Soil Organic Matter Levels Research Articles

Using pack animals instead of tractors in Central Italy's protected areas: No evidence of reduced soil disturbance

In thinning operations in Mediterranean beech forests, pack animals are often used when topographic conditions do not allow for the use of mechanisation to perform logging operations. Otherwise, mechanised extraction is the primary choice. In an effort to reduce soil disturbance caused by mechanised ground-based logging, the forest authorities who guard protected areas have been mandating animal logging at all logging sites in recent years. Since no comparative scientific trials of soil disturbance of these two extraction systems have ever been conducted in the target setting, there is no scientific evidence to sustain this approach. On this basis, we chose two study areas where the forest authorities mandated animal logging. Each study area consists of three sub-compartments, one unharvested, one harvested by animals, and one harvested by tractor in the same year (2021). We examined soil compaction, soil organic matter, and soil microarthropod biodiversity in animal skid trails, tractor skid trails, soil unaffected by extraction methods, and unharvested control sites in each study areas. We used linear mixed-effects models, indicating the study area as random intercept, to investigate the effect of the experimental treatments on the target soil features, and to check the relationship among soil physico-chemical parameters and soil microarthropod biodiversity. We discovered that only the animal and tractor skid trails showed signs of disturbance in terms of soil compaction and organic matter loss. Additionally, there was a significant decline in the biodiversity of soil microarthropods in both the skid trail types, with values of the QBS-ar index which were practically halved in comparison to the control area. We did not find any significant difference in the values in the tractor and animal skid trails for any of the examined soil characteristics. Low soil microarthropod biodiversity was found to be correlated with high soil compaction in terms of penetration resistance and low soil organic matter levels, according to linear mixed-effects models. Despite our preliminary findings, we made it clear that the short wood system by a tractor fitted with forwarding bins is unquestionably a very soil-disturbing extraction system, that ought to be avoided when conducting logging operations in protected areas. However, pack animals are not a suitable solution to reduce soil disturbance. Other extraction systems such as chute, small-scale cable yarders, as well as combination of animals and machine avoiding extensive traffic on the forest soil, are better solutions to the fundamental issue of low-impact logging in protected areas.

Analysis of Physicochemical Properties, Enzyme Activity, Microbial Diversity in Rhizosphere Soil of Coconut (Cocos nucifera L.) Under Organic and Chemical Fertilizers, Irrigation Conditions

The application of chemical fertilizers and organic fertilizers, as well as irrigation, is an important agricultural practice that can increase crop yields and affect soil biogeochemical cycles. This study conducted coconut field experiments to investigate the effects of conventional fertilization (NCF), optimized fertilization (MCF), conventional fertilization + organic fertilizer (NOF), optimized fertilization + organic fertilizer (MOF), conventional fertilization + organic fertilizer + irrigation (NOFW), and optimized fertilization + organic fertilizer + irrigation (MOFW) treatments on soil physicochemical properties, soil enzyme activity, bacterial and fungal community structure and diversity, and compared the controls (CK, non-fertilizer and non-irrigation). The results showed that MOFW significantly increased soil electrical conductivity (EC), organic matter (OM), alkaline nitrogen (AN), available phosphorus (AP), available potassium (AK), available calcium (ACa), and available magnesium (AMg) levels. At the same time, it also significantly enhanced the activities of soil catalase (CE), polyphenol oxidase (POE), sucrase (SE), urease (UE), acid protease (APE), and acid phosphatase (APPE) (p < 0.05). The PCA analysis of soil microorganisms in the coconut rhizosphere soil showed indicated significant changes in bacteria and fungi community structure under fertilization treatments. The fertilization application leaded to an increase in the relative abundance and diversity of bacteria, but a decrease in fungi. Acidobacteriota, Proteobacteria, and Actinobacterota were the dominant bacterial phyla, and Ascomycota, Basidiomycota, Rozellomycota, and Mortierellomycota were the significant fungal phyla. Compared with CK, MOFW significantly increased the abundance of Acidobacteriota, Proteobacteria, Basidiomycota, and Mortierellomycota. Redundancy analysis (CCA) and Mantel test further revealed that pH, EC, OM, and AP were the main soil fertility factors driving changes in microbial communities. CE, SE, UE, APE, APPE were significantly correlated with microbial communities. Compared with NOFW, MOFW has a lower proportion of N, P, and K fertilizers in its fertilizer composition. The results indicated that MOFW can better improve the nutrient and enzyme status of the soil, which is a promising method for maintaining the balance of soil microorganisms in coconut orchards, and accordingly, reducing chemical fertilizers within a certain range can not only ensure consistency with conventional fertilizers, but also effectively improve soil conditions.

