Soil Development Research Articles

Forest catchment structure mediates shallow subsurface flow and soil base cation fluxes

Hydrologic behavior and soil properties across forested landscapes with complex topography exhibit high variability. The interaction of groundwater with spatially distinct soils produces and transports solutes across catchments, however, the spatiotemporal relationships between groundwater dynamics and soil solute fluxes are difficult to directly evaluate. While whole-catchment export of solutes by shallow subsurface flow represents an integration of soil environments and conditions but many studies compartmentalize soil solute fluxes as hillslope vs. riparian, deep vs. shallow, or as individual soil horizon contributions. This potentially obscures and underestimates the hillslope variation and magnitude of solute fluxes and soil development across the landscape. This study determined the spatial variation and of shallow soil base cation fluxes associated with weathering reactions (Ca, Mg, and Na), soil elemental depletion, and soil saturation dynamics in upland soils within a small, forested watershed at the Hubbard Brook Experimental Forest, NH. Base cation fluxes were calculated using a combination of ion-exchange resins placed in shallow groundwater wells (0.3 – 1 m depth) located across hillslope transects (ridges to lower backslopes) and measurements of groundwater levels. Groundwater levels were also used to create metrics of annual soil saturation. Base cation fluxes were positively correlated with soil saturation frequency and were greatest in soil profiles where primary minerals were most depleted of base cations (i.e., highly weathered). Spatial differences in soil saturation across the catchment were strongly related to topographic properties of the upslope drainage area and are interpreted to result from spatial variations in transient groundwater dynamics. Results from this work suggest that the structure of a catchment defines the spatial architecture of base cation fluxes, likely reflecting the mediation of subsurface stormflow dynamics on soil development. Furthermore, this work highlights the importance of further compartmentalizing solute fluxes along hillslopes, where certain areas may disproportionately contribute solutes to the whole catchment. Refining catchment controls on base cation generation and transport could be an important tool for opening the black box of catchment elemental cycling.

Mitigation of heavy metal toxicity in pigeon pea by plant growth promoting Pseudomonas alcaliphila strain PAS1 isolated from contaminated environment.

The risk of arsenic contamination is rising globally, and it has negative impacts on the physiological processes and growth of plants. Metal removal from contaminated soils can be accomplished affordably and effectively with plant growth promoting rhizobacteria (PGPR)-based microbial management. From this angle, this research evaluated the mitigation of arsenic toxicity using the bacteria isolated from contaminated site, Mettur, Salem district, South India. The newly isolated bacterial strain was screened for plant growth promotion potential and arsenic tolerance such as (100ppm, 250ppm, 500ppm, 800ppm and 1200ppm). The metal tolerant rhizobacteria was identified using 16S rRNA gene sequence analysis as Pseudomonas alcaliphila strain PAS1 (GenBank accession number: OQ804624). Pigeon pea (Cajanus cajan) plants were used in pot culture experiments with varying concentrations of arsenic, (5ppm, 10ppm and 25ppm) both with and without bacterial culture, for a period of 45days. At the concentration of 25ppm after the application of PAS1 enhanced the plant growth, protein and carbohydrate by 35.69%, 18.31% respectively. Interestingly, P. alcaliphila strain PAS1 significantly reduced the stress-induced elevated levels of proline, flavonoid, phenol and antioxidant enzyme in pigeon pea plants was 40%, 31.11%, 27.80% and 20.12%, respectively. Consequently, PAS1 may significantly reduce the adverse effects that arsenic causes to plant development in acidic soils, improve plant uptake of nutrients, and increase plant production. The findings of this study reveal that P. alcaliphila PAS1 is intrinsic for phytoremediation by reducing arsenic accumulation in the root and shoot.

