprayed with pesticides according to conventional requirements of the region. Biochars improved soil properties by 10-23% during the first and second years while positive effects of biochars on weed growth were drastically higher (60-78% higher weed density) during the whole period of this study most likely due to increase in bioavailability of nutrient shortly after biochar amendment and indirect positive effects of biochars on soil physical properties as well. Consequently, biochar macro- and micro-nutrient will be utilized by weed plants with higher efficacy compared with crop plants.

Combined effects of biochar properties and soil conditions on plant growth: A meta-analysis

Biochar application in agricultural soils can be highly beneficial to plant productivity. However, how plant productivity response (PPR) [% change of plant yield from control (without biochar application)] to biochar application is affected by biochar properties, soil conditions, and their combinations is still unclear. Therefore, a meta-analysis based on 1254 paired comparisons from 153 published studies was conducted. The grand mean of PPR was estimated to be 16.0 ± 1.3%, regardless of biochar/soil conditions. Meanwhile, a large variation of PPR from -31.8% to 974% was also observed under different biochar or/and soil conditions. Specifically, biochar properties including pH, cation exchange capacity (CEC), contents of carbon and ash, bulk density, and soil conditions including texture, pH, CEC, nitrogen content, and C/N ratio significantly affected the results of PPR to biochar addition. Furthermore, the liming effect, improvement in soil physical structure, and increased nutrient use efficiency were suggested as the key mechanisms for the positive PPR in biochar-amended soils. Moreover, PPR could be significantly affected (strengthened or weakened) by the combined effect of biochar properties and soil conditions. Overall, the application of biochars with high ash content (or low carbon content) into sandy soils or acidic soils is highly recommended for increasing plant productivity. This meta-analysis will provide helpful information to elucidate the combined effect of biochar properties and soil conditions on plant growth, which is critical for developing engineered biochar with specific functionality to promote plant production and food security.

Effects of plant growth-promoting rhizobacteria on co-inoculation with Bradyrhizobium in soybean crop: a meta-analysis of studies from 1987 to 2018

Background

The co-inoculation of soybean with Bradyrhizobium and other plant growth-promoting rhizobacteria (PGPR) is considered a promising technology. However, there has been little quantitative analysis of the effects of this technique on yield variables. In this context, the present study aiming to provide a quantification of the effects of the co-inoculation of Bradyrhizobium and PGPR on the soybean crop using a meta-analysis approach.

Methods

A total of 42 published articles were examined, all of which considered the effects of co-inoculation of PGPR and Bradyrhizobium on the number of nodules, nodule biomass, root biomass, shoot biomass, shoot nitrogen content, and grain yield of soybean. We also determined whether the genus of the PGPR used as co-inoculant, as well as the experimental conditions, altered the effect size of the PGPR.

Results

The co-inoculation technology resulted in a significant increase in nodule number (11.40%), nodule biomass (6.47%), root biomass (12.84%), and shoot biomass (6.53%). Despite these positive results, no significant increase was observed in shoot nitrogen content and grain yield. The response of the co-inoculation varied according to the PGPR genus used as co-inoculant, as well as with the experimental conditions. In general, the genera Azospirillum, Bacillus, and Pseudomonas were more effective than Serratia. Overall, the observed increments were more pronounced under pot than that of field conditions. Collectively, this study summarize that co-inoculation improves plant development and increases nodulation, which may be important in overcoming nutritional limitations and potential stresses during the plant growth cycle, even though significant increases in grain yield have not been evidenced by this data meta-analysis.

Effects of plant growth-promoting rhizobacteria on co-inoculation with Bradyrhizobium in soybean crop: a meta-analysis of studies from 1987 to 2018

BACKGROUND

The co-inoculation of soybean with Bradyrhizobium and other plant growth-promoting rhizobacteria (PGPR) is considered a promising technology. However, there has been little quantitative analysis of the effects of this technique on yield variables. In this context, the present study aiming to provide a quantification of the effects of the co-inoculation of Bradyrhizobium and PGPR on the soybean crop using a meta-analysis approach.