Effect of Some Ecological Factors on Earthworms (Lumbercus terrestris) in Wasit Governorate

Monthly earthworm samples were collected from two locations in Suwairah City‎ of Wasit Governorate. where the first location was northwest of the district and is characterized by an abundance of citrus trees such as orange, lemon and Punica granatum as well as many palm trees of different types, the second area is characterized by an abundance of vegetable plants like Cauliflower, Allium cepa, and Brassica oleracea. Soil temperature, moisture, pH, texture and organic matter levels were measured at all sample sites. Soil temperature ranged between 11C° to 50C° as recorded during February and August respectively. The values of PH have ranged between 6.8 to 8.0. Soil moisture and Organic matter content were highest in Region (B) samples, 40% and 6.6% respectively. However, lowest organic matter and soil moisture percentage were 17% and 3.13% recorded at in Region (A) samples respectively. All sites were characterized by loamy acidic reactive soils.

Effects of Compost Application of Green Waste on Soil Properties: A Meta-Analysis

Objective: With the accelerating urbanization process, the garden area is gradually expanding, and the production of green waste is also increasing. Composting green waste can not only reduce environmental pollution caused by incineration and landfill and improve the utilization efficiency of resources but also improve the soil and increase soil productivity. The study aims to investigate the comprehensive impact of green waste compost (GWC) application on soil nutrient conditions. Through comprehensive data analysis, the impact of compost application of green waste on soil properties was revealed as a reference for compost application and fertilizer reduction. Methods: Based on meta-analysis, we quantitatively investigated the response of soil properties to the application of green waste, collected published experimental data, and integrated 25 domestic and international literature to analyze the effects of different soil properties on soil nutrients. Literature was used to analyze the impact of different application rates of GWC on the physicochemical properties of soils with varying pH levels. The results were compared to control conditions with no GWC application. Results: The application of significantly improved soil quality by reducing soil bulk density and increasing the levels of soil organic matter, organic carbon, total nitrogen, available phosphorus, available potassium, and dehydrogenase activity. The increases in available potassium and soil organic carbon were consistently significant across all subgroups. However, the effects on available phosphorus and organic matter varied in significance depending on initial soil pH. Soil bulk density was influenced by the GWC content, while dehydrogenase activity showed significant effects only when initial soil pH was ≥8. Total nitrogen levels were significantly impacted by GWC application in soil with an initial pH of <8 and at GWC contents of ≥50%. Conclusion: The application of green waste compost demonstrates a positive effect on soil improvement. This study provides a comprehensive database that supports the use of GWC in enhancing soil quality and reducing the need for chemical fertilizers.

Effects of aerial liming on soil chemical and biological properties in metal contaminated and inaccessible lands in Ontario (Canada).

The manual addition of lime to soil, in addition to tree planting and fertilization have been the dominant strategy described in restoration protocols for ecosystems damaged by acid rain and metal contamination. Investigations on aerial-limed soils in inaccessible lands are limited. The objective of this study was to assess the effects of aerial liming on soil pH, organic matter, microbial biomass, and enzymatic activities, and aboveground plant population quality in metal-contaminated lands in northern Ontario, Canada. Soil samples were collected from three sites around the City of Greater Sudbury with each pair being composed of a reclaimed (areal-limed) site and an adjacent undisturbed (unlimed) area. Soil physico-chemistry, microbial biomass (assessed by Phospholipid fatty acid analysis) and enzymatic activities were analyzed. Soil pH was higher in limed sites compared to unlimed at recently restored sites (Baby Lake and Wahnapitae) but not at the oldest reclaimed site (HWY 80 N). Organic matter was higher in limed areas compared to the unlimed reference site only at most recently reclaimed site at Baby Lake. Aboveground plant population health was visibly improved in limed sites compared to unlimed areas. Metal concentrations of iron (Fe) and arsenic (As), total microbial biomasses, gram-negative bacterial, fungal, and eukaryotic biomasses were all significantly increased in the limed soils compared to the unlimed samples. The same trend was observed for the activities of three of the enzymes tested, β-N-acetylglucosaminidase (BG), aryl sulfatase (AS), and glycine aminopeptidase (GAP). Interestingly, strong positive correlations between the levels of soil organic matter, microbial biomasses, and NAGase and ALP activities were observed. Although expensive, aerial liming is effective in restoring inaccessible sites impacted by smelting operations where other methods cannot easily be used.

