Soil Nutrient Levels Research Articles

Characterisation and Mapping of Soils in Major Coffee Growing Regions of Uganda

There is limited information on the soil nutrient status, site specific fertilizer and agronomic recommendations for coffee in Uganda hence limiting its production and productivity. Therefore, this study was undertaken to characterize the soils under coffee farms and provide fertilizer and land management recommendations for coffee farming in selected districts in Uganda. 717 soil samples were collected from 45 coffee growing districts that were purposively selected to represent the major coffee growing regions of Eastern, Northern, Western, Mid-west and West Nile. 35 districts were sampled from Robusta coffee growing areas and 10 districts from Arabica coffee growing areas. Parameters considered in the laboratory analysis included; pH, total organic carbon, total nitrogen, available P, exchangeable Calcium (Ca), Sodium (Na), Magnesium (Mg), and Potassium (K) and micro elements: Iron (Fe), Zinc (Zn), Copper (Cu), Manganese (Mn) and Boron, soil texture, bulk density and hydraulic conductivity. Soil nutrient levels distribution maps for Robusta and Arabica coffee growing regions were generated in ArcGIS for the entire country. The soil chemical and physical properties were subjected to analysis of variance using Genstat 14th edition. The soil mapping results showed that, the overall average soil macro-nutrients concentrations were significantly different across regions (p < 0.05) with Eastern having the highest levels of macro elements (CEC of 19.28 meq/100 g, Base Saturation (BS) of 43.40%, pH of 5.78, N of 0.20%, K of 1.64 meq/100 g, P of 107.68 mg/kg and OM of 3.31%) followed by Western region. No significant difference (p > 0.05) was recorded for the micronutrients across the different regions, except Zn (p < 0.05). This study showed that Phosphorus and Potassium were generally moderate to high levels in most of the regions sampled while Nitrogen and organic matter were moderate to low. Results from this study provide a general picture of the nutrient status across all coffee growing regions in Uganda and highlight the required modifications for increased production and productivity.

Changes in Nutrient-Regulated Soil Microbial Communities in Soils Concomitant with Grassland Restoration in the Alpine Mining Region of the Qilian Mountains

In response to the significant ecological damage caused by unsustainable mining practices in the Qilian Mountains, ecological restoration projects have been undertaken in recent years. Analyzing the changes in soil microbial communities during the restoration process of mine meadows helps to reveal the mechanism of the restoration process in alpine mining areas. To explore the characteristics of soil microbial community distribution and their relationships with soil environmental factors during the restoration of alpine grasslands in the Qilian Mountains, we conducted surveys and analyses in two restoration levels low restoration (LR) and high restoration (HR) in the eastern Qilian Mountains, along with an undisturbed natural grassland control (NG). We found that as the degree of high-altitude mining area recovery increases, there were significant increases in vegetation cover, vegetation height, above-ground biomass, vegetation Shannon–Wiener index, soil organic carbon (SOC), soil water content (SWC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available phosphorus (AP), and available nitrogen (AN). Conversely, soil pH and electrical conductivity (EC) significantly decreased, with soil pH decreasing from 6.93 to 4.13. Restoration of high-altitude mining area grasslands significantly alters the distribution and composition of soil bacteria and fungi, while the impact on soil microbial community changes was not significant. Notably, with increasing recovery level, the dominant bacterial phyla are Acidobacteria and Proteobacteria, while the dominant fungal phyla are Ascomycota and Basidiomycota. These results indicate that changes in vegetation and soil properties both affect the composition of soil microbial communities, with soil properties having a greater influence. Soil fertility and nutrient levels emerge as the primary drivers influencing soil microbial composition communities and the degree of high-altitude mining area grassland recovery.

Moso bamboo (Phyllostachys edulis) expansion enhances soil pH and alters soil nutrients and microbial communities

