Increased Soil Cation Exchange Capacity Research Articles

Effects of Balancing Exchangeable Cations Ca, Mg, and K on the Growth of Tomato Seedlings (Solanum lycopersicum L.) Based on Increased Soil Cation Exchange Capacity

(1) Background: Previous research has demonstrated that the cation exchange capacity (CEC) of soil and the balance of exchangeable cations Ca, Mg, and K are key factors affecting plant growth and development. We hypothesized that balancing exchangeable cations based on increased CEC would improve plant growth and development. (2) Methods: This study conducted a two-phase experiment to evaluate methods for increasing soil CEC and the effects of increasing CEC and balancing Ca, Mg, and K on plant growth. Therefore, we first conducted a soil culture experiment using organic fertilizer, montmorillonite, and humic acid to investigate fertilizers that can effectively increase CEC in the short term. Then, a tomato seedling pot experiment was conducted using the control (CK) and OMHA fertilizer-treated soils collected from soil culture experiments. The CK and OMHA treatment soils were constructed with balanced exchangeable cations and an unbalanced control, respectively. (3) Results: The soil culture experiments revealed that the combination of organic fertilizer, montmorillonite, and humic acid (OMHA treatment) had the most significant effect on increasing CEC. The CEC of the OMHA treatment increased by 41.07%, reaching 27.10 cmol·kg−1. The tomato pot experiments demonstrated that balancing the exchangeable cations in OMHA soil improved the Mg and K nutrition of tomato seedlings and significantly increased SPAD, leaf nitrogen content, and dry weight, while balancing the exchangeable cations in CK soil improved only the K nutrition of tomato seedlings. (4) Conclusions: Overall, balancing exchangeable cations based on increasing CEC can improve soil nutrient availability and alleviate the competition effects of Ca, Mg, and K cations. Low CEC and imbalanced exchangeable cations can be detrimental to tomato seedling growth.

Bioremediation of chlorpyrifos-contaminated soil with biduri plant (Calotropis gigantea), bacteria, and biochar: Soil fertility impact

During the Industrial Revolution, agriculture was linked to environmental issues. One issue is pesticide pollution. Bioremediation is needed because plant diseases and pests cause farmers to use pesticides excessively, polluting and decreasing soil production. This study evaluated soil fertility from bioremediation with biduri plants, bacteria, and biochar on chlorpyrifos-polluted shallot-growing soil in Brebes Regency. This type of research was an experiment in a greenhouse, using a factorial experimental design with a completely randomized design, consisting of two factors, namely bioremediation agent (A0: without bioremediation agent, A1: Atlantibacter hermannii, A2: bacterial consortium) and coconut shell biochar (B0: without biochar, B1: with biochar). There were six treatment combinations, then replicated three times for each treatment, so there were 18 treatment units. The data were statistically analyzed using ANOVA, Duncan Multiple Range Test, and Pearson correlation. The results showed that the best treatments that were able to improve soil fertility after bioremediation were treatments A1B0 (Atlantibacter hermannii + without biochar), A2B0 (bacterial consortium + without biochar), and A2B1 (bacterial consortium + with biochar). The A1B0 treatment (Atlantibacter hermannii + without biochar) increased the pH by 4.97%, and the soil available P was 12 times higher than the initial soil. The A2B0 (bacterial consortium + without biochar) treatment increased soil cation exchange capacity by 99.81% and soil organic C by 116% higher than the initial soil. The A2B1 (bacterial consortium + with biochar) treatment increased soil total N by 37.50% and available K by 38.47%, higher than the initial soil.

Research Progress of Biochar and Pollution Control

In recent years, due to the impact of climate change caused by the emission of greenhouse gases such as carbon dioxide, nitrous oxide and methane, scientists have begun to pay attention to the use of biochar, because it helps to capture and remove greenhouse gases in the atmosphere by means of biochar storage, converting it into a very stable form and storing it in the soil for thousands of years. This paper focuses on the hazards of organic pollutants, the treatment of pollutants by biochar and the benefits of environmental remediation. Biochar is the product of biomass energy raw material after pyrolysis, and its main component is carbon molecule. In terms of pollution treatment, biochar has a strong adsorption capacity for organic pollutants such as phenol, and can also improve soil heavy metal pollution by increasing soil cation exchange capacity (CEC) and PH. In addition, biochar is also used in low-temperature NH3-SCR denitrification catalysts to deal with nitrogen oxides in atmospheric pollutants and other aspects. Biochar is easy to ignite, non-polluting, smokeless and tasteless, less residue after combustion, light weight and high calorific value, the use of performance is better than most similar materials, known as the main force of human new energy and future fuel. The purpose of this paper is to provide the basis and reference for the development of biochar basic science and application technology.

