Soil gross nitrogen (N) mineralization (GNM), a key microbial process in the global N cycle, is mainly controlled by climate and soil properties. This study provides for the first time a ...comprehensive analysis of the role of soil physicochemical properties and climate and their interactions with soil microbial biomass (MB) in controlling GNM globally. Through a meta‐analysis of 970 observations from 337 published papers from various ecosystems, we found that GNM was positively correlated with MB, total carbon, total N and precipitation, and negatively correlated with bulk density (BD) and soil pH. Our multivariate analysis and structural equation modeling revealed that GNM is driven by MB and dominantly influenced by BD and precipitation. The higher total N accelerates GNM via increasing MB. The decrease in BD stimulates GNM via increasing total N and MB, whereas higher precipitation stimulates GNM via increasing total N. Moreover, the GNM varies with ecosystem type, being greater in forests and grasslands with high total carbon and MB contents and low BD and pH compared to croplands. The highest GNM was observed in tropical wet soils that receive high precipitation, which increases the supply of soil substrate (total N) to microbes. Our findings suggest that anthropogenic activities that affect soil microbial population size, BD, soil substrate availability, or soil pH may interact with changes in precipitation regime and land use to influence GNM, which may ultimately affect ecosystem productivity and N loss to the environment.
By a meta‐analysis of 970 observations from 337 published papers, we found that gross N mineralization (GNM) is driven by soil microbial biomass and dominantly influenced by soil bulk density and precipitation, whereby GNM increases with increasing soil microbial biomass and precipitation and decreasing soil bulk density. The higher total soil N and soil pH accelerate GNM via increasing soil microbial biomass. We suggest that management activities that affect soil microbial population size, soil bulk density, soil substrate availability, or soil pH may interact with future changes in precipitation regime to influence GNM, and ultimately, ecosystem productivity.
Soil gross nitrification (GN) is a critical process in the global nitrogen (N) cycle that results in the formation of nitrate through microbial oxidation of ammonium or organic N, and can both ...increase N availability to plants and nitrous oxide emissions. Soil GN is thought to be mainly controlled by soil characteristics and the climate, but a comprehensive analysis taking into account the climate, soil characteristics, including microbial characteristics, and their interactions to better understand the direct and indirect controlling factors of GN rates globally is lacking. Using a global meta‐analysis based on 901 observations from 330 15N‐labeled studies, we show that GN differs significantly among ecosystem types, with the highest rates found in croplands, in association with higher pH which stimulates nitrifying bacteria activities. Autotrophic and heterotrophic nitrifications contribute 63% and 37%, respectively, to global GN. Soil GN increases significantly with soil total N, microbial biomass, and soil pH, but decreases significantly with soil carbon (C) to N ratio (C:N). Structural equation modeling suggested that GN is mainly controlled by C:N and soil total N. Microbial biomass and pH are also important factors controlling GN and their effects are similar. Precipitation and temperature affect GN by altering C:N and/or soil total N. Soil total N and temperature drive heterotrophic nitrification, whereas C:N and pH drive autotrophic nitrification. Moreover, GN is positively related to nitrous oxide and carbon dioxide emissions. This synthesis suggests that changes in soil C:N, soil total N, microbial population size, and/or soil pH due to anthropogenic activities may influence GN, which will affect nitrate accumulation and gaseous emissions of soils under global climate and land‐use changes.
Using a global meta‐analysis based on 901 observations from 330 15N‐labelled studies, we show that gross nitrification rate (GN) is mainly controlled by soil carbon‐to‐nitrogen stoichiometry and soil total nitrogen. Soil microbial biomass and pH are also important factors controlling GN. Mean annual precipitation and mean annual temperature affect GN by altering soil carbon‐to‐nitrogen stoichiometry and/or soil total nitrogen. GN is positively related to nitrous oxide and carbon dioxide emissions. We suggest that changes in soil substrate quantity and quality due to anthropogenic activities may influence GN, which will affect nitrate accumulation and gaseous emissions of soils under global climate changes.