Amid global environmental concerns, the issue of bamboo expansion has garnered significant attention due to its extensive and profound impacts on the ecosystems. Bamboo expansion occurs in native and introduced habitats worldwide, particularly in Asia. However, the effects of bamboo expansion on soil pH, nutrient levels, and microbial communities are complex and vary across different environments. To address this knowledge gap, we conducted a meta-analysis with 2037 paired observations from 81 studies. The results showed that soil pH increased by 6.99 % (0-20 cm) and 4.49 % (20-40 cm) after bamboo expansion. Notably, soil pH increased more in the coniferous forest with bamboo expansion than in the broadleaf forest. Soil pH progressively increased over time since the establishment of bamboo stands. The extent of soil pH elevation was significantly positively correlated with the proportion of bamboo within the forest stand and mean annual solar radiation. In contrast, it was significantly negatively correlated with the mean annual temperature. The elevation of pH is closely related to expansion stage and expanded forest type rather than primarily shaped by climatic factors across a large scale. We also found that bamboo expansion into coniferous forests brought about a notable 14.14 % reduction in total nitrogen (TN). Varied expansion stages resulted in TN reductions of 6.88 % and 7.99 % for mixed forests and bamboo stands, respectively, compared to native forests. Pure bamboo stands exhibited a remarkable 30.39 % increase in ammonium nitrogen and a significant 21.12 % decrease in nitrate nitrogen compared to their native counterparts. Furthermore, bamboo expansion contributed to heightened soil fungal diversity. Taken together, our findings highlight that bamboo expansion leads to an increase in soil pH and alters soil N components and fungal microbial communities, providing valuable insights for future ecological conservation and resource management.

Positive Changes in Fruit Quality, Leaf Antioxidant Defense System, and Soil Fertility of Beni-Madonna Tangor Citrus (Citrus nanko × C. amakusa) after Field AMF Inoculation

Citrus plants rely heavily on arbuscular mycorrhizal fungi (AMF) due to their lack of root hairs. Most experiments have been conducted with AMF inoculation under potted conditions, while field inoculation of AMF on citrus, especially a high economic hybrid tangor variety Beni-Madonna (Citrus nanko × C. amakusa), has been rarely recorded. This study aimed to analyze the effects of two AMF inoculations (a single Funneliformis mosseae and a mixture of F. mosseae, Diversispora versiformis, and Rhizophagus intraradices) on the internal and external fruit quality, leaf antioxidant defense system, and soil fertility and structure of top-worked Beni-Madonna tangor citrus trees. Three and a half years after AMF inoculations, soil hyphal length and root mycorrhizal colonization rate increased by 61.2–101.8% and 15.85–29.6% in inoculated plants, respectively. Inoculated trees had higher external fruit coloration value, fruit horizontal diameter, and fruit weight, and lower fruit rigidity than uninoculated trees. AMF-inoculated trees had higher glucose levels of fruit peels, fructose and sucrose levels of fruit fleshes, and the ratio of fruit soluble solids/titratable acids, as well as lower titratable acids concentrations than non-AMF-inoculated trees. AMF inoculation significantly increased leaf nitrogen balance index, chlorophyll index, peroxidase, catalase, superoxide dismutase, and glutathione reductase activities, as well as reduced glutathione and oxidized glutathione concentrations, resulting in lower hydrogen peroxide and malondialdehyde levels when compared to the uninoculated treatment. In addition, inoculated trees presented higher soil nutrient levels, including organic carbon, available K, and Olsen-P as, well as soil aggregate stability (based on mean weight diameter) than uninoculated trees. This study concluded that field AMF inoculation improved fruit quality, enhanced leaf antioxidant defense system, and improved soil fertility of Beni-Madonna trees, with mixed AMF being prominent in improving fruit quality and F. mosseae being prominent in enhancing leaf antioxidant defense system and improving soil fertility.

Interplays between plants and environmental factors determine pullout resistance on different revegetated slopes in mining areas

Plant roots play a crucial role in enhancing soil stability and protecting slopes during ecological restoration, particularly in mining areas where external-soil spray seeding is employed. However, the relationship between plant root pullout resistance and environmental factors on different types of slopes remains unclear. In this study, we investigated the interactions between the pullout resistance of a dominant species, Artemisia gmelinii, and environmental factors on three slope types (rocky, geotechnical, and soil) using multi-group structural equation modeling. Our findings reveal that the pullout resistance of plant roots was strongly influenced by various factors, including but not limited to biological factors such as plant height and biomass. It showed a positive correlation between soil silt content and soil nutrient levels. Notably, the pullout resistance on soil slopes was significantly higher than on rocky slopes. Furthermore, the impact of soil nutrients and texture on pullout resistance was more pronounced on geotechnical and soil slopes compared to rocky slopes. Multi-group structural equation modeling highlighted that among all environmental factors, slope gradient and underground biomass had the most significant influence on pullout resistance across all slope types. Specifically, slope gradient had a greater effect on soil slopes, whereas underground biomass played a more prominent role on rocky and geotechnical slopes. Overall, our study suggests that when implementing external-soil spray seeding in mining areas, it is crucial to consider the interplay between plant roots and environmental factors, including slope properties. This holistic approach is crucial for maximizing the effectiveness of plants in slope protection during eco-engineering projects.