Soil moisture content estimation of drip-irrigated citrus orchard based on UAV images and machine learning algorithm in Southwest China

Soil moisture content (SMC), as a pivotal component in the energy and matter exchange processes within the soil-plant-atmosphere continuum, plays a crucial role in surface water dynamics, energy fluxes, and carbon cycling within ecosystems. The development of remote sensing technology has offered new perspectives for monitoring soil moisture at regional scales. Unmanned aerial vehicles (UAV) equip with multispectral have distinct advantages for vegetation monitoring, including rapidity and cost-effectiveness, which has superior applicability and practicality. Therefore, in a 5a "Daya" late-maturing citrus orchard, the vegetation index (VI) and texture feature (TF) information of citrus canopy based on UAV multi-spectral images were extracted, and soil and plant analyzer development (SPAD) of citrus was collected. These different data sources were integrated into the framework of the random forest algorithm (RF) and genetic algorithm-optimized random forest (GA-RF) to evaluate the accuracy of surface SMC (SSMC) estimation in citrus orchard. The Biswas model was utilized to simulate the root zone SMC (RSMC). The spatiotemporal variations of SMC in citrus orchard were analyzed, and the potential of low-cost sensor-equipped drones in rapidly acquiring spatial and temporal distribution information of SMC at a large regional scale was explored. The results indicated that the GA-RF models outperformed the RF models in estimating citrus orchard SMC (with R2 ranging from 0.502 to 0.949 and RMSE ranging from 0.552 % to 3.166 % for GA-RF, compared to R2 ranging from 0.430 to 0.936 and RMSE ranging from 0.587 % to 3.449 % for the RF). The GA-RF models using VI+SPAD as inputs exhibited the best performance for SMC at depths of 5 cm, 10 cm, 20 cm and 40 cm (SMC5, SMC10, SMC20 and SMC40) across citrus growth stages (R2 ranging from 0.793 to 0.949 at 5 cm, R2 ranging from 0.702 to 0.938 at 10 cm, R2 ranging from 0.714 to 0.927 at 20 cm). In bud bust to flowering, young fruit and fruit maturation stages (stage Ⅰ, ⅠⅠ and ⅠⅤ), all models demonstrated good accuracy in estimating SMC at depth of 10 cm (R2 ranging from 0.567 to 0.908 in stage Ⅰ, with R2 ranging from 0.681 to 0.916 in stage ⅠⅠ and R2 ranging from 0.579 to 0.938 in stage ⅠⅤ). In fruit expansion stage (stage III), the models performed best in predicting SMC5 (R2 ranging from 0.698 to 0.861). The Biswas model was constructed to simulate SMC40 by utilizing the inverted SMC10 and SMC20, thereby generating spatiotemporal distribution maps of SMC at different depths in citrus orchard. The SSMC was susceptible to environmental factors, exhibiting significant spatiotemporal heterogeneity. In summary, this study illustrated that the integration of multiple data sources into GA-RF enhanced the estimation performance of SMC at different growth stages of late-maturing citrus orchard in the Southwest China. Additionally, it enabled the rapid and efficient monitoring of spatiotemporal variations in SMC, providing an effective method and practical foundation for precision irrigation and improved water use efficiency.

Impact of urea nutrition on soil and plant chemical variables and development of Mexican lime

Impact of urea nutrition on soil and plant chemical variables and development of Mexican lime

Phosphorus dynamics across a 450 ka vertical chronosequence of loess derived (paleo)soils in central US

Pedogenesis entails profound changes in terrestrial phosphorus (P) dynamics, yet means to understand how time- and climate-induced soil weathering impacts P-cycling over geologic timescales remain relatively limited to space-for-time substitution approaches with multi-site chronosequences. We tested an alternative approach for evaluating terrestrial P dynamics described by the Walker-Syers model by measuring P pools in a ~ 450 ka loess–paleosol sequence. This vertical chronosequence reflects episodic proglacial loess deposition during multiple glaciations and interglacial soil development in central North America in a four-stage loess–paleosol sequence that initiated with the pre-Illinois Episode glaciation. Changes in P pools estimated by sequential fractionation aligned with the Walker-Syers P model for interglacial periods but not glacial periods, possibly reflecting limited soil weathering in cooler and drier conditions of the latter. Total P decreased from 797 to 328 mg/kg with depth and was higher in paleosols than underlying loess parent materials. During glacial periods, primary P increased due to loess deposition and decreased during interglacial periods concomitantly with increased non-occluded and occluded secondary P pools, the extent of which reflected differences in weathering environments of paleoclimatic conditions and loess accumulation rates. That P fractions reflected the Walker-Syers model demonstrates that single-site vertical chronosequences have potential for evaluating long-term soil P dynamics.

