盐碱地柽柳“盐岛”和“肥岛”效应及其碳氮磷生态化学计量学特征

Soil pH and electrical conductivity (EC) are two major chemical properties affecting nutrient availability and rice grain yield. Therefore, this study was conducted to investigate the variation of pH and EC in the topsoil layer (0-15 cm) of rice fields as affected by major water source used for rice cultivation, rice-based cropping system adopted and rice growing soil orders in different agro-climatic zones (ACZs) in Sri Lanka. A total of 998 soil samples were collected from lowland rice fields. Both pH and EC were measured in 1:5 soil: water extracts. The pH of soil samples was in the range of 3.0-7.7 with a mean value of 5.0. Moreover, 75% of the soil samples had pH values below the optimum range for rice cultivation (5.5-7.0). Values of pH observed in Dry Zone soils were higher (5.2) than those in Wet Zone (4.4). Soil EC values ranged between 1.0 - 3,100 μScm−1 with a mean value of 148.5 μScm−1. Soil EC was similar among climatic zones (P>0.05). Upcountry Intermediate zone recorded the highest soil EC than that in other ACZs (P<0.05). Moreover, 73%, 22%, 3%, 2% and 0.1% of soil samples recorded EC values in the ranges of less than 150 (non-saline), 150-400 (slightly saline), 400-800 (moderately saline), 800-2000 (highly saline) and more than 2000 (very highly saline) μScm−1, respectively. Considering micro (e.g. paddy track) and macro (e.g. ACZ) scale spatial heterogeneity in soil pH and EC, appropriate site-specific strategies need to be adopted to improve soil pH and EC to suit sustainable rice crop production.

Conversion of coastal mudflats to agricultural soil is one of the most important land use practices in Eastern China. However, effects of soil profile and reclamation time on soil microbial community, which play an important role in soil nutrient cycling, are still poorly documented. Soil profile (0–15 cm, 15–30 cm, 30–45 cm) samples were collected from four sites with different reclamation ages (R12: 12 years, R38: 38 years, R68: 68 years, R100: 100 years) in Rudong County, Nantong, Jiangsu, China. Soil bacterial communities were determined via Illumina 16S rRNA gene high-throughput sequencing. Soil electrical conductivity (EC) responded more rapidly to reclamation time than soil pH. Soil total carbon and nitrogen increased with increasing reclamation age. Soil available nutrients (ammonium, nitrate, dissolved organic carbon, and available phosphorus) were affected by the agricultural practice and did not show a unanimous tendency between different reclaimed sites. Proteobacteria, Acidobacteriota, and Bacteroidota dominated the bacterial community across different sites and soil profiles. However, Methylomirabilota- and Nitrospirota-associated species, which are involved in nitrogen cycling, increased with increasing soil depth. Canonical correspondence analysis (CCA) showed that bacterial community was grouped by soil depth and also significantly affected by soil pH, EC, and reclaimed time. Moreover, co-occurrence network analysis showed a potential role of low abundant phyla besides dominant phyla in stabilizing the bacterial community, and the connection between soil properties and bacterial amplicon sequence variant (ASV) numbers would shift along soil profiles. Reclamation time of the coastal mudflats is not the only reason for the shift of bacterial community. Here, we found soil profile had a strong influence on soil bacterial composition in the coastal reclaimed wheat-maize rotation soils.