Potential Use of Plant Growth-Promoting Bacteria to Enhance Growth and Soil Fertility in Marginal Areas: Focus on the Apulia Region, Italy

Soil degradation is a global problem and refers to the reduction or loss of the biological and economic productive capacity of the soil resource. In Europe, the countries most affected by soil degradation are undoubtedly those of the Mediterranean basin. Among these, Italy shows clear signs of degradation, with different characteristics, especially in the southern regions, where climatic and meteorological conditions strongly contribute to it. Apulia, the Tavoliere plain in particular, is a fragile and very sensitive ecosystem due to its intrinsic characteristics and the level of anthropic exploitation. Agricultural production pays the highest price, as increasing desertification due to climate change and the loss of agricultural land severely limit the extent of land available to produce food for an ever-growing population. Plant growth-promoting bacteria (PGPB) could be a low-cost and long-term solution to restore soil fertility, as they provide a wide range of benefits in agriculture, including increasing crop productivity, improving soil nutrient levels and inhibiting the growth of pathogens. This review shows how PGPB can be used to improve the quality of soils, their impact on agriculture, their tolerance to abiotic stresses (drought, salinity, heavy metals and organic pollutants) and their feasibility. The use of PGPB could be promoted as a green technology to be applied in marginal areas of Apulia to increase soil fertility, reduce pollution and mitigate the impacts of abiotic stresses and climate change. This is supported by a series of studies showing that the growth of plants inoculated with PGPB is superior to that of non-inoculated plants.

The Impact of Agricultural Polymer Application and Irrigation Frequency on the Availability of (NPK) in Soil and the Productivity of Wheat (Triticum aestivum L.) Cultivated in Sandy Soil

A field experiment was conducted at the Al-Bandar Research Station of the College of Agriculture - Al-Muthanna University to investigate the impact of agricultural polymer application and the frequency of irrigation on soil nutrient levels and wheat yield in sandy soil during the agricultural season of 2022-23. The experiment followed a split-plot design with three replications. The experimental design consisted of five levels of agricultural polymer, denoted as P0, P1, P2, P3, and P4, which were applied at rates of 0, 25, 75, 50, and 100 kg ha-1, respectively. These levels were assigned to the secondary plot. Additionally, the main plot was assigned four levels of the number of watering, denoted as R1, R2, R3, and R4, corresponding to 6, 7, 8, and 9 watering, respectively. The findings of the statistical analysis indicate that the inclusion of various concentrations of agricultural polymer resulted in an enhancement of nutrient availability in the soil. Specifically, the highest concentration (P3) had a significant impact on both the biological yield and the levels of soil NPK. The average values for these parameters were observed to be 13.36 mg.ha-1 and 36.30 mg N kg-1 soil, 26.83 mg P kg-1 soil, and 251.0 mg P kg-1 soil, respectively. Regarding the P2 level, it exerted an impact on the grain yield, resulting in an average of 5.41 mg ha-1. The impact of various irrigation methods on soil nutrient availability was found to be insignificant. However, a significant relationship was observed between the levels of agricultural polymers and the number of irrigations, affecting all the traits under investigation.

Environmentally benign approach to formulate nanoclay/starch hydrogel for controlled release of zinc and its application in seed coating of Oryza Sativa plant

Improper use of conventional fertilizers has been linked to adverse effects on soil nutrient levels. To mitigate the negative impact of surface feeding fertilizers and reduce environmental pollution, a new type of seed coating material has been developed to provide nutrients in close proximity to the growing seed. In this study, a biodegradable seed coating film encapsulating micronutrients was fabricated by incorporating montmorillonite into a starch matrix using the melt processing technique. The dispersion of montmorillonite within the starch matrix was examined using X-ray diffraction (XRD), infrared spectroscopy (IR), and thermal gravimetric analysis (TGA). The results revealed polar interactions among starch, silicate layers, and the hydrogel. The XRD analysis demonstrated a shift in the diffraction peak (001) of the Zinc/montmorillonite/starch/glycerol nanocomposite film from 6.2° to 4.9°, indicating the successful intercalation of Zinc, starch, and glycerol. Furthermore, the inclusion of nanoclay improved the thermal stability of the resulting polymer composite and enhanced its ion exchange capacity, water retention, and micronutrient retention. The time-dependent release of zinc micronutrient from the montmorillonite/starch/glycerol composite film was investigated in Zn-deficient soil extract over a 20-day period. The composite film demonstrated extended release behavior of Zn2+. Subsequently, rice seeds were coated with the zinc-containing composite film using a dip-coating method, and their performance in Zn-deficient soil was evaluated. The results indicated that zinc-coated seeds exhibited improved germination percentage, vegetative growth, and yield compared to uncoated seeds.

