Soil Nutrient Pools Research Articles

Groundwater table prediction and seasonal variation influenced by short rotation willow plantation on marginal riparian lands of the Prairie potholes in Canada

Shallow groundwater consumption via phreatophytic transpiration and resulting vegetation-linked groundwater table (GWT) fluctuation is a typical soil hydrological process in wetland riparian areas. However, upland and riparian land use alterations may further influence the shallow GWT fluctuation, temporally and spatially. In this multi-year field study, we investigated whether introducing short rotation willow (SRW) positively or negatively affects the shallow GWT, soil water availability, and soil health on marginal riparian lands of the Prairie Pothole Region (PPR). We compared the impact of SRW on these parameters to two common land uses: annual crop (AC) and pasture (PA). Depth to GWT was monitored via data loggers from 28 wells in two semi-arid PPR sites. The GWT depth varied by land use practices only in site B (p < 0.001; PA > SRW = AC) but not significantly in site A (p = 0.325), and the patterns were inconsistent between sites. In GWT depth prediction, the performance of Artificial Neural Network (ANN) was better than Autoregressive Integrated Moving Average (ARIMA) models but was inconsistent alike with field observations. The GWT depth responded to seasonal precipitation and potential evapotranspiration (ET) patterns. The monthly GWT fluctuations peaked between June and August due to increased precipitation, while they were lower during May and September with reduced precipitation; however, these variations were not significant (p > 0.05). Higher precipitation and lower potential ET throughout the wet year (i.e., in 2014) significantly (p < 0.05) raised GWT (i.e., decreased depth to GWT) under all land uses, and vice versa. Our study indicated that planting SRW in marginal riparian land of the PPR would not negatively impact shallow GWT or soil water availability. Moreover, the SRW plantation could also help manage soil salinity without severely depleting the soil's nutrient pools or diminishing soil quality and health indicator parameters measured during the first rotation.

Grazing period management affects the accumulation of plant functional groups, and soil nutrient pools and regulates stoichiometry in the desert steppe of Northwest China

To understand how nutrient cycling and sequestration are influenced by different grazing periods, the C:N:P stoichiometry features of the plant–soil interface in the desert steppe were measured and evaluated. The 5-year seasonal grazing experiment employed four grazing period treatments: traditional time of grazing (TG), early termination of grazing (EG), delayed start of grazing (DG), and delayed start and early termination of grazing (DEG). Additionally, fenced off desert steppe served as the control. The grazing periods each had a differing impact on the C:N:P stoichiometry in both plant functional group and soil depth comparisons. Compared to the EG, DG, and DEG treatments, the TG treatment had a more significant impact on the C, N, and P pools of grass, as well as the C:P and N:P ratios of forbs, but had a reduced effect on the C:P and N:P ratios of legumes. In contrast to plants, the DG treatment exhibited greater advantages in increasing C pools within the 0–40 cm soil layer. Furthermore, in the 10–20 cm soil layer, the C:P and N:P ratios under the EG treatment were significantly higher, ranging from 8.88% to 53.41% and 72.34%–121.79%, respectively, compared to the other treatments (TG, DG, and DGE). The primary drivers of the C, N, and P pools during different grazing periods were above-ground biomass (AGB) and litter biomass (LB). Both lowering the plant C:P and N:P ratios and considerably raising the plant P pool during different grazing periods greatly weakened the P limitation of the desert steppe environment. It is predicted that delayed start grazing might be a management strategy for long-term ecosystem sustainability, as it regulates above-ground nutrient allocation and has a positive effect on soil C and N pools.

Maize/soybean intercropping increases nutrient uptake, crop yield and modifies soil physio-chemical characteristics and enzymatic activities in the subtropical humid region based in Southwest China