This study aimed to elucidate the response of soil microbial communities to saline soil amelioration via biological organic fertilizer. A year-long experiment was conducted on coastal saline soil, employing water and fertilizer strategies. Three treatments were compared: dry field (control, CK), paddy field (W), and combined dry and irrigated fields with biological organic fertilizer (BW). Soil DNA was extracted and sequenced using high-throughput methods, revealing significant reductions in soil electrical conductivity (EC) and pH with W and BW treatments. Moreover, the BW treatment notably increased soil organic carbon content by 17.2%, as well as soil urease and alkaline phosphatase activity. Fungal community richness increased, with the BW treatment showing a 36% rise in the ACE index and a 24% increase in the Shannon index, while the Simpson index decreased by 59%. Dominant fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota, with Basidiomycota prevailing at the genus level. Redundancy analysis (RDA) indicated that soil pH, EC, and organic carbon were key determinants of fungal community distribution, with the BW treatment correlating negatively with pH and salt and positively with soil organic carbon (SOC). Fungal functional groups varied among treatments, with saprophytic fungi predominating, but the BW treatment showed a higher relative abundance of animal pathogenic fungi. In summary, the integration of biological organic fertilizer with flooding ameliorates soil properties and influences the changes in soil fungal community structure and function in the short term. These results could enhance the scientific basis for the efficient utilization and development of saline soil resources in coastal areas.

Land use conversion on river plain has profound impacts on soil characteristics and elemental stoichiometry. Four wetland types (Riparian lower‐beach wetland [RLW], Riparian higher‐beach wetland [RHW], Cultivated wetland [CW] and Mesophytic wetland [MW]) were selected in the lower Yellow River area to investigate the consequence of wetland type conversion on soil carbon (C), nitrogen (N) and phosphorus (P) stoichiometry. The results demonstrated that wetland conversion induced significant spatio‐temporal variations in soil C, N and P stoichiometry and physicochemical characteristics in soil. Frequent agricultural activities (fertilizer input) raised the nutrient content of natural wetland, particularly in surface soil (0–30 cm). Soil volumetric water content (VWC), soil bulk density (SBD), pH and soil enzyme activity varied significantly in different wetlands. Total carbon (TC) and total nitrogen (TN) contents in MW decreased with increasing soil depth (<40 cm layers), as did TN and total phosphorus (TP) contents in CW. On the other hand, TC, TN and TP contents in RLW and RHW did not change significantly with soil depth. However, the contents of TOC, and Fe/Al‐P, etc., varied among soil layers and among wetland types. Furthermore, the stoichiometric characteristics changed significantly in some soil layers, with mean values being less than the Chinese average. Statistically, significant positive correlations were determined between TC and TN ( r = .56), TDC and TP ( r = .62), N:P and pH ( r = .57) ( p < .05) and and pH ( r = .66, p < .01). VWC was negatively correlated with pH ( r = −.56, p < .05), while C/P was negatively associated with soil temperature (ST) and SBD ( r = −.55, r = −.64, p < .05). TDC, IP, TN, Fe/Al‐P and ST were identified as the dominant factors, with the percentage of variance 41%, 20%, 12%, 9% and 6% respectively. These findings have a great scientific significance for the ecological conservation of wetlands in the lower Yellow River area.

The study’s specific objective is to identify prospective cashew nut (Anacardium occidentale) producing areas in the Bankura district based on soil availability and land suitability in red and lateritic soil. The index of crop suitability (ICS) analysis was carried out utilizing the Fuzzy-analytical hierarchy process (F-AHP) approach and 16 geo-environmental variables such as soil texture, soil organic carbon (OC), Soil electrical conductivity (EC), soil pH, slope, rainfall, etc. The criteria were also developed following FAO's crop suitability index for the distinction between S (suitable) and N (unsuitable) order. According to the cashew suitability class, 9.24% of cashew growth regions can be categorised as highly suitable, 34.57% as moderately suitable, and 19.59% as marginally suitable. The F-AHP weight shows the important factors of cashew cultivation that are soil OC and EC. The results demonstrate that cashew production is more beneficial in the red and lateritic soil.