The use of animal manure for improving chemical properties of degraded Ultisol, yield, and secondary metabolic of Zingiber montanum

Ultisols in Indonesia have the potential for agricultural development, but the soils have low pH and nutrient contents that hinder plant growth and yield. Using animal manure can be an alternative to improve soil productivity and crop yields. This study aimed to examine the effects of animal manure on the chemical properties of Ultisol, yield, and secondary metabolic of <em>Zingiber montanum</em>. The treatments tested were combinations of types of manure (cow and chicken manure) and manure application levels, namely P0 (control), P1 (cow manure 20 t/ha), P2 (cow manure 40 t/ha), P3 (cow manure 60 t/ha), P4 (chicken manure 20 t/ha), P5 (chicken manure 40 t/ha), and P6 (chicken manure 60 t/ha). The results showed that the application of chicken manure of 60 t/ha increased N and P contents of the soil, and the application of cow manure of 60 t/ha increased soil cation exchange capacity. The application of cow manure of 60 t/ha gave the highest plant height, the number of leaves, and the number of at 18 weeks after planting, while the application of chicken manure dose of 60 t/ha produced the longest plant roots. The highest fresh and dry rhizome weight was observed for the 60 t/ha cow manure treatment. The highest secondary metabolic levels in each parameter were found in dry rhizomes (phenolic, flavonoid, and tannin) and fresh rhizomes (phenolic and flavonoid), with the highest tannin compound in the treatment of 40 t chicken manure/ha. The application of chicken manure at a dose of 60 t/ha resulted in a strong antioxidant yield in fresh and dry rhizomes.

Change of tetracycline speciation and its impacts on tetracycline removal efficiency in vermicomposting with epigeic and endogeic earthworms

Tetracycline pollution is common in Chinese arable soils, and vermicomposting is an effective approach to accelerate tetracycline bioremediation. However, current studies mainly focus on the impacts of soil physicochemical properties, microbial degraders and responsive degradation/resistance genes on tetracycline degradation efficiencies, and limited information is known about tetracycline speciation in vermicomposting. This study explored the roles of epigeic E. fetida and endogeic A. robustus in altering tetracycline speciation and accelerating tetracycline degradation in a laterite soil. Both earthworms significantly affected tetracycline profiles in soils by decreasing exchangeable and bound tetracycline but increasing water soluble tetracycline, thereby facilitating tetracycline degradation efficiencies. Although earthworms increased soil cation exchange capacity and enhanced tetracycline adsorption on soil particles, the significantly elevated soil pH and dissolved organic carbon benefited faster tetracycline degradation, attributing to the consumption of soil organic matter and humus by earthworms. Different from endogeic A. robustus which promoted both abiotic and biotic degradation of tetracycline, epigeic E. foetida preferently accelerated abiotic tetracyline degradation. Our findings described the change of tetracycline speciation during vermicompsiting process, unraveled the mechanisms of different earthworm types in tetracycline speciation and metabolisms, and offered clues for effective vermiremediation application at tetracycline contaminated sites.

Biochar related treatments improved physiological performance, growth and productivity of Mentha crispa L. plants under fluoride and cadmium toxicities