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Nanotechnology has received much attention because of its distinctive properties and many applications in various fields. Nanotechnology is a new approach to increase agricultural ...production with premium quality, environmental safety, biological support, and financial stability. Ecofriendly technology is becoming progressively important in modern agricultural applications as alternatives to traditional fertilizers and pesticides. Nanotechnology offers an alternative solution to overcome the disadvantages of conventional agriculture. Therefore, recent developments in using nanoparticles (NPs) in agriculture should be studied. This review presented a novel overview about the biosynthesis of NPs, using NPs as nano-fertilizers and nano-pesticides, the applications of NPs in agriculture, and their role in enhancing the function of biofactors. We also, show recent studies on NPs-plant interactions, the fate and safety of nanomaterials in plants, and NPs' function in alleviating the adverse effects of abiotic stress and heavy metal toxicity. Nano-fertilizers are essential to reduce the use of inorganic fertilizers and reduce their antagonistic effects on the environment. Nano-fertilizers are more reactive, can penetrate the epidermis allowing for gradual release, and targeted distribution, and thus reducing nutrients surplus, enhancing nutrient use efficiency. We also, concluded that NPs are crucial in alleviating abiotic stress and heavy metal toxicity. However, some studies reported the toxic effects of NPs on higher plants by induction of oxidative stress signals via depositing NPs on the cell surface and in organelles. The knowledge in our review article is critical in defining limitations and future perspectives of using nano-fertilizers as an alternative to conventional fertilizers.
Egypt is the largest nitrogen (N) fertilizer consumer in Africa. However, its nitrogen use efficiency (NUE) is low, and the relationships between both dietary options and the NUE trend with reactive ...N (Nr) release into the environment in Egypt have not yet been studied. In this study, we estimated the changes in the N budget and NUE in Egypt during the past 56 years (1961–2016). We also calculated particular virtual N factors (the average amount of Nr released to the environment during food production per unit of N consumption) for major food items to estimate their N footprints (NF). The total N input to croplands increased from 136 kg N ha−1 y−1 (1961–1970) to 307 kg N ha−1 y−1 (2010–2016), while the total crop N uptake increased from 101 kg N ha−1 y−1 to 136 kg N ha−1 y−1, indicating a decrease of NUE from 71% (1960s) to 44% during 2010–2016. Gaseous N emissions of NH3, N2O, and NO increased from 97, 5.6, and 8.3 Gg N y−1 to 339, 29, and 39 Gg N y−1. The total per capita food NF increased from 15 kg N capita−1 y−1 (1961-1970) to 26 kg N capita−1 y−1 (2010–2016). There was a change in the average per capita food consumption NF and food production NF from the 1960s (3.2 and 11.3 kg capita−1 y−1) to 2010–2016 (5.9 and 20.3 kg N capita−1 y−1). There is a dire need to increase the NUE and decrease the food NF in Egypt to minimize the negative consequences of Nr on the environment.
•The applied rate of nitrogen (N) in Egypt is one of the highest in the world.•The total N input to croplands increased from 136 kg N ha−1 y−1 (1960s) to 307 kg N ha−1 y−1 (2010–2016).•Gaseous N emissions of NH3, N2O, and NO increased from 97, 5.6, and 8.3 Gg N y−1 to 339, 29, and 39 Gg N y−1•Nitrogen use efficiency reduced from 71% in 1960s to 44% during 2010–2016.•N footprint elevated from 14 to 26 kg N capita−1 y−1 over the last five decades.
Green approaches for improving plant performance using natural supplementations are highly seeking. Following a preliminary study conducted on contaminated saline (EC = 7.75 dS m−1) and normal (EC = ...1.4 dS m−1) soils, two main field trials were conducted to study the potential effects of licorice root (LRE; 0.5%) and moringa seed (MSE; 0.5%) extracts, supplemented to soil through irrigation water (SA) and/or as foliar spray (FS), on performance, physio-biochemical components, antioxidant defense system, and contaminants contents of Capsicum annuum plants grown on heavy metals-contaminated saline soil. Both extracts were applied in single treatments such as LRE-SA, MSE-SA, LRE-FS, and MSE-FS or in integrations like LRE-SA+LRE-FS, LRE-SA+MSE-FS, MSE-SA+LRE-FS, and MSE-SA+MSE-FS. The preliminary study results showed significant reductions in plant performance (growth and yield), chlorophylls content and significant increase in Cd content due to heavy metals and salt stress. However, LRE and MSE applied singly or in combinations positively modified these parameters compared to the control (SA and FS were applied with tap water). On the other hand, these parameters were not responded to LRE and/or MSE applications on the normal soil. The main studies results showed that all single or integrative treatments significantly increased plant growth and yield, leaf contents of leaf photosynthetic pigments, free proline, total soluble sugars, N, P, and K+, ratio of K+/Na+, and activities of CAT, POX, APX, SOD, and GR. In contrast, contaminants; Na+, Cd, Cu, Pb and Ni contents in plant leaves and fruits were significantly reduced on heavy metals-contaminated saline soil compared to the control. Additionally, all integrative treatments significantly exceeded all single treatments in this concern. The integrative MSE-SA+LRE-FS was the best treatment that is recommended to be used to maximize pepper plant performances and minimize plant contaminant contents on contaminated saline soils.