To understand how the soil microbial community structure responds to vegetation restoration in alpine mining areas, this study specifically examines the grassland ecosystem in the Qianmalong mining area of the Qilian Mountains after five years of artificial restoration. High-throughput sequencing methods were employed to analyze soil bacteria and fungi microbial characteristics in diverse grassland communities. Combined with modifications in vegetation diversity as well as soil physicochemical properties, the impact of vegetation restoration on soil microbiome diversity in this alpine mining area was investigated. The findings indicated that the dominant plants were Cyperus rotundus, Carex spp., and Elymus nutans. As the extent of the grassland's restoration increased, the number of plant species, importance values, and plant community diversity showed an increasing trend. The plant functional groups were mainly dominated by Cyperaceae, followed by Poaceae. Plant height, density, plant cover, frequency, and aboveground biomass showed an increasing trend, and soil water content (SWC) increased. While soil pH and soil electrical conductivity (EC) exhibited a declining trend, available phosphorus (AP), total phosphorus (TP), total nitrogen (TN), nitrate nitrogen (NO3-N), soil organic carbon (SOC), and soil water content (SWC) showed an increasing trend. The dominant bacterial communities were Actinobacteriota, Proteobacteria, Acidobacteriota, Chloroflexi, Firmicutes, and Gemmatimonadota, while the dominant fungal communities were Ascomycota, Mortierellomycota, Basidiomycota, unclassified_k_Fungi, and Glomeromycota. Significant differences were detected within soil microbial community composition among different degrees of restoration grasslands, with bacteria generally dominating over fungi. SWC, TP, and TN were found to be the main soil physicochemical factors affecting the distribution of soil bacterial communities' structure; however, SOC, TN, and NO3-N were the primary factors influencing the soil distribution of fungal communities. The results of this study indicate that different degrees of vegetation restoration in alpine mining areas can significantly affect soil bacterial and fungal communities, and the degree of restoration has varying effects on the soil bacteria and fungi community structure in alpine mining areas.

Spatial and seasonal distribution of carbon, nitrogen, phosphorus, and sulfur and their ecological stoichiometry in wetland soils along a water and salt gradient in the Yellow River Delta, China

In order to explore different forest types effects on soil chemical properties, four stand types, namely pure Cunninghamia lanceolata forest, pure Cryptomeria fortunei forest, pure Liriodendron chinense forest and Cryptomeria fortune × Phoebe zhennan mixed forest, were selected as the research objects, and the difference of soil chemical properties and the organic contents of different forest types were analyzed by variance analysis. The results showed that there were significant differences in soil pH, available potassium, total phosphorus, total potassium and total nitrogen among different forest types, but there were no significant differences in available phosphorus, alkali-hydrolyzable nitrogen, and soil organic matter. The soil pH value of the four forest stands was between 4.02 and 5.33, which was acidic, and increased with the increase of soil depth. The contents of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable and available phosphorus in different forests types all decreased with the increase of the soil depth. The 0~10cm total phosphorus content of soil in four different forest stands was higher than that of 10~20 cm. The soil total potassium content of pure C. lanceolata forest, pure C. fortunei forest and pure L. chinense forest all fluctuated up and down with the increase of the soil depth, while the content of C. fortune × P. zhennan mixed forest increased gradually. The contents of soil alkali-hydrolyzable nitrogen and available phosphorus in soil of four forest stands all decreased with the increase of soil depth. The soil available potassium content of pure C. lanceolata forest and pure C. fortunei forest increased first and then decreased, while that of pure L. chinense forest and C. fortune × P. zhennan mixed forest increased gradually. The average phosphorus supply intensity of the four stands at the soil layer of 0~10cm, 10~20cm, 20~40cm and 40~60cm was 2.64%, 2.71%, 2.57% and 2.61%, respectively. Soil K supply intensity of pure L. chinense forest and C. fortunei × P. zhennan mixed forest increased with the increase of soil layer, while that of pure C. fortunei forest first increased and then decreased.