Intercropping, a widely adopted agricultural practice worldwide, aims to increase crop yield, enhance plant nutrient uptake, and optimize the utilization of natural resources, contributing to sustainable farming practices on a global scale. However, the underlying changes in soil physio-chemical characteristics and enzymatic activities, which contribute to crop yield and nutrient uptake in the intercropping systems are largely unknown. Consequently, a two-year (2021–2022) field experiment was conducted on the maize/soybean intercropping practices with/without nitrogen (N) fertilization (i.e., N0; 0 N kg ha−1 and N1; 225 N kg ha−1 for maize and 100 N kg ha−1 for soybean ) to know whether such cropping system can improve the nutrients uptake and crop yields, soil physio-chemical characteristics, and soil enzymes, which ultimately results in enhanced crop yield. The results revealed that maize intercropping treatments (i.e., N0MI and N1MI) had higher crop yield, biomass dry matter, and 1000-grain weight of maize than mono-cropping treatments (i.e., N0MM, and N1MM). Nonetheless, these parameters were optimized in N1MI treatments in both years. For instance, N1MI produced the maximum grain yield (10,105 and 11,705 kg ha−1), biomass dry matter (13,893 and 14,093 kg ha−1), and 1000-grain weight (420 and 449 g) of maize in the year 2021 and 2022, respectively. Conversely, soybean intercropping treatments (i.e., N0SI and N1SI) reduced such yield parameters for soybean. Also, the land equivalent ratio (LER) and land equivalent ratio for N fertilization (LERN) values were always greater than 1, showing the intercropping system’s benefits in terms of yield and improved resource usage. Moreover, maize intercropping treatments (i.e., N0MI and N1MI) and soybean intercropping treatments (i.e., N0SI and N1SI) significantly (p < 0.05) enhanced the nutrient uptake (i.e., N, P, K, Ca, Fe, and Zn) of maize and soybean, however, these nutrients uptakes were more prominent in N1MI and N1SI treatments of maize and soybean, respectively in both years (2021 and 2022) compared with their mono-cropping treatments. Similarly, maize-soybean intercropping treatments (i.e., N0MSI and N1MSI) significantly (p < 0.05) improved the soil-based N, P, K, NH4, NO3, and soil organic matter, but, reduced the soil pH. Such maize-soybean intercropping treatments also improved the soil enzymatic activities such as protease (PT), sucrose (SC), acid phosphatase (AP), urease (UE), and catalase (CT) activities. This indicates that maize-soybean intercropping could potentially contribute to higher and better crop yield, enhanced plant nutrient uptake, improved soil nutrient pool, physio-chemical characteristics, and related soil enzymatic activities. Thus, preferring intercropping to mono-cropping could be a preferable choice for ecologically viable agricultural development.

Shrubs exhibit competitive interactions with herbaceous plants and shape community assemblage and functional composition in the alpine western Himalaya

AbstractQuestionsIn the alpine region of the Himalaya, shrubs play a vital role in maintaining the diversity and functional composition of associated herbaceous communities through competition–facilitation interactions under varying environmental stress conditions. In this study, we specified the following questions: (1) what is the mode of interaction between dominant shrubs and the associated herbaceous communities; (2) how do differences in resource availability between contrasting microhabitats mediate interactions between shrub and herbaceous communities; and (3) how do dominant shrubs influence the functional composition of herbaceous communities under the canopy as compared to ones in the open?Study areaAn alpine region of the western Himalaya, in India (32.24–33.15° N, 76.51–78.13° E).MethodsField studies were conducted to evaluate the canopy effects of alpine shrubs such as Caragana versicolor, Juniperus polycarpos and Rhododendron anthopogon on species richness, abundance and functional composition of coexisting herbaceous communities.ResultsThe dominant alpine shrubs of the western Himalaya exert competitive interactions with associated herbaceous communities and have low species richness and abundance under their canopies compared to open habitats. Further, contrary to expectations, competitive interactions were more prominent at higher elevations than at lower ones, especially for J. polycarpos and C. versicolor. Although the shrub undercanopies possessed richer soil nutrient pools, this did not contribute toward the facilitation of herbaceous species under the canopies. Moreover, herbaceous species under the canopies were found to exhibit resource‐acquisitive functional strategies, whereas those in the open were resource‐conservative.ConclusionsThe interaction between dominant alpine shrubs and the herbaceous community of the western Himalaya is competitive in nature, which influences species and functional composition and reorganizes herbaceous community assembly. Moreover, under future climate change scenarios the dominance of these shrubs will favour those herbaceous species that possess more competitive and resource‐acquisitive functional strategies.