Modification of biochar with chemical reagents is an effort to increase the efficiency of this organic material to adsorb environmental pollutants. Typically, these chemically modified materials have special structural specifications that allow the adsorption and stabilization of high levels of environmental pollutants. Therefore, this research was carried out to assess the possible effects of solid and chemically engineered biochars (non-biochar, solid biochar, modified biochar with H2O2, KOH, and H3PO4) on reducing fluoride and cadmium toxicities (non-toxic, 600 mg NaF kg−1 soil, 60 mg Cd kg−1 soil and 600 mg NaF kg−1 soil + 60 mg Cd kg−1) in mint plants (Mentha crispa L.). The application rate of biochar and modified biochars was 25 g kg−1 soil. The addition of biochar and especially engineered biochars to the soil reduced the availability of fluoride and cadmium to the plants. Biochar and chemically modified biochars increased soil cation exchange capacity (CEC) (up to 31%), pH (up to 11%), leaf area (up to 22%), chlorophyll content index (up to 19%), maximum efficiency of photosystem II (up to 32%), biomass (up to 21%) and essential oil production (up to 28%) in mint plants. On the other hand, biochar-related treatments reduced the reactive oxygen species generation, antioxidant enzymes activities, and lipid peroxidation in the root (up to 41%) and leaf tissues (up to 40%). In general, modified biochars showed a better effect than solid biochar in reducing fluoride and cadmium toxicities. The H3PO4-modified biochar was a bit more successful than other biochar-related treatments in increasing mint performance under fluoride and cadmium toxicities. Therefore, the chemically engineered biochars are the superior treatments to improve mint growth and productivity under fluoride and cadmium toxicities, because of their excellent physicochemical specifications such as high level of CEC, functional groups, and specific surface area.

Assessing the Effect of Intensive Agriculture and Sandy Soil Properties on Groundwater Contamination by Nitrate and Potential Improvement Using Olive Pomace Biomass Slag (OPBS)

The relationship between agricultural activities, soil characteristics, and groundwater quality is critical, particularly in rural areas where groundwater directly supplies local people. In this paper, three agricultural sandy soils were sampled and analyzed for physicochemical parameters such as pH, water content, bulk density, electrical conductivity (EC), organic matter (OM), cation exchange capacity (CEC), and soil grain size distribution. Major and trace elements were analyzed by inductively coupled plasma-optical emission spectrometry (ICP/OES) to determine their concentrations in the fine fraction (FF) of the soils. Afterward, the elemental composition of the soils was identified by X-ray powder diffraction (XRD) and quantified by X-ray fluorescence (XRF). The surface soil characteristics were determined by the Brunauer–Emmett–Teller (BET) method, whereas the thermal decomposition of the soils was carried out using thermogravimetric analysis and differential scanning calorimetric (TGA-DSC) measurements. The morphological characteristics were obtained by scanning electron microscopy (SEM). Afterward, column-leaching experiments were conducted to investigate the soil’s retention capacity of nitrate (NO−3). Parallelly, a chemical and physical study of olive pomace biomass slag (OPBS) residue was carried out in order to explore its potential use as a soil additive and improver in the R’mel area. The OPBS was characterized by physicochemical analysis, assessed for heavy metals toxicity, and characterized using (XRD, XRF, SEM, and BET) techniques. The results show that the R’mel soils were slightly acidic to alkaline in nature. The soils had a sandy texture with low clay and silt percentage (<5% of the total fraction), low OM content, and weak CEC. The column experiments demonstrated that the R’mel irrigated soils have a higher tendency to release large amounts of nitrate due to their texture and a higher degree of mineralization which allows water to drain quickly. The OPBS chemical characterization indicates a higher alkaline pH (12.1), higher water content (7.18%), and higher unburned carbon portion (19.97%). The trace elements were present in low concentrations in OPBS. Macronutrients in OPBS showed composition rich in Ca, K, and Mg which represent 10.59, 8.24, and 1.56%, respectively. Those nutrients were quite low in soil samples. Both XRD and XRF characterization have shown a quasi-dominance of SiO2 in soil samples revealing that quartz was the main crystalline phase dominating the R’mel soils. Oppositely, OPBS showed a reduced SiO2 percentage of 26,29% while K, Ca, and P were present in significant amounts. These results were confirmed by XRF analysis of OPBS reporting the presence of dolomite (CaMg, (CO3)2), fairchildite (K2Ca (CO3)2), and free lime (CaO). Finally, the comparison between the surface characteristic of OPBS and soils by BET and SEM indicated that OPBS has a higher surface area and pore volume compared to soils. In this context, this study suggests a potential utilization of OPBS in order to (1) increase soil fertility by the input of organic carbon and macronutrients in soil; (2) increase the water-holding capacity of soil; (3) increase soil CEC; (4) stabilize trace elements; (5) enhance the soil adsorption capacity and porosity.