Characteristics of Bacterial Community Structure and Function in Artificial Soil Prepared Using Red Mud and Phosphogypsum.

The preparation of artificial soil is a potential cooperative resource utilization scheme for red mud and phosphogypsum on a large scale, with a low cost and simple operation. The characteristics of the bacterial community structure and function in three artificial soils were systematically studied for the first time. Relatively rich bacterial communities were formed in the artificial soils, with relatively high abundances of bacterial phyla (e.g., Cyanobacteria, Proteobacteria, Actinobacteriota, and Chloroflexi) and bacterial genera (e.g., Microcoleus_PCC-7113, Rheinheimera, and Egicoccus), which can play key roles in various nutrient transformations, resistance to saline-alkali stress and pollutant toxicity, the enhancement of various soil enzyme activities, and the ecosystem construction of artificial soil. There were diverse bacterial functions (e.g., photoautotrophy, chemoheterotrophy, aromatic compound degradation, fermentation, nitrate reduction, cellulolysis, nitrogen fixation, etc.), indicating the possibility of various bacteria-dominated biochemical reactions in the artificial soil, which can significantly enrich the nutrient cycling and energy flow and enhance the fertility of the artificial soil and the activity of the soil life. The bacterial communities in the different artificial soils were generally correlated with major physicochemical factors (e.g., pH, OM, TN, AN, and AP), as well as enzyme activity factors (e.g., S-UE, S-SC, S-AKP, S-CAT, and S-AP), which comprehensively illustrates the complexity of the interaction between bacterial communities and environmental factors in artificial soils, and which may affect the succession direction of bacterial communities, the quality of the artificial soil environment, and the speed and direction of the development and maturity of the artificial soil. This study provides an important scientific basis for the synergistic soilization of two typical industrial solid wastes, red mud and phosphogypsum, specifically for the microbial mechanism, for the further evolution and development of artificial soil prepared using red mud and phosphogypsum.

Bio-control of soil-borne virus infection by seed application of Glycyrrhiza glabra extract and the rhamnolipid Rhapynal

Main conclusionSeed-application of the natural products protects sugar beet and wheat plants against infection with plasmodiophorid-transmitted viruses and thus may represent an efficient, environmentally friendly, easy and cost effective biocontrol strategy.In times of intensive agriculture, resource shortening and climate change, alternative, more sustainable and eco-friendly plant protection strategies are required. Here, we tested the potential of the natural plant substances Glycyrrhiza glabra leaf extract (GE) and the rhamnolipid Rhapynal (Rha) applied to seeds to protect against infection of sugar beet and wheat with soil-borne plant viruses. The soil-borne Polymyxa betae- and Polymyxa graminis-transmitted viruses cause extensive crop losses in agriculture and efficient control strategies are missing. We show that GE and Rha both efficiently protect plants against infection with soil-borne viruses in sugar beet and wheat when applied to seeds. Moreover, the antiviral protection effect is independent of the cultivar used. No protection against Polymyxa sp. was observed after seed treatment with the bio-substances at our analysis time points. However, when we applied the bio-substances directly to soil a significant anti-Polymyxa graminis effect was obtained in roots of barley plants grown in the soil as well as in the treated soil. Despite germination can be affected by high concentrations of the substances, a range of antiviral protection conditions with no effect on germination were identified. Seed-treatment with the bio-substances did not negatively affect plant growth and development in virus-containing soil, but was rather beneficial for plant growth. We conclude that seed treatment with GE and Rha may represent an efficient, ecologically friendly, non-toxic, easy to apply and cost efficient biocontrol measure against soil-borne virus infection in plants.