Heathland management affects soil response to drought

Abstract Drought can affect ecosystem functioning by altering plant–soil interactions, posing a significant threat to vulnerable ecosystems like heathlands. In heathlands, ongoing nitrogen deposition increases the dominance of fast‐growing grasses over the slow‐growing shrub Calluna vulgaris. These changes above‐ground can influence soil dynamics and heathlands' responses to drought. Here, we assessed whether the legacy effects of drought on heathland soils depended on mowing times as a management practice commonly used to regenerate Calluna and decrease the abundance of fast‐growing grasses. Using a long‐term field experiment, we investigated if soil response to drought differed under Calluna and grasses, as well as under Calluna plants of different growth stages through different mowing times. We hypothesized that drought would decrease soil C and nutrient pools underneath grasses and younger Calluna plants through its impact on soil microbial communities. Our results show that long‐term drought decreased soil C but only underneath grasses and old Calluna, while under young Calluna, soil C increased under drought when compared to control conditions. Bacterial and fungal community composition differed between drought and control and were affected by the growth stage of Calluna but not by plant growth strategies. Furthermore, drought and Calluna growth stage‐induced changes in bacterial communities directly affected total soil C and indirectly by reducing microbial C, which was positively related to total soil C. Synthesis and applications. Understanding ecosystem response to drought is crucial for maintaining biodiversity and mitigating climate change feedbacks. Heathlands are threatened by high nitrogen deposition, a lack of management and an increasing frequency of drought. Our results emphasize the importance of frequent mowing (decadal) as a management practice that promotes a younger and more Calluna‐dominated plant community for reducing soil C losses under future climate change‐induced drought conditions. The active management of heathlands is essential not only for keeping above‐ground vegetation dynamics, but also for maintaining below‐ground soil nutrient and carbon pools.

Prolonged drought moderates flood effects on soil nutrient pools across a rainfall gradient

Climate change is manifesting through increased intensity and frequency of extreme events such as droughts and floods. Drought causes significant stress by limiting water availability, resulting in reduced plant growth and belowground carbon (C) inputs as well as plant nutrient uptake and microbial activity, thus impacting C and nutrient cycling. Severe floods can increase leaching of nutrients, which affect nutrient availability for plants and microorganisms potentially compounding drought-induced effects on C and nutrient cycles. However, few studies have assessed the interactions between drought and floods, constraining our ability to predict ecosystem-level effects of projected climate shifts toward fewer but larger rainfall events with longer dry spells between events. We conducted a study to assess how long-term drought moderates the effect of flooding on soil C, nitrogen (N) and phosphorus (P) pools across a rainfall gradient in south-eastern Australia. We collected soil monoliths from field rainfall manipulation facilities with a 5–7 years history of simulated reduced rainfall at three sites representing a rainfall gradient (∼200–800 mm) and exposed them to a 1-in-100-year flood event under laboratory conditions. We assessed nutrients and C in soil and microbial pools before and after the flood and in flood-induced leachates. The results showed that flooding caused significantly greater losses of N in leachates, with greater effect sizes in the drought treatments compared to ambient rainfall. This response was particularly pronounced for nitrate (152 % increase on average), especially at the site with the highest mean annual precipitation (>25-fold increase). This suggest that drought may significantly reduce the capacity of ecosystems to retain N following flood events, particularly in mesic ecosystems where C and nutrient pools are greater.

Crops use inorganic and labile organic phosphorus from both high‐ and low‐availability layers in no‐till compost‐amended soils

AbstractOrganic fertilization in no‐till soils increases soil organic matter and nutrient pools primarily in surface soils. However, little is known about how microbial activity affects crop access to phosphorus (P) forms at the surface, where the organic fertilizer is applied, and the subsurface, the main rooting zone. We aimed to study the changes in organic and inorganic P (Po; Pi) forms and compounds in no‐till compost amended surface (0–5 cm) and subsurface (5–15 cm) soils growing a crop rotation for 2 years in pots. Crops were grown in pots with compost amended to the soil surface, while unamended and compost‐amended pots without crops were used as controls. We measured changes in microbial C (carbon), soluble C, total Po and Pi forms, the moderately accessible EDTA‐NaOH‐Pi (‐Po), and labile NaHCO3‐Pi (‐Po). P compounds in the EDTA‐NaOH extract were measured by 31P‐NMR. Compost addition increased the levels of total Pi and although it had no effect on total Po, increases of inositol, other phosphate monoesters and orthophosphate diesters could be observed. After the application of compost, the amount of total organic C, soluble carbon and all P forms increased in surface soil, while in the subsurface soil, there was a reduction in organic C and an increase in soluble C, total Pi, EDTA‐NaOH‐Pi and NaHCO3‐Pi and the EDTA‐NaOH‐Po and labile NaHCO3‐Po. Growing crops reduced all measured Pi forms and labile NaHCO3‐Po, increased EDTA‐NaOH‐Po in surface soils and had no observable impact on total Po in either organic C‐enriched surface or organic C‐reduced subsurface soils. Crops mostly used Pi from the low P availability C‐reduced subsurface layer, where NaHCO3‐Po pools also decreased. Large reductions in NaHCO3‐Po and increased levels of IHP and other‐monoesters in crop‐growing organic C‐enriched surface layers may suggest microbial formation of monoesters Po and crop use of labile Po pools. In summary, Po formation in C‐enriched surface layers and the mobilization of all Pi forms throughout the soil profile are particularly important findings for the understanding of P dynamics in compost‐amended no‐till systems.