Grazing Impacts on Soil Enzyme Activities Vary with Vegetation Types in the Forest-Steppe Ecotone of Northeastern China

Grazing impacts soil enzyme activities by changing soil conditions and microbial functions. Yet, the specific effects of grazing on soil enzymes in different northeastern China forest-steppe vegetation types remain poorly understood. To examine this, catalase (CA), urease (UA), and cellulase (CEA) activities were measured in different vegetation types (NS, MF, CP, GL) under both grazing and non-grazing conditions. Soil microbial biomass carbon and nitrogen (MBC and MBN) and other soil factors were also studied to gauge their impact on enzyme activities. The results indicated that enzyme activities were influenced by grazing, soil nutrient levels, mineralization, and microbial biomass carbon and nitrogen content. Grazing exerted the most significant influence on UA. CEA was predominantly affected by the content of biomass nitrogen and soil mineralization. CA, on the other hand, was primarily influenced by soil nutrient levels. Grazing influenced enzyme activities differently based on vegetation type. Under grazing, CA showed higher values in NS, MF, CP, and GL (4.09, 2.42, 3.26, and 3.90 mL 0.1 mol L−1 KMnO4 g−1 soil 20 min−1, respectively) with increases ranging from 32.52% to 505.00% (p < 0.05). Additionally, UA values were significantly higher in MF and CP (0.24 and 0.59 mg NH4+-N g−1 soil d−1, respectively) with increases of 66.67% and 156.00%, while UA and CEA were lower in GL, showing reductions of 78.79% and 166.67% (p < 0.05) (0.33 NH4+-N g−1 soil d−1 and 0.06 mg glucose g−1 soil 72 h−1, respectively) under grazing conditions. These findings underscore the importance of vegetation types in the grazing effects on soil enzymes at the forest-steppe ecotone and suggest that further efforts should be made to strengthen grassland grazing management to mitigate negative impacts on soil environmental health.

Low variation in microbial carbon sequestration between farmland and apple orchards in typical loess-covered regions

The cultivation of deep-rooted vegetation greatly alters the tradeoffs between water and carbon dynamics, yet their impact on microbial carbon sequestration (MCS) remains inadequately documented, particularly in thick vadose zones. This information is crucial for global climate mitigation and ecosystem service enhancement. As such, we collected triplicate samples for each land use type, exploring the abundance and structure of cbbL-harboring microbial communities within 10-m deep profiles under cultivated farmland and two apple orchards of varying ages (n = 72). Our findings indicated a shift from water-dominated (improved water retention at the expense of reduced carbon sequestration) to carbon-dominated benefits (enhanced carbon sequestration at the expense of decreased water retention) in deep soil layers (2–10 m) after the transformation from farmland to apple orchards. Despite the lack of significant differences among the three land use types, the gene abundances and microbial diversity indices reduced with soil depths because of variations in substrates, resources, and microenvironments. The cbbL-harboring microorganisms consisted of 5 phyla, 7 classes, 19 orders, 30 families, and 55 genera, with Proteobacteria as the predominant bacterial phylum. The relative contributions of different genera varied with soil depths, reflecting their distinct survival strategies. The microbial network was positively connected in various soil layers under farmland and apple orchards. Furthermore, the results of correlation, redundancy analysis, and structural equation modeling jointly indicated that plant roots and soil properties, including total nitrogen and organic carbon, governed MCS processes in deep unsaturated zones. Specifically, the low microbial variation between farmland and apple orchards can be attributed to the predominant effects of climatic and pedogenic factors on soil properties, the restricted contribution of plant roots to soil nutrient levels per unit depth, and the adverse effects of plant-induced ecohydrological consequences on root systems and microbial populations. This study offers new insights within thick vadose zones containing deep-rooted plants, thereby contributing to a better understanding of global terrestrial carbon cycle processes.

