These days, one of the main issues preventing agricultural development is salinized soils. Potassium fulvic acid (PFA) not only regulates plant growth, but also improves the soil nutrient content and physical structure, which makes it a soil conditioner worth promoting. Nevertheless, the research conducted thus far on the subject of PFA with regard to plant growth and inter-root microbial communities remains somewhat limited in scope. In this study, a pot experiment was conducted to simulate both the normal environment and salt stress environment. The objective of this experiment was to verify the effect of PFA on the growth of blueberry (Vaccinium corymbosum L.) as well as its effect on the soil physical and chemical indices and the soil microbial community structure. The findings demonstrated that the implementation of potassium fulvic acids exhibited a minimal impact on the growth of blueberry plants under standard environmental conditions. However, it was observed to exert a substantial effect on enhancing various physiological parameters, including plant height, root activity, and chlorophyll synthesis, particularly in response to salt stress. PFA led to a substantial augmentation in the soil organic matter content, alongside a notable rise in the alkali-hydrolyzable nitrogen (AN) and available potassium (AK) content. Concurrently, PFA caused a notable escalation in the activities of soil urease, sucrase, acid phosphatase, and catalase (p < 0.05) in the salt-stressed environment. PFA increased the abundance of Acidobacteria, Myxococcota, Ascomycota, and Fungi_phy_Incertae_sedis under salt stress, which was mainly related to the decrease in electrical conductivity (EC) values and increase in soil acid phosphatase (S-ACP) activity. It is evident that the implementation of PFA is advantageous in enhancing the saline environment, mitigating the impact of salt damage on blueberries and establishing a foundation for the expansion of cultivated areas and the sustainable cultivation of blueberries.

Nitrogen fertilizers have a significant impact on the growth of rice. The overuse and inappropriate application of nitrogen fertilizers have resulted in environmental pollution, in addition to subjecting both humans and livestock to negative health hazards. Finding a viable substitute for traditional nitrogen fertilizers is crucial and essential to help improve crop yield and minimize environmental damage. Nano-nitrogen fertilizers offer a possible alternative to traditional fertilizers due to a slow/controlled release of nitrogen. The present work aimed to study the effect of a slow-release urea nanofertilizer on soil ammonical (NH4-N) and nitrate-N (NO3-N) content, culturable soil microflora, and soil enzyme activities in three different soil samples procured from Ludhiana and Patiala districts through a soil column study. Seven treatments, including 0, 50 (75 kg/ha N), 75 (112.5 kg/ha N), and 100% (150 kg/ha N) of the recommended dose (RD) of conventional urea and nano-urea fertilizer were applied. The leachate samples collected from nano-urea treatment exhibited NH4-N for the first two weeks, followed by NO3-N appearance. The higher NH4-N and NO3-N contents in the leachate were recorded for light-textured soil as compared to medium- and heavy-textured soil samples. The soil microbial counts and enzyme activities were recorded to be maximum in light-textured soils. Therefore, this slow-release formulation could be more useful for light-textured soils to decrease applied N-fertilizer losses, as well as for improving the soil microbial viable cell counts and soil enzyme activities. The effect of urea nanofertilizer on the growth and yield of direct-seeded rice (Oryza sativa L.) was also evaluated under field conditions. Both studies were performed independently. Numerically, the highest shoot height, fresh and dry shoot weight, and significantly maximum total chlorophyll, carotenoid, and anthocyanins were recorded in the T2 (100% RDF through nano-urea) treatment. The yield-attributing traits, including the number of filled grains and thousand-grain weight, were also recorded to have increased in T2 treatment. A numerical increase in NPK for plant and grain of rice at 100% RDN through nano-urea was recorded. The soil application of the product exhibited no negative effect on the soil microbial viable cell count on different doses of nano-urea fertilizer. The soil nitrogen fixer viable counts were rather improved in nano-urea treatments. The results reflect that nano-urea fertilizer could be considered as a possible alternative to conventional fertilizer.