Towards a better understanding of soil nutrient dynamics and P and K uptake

AimBalanced crop nutrition is key to improve nutrient use efficiency and reduce environmental impact of farming systems. We developed and tested a dynamic model to predict the uptake of P and K in long-term experiments to better understand how changes in soil nutrient pools affect nutrient availability in crop rotations.MethodsOur RC-KP model includes labile and stable pools for P and K, with separate labile pools for placed P and organic fertilizers including farm yard manure (FYM). Pool sizes and crop-specific relative uptake rates determined potential uptake. Actual crop uptake from labile pools was based on concepts developed by Janssen et al. (Geoderma 46:299-318, 1990). The model was calibrated on three long-term experiments from Kenia (Siaya), Germany (Hanninghof) and the United Kingdom (Broadbalk) to estimate parameter values for crop-specific relative uptake rates and site-specific relative transfer rates.ResultsThe model described N, P and K uptake accurately with a Nash-Sutcliff modelling efficiency of 0.6–0.9 and root mean squared errors of 2.6–3.4 kg P ha−1 and 14–20 kg K ha−1. Excluding organic labile pools did not affect model accuracy in Broadbalk in contrast to Hanninghof where Mg deficiencies affected crop uptakes in treatments without Mg or FYM.ConclusionsThis relatively simple model provides a novel approach to accurately estimate N, P and K uptake and explore short- and long-term effects of fertilizers in crop rotations. Interactions between limiting nutrients affecting actual nutrient uptake were captured well, providing new options to include N, P and K limitations in crop growth models.

Impacts of Tropical Rainforest Conversion on Soil Nutrient Pools in Viti Levu, Fiji

Impacts of Tropical Rainforest Conversion on Soil Nutrient Pools in Viti Levu, Fiji

Plant invasion shifts soil microbiome and physico-chemical attributes along an elevational gradient in Kashmir Himalaya.

Soil microbial communities, being situated at the interface of aboveground plant and belowground soil systems, can play a pivotal role in determining ecosystem response to the drivers of global environmental change, including invasive species. In mountains, invasive plants occurring along elevational gradients offer a unique natural experimental system to investigate the impact of invasions in determining patterns and relationships of soil microbial diversity and nutrient pools at much shorter spatial distances. Here, we studied the impact of a global plant invader, Leucanthemum vulgare, on the diversity of soil microbiome and physico-chemical attributes along an elevational gradient (1760-2880m) in Kashmir Himalaya. We used Illumina MiSeq platform to characterize the soil microbiome in pair-wise invaded and uninvaded plots at four different sites along the gradient. We found a total of 1959 bacterial operational taxonomic units (OTUs) belonging to 152 species, and a relatively higher number of 2475 fungal OTUs belonging to 589 species. The α-diversity of soil microbiome showed a gradual increase from low to high elevation and differed significantly (p < 0.05) between the invaded and uninvaded plots. The β-diversity revealed distinct microbiome clustering among the sampling sites. Plant invasion also altered soil physico-chemical attributes along the elevational gradient. Overall, our findings suggest that the L. vulgare-induced shifts in soil microbiome and nutrient pools may be a belowground self-reinforced mechanism to facilitate its successful invasion along the elevational gradient. Our study provides new insights into invasive plant-microbe relationships with wide implications for climate warming-driven elevational range shifts in mountains.