METHODS

A total of 42 published articles were examined, all of which considered the effects of co-inoculation of PGPR and Bradyrhizobium on the number of nodules, nodule biomass, root biomass, shoot biomass, shoot nitrogen content, and grain yield of soybean. We also determined whether the genus of the PGPR used as co-inoculant, as well as the experimental conditions, altered the effect size of the PGPR.

RESULTS

The co-inoculation technology resulted in a significant increase in nodule number (11.40%), nodule biomass (6.47%), root biomass (12.84%), and shoot biomass (6.53%). Despite these positive results, no significant increase was observed in shoot nitrogen content and grain yield. The response of the co-inoculation varied according to the PGPR genus used as co-inoculant, as well as with the experimental conditions. In general, the genera Azospirillum, Bacillus, and Pseudomonas were more effective than Serratia. Overall, the observed increments were more pronounced under pot than that of field conditions. Collectively, this study summarize that co-inoculation improves plant development and increases nodulation, which may be important in overcoming nutritional limitations and potential stresses during the plant growth cycle, even though significant increases in grain yield have not been evidenced by this data meta-analysis.

Target genes for plant productivity improvement

The use of chemical fertilizers and pesticides, as well as the development of high-yielding varieties enabled substantial increase in crop productivity during the 20th century. However, the increase in yield over the last two decades has been slower. It is thought that further improvement in productivity of the major crop species using traditional cultivation methods is limited. Therefore, the use of genetic engineering seems to be a promising approach. There is ongoing research concerning genes that have an impact on plant growth, development and yield. The proteins and miRNAs encoded by these genes participate in a variety of processes, such as growth regulation, assimilate transport and partitioning as well as macronutrient uptake and metabolism. This paper presents the major directions in research concerning genes that may be targets of genetic engineering aimed to improve plant productivity.

Adaptation of primocane fruiting raspberry plants to environmental factors under the influence of Bacillus strains in Western Siberia

In geographical locations with a short vegetative season and continental climate that include Western Siberia, growing primocane fruiting raspberry varieties becomes very important. However, it is necessary to help the plants to overcome the environmental stress factors. This study aimed to evaluate the impact of the pre-planting treatment of primocane fruiting raspberry root system with Bacillus strains on the following plant development under variable environmental conditions. In 2012, Bacillus subtilis RCAM В-10641, Bacillus amyloliquefaciens RCAM В-10642, and Bacillus licheniformis RCAM В-10562 were used for inoculating the root system of primocane fruiting raspberry cultivar Nedosyagaemaya before planting. The test suspensions were 10⁵ CFU/ml for each bacterial strains. The effects of this treatment on plant growth and crop productivity were estimated in 2012-2015 growing seasons differed by environmental conditions. The pre-planting treatment by the bacterial strains increased the number of new raspberry canes and the number of plant generative organs as well as crop productivity compared to control. In addition, these bacilli acted as the standard humic fertilizer. Variable environmental factors such as air temperature, relative humidity, and winter and spring frosts seriously influenced the plant biological parameters and crop productivity of control plants. At the same time, the pre-planting primocane fruiting root treatment by Bacillus strains decreased the negative effects of abiotic stresses on plants in all years of the research. Of the three strains studied, B. subtilis was shown to reveal the best results in adaptation of primocane fruiting raspberry plants to environmental factors in Western Siberia. For the first time, the role of Bacillus strains in enhancing frost resistance in primocane fruiting raspberry plants was shown. These bacilli are capable of being the basis of multifunctional biological formulations for effective plant and environmental health management in growing primocane fruiting raspberry.

Jalal A. Aliyev (1928-2016): a great scientist, a great teacher and a great human being

Jalal A. Aliyev was a distinguished and respected plant biologist of our time, a great teacher, and great human being. He was a pioneer of photosynthesis research in Azerbaijan. Almost up to the end of his life, he was deeply engaged in research. His work on the productivity of wheat, and biochemistry, genetics and molecular biology of gram (chick pea) are some of his important legacies. He left us on February 1, 2016, but many around the world remember him as he was engaged in international dialog on solving global issues, and in supporting international conferences on ''Photosynthesis Research for Sustainability" in 2011 and 2013.