A pedological characterization of hilly soils developed on basement complex terrain was carried in Minna, Niger State, Nigeria. The site was delineated into three physiographic units (positions) and designated as summit, shoulder and foot slope. Two modal profile pits were excavated in each unit to permissible depths, giving a total of six (6) profiles. The soil samples were analysed in the laboratory following standard analytical procedures. Particle size analysis showed dominance of sand over other mineral fractions irrespective of the physiographic units. Silt was next to sand in dominance and clay particle was the least in particle size. Bulk density increased with increasing soil depth in all the physiographic positions while porosity decreased down the profiles. Soil reaction (pH) ranged from moderately acid to slightly acidic in all the terrains. Organic carbon, total nitrogen and available P decreased with the increased in soil depth in all the landforms. Calcium and Magnesium were moderate while Potassium rated high in the sampled soils. The mean Na in the sampled soils rated low to moderate. Cation Exchange Capacity (CEC) in the soils rated moderate while percentage base saturation (BS) rated high. The soils are non- sodic and the electrical conductivity (EC) values are low. Thesoils of summit and shoulder were classified as Typic Paleustalfs while the footslope soils were classified as Typic Paleudalfs. The soils were classified as Plinthosols when correlated with WRB for soil resource.

A farm's soil moisture and soil electrical conductivity (EC)readings are extremely valuable for a farmer. They can help her reduce water use and improve productivity. However, the high cost of commercial soil moisture sensors and the inaccuracy of sub-1000 dollar EC sensors have limited their adoption. In this paper, we present the design and implementation of a system, called Strobe, that senses soil moisture and soil EC using RF propagation in existing Wi-Fi bands. Strobe overcomes the key challenge of limited bandwidth availability in the 2.4 GHz unlicensed spectrum using a novel multi-antenna technique. It maps the propagation time and amplitude of Wi-Fi signals received by different antennas to the soil permittivity and EC, which in turn depend on soil moisture and salinity. Our experiments with USRP, WARP, and commodity Wi-Fi cards show that Strobe can accurately estimate soil moisture and EC using Wi-Fi, thereby showing the potential of a future where a farmer can sense soil in their farm without investing 1000s of dollars in sensing tools.

Desiccation of the Aral Sea left a vast area of unstable, saline, and barren seafloor. In response, afforestation using indigenous trees, mainly Haloxylon species, has been performed to ameliorate the soil. This study examined 1) changes in topsoil chemical properties after vegetation establishment based on 30-year chronosequence of afforested sites and 2) dynamics in the topsoil properties in two cases of naturally vegetated versus afforested areas. In August 2019, soils were sampled from the northeastern Aral Sea bed, Kazakhstan, where the shoreline retreated during the 1970s. We selected a non-saline area without any vegetation, a visibly salinized area without any natural vegetation, and 12 paired sites with predominantly sandy soil texture that were naturally vegetated or afforested during 1990, 2000, 2005, 2008, 2013, and 2017. In the 0‒10 cm soil layer, 3 points were sampled in each site and we analyzed soil pH, electrical conductivity (EC), total dissolved solids (TDS), exchangeable sodium percentage (ESP), total nitrogen (TN) and carbon (TC), total organic carbon (TOC), available phosphorus concentration (P2O5), exchangeable cation concentrations (K+, Mg2+, Ca2+, and Na+), and cation exchange capacity (CEC). The soil samples in chronosequence sites showed a wide range of EC, without any significant temporal trend. The pH ranged between 8.5 and 10.0, characterized soil as alkaline. CEC ranged from 9 to 45 cmolc kg-1. Soil pH, EC, and TDS variations among the chronosequence sites (natural or afforested) were not statistically significant. In contrast, we observed marginal increases in K+ and P2O5 after the vegetation establishment. Also, TN and TOC concentrations increased over time, significantly faster in afforested than in naturally vegetated sites. However, TC contents showed a sudden decrease in the oldest natural vegetation. This result may be partly attributed to the spatial variability in sampling locations used for the chronosequence analysis. Lastly, there were strong positive correlations among TOC, TN, K+, and P2O5; which imply an increase in soil organic materials’ contribution to nutrient accumulation and overall soil quality. In conclusion, afforestation contributed to soil amelioration but this effect was also observed in naturally vegetated sites.

