Soil Leaching Research Articles

Allelopathic potential of warm‐season turfgrass species as an alternative management strategies for weed control

AbstractAlternative cultural methods, such as the selection of a turfgrass species and cultivars, need to be investigated as a weed control tactic since certain turfgrass species/varieties demonstrate potential for weed suppression. The objective of this experiment was to assess the allelopathic potential of common warm‐season turfgrass species (Eremochloa ophiuroides, Stenotaphrum secundatum, and Zoysia japonica) on common turf weeds (Digitaria sanguinalis, Eleusine indica, and Poa annua). Greenhouse and laboratory experiments were conducted to evaluate the effect of turfgrass competition, leaf extracts, and soil leachates on the germination and growth of weed species. Leaf extracts were more effective in suppressing weed species germination and growth than soil leachates. Zoysiagrass leaf extracts reduced the germination of P. annua by 16% and the coleoptile length of E. indica L. by 47% compared to deionized water control. Turfgrass species’ leaf extract stimulates annual bluegrass's coleoptile growth while inhibiting its radicle growth. Warm‐season turfgrass soil leachates did not suppress the germination and radicle growth of weed species. Eremochloa ophiuroides soil leachates were effective in suppressing D. sanguinalis coleoptile length. In this experiment, limited allelopathic effects of turfgrass species were noted. Poa annua germination and growth were reduced in a densely established turf, indicating that turfgrass species were equally inhibitory when competition was present. These results suggest that maintaining a dense and strong turf sward that can outcompete weeds for light, nutrients, and water is a more successful weed management technique than selecting a turfgrass species based on potential allelopathic effects.

Allelopathic potential of cool‐season turfgrass species as an alternative management strategy for weed control

AbstractHerbicides are a common input in turfgrass systems. Selecting turfgrass species that have either the ability to out‐compete weeds or inhibit their germination and establishment is a primary integrated weed management strategy to reduce herbicide use. The objective of this experiment was to assess the allelopathic potential of common cool‐season turfgrass species (Festuca arundinacea, Festuca brevipila, Festuca rubra ssp. rubra, Festuca rubra ssp. littoralis, Festuca rubra ssp. commutata, Lolium perenne, and Poa pratensis) on common turf weeds (Digitaria sanguinalis, Eleusine indica, Poa annua, and Taraxacum officinale). Greenhouse and laboratory experiments were conducted to evaluate the effect of turfgrass competition, leaf extracts, and soil leachates on the germination and growth of weed species. Leaf extracts and soil leachates of turfgrass species generally had more effect on radicle growth than on germination and coleoptile (or hypocotyl) growth. Cool‐season turfgrass leaf extracts did not suppress the gemination of P. annua, D. sanguinalis, or E. indica. P. pratensis leaf extracts were effective in suppressing Taraxacum officinale germination and emergence. Poa annua emergence and development were significantly lower when seeded into dense, established cool‐season turfgrasses. All turfgrass species were equally inhibitory when the turf was dense and competition was present. Limited allelopathic effects were noted in this experiment. Rather than picking a turfgrass species for potential allelopathic effects, these results point to the more effective weed management strategy of maintaining a dense and robust turf sward capable of outcompeting weeds for light, nutrients, and water.

Riparian Soil Heavy Metal Contamination and Pollution Assessment and Management Planning Integrating Multiple Indices, Statistical and Geospatial Approaches.