Higher colonization but lower diversity of root-associated arbuscular mycorrhizal fungi in the topsoil than in deep soil

Arbuscular mycorrhizal fungi (AMF) colonizing plant roots play a pivotal role in maintaining soil nutrient cycling and ecosystem stability, and this role may vary in different habitat environments. However, the influence of soil depth on root AMF colonization, diversity, and the complex interactions among AMF taxa is still not well understood. In this study, we investigated the frequency, intensity, and abundance of root AMF colonization, as well as root AMF diversity, composition, and co-occurrence patterns across three soil depths: 0–20 cm, 20–40 cm, and the soil-rock mixing layer. Soil nutrients (e.g., organic matter, nitrogen, and phosphorus) and root biomass were higher in the 0–20 cm layer than in the soil-rock mixing layer, while soil pH showed an opposite relationship. The higher root biomass in the upper soil layer may enhance root secretions and exudates, thereby promoting root AMF colonization. In contrast, the lower soil nutrient content and higher soil pH observed in the 20–40 cm and soil-rock mixing layers may contribute to greater AMF diversity in the deeper soil layers compared to the topsoil. Although no significant differences were observed in the composition of the root AMF community, specific amplicon sequence variants affiliated with Glomus, Racocetra, and unclassified taxa were more enriched in the 20–40 cm and soil-rock mixing layers compared to the 0–20 cm layer. Network analysis revealed that deep soil, compared to topsoil, enhances interactions among root AMF by intensifying competitive relationships. This suggests that the complex interactions among root AMF taxa within deep soil contribute to the resilience of root AMF in resource-scarce conditions, particularly in the 20–40 cm layer and the soil-rock mixing layer. At the genus level, Glomus, Racocetra, and unclassified taxa emerged as keystone taxa due to their prominent linkage with other root AMF groups. Collectively, the results suggest that higher soil nutrient levels and root biomass can promote root mycorrhizal colonization but suppress AMF diversity and weaken interactions among root AMF taxa in the upper soil layer compared to deeper soil layers. Furthermore, the distinct functions of AMF colonization and diversity at different soil depths should be considered when evaluating vegetation reconstruction in karst ecosystems with varied soil depth distribution.

Effects of long-term conservation tillage on N2 and N2O emission rates and N2O emission microbial pathways in Mollisols

Conservation tillage is widely used in farmland management for soil carbon sequestration, but it can also lead to potential emissions of nitrous oxide (N2O). Therefore, our study is aimed to investigate the effects of 15 years of no-tillage combined with four straw mulching levels of 0 % (NT0), 33 % (NT33), 67 % (NT67), and 100 % (NT100) compared to ridge tillage (RT) on the rates of N2O and N2 emissions and the respective contributions of four microbial pathways to N2O emissions. The incubation experiments were conducted at two different moisture levels (55 % and 100 % WFPS) by using dicyandiamide inhibition and 15N-labeling techniques. Soil samples were collected from the 0–20 cm and 20–40 cm soil depths across three maize growth stages: seedling, jointing, and maturity. Our results showed that conservation tillage significantly decreased the N2O + N2 emission at 55 % WFPS, but it has a reverse influence in N2O + N2 emission at 100 % WFPS. The proportion of N2O in gaseous N loss were higher at 100 % WFPS than at 55 % WFPS. Among the four microbial pathways for N2O emissions, autotrophic nitrification was the dominant pathway 55 %WFPS. The contribution of autotrophic nitrification remarkably decreased, co-denitrification and denitrification increased at 100 %WFPS. Overall, at 100 % WFPS, N2O emissions from all major microbial pathways were positively correlated with GWC, temperature, TC, TN, NH4+-N, and NO3−-N, but negatively correlated with soil pH and C/N ratios. Our results suggest that long-term conservation tillage increases N2O and N2 emissions from the soil under water-saturated conditions by regulating soil nutrient levels, soil moisture, and microbial pathways. Therefore, we should consider the impact of conservation tillage on N2O emission risk when we attach importance to the role of conservation tillage in improving soil quality and increasing crop yields.