Holocene landscape transformation of lake basins of Central Mexico based on volcanic soil development: a first exploratory study from micromorphology to magnetic mineralogy

Holocene landscape transformation of lake basins of Central Mexico based on volcanic soil development: a first exploratory study from micromorphology to magnetic mineralogy

Precariously Balanced Rocks in Northern New York and Vermont, U.S.A.: Ground-Motion Constraints and Implications for Fault Sources

ABSTRACT Precariously balanced rocks (PBRs) and other fragile geologic features have the potential to constrain the maximum intensity of earthquake ground shaking over millennia. Such constraints may be particularly useful in the eastern United States (U.S.), where few earthquake-source faults are reliably identified, and moderate earthquakes can be felt at great distances due to low seismic attenuation. We describe five PBRs in northern New York and Vermont—a region of elevated seismic hazard associated with historical seismicity. These boulders appear to be among the most fragile PBRs in the region, based on reports from hobbyists. The PBRs are glacial erratics, best evidenced by glacial striations on bedrock pedestals. The pedestals themselves are locally high knobs, often situated on regionally high topography; this setting limits soil development and indicates that any outwash deposits were likely ephemeral. As a result, PBR ages can be reliably established by the retreat of the last continental ice sheet, ∼15–13 ka. To quantify the fragility of the PBRs, we surveyed them with ground-based light detection and ranging and calculated geometric parameters from the point clouds, field observations, and seismic responses. Preliminary validation of the 2023 time-independent U.S. National Seismic Hazard Model (NSHM) shows that the existence of PBRs is generally consistent with the median site-specific hazard curves. Only the Blue Ridge Road site suggests a modest reduction in hazard. To visualize the ensemble of data, we mapped the minimum permissible distance to potential source faults around each PBR site as a function of source magnitude by using the ground-motion models from the 2023 NSHM. Viewed in this manner, our data are consistent with potential M∼6.5 earthquake-source faults in many parts of the Lake Champlain Valley and northern Adirondack Mountains. Our work illustrates a potential pathway for better constraining earthquake-source faults in regions of cryptic faults.

Establishment of Nitrogen-Fixing Frankia, Arbuscular Mycorrhizal Fungi, and Their Effects on Alder (Alnus glutinosa L.) Growth in Post-Mining Heap Soils

Planting nitrogen-fixing plants in post-mining sites and similar degraded areas is a common approach to speed up soil development and buildup of the nitrogen pool in soil organic matter. The aim of this study was to explore if slower growth of alder seedlings in initial post-mining sites results from adverse soil conditions or lack of microbial symbionts. To address this question, we sampled young soil (age 15 years) and more developed soil (age 70 years) from heaps after coal mining near Sokolov (Czech Republic). Soil samples were sterilized and not inoculated or inoculated with arbuscular mycorrhizal fungi (AMF) or AMF + Frankia, followed by planting with alder (Alnus glutinosa) seedlings germinated and precultured under sterile conditions. The effect of soil age on alder growth appeared to be non-significant. The only significant growth effect was seen with Frankia inoculation, implicating this inoculum as a key factor in later succession in post-mining soils. When the soil was fully inoculated, alder biomass was higher in developed soil supplied with iron (Fe) and phosphorus (P), indicating that iron and phosphorus availability may affect alder growth. In young soil, alder growth was highest with a combination of iron, phosphorus, and sulfur (S), and a positive effect of sulfur in young soil may correspond with a reduced, alkaline soil pH and increased phosphorus and iron availability.

Addressing Soil Acidity Challenges: Promoting Tea Production as Alternative Crop in Ethiopia -- Review