This research assesses heavy metal contamination within the riparian zone of the Danro River, a tributary of the Ganges River basin in India, particularly impacted by sand mining activities. The study conducted analyses on major and trace elements in soil samples, focusing on those identified as ecologically hazardous by the Water Framework Directive of India. Utilizing a combination of indices (Enrichment Factor, Pollution Load Index, and Index of geo-accumulation) and statistical techniques such as Principal Component Analysis (PCA), the investigation aimed to evaluate contamination severity, ecological risks, and pollution sources. Results revealed arsenic concentrations ranging from 0.00-0.54 mg/kg to 117-136 mg/kg, and ecological risks for cadmium exceeding 30. PCA identified three dominant factors explaining over 95% of variance. This study also employed the Analytic Hierarchy Process (AHP) method to assess land use suitability. Results unveiled that chromium and nickel predominantly stemmed from natural origins, while arsenic, cadmium, lead, and zinc exhibited a mixed origin. While most sites displayed low to moderate contamination, south-western portion of the basin demonstrated significantly elevated copper concentrations. Cadmium emerged as a particular concern, posing downstream ecological risks alongside chromium, nickel, and zinc, surpassing established thresholds. Further examination using PCA analysis pinpointed three primary pollution sources: traffic emissions, industrial activities, and natural processes. The research concludes by proposing a novel approach for remediation, including the Miyawaki technique alongside traditional methods like electrokinetic remediation and soil leaching. Policy suggestions advocate for collaborative efforts between economic entities and governments to promote sustainable practices that minimize heavy metal pollution.

Quantifying the environmental fate and source of nitrate contamination using dual-isotope tracing coupled with nitrogen cascade model on the basin scale.

Nitrate (NO3-) contamination in riverine networks has threatened the environment and human health. Clarifying the NO3- source and environmental fate within the basin under different underlying surfaces is essential for water body protection, especially China's two mother rivers. A series of combination methods were established i.e., field survey, index measurements, isotope-tracing techniques, and material flow analysis in four typical basins to investigate the spatiotemporal variation and source of NO3- pollution and nitrogen cascade characteristics. The dual-isotope coupled with MixSIAR model revealed that manure and sewage were the major NO3- source in the irrigation basin (WY, 76.7%), hilly mountainous basin (YC, 52.3%), and plateau lake basin (DC, 48.7%). However, for the plain-river network basin (CZ), soil leachate was the main source (55.5%). In terms of the N losses to water within agri-environment system, livestock-breeding system in three basins made the biggest contribution among the systems, WY (77.3%), YC (47.3%), and DC (41.8%). While in CZ, about 34.4% of N was delivered from the crop-production system. The N cascade model verified the results of isotope-tracing techniques for each basin. The study provides new insight into NO3--tracing combining hydrogeochemical indicators, isotopic-tracing techniques, and material flow analysis and guides strategies for mitigating the negative impacts of NO3- pollution on aquatic environments on basin scale.

Mycorrhizal fungi mitigate cadmium leaching losses by decreasing the inorganic cadmium proportion in soil solutions.

Arbuscular mycorrhizal fungi (AMF) are common in cadmium (Cd)-contaminated soil. However, the effects of AMF on Cd migration in contaminated soil are still poorly understood. A pot experiment involving a control without AMF inoculation (CK), inoculation with AMF (AMF), and bacterial filtrate of the AMF inoculant (LY) was conducted in the present study. AMF caused an increase in total glomalin-related soil protein (T-GRSP) of 12.2 % and in the exudation of low-molecular-weight organic acids (LMWOAs), such as citric acid, malic acid, oxalic acid, and free amino acids, by maize roots of 30.4 %-200.0 % but caused a decrease in the Cd contents of the maize shoots and roots by 53.2 % and 47.2 %, respectively compared those of the CK. Moreover, AMF decreased the Cd concentration in the leachate by 36.0 %-76.3 % by reducing the proportion of Cd2 + and inorganic Cd complexes in the soil solution and leachate by 26.2 %-85.7 %, and increasing the proportion of organic Cd complexes. Structural equation analysis revealed that the GRSP and LMWOAs were the primary factors driving the potential of AMF to reduce Cd leaching loss from polluted soil. The adsorption of Cd ions by quartz sand increased with the application of GRSP and LMWOAs, which resulted in a 27.6 %-69.5 % reduction in Cd leaching loss in the sand column. In the soil with AMF, the proportion of organic-bound Cd increased and the proportion of inorganic-bound Cd decreased by promoting the secretion of LMWOAs via mycelium, thus reducing Cd leaching loss.