Prediction of soil nutrients through PLSR and SVMR models by VIs-NIR reflectance spectroscopy

Though soil nutrients play important roles in maintaining soil fertility and crop growth, their estimation requires direct soil sampling followed by laboratory analysis incurring huge cost and time. In this research work, soil nutrients were predicted using VIs-NIR reflectance spectroscopy (range 350–2500 nm) with Partial Least Squares Regression (PLSR) and Support Vector Machine Regression Model (SVMR) model through principal component analysis. Two hundred soil samples were collected from Tarekswar, Hooghly, West Bengal, India to predict eight selected soil nutrients, such as soil organic carbon (OC), pH, available nitrogen (N), available phosphorus (P), available potassium(K), electric conductivity (EC), zinc (Zn) and soil texture (sand, silt, and clay) levels. The OC content was predicted with sound accuracy (R2: 0.82, RPD: 2.28, RMSE: 0.13, RPIQ: 4.15 FD-SG), followed by P (R2: 0.71, RPD: 1.83, RMSE: 4575, RPIQ: 3.44 1st derivative). The soil parameters sensitive to the particular band of visible spectrum were also identified viz. wavelengths of 409, 444, 591 and 592 nm for OC, 430 and 505 nm for P, 464 nm for K; 580 nm for Zn, 492,511,596 and 698 nm for N; 493, 569 and 665 nm for EC; 492,567 and 652 nm for pH; 457 nm for sand and 515 nm for clay.The soil nutrient levels were predicted by PLSR and SVMR models through PCA and Sentinel 2 imagery and soil suitability map were also generated for seven soil parameters such as OC, pH, EC, N, P, K and clay content. Through map query tool in ArcGIS software environment the PLSR and SVMR model successfully identify the suitability class with level of accuracy of 87.2% and 88.9%, respectively, against the direct soil analysis based suitability mapping.The machine learning technique based soil nutrient and soil suitability prediction can be easily adopted in different regions. This will reduce the cost of laboratory soil analysis and optimize the total time requirement.

Soil nutrient levels regulate the effect of soil microplastic contamination on microbial element metabolism and carbon use efficiency

Microplastics (MPs) are emerging environmental contaminants in soil ecosystems that disrupt the soil carbon (C) pool. Therefore, the response of microbial metabolism to MP-contaminated soil is crucial for soil-C stabilization. We undertook factorial experiments in a greenhouse with three types of soil microplastics with three levels of soil nutrients and undertook soil physiochemical analyses after 60 days. The present study revealed how the presence of degradable polylactic acid (PLA) and non-degradable polyethylene (PE) MPs affects soil microbial nutrient limitation and C use efficiency (CUE) at varying nutrient concentrations. The presence of PLA in soil with low nutrient levels led to a significant increase (29%) in the activities of nitrogen (N)-acquiring enzymes. In contrast, the presence of MPs had no effect on C- and N-acquiring enzymes. The occurrence of PE caused a 41% reduction in microbial C limitation in high-nutrient soils, and microbial nutrient metabolism was limited by the occurrence of MPs in soils amended with nutrients. A strong positive correlation between microbial C and nutrient limitation in the soil indicates that addressing C limitation followed by amendment of soil with MPs could potentially intensify microbial N limitation in soils with varying nutrients. In comparison, the microbial CUE increased by 10% with the application of degradable MPs (PLA) to soils with a low nutrient status. These findings highlight the significant influence of both degradable PLA and non-degradable PE MPs on soil microbial processes and C dynamics. In conclusion, PLA enhances metabolic efficiency in nutrient-rich soils, potentially aiding C utilization, whereas PE reduces microbial C limitation, offering promise for soil C sequestration strategies. Our findings underscore the importance of considering MPs in soil ecosystem studies and in broader sustainability efforts.

Yield Performance of Intercropped Marantha arundinacea L. (Arrowroot) in Two Rubber Plantation Designs