A Review of the Current Status of Soil Organic Matter in China's Arable Land

Soil organic matter (SOM) in China's arable land is a critical foundation for maintaining agricultural productivity and ecosystem health. However, in recent years, the content of SOM has shown a declining trend due to unsustainable agricultural practices, excessive use of chemical fertilizers, and land degradation. This decline has adversely affected soil fertility, water retention capacity, biodiversity, and carbon sequestration. Although certain regions have seen improvements through the application of organic fertilizers, straw return, and conservation tillage, the overall SOM levels remain low. Therefore, there is an urgent need to develop comprehensive management strategies to increase SOM content, promote sustainable agricultural development, and protect the ecological environment.

Exchangeable acidity characteristics of farmland black soil in northeast China

Exchangeable aluminum (Exc-Al), an often overlooked yet indispensable soil parameter, predominantly contributes to soil exchangeable acidity. In this study, we utilized data from 53 sets of surface and subsurface black soil characteristics, including Exc-Al, exchangeable acid (Exc-acid), pH, soil organic matter (SOM), and available and total nutrient levels, to develop a neural network prediction model for estimating Exc-Al and Exc-acid in the black soil area of northeast China. The deterministic neural network model (NNM) was employed to predict Exc-Al and Exc-acid contents in 690 sets of surface and subsurface farmland soil samples with unknown Exc-Al and Exc-acid values. Subsequently, a black soil exchangeable acidity map for northeast China was generated through spatial interpolation. Our results revealed that the average Exc-Al and Exc-acid contents in the 53 surface soils were 0.82 and 0.93 cmol kg−1, respectively, while those in the corresponding subsurface soils were 0.58 and 0.70 cmol kg−1, respectively. Multi-layer perceptron (MLP) neural networks effectively simulated Exc-Al and Exc-acid contents in the surface and subsurface black soils, with calibrated determination coefficients (Radj2) of 0.95–0.96, relative root mean square errors (rRMSE) of 17.3%–24.8%, and statistical significance α at 0.001. The MLP estimations and spatial interpolations revealed that 2.0% and 17.6% of the surface black soil area, and 0% and 3.7% of the subsurface soil area exhibited Exc-Al content exceeding 2.0 and 1.0 cmol kg−1, respectively. Furthermore, 6.7% and 24.9% of the surface black soil area, and 0% and 6.3% of the subsurface soil area showed Exc-acid content exceeding 2.0 and 1.0 cmol kg−1, respectively. These findings break the limitation of relying solely on soil pH as the unique indicator, enrich our knowledge of black soil exchangeable acidity, and enhance our understanding of the black soil acidity status in northeast China.

Soil Fertility Dynamics and Identify the Most Limiting Nutrients Affecting Walnut Productivity in Nepal