A Review on Groundwater Pollution in India and their Health Problems

Any change in the physical, chemical, and biological properties of water makes it unfit for consumption. Currently, the main sources of groundwater pollution in India are water from domestic, industrial, and agricultural sources, which enter and contaminate the groundwater mainly through soil leaching. As India's industry continues to expand, pollution from groundwater exploitation and groundwater depletion are becoming an issue. Chemicals and road salts, air pollutants, contaminated soils, heavy metals, acidification, landfills, microbial contaminants, pesticides, and nitrate contamination from groundwater, sewage, wastewater, and septic tanks are the major groundwater pollution problems in India. The same elements of inorganic contaminants: are aluminum, nickel, arsenic, barium, cadmium, dissolved particles, iron, lead, and zinc—potential health problems. Organic contaminants - Volatile organic compounds (VOCs), pesticides, plasticizers, chlorinated solvents, dioxins, pharmaceuticals, and antibiotics are present in water and affect its quality. Drinking contaminated water can cause kidney damage, liver damage, cancer, skin damage, skin inflammation, weight loss, nervous system damage, respiratory problems, etc. problems for healthy people. This review is to identify the Major Groundwater Contamination Problems in India and their Potential health problems.

Blending of Slow-Release N Fertilizer and Urea Improve Rainfed Maize Yield and Nitrogen Use Efficiency While Reducing Apparent N Losses

Effective nitrogen (N) management practices are essential for achieving efficient and sustainable agricultural production. The purpose of this study was to improve N use efficiency (NUE) and minimize N loss by optimizing the rate and type of N fertilizer application while maintaining a high yield of maize. A two-year field experiment with U (urea), S (slow-release N fertilizer), and SU (blending of S and U) under four N application levels (N1: 90 kg ha−1, N2: 120 kg ha−1, N3: 180 kg ha−1, N4: 240 kg ha−1) was conducted to investigate their effects on ammonia (NH3) volatilization, residual soil nitrate N (), yield, NUE, apparent N losses of rainfed maize. NH3 volatilization in SU and S were 38.46% and 16.57% lower than that in U, respectively. SU and S were found to reduce the apparent N losses by 42.98% and 62.23%. SU decreased leaching in deep soils and increased content in topsoil. Compared with U and S, SU significantly increased yield, plant N accumulation, and NUE. SUN4 achieved the maximum maize yield and plant N accumulation, averaging 7968.36 kg ha−1 and 166.45 kg ha−1. In addition, the high yield and NUE were obtained when the mixing ratio of S and U was 53–58% and the N application rate was 150–220 kg ha−1. The findings highlight that SU effectively reduces N losses while ensuring high yield, which could be used as one of the optimal N fertilization strategies for rainfed maize in Northwest China.

A geochemical and palynological study of lake sediments at Mboandong, Cameroon: chemical weathering and vegetation linked to Holocene palaeoclimate

Geochemical and palynological analyses of core samples from Mboandong, a crater lake in western Cameroon, provide a record of response to climate and vegetation change in West Africa over the last 7000 years. Three palaeoclimatic phases were identified: a humid phase (6800-5700 cal. BP), characterized by a humid and warm palaeoclimate; a drying phase (5700-2000 cal. BP) with a less humid palaeoclimate; finally, a seasonal phase (2000 cal. BP to present), characterized by a seasonally varied, mainly humid and warm palaeoclimate. Pollen components show swamp and humid rainforest taxa being gradually replaced by semi-deciduous, regrowth and non-tree taxa such as grasses (Poaceae). There is a suggestion of increasing aridity over the last 200 years. The sediments are primarily weathered deposits mixed with volcanic eruptive material, rather than detritus derived from the UCC (upper continental crust). Chemical Index of Alteration (CIA) values are mostly high (mean 90.65%) and indicate a variable but mostly humid palaeoclimate. CIA values are most likely influenced by climate, as well as by runoff and physical erosion. Bands of volcanic ash are associated with frequent freshwater sponge spicules and diatoms, probably due to increased availability of silica. Ca and Na depletion is probably linked with soil leaching, while K depletion and Mg enrichment were probably caused by chemical alteration. Humid intervals may have higher organic carbon content, whereas increased amounts of iron occur in potentially drier intervals. A greatly increased presence of oil palm pollen (Elaeis guineensis) is interpreted as evidence of cultivation after 1700 cal. BP.