The prevalence of acidic soils in Ethiopia presents a significant obstacle to improving agricultural productivity and restricts the implementation of sustainable farming practices that could enhance food security. Acidic soils are typically defined by their high concentration of hydrogen ions and a lack of essential nutrients, which collectively create an environment that is less conducive to the growth of many vital staple crops. Consequently, farmers faced with these conditions often struggle to achieve optimal yields, which exacerbates food scarcity and undermines economic stability. To effectively combat the issues posed by acidic soils, it is imperative to adopt targeted soil management strategies that are specifically designed to address these challenges. This may include the implementation of soil reclamation techniques that aim to neutralize soil acidity and restore nutrient balance. Additionally, comprehensive initiatives must be undertaken to promote agricultural resilience, which could involve the cultivation of alternative crops that are better suited to thrive in acidic conditions, such as tea. This paper aims to provide a thorough examination of several key aspects related to the development and management of acidic soils in Ethiopia. It will investigate into the processes that contribute to the formation of acid soils, as well as the various types of acid soil present in the country, explore the distribution of acidic soils throughout Ethiopia, highlighting areas that are particularly affected and the implications for local farming practices. Furthermore, the analysis will address the specific impact of soil acidity on crop growth, yield, and quality. It will investigate how soil acidity influences the availability of essential nutrients for plants, thereby affecting the overall health and productivity of crops grown in these conditions. The promotion of tea production in Ethiopia is another critical topic that tea cultivation not only offers a viable alternative crop but also presents opportunities for economic development and diversification in agricultural systems. The mechanisms that confer aluminum resistance in tea plants will be discussed, as well as the ways in which aluminum can stimulate growth in these crops, thereby illustrating the unique resilience of tea plants in acidic environments. By addressing these complex issues holistically, the paper seeks to contribute valuable insights and foster a deeper understanding of how to navigate the challenges posed by acidic soils in the Ethiopian agricultural landscape.

Soil Genesis of Alluvial Parent Material in the Qinghai Lake Basin (NE Qinghai–Tibet Plateau) Revealed Using Optically Stimulated Luminescence Dating

Alluvial parent material soil is an important soil type found on the Qinghai–Tibet Plateau (QTP) in China. However, due to the limited age data for alluvial soils, the relationship between alluvial geomorphological processes and soil pedogenic processes remains unclear. In this study, three representative alluvial parent material profiles on the Buha River alluvial plain in the Qinghai Lake Basin, northeast QTP, were analyzed using the optical luminescence (OSL) dating method. Combined with physical and chemical analyses of the soil, we further analyzed the pedogenic process of alluvial soil. The alluvial parent material of the Buha alluvial plain predominately yielded ages between 11.9 and 9.1 ka, indicating that the alluvial soil began to form during the early Holocene. The development of the alluvial soil on the first-order terrace presents characteristics of entisol with multiple burial episodes, mainly between 8.5 and 4.0 ka, responding to the warm and humid middle Holocene and high lake levels.

Microscopic Mechanisms and Evolution Models of Crack Development in an Expansive Soil under Conditions of Rainfall Evaporation Cycles

Expansive soil is a special soil type that undergoes volume expansion during hygroscopicity and volume contraction during dehumidification. In this study, the effects of rainfall–evaporation cycles on the microscopic pores and cracks of expansive soils under different rainfall intensities were analyzed by simulating light rainfall, medium rainfall, and high-temperature drought environments using nuclear magnetic resonance (NMR) technology and image processing methods. The results showed that the micropores and small medium pores of the expanded soil gradually evolved into macropores during the cycling process, especially under stronger rainfall conditions. In addition, as the number of cycles increased, the expanded soil showed irrecoverable pore changes, which ultimately led to the scattering damage of the soil. By processing the surface crack images of expansive soils, the process of crack development was categorized into four stages, and it was found that the evaporation cycle of medium rainfall intensity caused the main cracks of expansive soils to develop more rapidly. A quantitative relationship model between the average crack width and the number of cycles as well as porosity was constructed, and the regression coefficient of determination R2 reached 0.98, 0.96, and 0.84, respectively. This study simulates the effects of real rainfall conditions on expansive soils and investigates the mechanism and evolution of cracks in expansive soils, which is of great theoretical and practical significance.

Simultaneously predicting SPAD and water content in rice leaves using hyperspectral imaging with deep multi-task regression and transfer component analysis.