Changes in soil organic carbon and nutrient pools in aggregate‐sized fractions along a chronosequence of wolfberry (Lycium barbarum L.) plantations in arid areas of Northwest China

AbstractDifferent land use and management actions can affect soil aggregates (SAs) and nutrient stocks, which are crucial for sustainable agriculture. The impacts of various chrono‐sequences on the soil aggregate structure, soil organic carbon (SOC) and nutrients associated with aggregate fractions in wolfberry (Lycium barbarum L.) plantations are still not fully understood. This study examined the composition and stability of SAs, SOC, total nitrogen (TN), available phosphorus (AP) and exchangeable cations (K+, Na+, Ca2+ and Mg2+) in bulk soil and various aggregate‐size fractions from five wolfberry plantations with varying ages (1, 4, 6, 10 and 13 years) and a corn field (0 years) in the arid region of northwest Ningxia in China. The results indicated that silt–clay (&lt;53 μm) fractions were dominant in the soil, accounting for 51%–66%, under different plantation ages. The proportion of the macro‐aggregates (&gt;250 μm) increased significantly, by 40%–47%, over the 4 years of wolfberry plantation. Likewise, the soil aggregate stability was improved, and total exchangeable bases (TEB) along with numerous cations concentrations (K+, Na+, Ca2+ and Mg2+) in SAs were significantly reduced as the wolfberry plantings became older. Both concentrations of SOC and TN in the soil aggregates peaked in the 13th year. The silt–clay fractions stored a considerable amount of SOC and nutrients. However, short‐term (under 6 years) cultivation of wolfberry reduced the stocks of SOC, TN and AP in the soil, while long‐term (over 10 years) cultivation increased them, particularly in macro‐aggregates. These findings indicated that long‐term wolfberry farming had several advantages, such as enhancing soil structure, accumulating SOC and nutrients and ameliorating alkaline soils, especially after 10 years, in the arid northwest of China.

Effects of Irrigation Scheduling and Nitrogen Levels on Soil Nutrient and Their Uptake in Radish (Raphanus Sativus L.) in Mid Hills of North-Western Himalayas, India

ABSTRACT Irrigation and N are the main two limiting factors for the radish growth and soil nutrient pool. Inappropriate irrigation and nitrogen application can negatively affect the soil nutrient status and accelerate nutrient losses which can lead to ground water pollution and soil degradation. In this study, four irrigation schedules viz. I0 (no irrigation), I1-IW/CPE = 0.8, I2-IW/CPE = 1.0, I3-IW/CPE = 1.2 and three N levels i.e. N0 (no N application), N1 (75% RDN) and N2 (100% RDN) were evaluated and replicated thrice in a RBD (factorial) during 2016–17 and 2017–18 at experimental farm of Dr YSP University of Horticulture and Forestry Nauni, Solan (HP), on sandy loam soil. Results revealed that irrigation and nitrogen levels had a significant effect on soil nutrient contents and maximum available N, P contents were observed under N2I1, N0I0 respectively, while available K, Ca, Mg and sulfate sulfur were highest under N2I3. Nutrient uptake significantly enhanced with increase in irrigation and N levels due to their solubilility and mobility. Lowest values were recorded under control. Nitrogen use efficiency decreased with increase in nitrogen levels. Results of study could be highly supportive in selecting appropriate irrigation schedule (I3) and N (100% RDN) level for fertility and efficient management of scarce water resources.

Long-term successive rotation affects soil microbial resource limitation and carbon use efficiency in Chinese fir (Cunninghamia lanceolata) monoculture plantations