The Application of Straw Return with Nitrogen Fertilizer Increases Rice Yield in Saline–Sodic Soils by Regulating Rice Organ Ion Concentrations and Soil Leaching Parameters

Soil salinization is a severe environmental problem that restricts crop productivity. Straw amendment could increase the fertility of saline–sodic soils by improving soil physical properties and carbon sequestration; however, the chemical mechanism of saline soil improvement via straw reclamation is not clear. This study aimed to investigate the effects of straw return with nitrogen fertilizer on soil leaching characteristics, rice organ ion concentrations, and yield. Therefore, a soil column leaching experiment was conducted in 2021 in Baicheng, Jilin Province, using two straw application rate treatments (0 and 8 t hm−2) and three nitrogen application rate treatments (0, 180, and 360 kg hm−2). The results revealed the following: 1. The combination of straw return and nitrogen fertilizer significantly increased the soil leachate volume, leachate pH, Na+ concentration, and Na+/K+ ratio, thereby reducing Na+ stress on rice; 2. The application of nitrogen fertilizer during straw return effectively minimized soil nitrogen loss by lowering the ammonium and nitrate nitrogen concentrations in the soil leachate; 3. This combination also reduced plant Na+ concentrations while increasing plant K+ concentrations, thus improving the Na+/K+ ratio in the plants; 4. Straw return with nitrogen fertilizer significantly enhanced rice yield, which increased with higher nitrogen application rates. In summary, the integration of straw return with nitrogen fertilizer not only regulates rice salinity tolerance but also boosts rice yield, presenting a novel approach for improving saline–sodic soils.

The Effects of Heavy Metals on Enzyme Activity and Microbial Biomass of the Soil Around the Waste Disposal Site (Case Study of Saravan - Iran)

ABSTRACT Municipal solid waste is considered an environmental threat in Iran. The study was performed on soil near the Saravan dumpsite and measured the concentrations of 8 metals (Zn, Cu, As, Hg, Pb, Cr, Cd, and Ni) in soil, by inductively coupled plasma mass spectrometry. The average content of As, Cu, Cr, Pb, Zn, Hg, Ni, and Cd in soil were 10.48, 20.22, 19.07, 24.95, 28.83, 0.13, 19.91, and 0.1 mg/kg, respectively. The mobility factors based on water-soluble and exchangeable fractions were As (8.85%), Zn (4.19%), Pb (1.85%), Cu (1.60%), and Cr (0.02%), and not detectable for Hg, Ni, and Cd. Evaluation of metals contamination by pollution index, integrated pollution index, and Nemerowʼs pollution index for each metal showed that PI for all metals except Hg was in the range of low to moderate, and for Hg, 50% in high pollution grade; the average of the IPI (1.21), indicated a moderate pollution condition; the mean value of the PINemerow (1.20), which was in slight pollution grade. The correlations between total concentrations of metals, and bioavailable fractions with microbial biomass carbon, basal respiration, microbial quotient, metabolic quotient, urease, and alkaline phosphatase activities were moderate (r = 0.4-0.6). The activity of urease was from 37.79 to 1414.31 µg N gˉ1 dm.2 hˉ1 and alkaline phosphatase from 34.66 to 698.78 µg nitrophenyl gˉ1 dm. hˉ1. Due to the rainy climate and the continuous leaching of the surface soil, we suggested performing waste separation and the treatment of leachate produced before flowing downstream.