Water content and chlorophyll content are important indicators for monitoring rice growth status. Simultaneous detection of water content and chlorophyll content is of significance. Different varieties of rice show differences in phenotype, resulting in the difficulties of establishing a universal model. In this study, hyperspectral imaging was used to detect the Soil and Plant Analyzer Development (SPAD) values and water content of fresh rice leaves of three rice varieties (Jiahua 1, Xiushui 121 and Xiushui 134). Both partial least squares regression and convolutional neural networks were used to establish single-task and multi-task models. Transfer component analysis (TCA) was used as transfer learning to learn the common features to achieve an approximate identical distribution between any two varieties. Single-task and multi-task models were also built using the features of the source domain, and these models were applied to the target domain. These results indicated that for models of each rice variety the prediction accuracy of most multi-task models was close to that of single-task models. As for TCA, the results showed that the single-task model achieved good performance for all transfer learning tasks. Compared with the original model, good and differentiated results were obtained for the models using features learned by TCA for both the source domain and target domain. The multi-task models could be constructed to predict SPAD values and water content simultaneously and then transferred to another rice variety, which could improve the efficiency of model construction and realize rapid detection of rice growth indicators. © 2024 Society of Chemical Industry.

Mitigation of soil salinity by addition of different rice straw biochar doses in salt-affected acid soil

The current study was carried out to evaluate the effect of rice straw biochar amendment and to identify the appropriate dose of biochar application to reduce soil acidity, salinity, toxicity, and sodicity in salt-affected acid soils. The rice straw biochar at 4 different rates of 0%, (control) 1%, 3%, and 5% (w/w) was mixed with 6 salt-affected acid soils: S1 (non-saline), S2 and S3 (low saline), and S4, S5, and S6 (moderate saline). The mixture was continuously shaken in distilled water for 7 days. The biochar application significantly increased soil pH and saturated electrical conductivity (ECe) with an increasing biochar application rate compared with the control. Significant decreases in sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) values below the critical level of sodicity were observed above the biochar application rate of 1%. Soluble chloride (Cl–) and soluble and exchangeable sodium (Na+) were significantly reduced above the biochar application rate of 1%. The biochar application (≥ 1%) led to a significant increase in soluble and exchangeable potassium (K+) and declines in soluble and exchangeable calcium (Ca2+) and magnesium (Mg2+). This study concluded that the biochar application rate of 1% was suitable for reducing soil acidity to a safe level for rice plants. The rice straw biochar application improved soil toxicity and sodicity by reducing soluble Cl– and soluble and exchangeable Na+, decreasing SAR and ESP. The biochar application also increased available K+, essential for rice plant growth and development in salt-affected soils.

Rock outcrops as interglacial refugia for plants: Ecological evidence from the forest‐steppe transition of Patagonia

AbstractIn the forest‐steppe transition of Patagonia from Argentina, the intense physical variability promotes the occurrence of contrasting vegetation units, among which is the saxicolous meadow developed on rock outcrops. In temperate and tropical regions, these geoforms of highly variable climate and topography, and poor soil development play an ecological and evolutionary role disproportionate to their reduced area. In Aguas Frías (38°46′S, 70°54′W), the range, diversity, density and adaptation of vascular plant species growing in the saxicolous meadow were compared to those of the surrounding steppe, forest and hygrophilous meadow. We hypothesize that rock outcrops exhibit a compositionally and functionally divergent, cold‐adapted flora of a previously more widespread distribution, allowing them to be categorized as refugia for species whose range retreated during the current interglacial. In comparison to the other units, the saxicolous meadow exhibited a small area, low plant cover, high total, native and rare species richness, high density and diversity of species, high richness of unique families and species and an exclusive presence of (rock) ferns. It also presented a high richness of endemic species with more extreme latitudinal and altitudinal distribution, particularly >46° S and >3000 m a.s.l. The similarity of species between the saxicolous meadow and the other units was low. Chamaephytes and nanophanerophytes were dominants, hemicryptophytes and geophytes were infrequent and mesophanerophytes and therophytes were absent. Equivalent results in terms of area of rock outcrops, and origin, strategy, composition, diversity and range of species were found in different regions. The biological and physical attributes would allow these outcrops to be characterized as reduced habitats of high diversity which could be acting as refugia for cold‐adapted plants. Conservation actions must prevent and mitigate the effects of fire, biological invasion and cattle grazing that represent the current threats to this ecosystem.