Developing rubber agroforestry systems is crucial to ensure the sustainable development of natural rubber cultivation. This study focuses on the starch crop Maranta arundinacea (arrowroot) and assesses its productivity and influencing factors when intercropped in 6–7-year-old conventional single-row and double-row rubber plantations. We analyze various aspects, including light resources, root distribution, soil nutrients, arrowroot growth characteristics, and product quality. The results indicate that the daily average photosynthetically active radiation (PAR) in the double-row rubber agroforestry system intercropping area ranges from 896.4 to 940.2 μmol·m−2·s−1. Additionally, the rubber tree roots near the intercropping area are less dense (107.0 g cm−3). In contrast, the conventional single-row rubber agroforestry system has a significantly lower daily average PAR of only 145.7 μmol·m−2·s−1, and the nearby rubber tree roots are more abundant (616.2 g cm−3). Although soil nutrient levels were slightly lower in the intercropping area on the double-row treatment compared to the single-row treatment, there was no statistical difference (p < 0.05). Arrowroot’s photosynthetic capacity in the double-row rubber agroforestry system intercropping area is significantly greater than in the single-row rubber agroforestry system intercropping area. The yield per unit area in the former (23.46–27.47 t·ha−1) is also significantly higher than in the latter (2.87–4.75 t·ha−1, p < 0.05), with higher starch content. Therefore, arrowroot exhibits higher productivity when intercropped in double-row rubber agroforestry systems, making it suitable for establishing a “rubber–arrowroot” agroforestry model to enhance the yield per unit area of rubber plantations.

Influence of Phoebe bournei (Hemsl.) Replanting on Soil Carbon Content and Microbial Processes in a Degraded Fir Forest

Replanting is a widely used method for improving the health and carbon sequestration capacity of degraded forests. However, its impact on soil carbon pools remains controversial. This study investigated the effects of replanting broadleaf Phoebe bournei (Hemsl.) Yang in a typical degraded fir forest. Soil carbon content, nutrient levels, and microbial community structure and function were measured at 0, 5, 8, and 12 years after replanting. The degraded fir forests were originally limited in nitrogen and phosphorus. Phoebe bournei replanting significantly increased soil total carbon but reduced total nitrogen and phosphorus levels, resulting in increased soil carbon:nitrogen, carbon:phosphorus, and nitrogen:phosphorus ratios. Microbial biomass carbon, nitrogen, and phosphorus were all significantly reduced, whereas microbial carbon:phosphorus and nitrogen:phosphorus ratios were enhanced. Enzyme activities related to nutrient cycling and carbon decomposition (acidic invertase, polyphenol oxidase, peroxidase, urase, nitrate reductase, and acidic phosphatase activities) were significantly lowered by replanting. Microbial richness and diversity significantly increased, and microbial community composition changed significantly due to replanting. Structural equation modeling revealed the significant role of total phosphorus in microbial biomass, microbial community composition, and enzyme activity, highlighting it as the main factor accelerating soil carbon accumulation. Network analysis identified Leifsonia, Bradyrhizobium, and Mycolicibacterium members as key microbial players in the soil carbon cycle. In summary, P. bournei replanting exacerbated soil phosphorus deficiency, leading to a decrease in soil microbial biomass and changes in community structure, reduced nutrient cycling and carbon-decomposition-related enzyme activities, less litter decomposition, and increased organic carbon accumulation. These findings demonstrate the importance of nutrient limitation in promoting soil carbon accumulation and offer new insights for soil carbon regulation strategies in forestry.

Assessment of the effects of NPK fertilizer on edible yield and agro-biological parameters in a cowpea–amaranth intercrop

IntroductionEstimates indicate that food and nutritional demand in sub-Saharan African nutrient-poor soils will exceed the high population demand. Vegetables such as amaranth and cowpea are key in contributing to food and nutritional security. Fertilizers are used to mitigate low nutrient levels in soils. This study aimed to investigate the yield parameters of cowpea and amaranth vegetables.MethodsThe experiment was designed with a 2 × 4 factorial treatment structure in a completely randomized design, with intercropping and fertilizer level as treatment factors and with four replications.Results and discussionThe biomass of amaranth and cowpea increased with increased fertilizer application up to the level of 100% nitrogen, phosphorus, and potassium (NPK) fertilizer. A measure of land utilization showed values greater than one. Crop comparison showed that cowpea was more aggressive, had higher actual yield loss, and was highly competitive compared to amaranth. More income could be obtained from intercropping. The research shows the benefits of fertilizer application in improving the biomass of amaranth and cowpea. Overall, the application of NPK fertilizer at levels up to 100%, based on the results of this study, resulted in higher biomass accumulation and improved intercropping indices.