•Plant extracts (MSE+LRE) application improved growth and yield of doubled stressed (salinity+heavy metal) pepper plants.•Plant enzymatic and non-enzymatic antioxidants were improved by MSE+LRE application.•Mineral nutrients were restored in doubled stressed pepper plants by MSE+LRE application.•MSE+LRE application declined heavy metals accumulation in leaves and fruits of stressed plants.
Plant diseases and pests are risk factors that threaten global food security. Excessive chemical pesticide applications are commonly used to reduce the effects of plant diseases caused by bacterial ...and fungal pathogens. A major concern, as we strive toward more sustainable agriculture, is to increase crop yields for the increasing population. Microbial biological control agents (MBCAs) have proved their efficacy to be a green strategy to manage plant diseases, stimulate plant growth and performance, and increase yield. Besides their role in growth enhancement, plant growth-promoting rhizobacteria/fungi (PGPR/PGPF) could suppress plant diseases by producing inhibitory chemicals and inducing immune responses in plants against phytopathogens. As biofertilizers and biopesticides, PGPR and PGPF are considered as feasible, attractive economic approach for sustainable agriculture; thus, resulting in a “win-win” situation. Several PGPR and PGPF strains have been identified as effective BCAs under environmentally controlled conditions. In general, any MBCA must overcome certain challenges before it can be registered or widely utilized to control diseases/pests. Successful MBCAs offer a practical solution to improve greenhouse crop performance with reduced fertilizer inputs and chemical pesticide applications. This current review aims to fill the gap in the current knowledge of plant growth-promoting microorganisms (PGPM), provide attention about the scientific basis for policy development, and recommend further research related to the applications of PGPM used for commercial purposes.
Despite studies focusing on soil substrates (carbon and nitrogen) and heavy metal availability, the impact of diversified parent materials in arid alkaline regions has received little attention. To ...reveal the influence of parent material, we investigated four different parent materials: fluvio-marine, Nile alluvial, lacustrine, and aeolian deposits. We assessed the effect of soil parent materials through selected soil physical and chemical properties, such as clay content, bulk density, pH, and available phosphorus (AP). The Tukey HSD test (SPSS ver. 23) was used to assess the soils derived from these different sediments. Using the R “glmulti” package, we examined this effect in a model of mixed-effects meta-regression. The sum of Akaike weights for models that contained each element was used to estimate the importance of each factor. The average contents of soil organic carbon (SOC) and total N in alluvial deposits were greater (p < 0.001) than those of marine, aeolian, and lacustrine deposits. A multivariate analysis in arid regions revealed that parent material, soil pH, and the availability of P had the greatest effects on SOC concentration, whereas clay content, available P, soil pH, parent material, and bulk density had the greatest effects on soil total nitrogen. The average content of Fe in the aeolian deposits was greater (p < 0.001) than those of marine, alluvial, and lacustrine deposits, without any significant differences between the latter two deposits. We found that the highest average contents of zinc (Zn), manganese (Mn), and copper (Cu) were recorded in alluvial deposits, with significant differences between other deposits. Soil parent material was the major factor impacting soil iron (Fe) content, along with clay content and soil pH. However, soil bulk density was the most important factor controlling soil Zn and Mn contents, while SOC drove Cu content. This study will help in developing a more accurate model of the dynamics of soil substrates and availability of heavy metals by considering readily available variables, such as parent materials, soil pH, soil bulk density, and clay content.
Nitrification inhibition as an alleviation tool to decrease nitrogen (N) losses and increase N use efficiency (NUE) as well as reducing NO3− accumulation in plants is a promising technology. No study ...thus far has directly or indirectly to use the secondary metabolites extracted from Moringa (Moringa oleifera Lam) seeds as nitrification inhibitors. Moringa seed extract (MSE) was studied based on its content of phenolic compounds (PC) and for its antioxidant characteristic. A 2-year field experiment and 30-day incubation experiment were conducted with three treatments of control (CK), N fertilizer (300 kg N ha−1 and 200 mg N kg−1 soil for the field and incubation experiment, respectively), and N fertilizer with MSE (500 ppm as a TPC) to investigate the responses of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to MSE and the consequences for NUE and NO3− accumulation in potato tubers. Total phenolics amount was 144 mg gallic acid equivalent g−1 MSE, while flavonoid contents were 76.6 quercetin equivalent g−1 MSE. MSE showed antioxidant activity that was comparable to the standard antioxidants TBHQ and gallic acid. MSE application with N fertilizer retarded the nitrification process, as indicated by a higher NH4+-N and lower NO3−-N content, compared with N fertilizer application alone. NH4+-N content reduced to initial CK level on Day 20 under N fertilizer application alone. However, NH4+-N content decreased to initial control level on Day 30 when MSE was applied. The mechanisms resulted from curbing AOB growth by phenolic compounds (TPC, TF, TAC), leading to a delay in nitrification process. AOB increased significantly when N fertilizer was applied alone; on the contrary, AOA was not sensitive to N fertilizer (with and without MSE). Increase in NUE from 37.5% to 66.3% in potato plants under MSE application with N fertilizer was also observed compared with N fertilizer application alone. The highest NO3− accumulation (569 mg NO3− kg−1) in tubers was recorded under N fertilizer application without MSE. MSE application significantly decreased NO3− accumulation (92 mg NO3− kg−1) in tubers which is lower than the maximum value of accepting tubers (200 mg NO3− kg−1). The highest average of N uptake, fresh and dry weight, carotenoids, chlorophyll a, chlorophyll b and nitrate reductase activity was recorded when MSE was applied with N fertilizer. Accordingly, using of Moringa extracted secondary metabolites to suppress AOB growth in the soil is a significant strategy to reduce nitrification rate and N loss from soils, and therefore increase NUE as well as reducing NO3− accumulation in potato tubers.