This study aimed to assess the soil nutrient status in walnut orchards of different ages in Jajarkot district, Nepal, to understand soil fertility dynamics and identify the most limiting nutrients affecting walnut productivity. The research employed a randomized complete block design (RCBD) with three treatments representing different age groups of walnut orchards (1-5 years, 6-10 years, and 11-15 years), each replicated seven times across various municipalities. The study was conducted in Jajarkot district, Karnali Province, Nepal, encompassing municipalities including Nalgad, Junichadey, and Barekot, from March to April 2023. Soil samples were collected from multiple depths (1, 2, and 3 feet) in each orchard and analyzed for pH, soil organic matter (SOM), total nitrogen, available phosphorus, and available potassium. Data analysis included descriptive statistics, one-way analysis of variance (ANOVA), and correlation analyses to explore relationships between soil parameters and orchard age. The study showed that significant variations were observed among different age groups of walnut orchards for soil pH, SOM, nitrogen, phosphorus, and potassium levels. Soil pH decreased with orchard age, while SOM, nitrogen, and phosphorus tended to increase with orchard age. Phosphorus was identified as the most limiting nutrient across all sampled soils, followed by nitrogen and potassium. Moreover, strong correlations were found between orchard age and soil N (r = 0.894, p < 0.01) and P (r = 0.776, p < 0.01), underscoring age-dependent nutrient dynamics. The study highlights the critical role of orchard age in shaping soil nutrient dynamics in walnut orchards. Older orchards exhibited higher levels of SOM, nitrogen, and phosphorus, indicating the accumulation of organic matter and nutrients over time. Phosphorus emerged as the primary limiting nutrient, essential for root growth, flowering, and fruiting in walnut trees. These findings underscore the importance of targeted fertilization strategies to optimize soil fertility and sustain long-term walnut productivity in the region.

The critical role of organic matter for cadmium-lead interactions in soil: Mechanisms and risks

Understanding the interaction mechanisms between complex heavy metals and soil components is a prerequisite for effectively forecasting the mobility and availability of contaminants in soils. Soil organic matter (SOM), with its diverse functional groups, has long been a focal point of research interest. In this study, four soils with manipulated levels of SOM, cadmium (Cd) and lead (Pb) were subjected to a 90-day incubation experiment. The competitive interactions between Cd and Pb in soils were investigated using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray adsorption near-edge structure (XANES) analysis. Our results indicate that Pb competed with Cd for adsorption sites on the surface of SOM, particularly on carboxyl and hydroxyl functional groups. Approximately 22.6 % of Cd adsorption sites on humus were occupied by Pb. The use of sequentially extracted exchangeable heavy metals as indicators for environment risk assessments, considering variations in soil physico-chemical properties and synergistic or antagonistic effects between contaminants, provides a better estimation of metal bioavailability and its potential impacts. Integrating comprehensive contamination characterization of heavy metal interactions with the soil organic phase is an important advancement to assess the environmental risks of heavy metal dynamics in soil compared to individual contamination assessments.

Priming and balance of soil organic carbon differ with additive C:N ratios and long-term green manuring

The input of organic C strongly alters the magnitude and direction of the microbial mineralization of soil organic matter (SOM), a phenomenon known as the “priming effect” (PE). The C:N ratios of additives are expected to affect the intensity of PE as it balances the C and N requirements of microbial growth. Growing of green manure (GM) crops in agricultural system strongly regulates PE intensity as it enhances the level and stability of SOM. However, the driving factors of additive C:N ratios and long-term GM crops on PE remain unclear. We addressed this knowledge gap by performing a 92-day incubation of 10-year summer fallow-wheat and GM-wheat soils by adding mixtures of 13C-labelled glucose and ammonium sulfate differing in the C:N ratio (15 vs. 50). The PE was increased by 148–288 % due to the high C:N ratio of the added mixtures, indicating that the quality of input exerted effects on the PE across the two soils. The PE of green manured (GMd) soil was increased by 23 % (p < 0.05) compared with that of summer fallow soil, as microorganisms produce extracellular enzymes such as β-glucosidase and leucine aminopeptidase to co-metabolize SOM. Nevertheless, compared with the summer fallow soil, 26 % more glucose-C was sequestered in GMd soil to compensate for C loss. We propose a conceptual model of “N mining” and “co-metabolism” to explain the effect of additive C:N ratio on PE in the soils under different GM practices. The “N mining” is the main cause of PE when the additive C:N ratio is high, and the “co-metabolism” becomes the dominant factor in long-term GMd soil with high SOM content and stability. Our findings demonstrate the importance of long-term incorporation of GM-driven changes in organic C inputs and SOM content and stability in regulating PE and soil C dynamics. Understanding the C dynamics under long-term GM practices contributes to formulate optimized agricultural strategies for promoting C sequestration and accurately predict soil C dynamics in the future.