Both AOA and AOB contribute to nitrification and show linear correlation with nitrate leaching in purple soils with a wide nitrogen gradient

Ammonia oxidizers play an important role in nitrification that forms nitrate, the main form of leaching nitrogen (N). However, little is known about how ammonia oxidizers bridge long-term N fertilization levels and soil nitrate leaching. We conducted a field experiment in purple soil, investigating the interactions among soil physico-chemical parameters, ammonia-oxidizing microbial communities, and N leaching under 0, 90, 180, 270, and 360 kg N ha−1 yr−1 fertilization levels. We found that soil inorganic N leaching increased exponentially with increasing N application rate. N fertilization enhanced the abundances of the amoA gene in ammonia-oxidizing archaea (AOA) and bacteria (AOB), while partial least squares regression analysis revealed that AOA and AOB abundances were correlated with pH and soil organic carbon (SOC). Compared with no N fertilization, N application reduced AOA alpha diversity and increased AOB alpha diversity. AOA alpha diversity was associated with pH and bulk density, whereas soil SOC and inorganic N content were more important in predicting changes in AOB alpha diversity. A linear relationship was established between soil NO3−-N leaching, the potential nitrification rate (PNR), and the abundances of AOA and AOB. The association of soil NO3−-N leaching and PNR with both AOA and AOB abundances were further corroborated by Mantel test, random forest regression, and partial least squares path modelling. Furthermore, alterations in the AOB alpha diversity, soil pH and NH4+-N content also contribute to the increasing soil NO3−-N leaching along the N application rate. Our results suggest that AOA, which previous studies have found to be active only under low N conditions, can also contribute to nitrification and support soil NO3−-N leaching at a wide range of N gradients. Overall, this finding advances the current understanding of the relationship between soil N leaching and microbial functional properties to some extent.

Phosphorus leaching in high-P soils under maize silage and interseeding cover crop system

Managing soil phosphorus (P) in agroecosystems with high P levels is crucial to mitigate P loss in water sources without compromising yields. The objective of this study was to assess maize silage (Zea mays L.) + interseeding cover crop of annual ryegrass (Lolium multiforum) or using a relay cover crop and starter P (P0, P10, and P20) on (i) P leaching, (ii) changes in soil P status, and (iii) maize yield, cover crop biomass and P uptake. A six-year study was conducted between 2018 and 2023 in two sites. Leachate samples were collected every two weeks between 2021and 2023. The concentration of P in leachate exceeded 0.5 mg L–1 indicating a high risk of P leaching at the current levels of soil P. High concentration of P in leachate with a peak at 0.9 mg L–1 in August and 1.45 mg L–1 in October during 2021 and 2022 was pronounced under interseeded compared to relay cover crop system due to improve water infiltration contributing to the downward movement of P. In contrast, the concentration of P in leachate was high under relay cover crops in February and March particularly in 2023, which could be attributed to the delay in cover crops establishment and growth in early spring. The concentration of P extracted using anion exchange membranes (PO4AEMs) increased with increasing starter P rate during the first weeks after planting maize silage. There were spikes of PO4AEMs, reaching 1.18 and 1.73 µg cm–2 d–1 during the 4th, 7th, and 8th weeks after planting maize which coincided with high soil moisture content occurring after irrigation or rainfall events. The lack of dry matter yield response to starter P at harvest was due to high initial soil P. The soil P status remained significantly high averaging 196.6 mg kg–1 as Mehlich-3 P, despite negative cumulative P budgets. A close observation of the relationships among soil P indicators shows a trend of rapidly decreasing water extractable P under interseeding compared with relay cover crops. It is possible that the production of high biomass under interseeding cover crops increased the amount of P taken up from the soil. We conclude that interseeding cover crops within cash crops in high P soils could be effective at decreasing soil P, but could enhance P leached in the first years of cropping due to high water infiltration along the soil profile.

Response of Typical Shrubs Growth and Soil Nutrients to Graphene Addition in Impoverished Land of the Ulan Buh Desert.