Drip irrigation shapes the soil bacterial communities and enhances jujube yield by regulating the soil moisture content and nutrient levels

In the agricultural zones of the arid Xinjiang region of China, reducing irrigation is mandatory. However, irrigation affects the composition and diversity of the soil bacterial community which is vital to crop yield. To the best of our knowledge, very little research has been conducted on the relationships among the soil bacterial community, irrigation method, and yield as well as their underlying in jujube agroecosystems. Here, we investigated the soil physicochemistry and bacterial communities in jujube fields subjected to drip irrigation (DI) and traditional flood irrigation (FI), and their associations with yield at the flowering and fruit set (FFS) and end-of-growth (EG) stages. Under DI, the jujube yield was 8712.00 ± 24.54 kg/hm2, which was 7.64% higher than that obtained under FI (8094.33 ± 43.67 kg/hm2). DI increased the relative soil bacteria community diversity by decreasing the moisture content and increasing the nutrient levels in the soil. DI also transformed the soil bacterial community so that Bacteroidota predominated at the FFS stage and the probiotics Chloroflexi and Firmicutes predominated at the EG stage. A co-occurrence network analysis showed that DI created stable complex Soil bacteria communities in jujube fields, Though Dependentiae and Deferriberota had low relative abundance, they were nonetheless key nodes in the soil bacterial community network. A neutral community model (NCM) revealed that stochastic processes drove the soil bacterial community assembly whereas DI promoted deterministic processes by regulating the soil moisture content and nutrient levels. Partial least squares path modeling (PLS-PM) disclosed that DI affected the soil bacterial community structure by decreasing the moisture content (−0.342 **) and increasing the nutrient levels (0.557 **) in the soil. The PLS-PM also demonstrated that the observed change in the soil bacterial community structure was the main reason for the increase in jujube yield (1.098 **). The present work provides insights into the mechanisms underlying the correlations between the soil bacterial community and crop yield in response to changes in the irrigation method.

Factors associated with foodborne pathogens and indicator organisms in agricultural soils

Soil can be a route for contamination of fresh fruits and vegetables. While growers routinely manage soil nutrient levels, little research exists on the synergistic or antagonistic effects of soil nutrients on foodborne pathogens. Data on foodborne pathogen prevalence in unamended soils is also relatively limited in literature. This study evaluated foodborne pathogen prevalence (Salmonella, Listeria monocytogenes) and concentration of indicator bacteria (total coliforms, generic Escherichia coli) in agricultural soils, and characterized associations between soil properties (e.g., macro- and micro-nutrient levels) and each microbial target. Three Virginia produce farms, representing different regions and soil types, were sampled four times over 1 year (October 2021–November 2022). For each individual farm visit, composite soil samples were collected from 20 sample sites (25 m2) per farm per visit for microbial and nutrient analysis (n = 240). Samples (25 g) were processed for Listeria spp. and Salmonella using a modified FDA BAM method; samples (5 g) were enumerated for generic E. coli and total coliforms (TC) using Petrifilm. Presumptive Listeria spp. and Salmonella isolates were confirmed by PCR using the sigB and invA genes, respectively. Soil nutrients from each sample were tested and evaluated for their association with each microbial target by Bayesian Mixed Models. Salmonella prevalence was 4.2% (10/240), with 90% (9/10) recovered on Farm C. Listeria spp. and L. monocytogenes prevalence were 10% (24/240) and 2.5% (6/240), respectively. When samples were positive for generic E. coli (107/240), the average concentration was 1.53 ± 0.77 log10 CFU/g. Soil pH was positively associated with L. monocytogenes [Odds Ratio (OR) = 5.5] and generic E. coli (OR = 4.9) prevalence. There was no association between Salmonella prevalence and any evaluated factor; however, Salmonella was 11.6 times more likely to be detected on Farm C, compared to other farms. Results show pathogen prevalence was relatively low in unamended soils, and that factors influencing prevalence and concentration varied by microbial target and farm.

Effect of phosphorus and potassium fertilization on summer greengram (Vigna radiata) varieties

This experiment suggests that the utilization of the greengram variety IPM 02-3 is advantageous due to its superiority in terms of performance and adaptability over other varieties investigated. Additionally, application of 50 kg/ha P2O5 and K2O demonstrates comparable performance and profitability to application of 60 kg/ha P2O5 and K2O, making it an economically favourable option. Soil fertility analysis revealed P and K's role in enhancing nutrient dynamics. The relation between soil nutrient levels and greengram yield underscores the multifaceted relationship. In summary, genetic factors, coupled with optimal nutrient management, synergistically affect the growth and yield of greengram.