Field study on the integration of a hydrogen-producing microbiome in restoring Phellinus noxius-affected rhizosphere

At National Kaohsiung University of Science and Technology (NKUST), a mesophilic anaerobic bioreactor system produces a hydrogen-producing microbiome (HMb) containing beneficial bacteria such as Bacillus sp. This HMb, known for degrading cellulose and remediating soil, is being tested in Kaohsiung City, Taiwan, to treat tree root rot caused by Phellinus noxius (P. noxius). The study aims to evaluate HMb's effectiveness in restoring the rhizosphere, enhancing soil health, and increasing tree resistance by assessing soil bioactivity and microbial diversity.Field experiments showed that HMb treatment improved tree health by 24 % at the highest health level but reduced it by 20 % at the next level. Post-treatment soil organic matter (SOM) and total Kjeldahl nitrogen (TKN) levels remained stable, indicating minimal impact on soil fertility. HMb also lowered soil pH in some plots, potentially suppressing pathogens and enhancing nutrient absorption. The study found that HMb increased microbial diversity in the rhizosphere, particularly Acidobacteria and Proteobacteria, which inhibited fungal growth. However, HMb had no significant impact on P. noxius populations. Overall, HMb treatment shows promise in enhancing plant health by improving microbial diversity and soil conditions, but further research is needed to understand its full impact on pathogen suppression and soil health restoration.

Implication of the root growth and soil macropores distribution on sugarcane yield in Takalar, Indonesia

This study examined the relationship between the decline in sugarcane productivity and the distribution of macropores and depth of root penetration in sugarcane plantations in Takalar during one planting period (October 2021-September 2022). There were five observation points (P1, P2, P3, P4, and P5) in one hectare of land to measure the distribution of soil macropores using methylene blue solution. Cross-sections of the soil were made to observe the presence of plant roots at a depth of 0-40 cm with a width of 60 cm. In each plot, disturbed soil samples were collected to measure soil texture, soil organic matter (SOM), nitrogen (N), phosphorus (P), and potassium (K) contents. Other measurement parameters were the infiltration rate and plant productivity. The results indicated that SOM and NPK levels at the research location were deficient, serving as the first indicators of problematic soil. Macropore observations revealed that macropores were distributed only at a less than 10 cm soil depth. This distribution limited the penetration of plant roots to a depth of 0-40 cm. The root length density (RLD) value indicated the absence of roots at depths of 30-40 cm in plots P2 and P3. The field findings explained why sugarcane production in Takalar only achieved 50%, around 40 t ha-1 from the first ratoon sugarcane harvest, instead of the expected 70-80 t ha-1.

Advancing Agricultural Sustainability: Smart Monitoring of Oil Palm Seedlings Through Innovative Image Processing Techniques

Good oil palm seedlings planted in Malaysia can enhance the nursery area, the economy, and rural employment. Nitrogen (N), potassium (K), \and magnesium (Mg) deficiencies in oil palm seedlings could have an adverse effect on growth and seedling quality. In contrast, excess fertiliser in oil palm seedlings could reduce macronutrients and soil organic matter levels. Moreover, various diseases appear on the oil palm seedling leaves resulting from nutrient deficiencies. Oil palm seedlings with nutrient deficiencies were more susceptible to pathogens and diseases than healthy oil palm seedlings. Thus, image processing made it possible to quickly and accurately control oil palm seedlings' growth and avoid diseases. In this research study, image processing was proposed to classify nutrient deficiencies in oil palm seedling leaves subjected to the three different fertiliser rates. The dataset for this research study was collected from a nursery and consisted of 868 images classified into four classes (Healthy, Nitrogen, Potassium and Magnesium). According to the experiment's findings, the Xception model achieved the highest percentage of classification accuracy, 98.60%, within a short time. It can be concluded that the proposed implementation of image processing for the classification of nutrient deficiencies in oil palm seedling leaves was effective. However, more datasets could be added in the future to achieve a better balance and enhance classification performance.