Graphene can promote plant growth and improve soil conditions, but its effectiveness in enhancing infertile soils in arid regions remains unclear. This study selected three typical shrubs from the Ulan Buh Desert Nitraria tangutorum, Xanthoceras sorbifolium, and Amygdalus mongolica as research subjects. Five graphene addition levels were set: 0 mg/L (C0), 25 mg/L (C1), 50 mg/L (C2), 100 mg/L (C3), and 200 mg/L (C4).A pot experiment was conducted in June 2023 to investigate the effects of graphene addition on shrub growth and soil nutrients. The results showed that the optimal graphene addition levels for A. mongolica, X. sorbifolium, and N. tangutorum were C2, C2, and C3, respectively. Compared with the control, the total biomass of the different shrubs increased by 185.31%, 50.86%, and 161.10%, respectively. However, when the graphene addition exceeded the optimal level, shrub biomass showed a decreasing trend with increasing graphene concentration. Total shrub biomass was positively correlated with soil available nitrogen and potassium, while redundancy analysis indicated that soil organic matter was the primary factor influencing shrub growth. This suggests that graphene promotes shrub growth by affecting soil organic matter and available nutrients. Therefore, graphene addition can enhance soil fertility in barren lands in arid regions and significantly promote shrub growth. However, due to soil leaching effects, this growth-promoting effect may decrease over time.

Predicting Behavior and Fate of Atmospheric Mercury in Soils: Age-Dating METAALICUS Hg Isotope Spikes with Fallout Radionuclide Chronometry.

Soils accumulate anthropogenic mercury (Hg) from atmospheric deposition to terrestrial ecosystems. However, possible reemission of gaseous elemental mercury (GEM) back to the atmosphere as well as downward migration of Hg with soil leachate influence soil sequestration of Hg in ways not sufficiently understood in global biogeochemical models. Here, we apply fallout radionuclide (FRN) chronometry to understand soil Hg dynamics by revisiting the METAALICUS experiments 20 years after enriched isotope tracers (198Hg, 200Hg, 201Hg, and 202Hg) were applied to two boreal watersheds in northwestern Ontario, Canada. Hg spikes formed well-defined peaks in organic horizons of both watersheds at depths of 3-6 cm and were accurately dated to the year of spike application in 6 of 7 cases (error = -0.8 ± 1.2 years). A seventh site was depleted by ca. 90% of both the 200Hg spike and background Hg, and the spike was dated 16 years older than its application. Robust FRN age models and mass balances demonstrate that loss of Hg is attributable to its specific physicochemical behavior at this site, but more work is required to attribute this to reemission or leaching. This study demonstrates the potential of FRN chronometry to provide insights into Hg accumulation, mobilization, and fate in forest soils.

Cocoa pod husk-derived organic soil amendments differentially affect soil fertility, nutrient leaching, and greenhouse gas emissions in cocoa soils

The depletion of soil nutrients and decline in yields on cocoa farms in west Africa over time force farmers to abandon their farms and look for new fertile land, thereby contributing to deforestation. Cocoa pod husks (CPH) are a major farm waste representing considerable export of nutrients from cocoa soils, particularly P and K. Here, the impacts of soil amendment with raw CPH residues, CPH compost, CPH biochar, or a CPH compost-biochar mixture on soil fertility, greenhouse gas (GHG) emissions, and nutrient losses via leaching were assessed in two laboratory experiments using two major soil types used for cocoa cultivation in Ghana (an acidic Ferralsol and an alkaline Nitisol). In Experiment 1, soil nutrient availability and CO2 and N2O emissions were quantified, whereas simulation and quantification of nutrient leaching were conducted in Experiment 2. Soil pH increased from 4.8 to 8.6 by 1.4- and 1.1-folds on average in amended Ferralsols and Nitisols, respectively. Soil electrical conductivity increased in soils amended with CPH compost and/or biochar. Addition of raw CPH caused remarkable microbial immobilisation of N and reduced N availability and leaching, whereas CPH compost and/or biochar addition increased soil nitrate availability but reduced soil ammonium availability. Leaching of Ca in Nitisols was reduced when CPH biochar was included in the soil amendment. While soil K availability increased in all amended soils, most notably when CPH biochar was included, soil P and Ca availabilities were greatest where CPH compost was included. Soil total GHG emission (CO2 plus N2O) increased in all amended Ferralsols and the Nitisols amended with CPH compost or raw CPH, with the latter remarkably increasing soil CO2 emission by up to 14.8-folds. Compared to sole CPH compost amendment, CPH compost-biochar mixture amendment reduced soil total GHG emission and N and P leaching. These findings show that composted and/or pyrolysed CPH can be judiciously used to enhance soil fertility in cocoa farms, particularly in acidic soils. Pyrolysed CPH is especially beneficial for reducing soil nutrient leaching and GHG emissions and thus for increasing the sustainability of cocoa production in Ghana and west Africa.