Long-term successive rotation has resulted in negative effects on stand productivity, soil nutrient pool and microbial diversity and function in monoculture tree plantations. However, how successive rotation influences soil microbial nutrient limitation and carbon use efficiency (CUE) and their linkage with resource carbon (C): nitrogen (N): phosphorus (P) stoichiometry remain largely unknown. To solve this puzzle, we compared the C:N:P stoichiometries of leaf litter, fine root and soil, as well as microbial biomass and enzyme activities among three Chinese fir (Cunninghamia lanceolata) plantations with first (FRP), second (SRP) and third (TRP) generations and a natural broad-leaved forest (BL). We found that long-term successive rotation of Chinese fir decreased litter biomass by 64.7% ∼ 80.9% and enhanced litter C:N ratio by 2.7% ∼ 36.0% compared to the BL. Successive rotation decreased the contents of dissolved organic C, total N, and soil C:P and N:P ratios, and resulted in an increased C:N imbalance between soil microorganisms and nutrients in the TRP generation. Long-term successive rotation increased microbial C limitation by 1.5% ∼ 11.1% but decreased N and P limitations by 127.3% ∼ 160.9% and 15.3% ∼ 37.5%, compared with the BL, and resulted in significant increases in microbial CUE and substrate-induced respiration rate of C to N sources in the TRP generation. Structural equation modeling suggested that successive rotation indirectly affected microbial CUE and SIR by changing litter C:N, enzyme C:N and soil C:N imbalance. Collectively, these findings indicated that long-term successive rotation aggravated soil microbial C (energy) limitation and affected microbial CUE and capacity due to the increased stoichiometric imbalance between their resources. Future management practices that could increase litter and soil quality could be helpful to decrease microbial C limitation and maintain microbial functionality for sustainable monoculture plantations.

Rainwater infiltration and nutrient recharge system significantly enhance the growth of degraded artificial forest in semi-arid areas with shallowly buried soft bedrock

The improvement of deep soil water and nutrient pools by maximizing in situ rainwater resource utilization and soil nutrient recharge is an important approach to promote slope vegetation restoration in the Chinese Loess Plateau, especially in areas with shallowly buried soft bedrock (Pisha Sandstone). However, the effects of integrated slope engineering measures (fish scale pits (a semicircle-shaped pit), infiltration holes, organic fertilizer) on runoff utilization, nutrient restoration and vegetation growth are not well known. This study combined rainwater infiltration and nutrient recharge (RINR), and evaluated the effect of RINR on soil water, organic carbon, total nitrogen storage and vegetation growth in a field experiment in slope artificial forestland (David peach, Prunus davidiana Franch) one year later (from 2018 to 2019). Four treatments: (1) rainwater infiltration and nutrient recharge (RINR) system (fish scale pit + infiltration hole + hole filling with 30% organic fertilizer and 70% surface loess, PHF treatment), (2) fish scale pit + infiltration hole + filling surface loess (PH treatment), (3) pure fish scale pit (P treatment) and (4) natural slope land (control, SL treatment, CK). The results showed that, compared with the control (162 mm), PHF, PH and P treatments increased the soil water storage of 0–100 cm soil layer by 37 mm, 76 mm and 30 mm, respectively. The RINR system (PHF treatment) had a significantly higher restoration effect of SOC and STN value than other treatments in all soil profiles (0–100 cm), especially at 40 cm. Compared with the control (2.42 kg/m2, 0.28 kg/m2), the RINR system 0–40 cm soil layer soil organic carbon storage increased by 320%, and total nitrogen storage increased by 129%. Meanwhile, changes in height of tree (David peach), crown width and annual branch length under RINR system increased by 0.18 m, 0.30 m and 0.33 m, respectively. Overall, the RINR system is an effective approach for enhancing the growth of degraded revegetation. This system is conducive to mitigating the water and nutrient scarcity and maintaining the persistence of vegetation restoration in arid and semi-arid areas with shallowly buried soft bedrock.

Linkages between bacteria and nutrient availabilities in slash‐and‐burn tropical soils vary with feeding‐habit ants

AbstractAs important structuring forces in forest ecosystems, ants can drive above‐ and belowground food‐webs and ecosystem functionality. It remains uncertain, however, about how different foraging‐habit ants shape symbiotic bacterial assemblies and nutrient cycling in nest soils. This study quantified the impacts of predatory and honeydew‐feeding ants on soil bacterial communities and nutrient pools in Xishuangbanna tropical forests restored from slash‐and‐burn agriculture. In contrast to reference soils, all ant nests increased the relative abundances of dominant copiotrophs and decreased those of preponderant oligotrophs in the bacterial communities, which was closely associated with the high levels of carbon (C) and nitrogen (N) in the nests. Honeydew‐feeding ants harbored a high abundance of bacterial trophic groups (i.e., γ‐Proteobacteria, Firmicutes, and Bacteroidetes) preferring low‐quality resource, owing to high increment (103%) in C concentration and low increase (69%) in N level compared to reference soils. In contrast, predatory ants sheltered a high assemblage of bacterial taxa (i.e., β‐Proteobacteria and δ‐Proteobacteria) favoring high‐quality resource, due to increased N level (135%) and decreased C:N ratio (35%) compared to reference soils. We concluded that the foraging‐habit ants shaped symbiotic bacterial assemblages primarily through differential modifications on level and allocation of soil C and N pools. Our results would further the understanding of the fauna roles in driving soil food‐webs as well as nutrient cycling.