Pengaruh Pemberian Zeolit Alam Teraktivasi terhadap Sifat Kimia Tanah Podsolik

Podsolic soil in South Kalimantan has a low fertility rate including pH, organic matter, cation exchange capacity (CEC), solubility P, and has a high solubility of aluminum (Al) and iron (Fe). It causes fixation P by Al and Fe in the form of Al-P and Fe-P, which makes P difficult to dissolve in the soil. Zeolite is an ameliorant that is capable of improving soil chemical properties based on its ability to carry out ion exchange, adsorption, absorb molecules, increase fertilizer efficiency, increase soil CEC, and the availability of Ca, K, and P ions, which can reduce aluminum content. The purpose of this study was to identify the pattern of relationships caused by application of activated natural zeolite on Podsolic soil against pH, CEC, available P, soluble Fe, and exchangeable Al. This study was a pot experiment weighing 0.5 kg of soil, carried out in a greenhouse and arranged using CRD a single factor . The incubation period was carried out for eight weeks with three replications. The results showed that there was a relationship between the zeolite dose activated against the available P (the linear regression equation Y = 0.6 + 0.032 X, R2 = 0.4969, and r = 0.7006*), while the doses of zeolite had no significant effect on pH, CEC, soluble Fe, and exchangeable Al.

Coordination of photosynthetic traits across soil and climate gradients.

"Least-cost theory" posits that C3 plants should balance rates of photosynthetic water loss and carboxylation in relation to the relative acquisition and maintenance costs of resources required for these activities. Here we investigated the dependency of photosynthetic traits on climate and soil properties using a new Australia-wide trait dataset spanning 528 species from 67 sites. We tested the hypotheses that plants on relatively cold or dry sites, or on relatively more fertile sites, would typically operate at greater CO2 drawdown (lower ratio of leaf internal to ambient CO2 , Ci :Ca ) during light-saturated photosynthesis, and at higher leaf N per area (Narea ) and higher carboxylation capacity (Vcmax 25 ) for a given rate of stomatal conductance to water vapour, gsw . These results would be indicative of plants having relatively higher water costs than nutrient costs. In general, our hypotheses were supported. Soil total phosphorus (P) concentration and (more weakly) soil pH exerted positive effects on the Narea -gsw and Vcmax 25 -gsw slopes, and negative effects on Ci :Ca . The P effect strengthened when the effect of climate was removed via partial regression. We observed similar trends with increasing soil cation exchange capacity and clay content, which affect soil nutrient availability, and found that soil properties explained similar amounts of variation in the focal traits as climate did. Although climate typically explained more trait variation than soil did, together they explained up to 52% of variation in the slope relationships and soil properties explained up to 30% of the variation in individual traits. Soils influenced photosynthetic traits as well as their coordination. In particular, the influence of soil P likely reflects the Australia's geologically ancient low-relief landscapes with highly leached soils. Least-cost theory provides a valuable framework for understanding trade-offs between resource costs and use in plants, including limiting soil nutrients.

Response of alkaline functional fertilizer on Cd absorption and transportation in soil-rice system

Reduction of cadmium accumulation in rice grain is of great significance for food safety. The purposes of this study were to investigate the efficacy and mechanism of alkaline functional fertilizer (AFF) on soil acid, available cadmium (Cd) and its and accumulation in rice through three field experiments in Hunan province with different soil type by use of conventional fertilizer as control. Results showed that soil pH value was increased with the amount of the AFF, the maximum increment of the pH was 1.65 units. Soil available Cd was reduced with increase of the AFF and soil pH value, and it decreased by 12 %, 38 % and 44 % in the three sites, respectively. The rice yield was related to the original or basal soil pH and available cadmium content. The yield increased by 4–16 %, 12–27 % and 9–24 %, respectively. Cd content of root, stem, leaf and polished rice reduced by 78.75 %, 88.05 %, 84.05 % and 80.38 % by use of the AFF in the three sites, respectively. The Cd content of polished rice would be declined below the allowable limit of food safety standard in China (0.2 mg·kg−1). The Cd enrichment coefficient (ERC) was in the order of root > stem > leaf > polished rice. The results of index of transport coefficient (TC) showed that Cd in polished rice mainly came from stem and leaf. The Cd content in the leaf and stem should be reduced first to reduce the Cd content of polished rice. The mechanism of the AFF reducing Cd uptake and accumulation lies in the fertilizer neutralizing both active and potential soil acid by slow release of OH–. The fertilizer was capable to increase soil cation exchange capacity and passivate Cd to reduce its bio-availability. Development and promotion of the AFF are significance to decline Cd transport in the soil–plant ecosystem and ensure food safety. The recommended economic fertilization rate of the AFF is 3000 to 4500 kg/ha.