Visual signal transduction for environmental stewardship: A novel biosensing approach to identify and quantify chlorpyrifos-related residues in aquatic environments

The pervasive presence of organophosphate pesticides (OPs), such as chlorpyrifos (CPF), in aquatic ecosystems underscores the urgent need for sensitive and reliable detection methods to safeguard environmental and public health. This study addressed the critical need for a novel biosensor capable of detecting CPF and its toxic metabolite, 3,5,6-trichloro-2-pyridinol (TCP), with high sensitivity and selectivity, suitable for field applications in environmental monitoring. The study engineered a whole-cell biosensor based on E. coli strains that utilize the ChpR transcriptional regulator and the vioABCE gene cluster, providing a distinct visual and colorimetric response to CPF and TCP. The biosensor's performance was optimized and evaluated across various water matrices, including freshwater, seawater, and soil leachate. The biosensor demonstrated high sensitivity with a broad linear detection range, achieving limits of detection (LODs) at 0.8 μM for CPF and 7.813 nM for TCP. The linear regression concentration ranges were 1.6–12.5 μM for CPF and 15.6–125 nM for TCP, aligning with environmental standard limits and ensuring the biosensor's effectiveness in real-world scenarios. This innovative biosensing approach offers a robust, user-friendly tool for on-site environmental monitoring, significantly mitigating OPs contamination and advancing current detection technologies to meet environmental protection standards.

Release of selected nutrients from polymer-coated fertilisers in the soil environment

The aim of the study was to evaluate the release of NH4-N and PO4-P from polymer-coated fertilisers in the soil environment, and to analyse their impact on pH and conductivity of the soil leachates. In this investigation mineral NPK(S) 6-20-30(7) fertiliser (as a starting material), commercial, controlled-release OsmocoteTM fertiliser (as a reference material) and four polymer-coated fertilisers have been used. Biodegradable polybutylene(succinate-co- dilinoleate), polyethylene(succinate-co-terepftalate) and chitosan have been used as coating materials. The experiments were conducted in the laboratory conditions, in PVC columns filled with air-dry soil. The nutrients release from the investigated materials was explained based on the diffusion mechanism and it was interpreted with the use of the Korsmeyer–Peppas kinetic model. Two mechanisms dominate in the release process of nutrients: the mechanism based on quasi-Fickian diffusion and non-Fickian (anomalous case) mechanism. The largest changes of pH and electrical conductivity (EC) of soil leachates occurred in the initial period of research for all tested fertilisers (pH: 9.5–20.3% – loamy sand (S1) 7.9–20.6% – sandy loam (S2); EC: 438–1667% – S1, 771–1509% – S2). The polymer coating significantly reduces the nutrient release from the fertiliser core. The size of these changes depends on the type and thickness of the polymer layer and the physicochemical properties of the soils.