Nitrogen deposition and drought significantly influence plant growth and soil physicochemical properties. This study investigates the effects of nitrogen deposition and water stress on the growth and physiological responses of Quercus dentata, and how these factors interact to influence the overall productivity. Two-year-old potted seedlings were selected to simulate nitrogen deposition and water stress. Nitrogen was applied at rates of 0 kgha-1year-1 (N0) and 150 kgha-1year-1 (N150). The levels of water stress corresponded to 80% (W80), 50% (W50), and 20% (W20) of soil saturation moisture content. High nitrogen (N150) significantly increased stem elongation and stem diameter by enhancing photosynthetic parameters, including P n (W80) and G s (W50), and maintained higher water use efficiency. Under drought conditions, nitrogen enhanced leaf water content, stabilized electrical conductivity, regulated antioxidant enzyme activity, and increased the accumulation of proline. However, under severe drought, nitrogen did not significantly improve biomass, highlighting the critical role of water availability. Additionally, increased nitrogen levels enhanced soil enzyme activity, facilitated the uptake of crucial nutrients like K and Zn. Mantel tests indicated significant correlations between soil enzyme activity, water use efficiency, and leaf Fe content, suggesting that nitrogen deposition altered nutrient uptake strategies in Q. dentata to sustain normal photosynthetic capacity under water stress. This study demonstrates that nitrogen deposition substantially enhances the growth and physiological resilience of Q. dentata under W50 by optimizing photosynthetic efficiency, water use efficiency, and nutrient uptake. However, the efficacy of nitrogen is highly dependent on water availability, highlighting the necessity of integrated nutrient and water management for plant growth.

Riparian soils, together with vegetation, play a crucial role in supporting biodiversity and driving biogeochemical processes within river ecosystems. Conservation of riparian soils and artificial planting are essential for river ecosystem recovery following land degradation. Researchers focus on examining soil nutrients, microbial biomass, and organic acid metabolism in the interactions between plants and soil along riverbanks. However, the seasonal responses of riparian soils to artificial plantations have been infrequently reported in the existing literature. This study investigates the influence of seasonal variations on soil conditions and the growth of artificially planted species in the riparian zones of the Three Gorges Dam Reservoir (TGDR) in China. The species sampled include Cynodon dactylon, Hemarthria altissima, and Salix matsudana. These species provide valuable insight into soil properties along riparian zones, assessing interactions across different seasons: T1 (spring), T2 (summer), and T3 (autumn). The results demonstrated significant seasonal changes in soil organic matter, ammonium nitrogen, nitrate nitrogen, and other indicators between T1 and T3. Apart from invertase activity in H. altissima soil, enzyme activity peaked during T1. Dominant soil bacteria were examined using high-throughput 16S rDNA sequencing, revealing that the available bacteria belong to 62 phyla and 211 classes. Among the most abundant were Proteobacteria and Actinobacteria, averaging over 60 % across all soil samples. Principal component analyses accounted for 62.81 % (T1), 50.57 % (T2), and 54.08 % (T3) of the variation observed in the study, indicating that soil properties were predominantly influenced by the different seasonal phases, assuming all other factors remained constant. Pearson correlation analysis (p < 0.05) identified strong positive correlations between physical properties and all three plant species during T1 (r <= 0.94), as well as significant negative correlations with bacterial communities in T2 and T3 (r <= -1.00). These findings suggest that the selected plant species are well-suited to cultivation in the riparian zone of the TGDR. This study enhances our understanding of seasonal dynamics in riparian environments, offering practical insights into their management.