Alternative Cover Crops and Soil Management Practices Modified the Macronutrients, Enzymes Activities, and Soil Microbial Diversity of Rainfed Olive Orchards (cv. Chetoui) under Mediterranean Conditions in Tunisia

In Tunisia, the olive is the most cultivated fruit crop in the northern region, where annual rainfall exceeds 400 mm. This olive-growing area is characterized by a wide coverage of marginal soil with a high slope gradient. Therefore, the inclusion of cover crops in olive orchards is a sustainable solution to enhance ecosystem productivity, improve soil fertility, and increase oil yields. This study aimed to investigate the short-term (two cropping seasons in 2021 and 2022) effects of different seeded cover crops and soil management practices on soil characteristics, as well as soil health by measuring soil enzyme activities and microbial diversity. Six cover crop types consisting of wheat, vetch, oat, fenugreek, a vetch–oat mixture, and spontaneous vegetation were tested in association with rainfed olive trees (cv. Chetoui) in the north of Tunisia and compared to a control (which was tilled periodically three times per year without intercropping). During the first cropping season, cover crops were cut as animal feed, and only residues were incorporated into the soil. However, during the second year, all cover crop biomass was incorporated into the soil. The results indicated that the dry biomass production and carbon uptake were significantly higher in grass species (wheat and oat). All of the cover crops, including the spontaneous vegetation, significantly increased soil organic matter (SOM) and macronutrient levels, mainly, available phosphorus. On the other hand, the highest level of soil nitrogen was found in the fenugreek cover crop. The soil enzyme activities in the cover crops of wheat, oat, and the vetch–oat mix were higher than those in the control. Together with the increase in soil organic matter (SOM), this demonstrates a significant improvement in soil health with cover crops. Furthermore, this study proves that the utilization of carbon sources was dominated by amides, amines, and amino acids in the fenugreek plot, while it was dominated by polymers and carboxylic acids in the case of the wheat and oat. Overall, this study demonstrates that seeding cover crops is a sustainable management practice not only to integrate livestock but also to improve soil health in semiarid olive orchards.

Effect of Zero Tillage on Soil Properties, Weed Dynamics and Performance of Chickpea under Rice –Chickpea Cropping System: A Review

In many nations across the world, farming is an important industry. Sustainable farming methods known as zero tillage systems entail planting seeds without tillage, which disturbs the soil. With this approach, crop residues from the previous year are left on the earth's surface and new plants are planted straight into the undisturbed soil, as opposed to plowing. This method aids in preserving the structure of the soil, decreasing soil erosion, retaining more water, and enhancing soil health. Farmers can benefit from enhanced soil health, decreased soil erosion, higher crop yields, and environmental sustainability by implementing sustainable farming practices. By limiting soil disturbance and shielding soil particles from the elements, this system aids in the reduction of soil erosion. Additionally contributes to improved soil structure, which raises soil fertility, and helps hold onto soil moisture, which lessens the need for irrigation. The amount of tillage and fuel used in zero-tillage systems can be less than in conventional tillage methods. In comparison to traditional tillage methods, systems require less fuel and tillage, which can save farmers money and lessen their carbon footprint. This is true because these systems raise soil organic matter levels, which in turn raise soil nutrient availability and improve soil fertility. Moreover, zero tillage systems can increase water retention in the soil, which can enhances crop growth and yield by improving soil structure and moisture retention, while also reducing weed competition. By reducing soil erosion, conserving soil moisture, and improving soil health, these systems help to promote environmental sustainability. Also reduce greenhouse gas emissions by reducing fuel usage and sequester carbon in the soil through the accumulation of crop residues. Therefore, farmers should adopt zero-tillage systems to enhance their productivity, reduce costs, and promote environmental sustainability.

Soil organic matter and total nitrogen as key driving factors promoting the assessment of acid-base buffering characteristics in a tea (Camellia sinensis) plantation habitat.