An Evaluation of Soil Development in Relation to Topography Over Sandstone Parent Material

An Evaluation of Soil Development in Relation to Topography Over Sandstone Parent Material

Effect of Almond Residue Soil Amendments and Irrigation Regiment on Organic Acid Development and Transport in Soil

Effect of Almond Residue Soil Amendments and Irrigation Regiment on Organic Acid Development and Transport in Soil

Impact of Bio-Organic Fertilizer Incorporation on Soil Nutrients, Enzymatic Activity, and Microbial Community in Wheat–Maize Rotation System

Excessive use of inorganic fertilizers disrupts soil nutrient balance and leads to soil degradation and a decrease in biodiversity. In contrast, bio-fertilizers enhance soil structure and fertility and promote plant growth and sustainable agriculture development. Therefore, this study focused on a rotation system of winter wheat and summer maize and aimed to explore the effects of applying chemical fertilizer (NPK) and bio-fertilizer (BF) in the winter wheat season on the sustainable soil development of current wheat and subsequent maize. Before sowing winter wheat four fertilization treatments were, respectively CK (100% NPK at 750 kg ha−1), A (60% NPK at 450 + 20% BF at 150 kg ha−1), B (60% NPK at 450 + 40% BF at 300 kg ha−1), and C (60% NPK at 450 + 60% BF at 450 kg ha−1), conducted. The results showed that treatment A (60% NPK + 20% BF) replacing the NPK at 300 kg ha−1 with BF at 150 kg ha−1 significantly soil nutrient contents, enzyme activity, and microbial metabolic activity. The study also found a positive correlation between soil parameters (total nitrogen, alkaline nitrogen, available phosphorus, organic matter, urease, and alkaline phosphatase in the winter wheat and maize cropping season). Furthermore, the soil microbial composition showed significant enrichment of Proteobacteria, Acidobacteria, Actinobacteria, and Firmicutes, and variations among treatments. Moreover, the application of biofertilizer enhanced the diversity of soil fungi species, particularly during the winter wheat season. This study highlights the importance of integrating biofertilizers with NPK fertilizer for agricultural system conversion and promoting agricultural production and sustainability.

Inversion of Cotton Soil and Plant Analytical Development Based on Unmanned Aerial Vehicle Multispectral Imagery and Mixed Pixel Decomposition

In order to improve the accuracy of multispectral image inversion of soil and plant analytical development (SPAD) of the cotton canopy, image segmentation methods were utilized to remove the background interference, such as soil and shadow in UAV multispectral images. UAV multispectral images of cotton bud stage canopies at three different heights (30 m, 50 m, and 80 m) were acquired. Four methods, namely vegetation index thresholding (VIT), supervised classification by support vector machine (SVM), spectral mixture analysis (SMA), and multiple endmember spectral mixture analysis (MESMA), were used to segment cotton, soil, and shadows in the multispectral images of cotton. The segmented UAV multispectral images were used to extract the spectral information of the cotton canopy, and eight vegetation indices were calculated to construct the dataset. Partial least squares regression (PLSR), Random forest (FR), and support vector regression (SVR) algorithms were used to construct the inversion model of cotton SPAD. This study analyzed the effects of different image segmentation methods on the extraction accuracy of spectral information and the accuracy of SPAD modeling in the cotton canopy. The results showed that (1) The accuracy of spectral information extraction can be improved by removing background interference such as soil and shadows using four image segmentation methods. The correlation between the vegetation indices calculated from MESMA segmented images and the SPAD of the cotton canopy was improved the most; (2) At three different flight altitudes, the vegetation indices calculated by the MESMA segmentation method were used as the input variable, and the SVR model had the best accuracy in the inversion of cotton SPAD, with R2 of 0.810, 0.778, and 0.697, respectively; (3) At a flight altitude of 80 m, the R2 of the SVR models constructed using vegetation indices calculated from images segmented by VIT, SVM, SMA, and MESMA methods were improved by 2.2%, 5.8%, 13.7%, and 17.9%, respectively, compared to the original images. Therefore, the MESMA mixed pixel decomposition method can effectively remove soil and shadows in multispectral images, especially to provide a reference for improving the inversion accuracy of crop physiological parameters in low-resolution images with more mixed pixels.