Invasive plants alter soil properties and nutrient dynamics: A case study of Anthemis cotula invasion in Kashmir Himalaya

Plant invasion is considerably affecting terrestrial ecosystems by modulating soil nutrient cycling and ecological processes. Below-ground processes are of paramount interest to understand the long-term influences as well as the management of the invaded soil ecosystems. We studied the impact of a global plant invader, Anthemis cotula L. (stinking chamomile; Asteraceae), on key soil physicochemical properties across eight sites in the Kashmir Himalaya, India. At each site, two types (invaded and un-invaded) of adjacent plots (20 × 20 m2) with or without A. cotula were chosen for soil sampling. Soil properties from both invaded and un-invaded plots were analysed. We found significant (P < 0.05) variations in the studied soil parameters in the invaded and un-invaded plots across the study sites. The contents of organic C, total K, total N, total P, available N, and available K were 10–60% higher in the invaded plots compared with the un-invaded plots, whereas the available P content was 21% higher in the un-invaded plots. The findings revealed that A. cotula invasion significantly alters soil nutrient levels by modulating different physicochemical properties in invaded plots, such as soil pH, electrical conductivity, water saturation percentage, and porosity. The influence of plant invasion on soil properties was clearly highlighted by Principal Component Analysis, with the majority of them ordinated towards invaded areas except for the available P and bulk density. Overall, A. cotula alters essential soil properties, thereby potentially influencing the soil nutrient pools and processes, which may further facilitate its establishment and invasion potential in the mountain ecosystems. This study underlines the importance of implementing measures for controlling the invasion of A. cotula, implementing soil reclamation strategies, and conserving native landscape characteristics in the invaded area.

Responses of Vegetation, Soil, and Microbes and Carbon and Nitrogen Pools to Semiarid Grassland Land-Use Patterns in Duolun, Inner Mongolia, China

Previous studies have observed that increased precipitation positively affects primary production in semiarid grasslands in Inner Mongolia, while soil carbon (C) and nitrogen (N) strongly influence how ecosystems respond to precipitation as well as anthropogenic disturbances under different management strategies. Therefore, in this study, we investigated the storage of organic C and N in four grassland sites with similar flora and landforms but with different grazing intensities to characterize how the storage and concentrations of C and N respond to relief from grazing pressure and precipitation. The concentrations of soil organic carbon (SOC), soil total nitrogen (STN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN), as well as the contents of soil bacteria and fungi in the 0–50 cm soil layers, were measured. The results showed that SOC, STN, MBC, and MBN storage varied greatly among the four grassland sites (p &lt; 0.05), with all decreasing significantly with grassland degradation and increasing greatly with the exclusion of grazing, i.e., the establishment of natural grassland (NG). More than 90% of C and 95% of N stored in the soil were lost due to heavy grazing, but the losses were smaller in other nutrient pools (including the aboveground biomass, litter, and roots). Interestingly, the proportion of the particle size fractions (clay, silt, and sand) had a stronger effect on limiting the soil and microbial nutrient pools compared to precipitation. The limited range of C and N storage found in these grassland soils indicated that enclosed fencing was a valuable management tool with a high potential to sequester C in the top meter of the soil, showing a stronger effect than precipitation. This study provides a theoretical basis for improving grassland recovery in semiarid areas that have been heavily grazed.