The issue of soil acidification in tea plantations has become a critical concern due to its potential impact on tea quality and plant health. Understanding the factors contributing to soil acidification is essential for implementing effective soil management strategies in tea-growing regions. In this study, a field study was conducted to investigate the effects of tea plantations on soil acidification and the associated acid-base buffering capacity (pHBC). We assessed acidification, pHBC, nutrient concentrations, and cation contents in the top 0-20cm layer of soil across forty tea gardens of varying stand ages (0-5, 5-10, 10-20, and 20-40years old) in Anji County, Zhejiang Province, China. The results revealed evident soil acidification due to tea plantation activities, with the lowest soil pH observed in tea gardens aged 10-20 and 20-40years. Higher levels of soil organic matter (SOM), total nitrogen (TN), Olsen phosphorus (Olsen-P), available iron (Fe), and exchangeable hydrogen (H+) were notably recorded in 10-20 and 20-40years old tea garden soils, suggesting an increased risk of soil acidification with prolonged tea cultivation. Furthermore, prolonged tea cultivation correlated with increased pHBC, which amplified with tea stand ages. The investigation of the relationship between soil pHBC and various parameters highlighted significant influences from soil pH, SOM, cation exchange capacity, TN, available potassium, Olsen-P, exchangeable acids (including H+ and aluminum), available Fe, and available zinc. Consequently, these findings underscore a substantial risk of soil acidification in tea gardens within the monitored region, with SOM and TN content being key driving factors influencing pHBC.

Utilizing the Fusion Characteristics of Multispectral and Electronic Noses to Detect Soil Main Nutrient Content

Soil nutrients are essential for plant growth, and it is crucial to accurately detect their levels. However, current methods for detecting soil nutrients still have low accuracy and high costs. In this study, we propose a multi-source fusion feature approach that combines multispectral image technology with electronic nose gas response technology to achieve rapid, high-precision, and cost-effective detection of soil nutrients, including soil organic matter (SOM), total nitrogen (TN), available potassium (AK), and available phosphorus (AP). To begin, a multispectral camera was used to collect spectral images and extract seven index features. Additionally, an electronic nose was used to collect soil pyrolysis gases to obtain the response curve and extract seven response features. These two sets of features were effectively fused to form a 106 × 98 fusion feature space. Secondly, principal component analysis (PCA) and Pearson correlation coefficient (PCC) algorithms were used to optimize and reduce the dimensionality of the fused feature space. Finally, a predictive model of the relationship between the feature space and the nutrient content of the soil samples was established using the random forest (RF) and partial least squares regression (PLSR) algorithms. The predictive performance of the model was used to evaluate the accuracy of soil nutrient detection. The results showed that the PLSR modeling of the optimized feature space of PCA achieved high accuracy in predicting the levels of main soil nutrients, with R2 values for SOM, TN, AK, and AP of 0.96, 0.95, 0.84, and 0.73, and the RMSE values of 0.56, 0.07, 3.21, and 3.70, respectively. Compared to using only electronic nose gas response technology, the soil nutrient detection with multi-source data features method in this study not only improved the accuracy for SOM and TN but also for metal elements AK and AP in soil. The spectral index features proposed in this study were able to compensate for the limitations of the electronic nose response features, and modeling with the fusion feature space resulted in an accurate prediction of SOM, TN, AK, and AP levels.

Effects of Intercropping and Nitrogen Application on Soil Fertility and Microbial Communities in Peanut Rhizosphere Soil

The intercropping of peanuts and sugarcane is a sustainable planting model that deserves in-depth research. For this study, two variables, i.e., intercropping status (peanut monocropping or sugarcane/peanut intercropping) and the level of nitrogen fertilization (low, medium, or high), were evaluated to analyze the effects of intercropping and nitrogen application on soil fertility and microbial communities in peanut rhizosphere soil. These analyses revealed that higher nitrogen application led to increased total nitrogen (TN), available nitrogen (AN), and soil organic matter (OM) levels in rhizosphere soil for both monocropped and intercropped peanuts, with a decrease in pH. Monocropped peanuts had higher TN, total phosphorus (TP), and total potassium (TK) levels compared to intercropped peanuts at the same nitrogen level but lower AN content and pH levels. The diversity of microbial communities in the rhizosphere soil of intercropped peanuts was significantly higher than that of monocropped peanuts under high levels of nitrogen fertilizer application. Higher levels of Gemmatimonadetes abundance were observed in intercropping rhizosphere soil, compared to that associated with peanut monocropping under low, middle, and high levels of nitrogen fertilizer application, whereas the opposite trend was observed for Chloroflexi abundance. Nitrospira abundance levels rose gradually in the monocropping treatment group, whereas the opposite trend was evident under intercropping conditions. Further analyses of nitrogen cycle-related genes demonstrated higher levels of nitrogen conversion cycle activity in intercropping peanut rhizosphere soil under low nitrogen levels, whereas nitrogen transformation cycle activity levels were higher in monocropping peanut rhizosphere soil under high levels of nitrogen amendment. It can be concluded that intercropping and nitrogen fertilizer application change the physical and chemical properties of soil, thus affecting the diversity and function of soil microbial communities in the peanut rhizosphere. These results offer a theoretical foundation for more efficient sugarcane/peanut intercropping systems.