Ecological stoichiometry is an important index that reflects the element cycle and ecosystem stability. In this study, two sites (sunny and shady slopes) and five forest ages (young stage, half-mature stage, near-mature stage, mature stage, and over-mature stage) in a Pinus tabuliformis plantation were chosen to illustrate the effects of forest ages and site conditions on the biomass and stoichiometric characteristics of leaves and soils in the temperate mountainous area of China. Except for young stage, the biomass of the leaves of P. tabuliformis on sunny slopes were higher than those on shady slopes in other forest ages, the average carbon content of the leaves in sunny slopes was higher than that in shady slope, while the average total nitrogen contents and average total phosphorus contents of the leaves showed the opposite of this. The biomass of leaves increased on sunny slopes, and increased first and then decreased in shady slopes with increasing forest ages. The contents of soil total carbon (STC) and soil total nitrogen (STN) decreased with increasing soil depth, while the soil total phosphorus (STP) and soil available phosphorus (SAP) contents displayed the opposite. In addition to SAP, the average content of STC, STN, and STP in shady slopes was higher than that in sunny slopes, and the ratio was the opposite. Except for STC: STN on shady slopes, the other ratios showed a downward trend with an increase in soil depth. Excluding the topsoil, the change trend of STC : STP and STN : STP in shady slopes and sunny slopes was consistent with forest ages. The results showed that forest ages and site conditions had significant effects on leaf biomass. The biomass of the leaves is mainly limited by nitrogen. These results have important significance in improving the refinement of local forestry management of Pinus tabuliformis plantations in the temperate mountainous area of China.

The accurate monitoring of soil salinization plays a key role in the ecological security and sustainable agricultural development of semiarid regions. The objective of this study was to achieve the best estimation of electrical conductivity variables from salt-affected soils in a south Mediterranean region using Sentinel-2 multispectral imagery. In order to realize this goal, a test was carried out using electrical conductivity (EC) data collected in central Tunisia. Soil electrical conductivity and leaf electrical conductivity were measured in an olive orchard over two growing seasons and under three irrigation treatments. Firstly, selected spectral salinity, chlorophyll, water, and vegetation indices were tested over the experimental area to estimate both soil and leaf EC using Sentinel-2 imagery on the Google Earth Engine platform. Subsequently, estimation models of soil and leaf EC were calibrated by employing machine learning (ML) techniques using 12 spectral bands of Sentinel-2 images. The prediction accuracy of the EC estimation was assessed by using k-fold cross-validation and computing statistical metrics. The results of the study revealed that machine learning algorithms, together with multispectral data, could advance the mapping and monitoring of soil and leaf electrical conductivity.

A global meta-analysis of the effects of irrigation with water containing salts on saline-alkali soils

Shrub-induced spatial heterogeneity of soil and hydrological properties are common in arid and semi-arid ecosystems. To examine the influence of shrubs on spatial patterns of soil physical, chemical and hydrological properties, the typical sand-fixation species, Caragana korshinskii, was studied in the Shapotou area of the Tengger Desert, China. Miniature cylinder infiltrometers were used to quantify the spatial variations of infiltration rate in the soils, and were installed at 20-cm intervals around the shrubs. Meanwhile, soil samples were collected at 0–5 cm depth every 10 cm to analyse their physical and chemical properties and soil moisture content. The results indicate that the various measured parameters showed a gradational change from sub-canopy to open space. The establishment of shrubs formed obvious “fertile islands” where more soil nutrients collected. The total nitrogen (TN), soil organic matter (SOM), electrical conductivity (EC) and surface soil moisture content decreased gradually from around shrub stems to the interspace. The sand content around shrub stems was significantly higher (p < 0.05), and decreased gradually from the centre towards the outside microsites. The silt and clay contents showed opposite variability characteristics. The variation of soil bulk density was less within 140 cm distance from the stem, and no abrupt change was found at the shrub’s drip line. No significant tendency was found for the soil pH values. The steady infiltration rates declined with increasing stem distance and then tended to be stable, and no abrupt change occurred at the position of the overhead canopy margin. The increase of infiltration rate was rapid nearer to the stem; the variability trend can be fitted by a log-log (power function) model. This study indicated the gradational change in soil and hydrological properties, which was not consistent with the binary division of shrubs into “canopy” and “interspace” zones.Editor Z.W. Kundzewicz