Effective microorganisms enhance the scavenging capacity of the ascorbate-glutathione cycle in common bean (Phaseolus vulgaris L.) plants grown in salty soils

No information is available regarding effective microorganisms (EM) influence on the enzymatic and non-enzymatic antioxidant defence system involved in the ascorbate-glutathione cycle under saline conditions. Therefore, as a first approach, this article focuses on the contribution of EM to the scavenging capacity of the ascorbate-glutathione cycle in salt-stressed plants. It investigates some mechanisms underlying alleviation of salt toxicity by EM application. Phaseolus vulgaris cv. Nebraska plants were grown under non-saline or saline conditions (2.5 and 5.0 dSm(-1)) with and without EM application. Lipid peroxidation and H2O2 content were significantly increased in response to salinity, while they decreased with EM application in both stressed and non-stressed plants. Activities of ascorbate peroxidase (APX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2) increased under saline conditions; these increases were more significant in salt-stressed plants treated by EM. Activities of monodehydroascorbate reductase (MDHAR; EC 1.6.5.4) and dehydroascorbate reductase (DHAR; EC 1.8.5.1) decreased in response to salinity; however, they were significantly increased in stressed plants treated with EM. Ascorbate and glutathione contents were increased with the increasing salt concentration; moreover they further increased in stressed plants treated with EM. Ratios of AsA/DHA and GSH/GSSG decreased under saline conditions, whereas they were significantly increased with EM treatment in the presence or in the absence of soil salinization. The EM treatment detoxified the stress generated by salinity and significantly improved plant growth and productivity. Enhancing the H2O2-scavenging capacity of the ascorbate-glutathione cycle in EM-treated plants may be an efficient mechanism to attenuate the activation of plant defences.

A meta-analysis of the response of soil respiration, net nitrogen mineralization, and aboveground plant growth to experimental ecosystem warming

Climate change due to greenhouse gas emissions is predicted to raise the mean global temperature by 1.0-3.5°C in the next 50-100 years. The direct and indirect effects of this potential increase in temperature on terrestrial ecosystems and ecosystem processes are likely to be complex and highly varied in time and space. The Global Change and Terrestrial Ecosystems core project of the International Geosphere-Biosphere Programme has recently launched a Network of Ecosystem Warming Studies, the goals of which are to integrate and foster research on ecosystem-level effects of rising temperature. In this paper, we use meta-analysis to synthesize data on the response of soil respiration, net N mineralization, and aboveground plant productivity to experimental ecosystem warming at 32 research sites representing four broadly defined biomes, including high (latitude or altitude) tundra, low tundra, grassland, and forest. Warming methods included electrical heat-resistance ground cables, greenhouses, vented and unvented field chambers, overhead infrared lamps, and passive night-time warming. Although results from individual sites showed considerable variation in response to warming, results from the meta-analysis showed that, across all sites and years, 2-9 years of experimental warming in the range 0.3-6.0°C significantly increased soil respiration rates by 20% (with a 95% confidence interval of 18-22%), net N mineralization rates by 46% (with a 95% confidence interval of 30-64%), and plant productivity by 19% (with a 95% confidence interval of 15-23%). The response of soil respiration to warming was generally larger in forested ecosystems compared to low tundra and grassland ecosystems, and the response of plant productivity was generally larger in low tundra ecosystems than in forest and grassland ecosystems. With the exception of aboveground plant productivity, which showed a greater positive response to warming in colder ecosystems, the magnitude of the response of these three processes to experimental warming was not generally significantly related to the geographic, climatic, or environmental variables evaluated in this analysis. This underscores the need to understand the relative importance of specific factors (such as temperature, moisture, site quality, vegetation type, successional status, land-use history, etc.) at different spatial and temporal scales, and suggests that we should be cautious in "scaling up" responses from the plot and site level to the landscape and biome level. Overall, ecosystem-warming experiments are shown to provide valuable insights on the response of terrestrial ecosystems to elevated temperature.