Impacts of soil, climate, and phenology on retention of dissolved agricultural nutrients by permanent-cover buffers

Nutrient losses from farms affects environmental and human health, but retention by riparian buffers can vary by nutrient identity, flow path, soil texture, seasonality, and buffer width. On conventional farms with corn, we test the relationships between levels of dissolved nitrogen (N) and phosphorus (P) in downslope surface-water, and flow paths relating to porewater in soils (to 40 cm deep), groundwater of the saturated zone (to 2.5 m deep), soil nutrient pools, and changes in plant biomass and tissue quality by season. We found that the major drivers of surface-water nutrients were multi-factor and nutrient-specific, variously relating to soil, climate, vegetation uptake, and tiling on clay soils. N retention was best explained by soil type, with 10 times more surface-water N in the sand versus clay setting, despite identical fertilization rates on corn. P retention was best explained by precipitation and time of year. Vegetation uptake was strongest for shallow-soil porewater, and was greatest in buffers where root biomass was 20 times greater by weight. We were unable to detect any impact of vegetative uptake on groundwater nutrients. Overall, peak nutrient inputs to surface-water were in early summer, fall, and winter – all times when plant uptake is low. Buffers appear to be a necessary component of nutrient capture on farms, but insufficient unless partnered with measures that reduce nutrient flows at times when plants are inactive.

Long-Term Traditional Fertilization Alters Tea Garden Soil Properties and Tea Leaf Quality in Bangladesh

Soil acidity is one of the major soil-degradation events throughout the world, and the long-term application of nitrogenous fertilizers is thought to be a main cause of soil acidity. In the present experiment, we collected soil and tea (Camellia sinensis L.) leaf samples from five representative tea gardens in Bangladesh and evaluated soil nutrient pools and biochemical properties of tea leaves. The results showed that there was a negative relationship between soil pH and the amount of applied nitrogenous fertilizers. Moreover, continuous application of traditional fertilizers over twenty-five years promoted not only the deficiency of phosphorus (P) and mineral-based cations, such as potassium (K+), calcium (Ca2+), and magnesium (Mg2+), but also increased manganese (Mn2+) and aluminum (Al3+) toxicity in soils, which suppressed the yield and quality of tea. Crucially, tea leaf production remained almost similar (average 1079.77 kg ha−1) from 1995 to 2015, while the application doses of urea, TSP, and MoP increased by 24.69%, 18.92%, and 16.67%, respectively, in garden soils. However, the pH value of soil declined up to 24% from 1992 to 2020 in the tested gardens. Consequently, the availability of K+, P, Ca2+, and Mg2+ decreased by 56%, 25%, 55%, and 49%, respectively, in those tea garden soils. In addition, the quality of tea leaves was severely affected, as evident by the reduced levels of total flavonoids, polyphenols, soluble solids, vitamin C, vitamin B1, and vitamin B2. Moreover, free-radical scavenging activity (DPPH), caffeine, and tannin concentration were increased in tea leaves, which indicated that tea plants were potentially being stressed. Therefore, we study concluded that long-term application of traditional nitrogenous fertilizers can be an important regulator of lowering garden soil pH, which reduces native soil nutrient pools and thereby the yield and quality of tea leaves.

Increasing the Contents of Paddy Soil Available Nutrients and Crop Yield via Optimization of Nitrogen Management in a Wheat-Rice Rotation System.

To explore the impact of nitrogen (N) rate during the wheat season and N fertilizer management during the rice season on carbon and soil nutrient pools in paddy soil, a wheat–rice rotation system for 2 successive years was implemented. In the rotation system, a conventional N rate (Nc; 150 kg/ha) and a reduced N rate (Nr; 120 kg/ha) were applied in the wheat season. Based on an application rate of 150 kg/hm2 N in the rice season, three N management models were applied, in which the application ratio of base:tiller:panicle fertilizer was 20%:20%:60% in treatment M1, 30%:30%:40% in treatment M2, and 40%:40%:20% in treatment M3. Zero N was used as the control (M0). Experimental results indicate that, under Nc, the M2 management model during the rice season, improvements were seen in paddy soil urease, organic carbon, and annual yield relative to other conditions. The average organic matter and total N associated with the M2 rice management model and conventional N application during the wheat season were 5.13% and 4.95% higher, respectively, relative to the use of a reduced N application rate during the wheat season. Similarly, the average total carbon content and annual yields were 6.61% and 5.56% higher under the model M2 with conventional N application during the wheat season, respectively, relative to reduced N application after the two-year study period. These findings indicate that production and carbon fixation in paddy fields can be optimized through a conventional N application rate during the wheat season, and an M2 N management model during the rice season in southern China under a wheat–rice rotation system.