A diagram shows the effect of N fertilizer and Moringa seed extract (MSE) on ammonia oxidizers, nitrogen use efficiency, potato tubers contamination with nitrate, and tubers yield of potato plants. Display omitted
•Moringa seed extract (MSE) showed antioxidants (AS) activity that was comparable to the standard AS.•MSE application with N fertilizer retarded the nitrification process.•AOB was inhibited when MSE was applied while AOA was not sensitive to N fertilizer and MSE.•MSE application significantly decreased NO3− accumulation in tubers below the allowable limit.•The application of MSE with N fertilizer significantly increased NUE and tubers yield.
Factors influencing rice (Oryza sativa L.) yield mainly include nitrogen (N) fertilizer, climate and soil properties. However, a comprehensive analysis of the role of climatic factors and soil ...physical and chemical properties and their interactions in controlling global yield and nitrogen use efficiency (e.g., agronomic efficiency of N (AEN)) of rice is still pending. In this article, we pooled 2293 observations from 363 articles and conducted a global systematic analysis. We found that the global mean yield and AEN were 6791 ± 48.6 kg ha−1 season−1 and 15.6 ± 0.29 kg kg−1, respectively. Rice yield was positively correlated with latitude, N application rate, soil total and available N, and soil organic carbon, but was negatively correlated with mean annual temperature (MAT) and soil bulk density. The response of yield to soil pH followed the parabolic model, with the peak occurring at pH = 6.35. Our analysis indicated that N application rate, soil total N, and MAT were the main factors driving rice yield globally, while precipitation promoted rice yield by enhancing soil total N. N application rate was the most important inhibitor of AEN globally, while soil cation exchange capacity (CEC) was the most important stimulator of AEN. MAT increased AEN through enhancing soil CEC, but precipitation decreased it by decreasing soil CEC. The yield varies with climatic zones, being greater in temperate and continental regions with low MAT than in tropical regions, but the opposite was observed for AEN. The driving factors of yield and AEN were climatic zone specific. Our findings emphasize that soil properties may interact with future changes in temperature to affect rice production. To achieve high AEN in rice fields, the central influence of CEC on AEN should be considered.
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•A systematic analysis of the drivers of rice yield and N use efficiency is conducted.•Soil cation exchange capacity is a key factor of N use efficiency in rice.•It is important for rice yield to improve soil quality under global change.
Dissimilatory nitrate reduction to ammonium (DNRA), the nearly forgotten process in the terrestrial nitrogen (N) cycle, can conserve N by converting the mobile nitrate into non-mobile ammonium ...avoiding nitrate losses via denitrification, leaching, and runoff. However, global patterns and controlling factors of soil DNRA are still only rudimentarily known. By a meta-analysis of 231 observations from 85 published studies across terrestrial ecosystems, we find a global mean DNRA rate of 0.31 ± 0.05 mg N kg
day
, being significantly greater in paddy soils (1.30 ± 0.59) than in forests (0.24 ± 0.03), grasslands (0.52 ± 0.15), and unfertilized croplands (0.18 ± 0.04). Soil DNRA was significantly enhanced at higher altitude and lower latitude. Soil DNRA was positively correlated with precipitation, temperature, pH, soil total carbon, and soil total N. Precipitation was the main stimulator for soil DNRA. Total carbon and pH were also important factors, but their effects were ecosystem-specific as total carbon stimulates DNRA in forest soils, whereas pH stimulates DNRA in unfertilized croplands and paddy soils. Higher temperatures inhibit soil DNRA via decreasing total carbon. Moreover, nitrous oxide (N
O) emissions were negatively related to soil DNRA. Thus, future changes in climate and land-use may interact with management practices that alter soil substrate availability and/or soil pH to enhance soil DNRA with positive effects on N conservation and lower N
O emissions.
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