Effect of Microplastics and Straw Addition on Nitrogen and Phosphorus Leaching in Orange Orchard Soils

To explore the effects of microplastic input and straw addition on nitrogen and phosphorus leaching in orange orchard soil, indoor soil column leaching simulation experiments were conducted on orange orchard soil in Dangyang City, Hubei Province. The experiment analyzed the effects of different treatments on the leaching characteristics of soil nitrogen and phosphorus. The results showed that： ① The increase in microplastic input increased the leaching capacity of the soil （TN, NO3--N, NH4+-N, and TP） when only microplastic input was added. ② Under the addition of straw, the input of microplastics increased, which reduced the leaching amount of TN and NO3--N in the soil, and increased the leaching amount of NH4+-N and TP in the soil. ③ Under the input of microplastics, the key influencing factors of soil nitrogen and phosphorus leaching were soil bulk density and water content. Under straw addition, it was mainly affected by soil carbon and nitrogen content. Among them, microplastic input and straw addition significantly increased soil pH, but their path coefficients for nitrogen and phosphorus leaching were not significantly correlated. The results showed that the effects of polypropylene microplastic input and straw addition on soil nitrogen and phosphorus leaching were related to the amount of microplastics input and whether straw was added. The results showed that the input of microplastics would increase the amount of soil nitrogen and phosphorus leaching. Although nitrogen leaching loss caused by microplastic input could be reduced under straw addition, soil phosphorus leaching loss was significantly increased.

Water dispersible carbon nanomaterials reduced N, P, and K leaching potential in sandy soils: A column leaching study

Carbon nanomaterials (CNMs) — amendments with carbon in nanoscale form —could potentially enhance fertilizer delivery efficiency in agriculture, but their interaction with soil properties and nutrient co-mobility, especially in coarse-textured soils, remain poorly understood. We conducted a column leaching study in repacked soil columns to compare the co-leaching of novel water-dispersible CNMs and soil nutrients across two levels of CNMs applications (200 & 400 mg kg−1), two fertilization rates (low:80 mg kg−1 of N, P and K and high: 200 mg N kg−1, 100 mg P kg−1, 200 mg K kg−1, applied as ammonium nitrate, potassium phosphate, and potassium nitrate) and two soils (Spodosol with pH = 5.1, Alfisol with pH = 6.5). We imposed 12 leaching events to each column, with each leaching event adding water equivalent to the soil-pore volume (250 mL), resulting in cumulative leaching of 3000 mL of water through each column. CNMs applications reduced cumulative leaching losses of NO3-N (Spodosol: 8–12 %, Alfisol: 9–19 %), NH4-N (Spodosol: 2–14 %, Alfisol: 9–14 %), P (Spodosol: 23–27 %, Alfisol: 23–36 %) and K (Spodosol: 17–23 %, Alfisol: 24–26 %) compared to fertilized columns without CNMs. CNMs increased soil pH by up to 0.3 units (Spodosol) or 0.5 units (Alfisol), while lowering electrical conductivity by 15–20 % at the high fertilization rate in both soils. Columns with water-dispersible CNMs accumulated 25–30 % more total C in the base sections of the Alfisol compared to the Spodosol, indicating faster downward movement through the soil profile. Overall, we demonstrated that CNMs have the potential to reduce nutrient leaching in coarse-textured soils, which could be particularly beneficial in high-input intensive agricultural systems.

Soil and water management perspectives for tropical and dryland areas of Africa

Soil and water are two natural resources that deliver various functional services to humanity. Advanced soil and water management is highly needed in the tropics. This revision focused on soil and water management issues in the tropics, soil and water management linkages to major soil functional groups (soil health, soil quality, soil fertility, water quality, and soil function), soil quality management and rehabilitation, and soil quality assessment. This study revealed that soil indictors are physical, chemical and biological, reflecting a better understanding of the major soil functional groups in an integrated soil water assessment for better soil and water management in the tropics. Regular checks and balances of comprehensive soil water management can lead to reduced soil erosion, increased water use efficiency, enhanced soil nutritional content, improved infiltration and water holding capacity, minimized runoff and surface soil leaching of pesticides and inorganic chemicals to groundwater reservoirs, increased decomposition and soil organic matter, enhanced soil biodiversity, and increased plant health and food security. To make this viable, an integrated assessment of soil water indicators and the application of sustainable soil water management approaches are needed. Regular checks and balances of the current status of soil and water quality and soil fertility must be given permanent priority.