Simple Summary Microorganisms and their enzymes are crucial to ensuring soil quality, health, and carbon sequestration. Their numerous reactions are essential for biogeochemical cycles. However, a comprehensive review is lacking to summarize the latest findings in agricultural and enzymatic research. Although the relationships between soil enzyme activities and different soil ecosystems, such as arctic and permafrost regions, tropics and subtropics, tundra, steppes, etc., have been intensively investigated, particularly in the context of climate changes, only a few reviews summarize the impact of climate change on soil enzyme activity. This review aims to highlight the main groups of microbial enzymes found in soil (such as alpha-glucosidases and beta-glucosidases, phosphatases, ureases, N-acetyl-glucosaminidases, peptidases, etc.), their role in the global nutrient cycles of carbon, nitrogen, phosphorus, sulfur, carbon sequestration, and the influence of intensive agriculture on microbial enzymatic activity, and the variations in enzyme activity across different climate zones and soil ecosystems. Furthermore, the review will emphasize the importance of microbial enzymes for soil fertility and present both current challenges and future perspectives.Abstract The extracellular enzymes secreted by soil microorganisms play a pivotal role in the decomposition of organic matter and the global cycles of carbon (C), phosphorus (P), and nitrogen (N), also serving as indicators of soil health and fertility. Current research is extensively analyzing these microbial populations and enzyme activities in diverse soil ecosystems and climatic regions, such as forests, grasslands, tropics, arctic regions and deserts. Climate change, global warming, and intensive agriculture are altering soil enzyme activities. Yet, few reviews have thoroughly explored the key enzymes required for soil fertility and the effects of abiotic factors on their functionality. A comprehensive review is thus essential to better understand the role of soil microbial enzymes in C, P, and N cycles, and their response to climate changes, soil ecosystems, organic farming, and fertilization. Studies indicate that the soil temperature, moisture, water content, pH, substrate availability, and average annual temperature and precipitation significantly impact enzyme activities. Additionally, climate change has shown ambiguous effects on these activities, causing both reductions and enhancements in enzyme catalytic functions.

Microbial processes, including extracellular enzyme (exoenzyme) production, are a major driver of decomposition and a current topic of interest in Arctic soils due to the effects of climate warming. While enzyme activity levels are often assessed, we lack information on the specific location of these exoenzymes within the soil matrix. Identifying the locations of different soil enzymes is needed to improve our understanding of microbial and overall ecosystem function. Using soil obtained from Utqiagvik, Alaska, our objectives in the study are (1) to measure the activity of enzymes in soil pore water, (2) to examine the distribution of activity among soil particle size fractions using filtration, and (3) to cross these particle size fraction analyses with disruption techniques (blending to shred and sonication to further separate clumped/ aggregated soil materials) to assess how tightly bound the enzymes are to the particles. The results of the soil pore water assays showed little to no enzyme activity (<0.05 nmol g soil(-1) h(-1)), suggesting that enzymes are not abundant in soil pore water. In the soil cores, we detected activity for most of the hydrolytic enzymes, and there were clear differences among the particle size and disruption treatments. Higher activities in unfiltered and 50-mu m filters relative to much finer 2-mu m filters suggested that the enzymes were preferentially associated with larger particles in the soil, likely the organic material that makes up the bulk of these Arctic soils. Furthermore, in the sonication + blending treatment with no filter, 5 of 6 hydrolytic enzymes showed higher activity compared to blending only (and much higher than sonication only), further indicating that enzyme-substrate complexes throughout the organic matter component of the soil matrix are the sites of hydrolytic enzyme activity. These results suggest that the enzymes are likely bound to either the producing microbes, which are bound to the substrates, or directly to the larger organic substrates they are decomposing. This close-proximity binding may potentially minimize the transport of decomposition products away from the microbes that produce them.