Understanding vermicompost and organic manure interactions: impact on toxic elements, nitrification activity, comammox Nitrospira inopinata, and archaea/bacteria.

Vermicompost is a substantial source of nutrients, promotes soil fertility, and maintains or increases soil organic matter levels. Potentially toxic elements (PTEs) in vermicompost impact on nitrification activity. However, it is yet unknown how vermicompost affects nitrifying bacteria and archaea, comammox Nitrospira inopinata (complete ammonia oxidizers), net nitrification rates (NNRs), and PTEs. The effects of vermicompost application on NNRs, potential nitrification rates (NPs), PTEs, and the abundances of comammox N. inopinata bacteria, nitrite-oxidizing bacteria (NOB), and ammonia-oxidizing bacteria (AOB)/archaea (AOA) were studied. NNRs and NPs were significantly higher (p < 0.05) in fresh cow-dung vermicompost (stored for 40days) as compared with other organic manure. The level of PTEs (Cu2+, Fe2+, Pb2+, Cd2+, and Zn2+) was significantly lower (p < 0.05) in vermicompost as compared with compost of waste material with Trichoderma and cow dung. Comammox N. inopinata, NOB, AOB, and AOA were significantly higher (p < 0.05) in stored cow-dung vermicompost (more than 1year) as compared with other organic manure. The results of the scatterplot matrix analysis suggested that Fe2+, total nitrogen (TN), soil organic carbon (SOC), and total carbon (TC) were linearly correlated (p < 0.001) with NNRs and NPs in vermicompost and organic manure. Similarly, comammox N. inopinata bacteria, NOB, AOB, and AOA were linearly correlated (p < 0.001) with NNR and NP. These results indicated that vermicompost promoted nitrification activity by increasing microbial diversity and abundance, supplying nutrients and organic matter for microbial growth, and facilitating complex microbial interactions. It may be concluded that the influence of vermicompost, which played a great role in PTE concentration reduction, increased chemical, and biological properties, increased the growth rate of nitrifying bacteria/archaea and the nitrogen cycle.

Determinants of organic soil fertilization methods use over time and in the face of climate vulnerability

Implementation of environment-friendly soil organic matter (SOM) enhancing technologies (SOMET) is crucial for addressing soil degradation. This study aims to examine the usage status of SOMET (i.e., organic fertilizer, manure, and compost) from the dimension of long-term non-usage, dis-usage, late-usage and long-term usage and identify the drivers of these four behaviors of usage. We utilized national representative datasets of 1659 Bangladeshi rice-farmers for the periods of 2013, 2016 and 2020 with climate hazards data. Households were categorized into long-term non-user (48%) who does not practice SOMET in any of three survey years, dis-user (29%) as the households who abandon SOMET after practicing a period of time, late-user (20%) for the households who apply SOMET a few years later than their peer, long-term user (3%) as the households who practice SOMET for three survey years. Ordered logit model was used to quantify drivers of likelihood of being the four above defined categories. SOMET use has been found to be highly constrained by climate hazards. Flood depth, salinity, heavy rainfall, storm and cyclone vulnerability decrease likelihood of long-term use and late-use while increase the probability of long-term non-use and dis-use (p≤0.01). Alternatively, the likelihood of long-term non-use and dis-use are 12% and 4% lower in drought-prone areas. Increasing drought experiences increase the probability of long-term use and late-use (p≤0.01). Higher SOM level decreases long-term non-use but induces dis-use. Other major drivers of SOMET long-term use are older household head, more educated women in households, larger farm-size, and higher livestock values. Considering these factors in developing and implementing policies could be instrumental in promoting SOMET application at farm-level. Long-term use is context-specific with various climate and socio-economic factors, thus, designing policies and strategies should emphasize contextual variations to promote usage continuities.