Information about the seasonal changes in soil enzyme activity along altitudinal gradients is key for understanding the responses of soil biochemical processes to ongoing climate change. Therefore, a 3-year in situ soil core incubation experiment was conducted along a 2431-m altitudinal gradient in an alpine-gorge region on the eastern Qinghai-Tibet Plateau, which includes dry valley shrubland, valley-mountain ecotone forest, subalpine coniferous forest, alpine coniferous forest and alpine meadow. The invertase, urease, and acid phosphatase activities in the soil organic layer (OL) and mineral layer (ML) were measured at five critical periods from 2013 to 2017. Higher soil enzyme activity was observed in the subalpine coniferous forest and alpine meadow, whereas lower activity was observed in the dry valley shrubland and valley-mountain ecotone forest. Overall, the seasonal sensitivity of soil enzyme activity decreased with increases in altitude. In the subalpine and alpine coniferous forests, the seasonal sensitivity of soil enzyme activity was significantly higher in the ML than in the OL. The key drivers of the seasonal variation in soil enzyme activity exhibited marked variation with changes in altitude, and these variations depended on the enzyme type and soil layer. Significant effects of temperature and precipitation on seasonal fluctuations in enzyme activities were observed at lower altitudes, whereas soil freeze-thaw cycles significantly affected the seasonal changes in acid phosphatase activity at higher altitudes. In addition, the seasonal variations in specific enzyme activities differed from those found for enzyme activities, which indicated that microorganisms might have mediated the effects of environmental factors on soil enzyme activity by altering the enzyme production efficiency. Briefly, the seasonal fluctuations in soil enzyme activity and their dominant drivers varied greatly among different altitudes in the alpine-gorge region, implying that soil biochemical processes will exhibit differential responses to ongoing climate change at different altitudes.

Peatland is a key component of terrestrial ecosystems in permafrost regions and have important effects on climate warming. Soil enzymes are involved in biogeochemical cycle of soil carbon (C), nitrogen (N) and phosphorus (P), which can be used as early sensitive indicators of soil nutrient changes caused by climate change. To predict the possible effects of permafrost degradation on soil enzymes in peatlands, ten peatlands from three types of permafrost regions along the permafrost degradation sequence (predominantly continuous permafrost region-predominantly continuous and island permafrost region-sparsely island permafrost region) in northeast China were selected to examine the activities of soil invertase, beta-glucosidase, urease and acid phosphatase and their relationships with soil physicochemical properties. The results demonstrated that permafrost type had significant effect on soil enzyme activities. Soil enzyme activities in predominantly continuous and island permafrost region were significantly higher than those in sparsely island permafrost region and predominantly continuous permafrost region. The activities of four soil enzymes were higher in 0-15 cm than 15-30 cm soil layer. Soil enzymes activities were positively correlated with soil ammonia nitrogen (NH4+-N), soil moisture content (SMC), total phosphorus (TP) and total nitrogen (TN), but negatively correlated with soil nitrate nitrogen (NO3--N). Soil inorganic nitrogen and moisture contents were the main factors affecting soil enzyme activities, with NH4+-N accounted for 41.6% of the variance, SMC 29.6%, and NO3--N 11.0%. These results suggested that permafrost degradation may change soil enzyme activities by changing soil physicochemical properties. In this study, only 0-30 cm peat soil in permafrost regions was collected during the complete thawing period of permafrost active layer, further studies should be placed on the change of soil enzyme activities in active layer and permafrost layer during freezing and thawing process in the southernmost location of northeast China in the Eurasia permafrost body and boreal forest belt.

Projected future decreases in snow cover associated with global warming in alpine ecosystems could affect soil biochemical cycling. To address the objectives how an altered snow removal could affect soil microbial biomass and enzyme activity related to soil carbon and nitrogen cycling and pools, plastic film coverage and returning of melt snow water were applied to simulate the absence of snow cover in a Tibetan alpine forest of western China. Soil temperature and moisture, nutrient availability, microbial biomass and enzyme activity were measured at different periods (before snow cover, early snow cover, deep snow cover, snow cover melting and early growing season) over the entire 2009/2010 winter. Snow removal increased the daily variation of soil temperature, frequency of freeze-thaw cycle, soil frost depth, and advanced the dates of soil freezing and melting, and the peak release of inorganic N. Snow removal significantly decreased soil gravimetric water, ammonium and inorganic N, and activity of soil invertase and urease, but increased soil nitrate, dissolve organic C (DOC) and N (DON), and soil microbial biomass C (MBC) and N (MBN). Our results suggest that a decreased snow cover associated with global warming may advance the timing of soil freezing and thawing as well as the peak of releases of nutrients, leading to an enhanced nutrient leaching before plant become active. These results demonstrate that an absence of snow cover under global warming scenarios will alter soil microbial activities and hence element biogeochemical cycling in alpine forest ecosystems. (C) 2013 Elsevier B.V. All rights reserved.