Modified Biochars and Their Effects on Soil Quality: A Review

Biochar (BC) has attracted attention due to its impacts on soil quality by enhancing soil fertility, carbon storage and contaminants immobilization. BC also induces changes in microbial community structure and enhances crop productivity in long term scenarios compared to many other organic amendments. However, information related to the role of modified BCs in altering the soil quality is still scarce. BC can be modified by using physical, chemical and microbial methods. Modified BC can change the functional groups, pore size, pore structure, surface area and chemical properties of soil, which plays a key role in changing the soil quality. The addition of modified BCs as soil amendment increased soil CEC (cation exchange capacity), EC (electron conductivity), pH, organic matter, hydraulic conductivity, soil porosity, infiltration rate, microbial activities (enzymes and community), nutrient profile and gas exchange properties, but it varies according to the soil structure and pervading environmental conditions. This study provides a basis for effective practical approaches to modifying BCs for improving soil quality.

Barley Straw Biochar and Compost Affect Heavy Metal Transport in Soil and Uptake by Potatoes Grown under Wastewater Irrigation

Wastewater can supplement freshwater in agriculture; however, it contains toxic heavy metals such as cadmium, chromium, and lead that are hazardous to humans and the environment. We investigated the effects of barley straw biochar, green and table waste compost, and their mix on heavy metal transport in soil and uptake by potatoes (Solanum tuberosum L.) irrigated with synthetic wastewater for two years. In both years, amending soil with compost significantly reduced (p ≤ 0.05) cadmium uptake in potato flesh, skin, roots, and stems; zinc uptake in potato skin and roots; and copper uptake in potato flesh due to increased soil cation-exchange capacity, dissolved organic carbon, and soil pH. Co-amending the soil with compost and 3% biochar significantly reduced (p ≤ 0.05) the bioavailability of cadmium, copper, and zinc in the contaminated soil. Relative to the non-amended soils, soil amendment with biochar, compost, and their mix affected neither the transport of chromium, iron, and lead in the soils nor their uptake by potatoes. It was concluded that amending soil with barley straw biochar and/or compost produced from city green table waste could be used to improve the safety of wastewater irrigated potatoes, depending on the biochar application rate and heavy metal type.

Soil amendment with a humic substance and arbuscular mycorrhizal Fungi enhance coal mine reclamation

Coal mine sites covered by sandy soils often have low nutrient and high heavy metal concentrations, making reclamation for agricultural uses challenging. Although the combined use of humic substances and soil biota has generated considerable research interest, little information is available regarding their synergistic effects. In a two year field study, we assessed the effects of sole and combined applications of a humic substance product called nano humus (150 g/m2 in soils), arbuscular mycorrhizal fungi (250 g inocula/m2 in soils), and fertilizer (37 g/m2 in soils) on soil chemical properties, soil heavy metals, and growth of alfalfa (Medicago ruthenica L.) and barley (Hordeum vulgare L.). Application of arbuscular mycorrhizal fungi with nano humus exhibited greatest effects in year two. Relative to untreated soils, they increased soil cation exchange capacity by 38%, total organic carbon by 36%, and available nitrogen, phosphorus, and potassium by 20 to 92%; they reduced concentrations of soil cadmium by 25% and of arsenic by 9%. Mycorrhizal colonization rate and soil heavy metal concentrations were significantly negatively correlated, suggesting an inhibition effect of metals on colonization. The combination of arbuscular mycorrhizal fungi and nano humus showed greatest impact on root and shoot biomass of alfalfa, which increased 18 and 12 times, respectively. Barley responded most positively to combinations of arbuscular mycorrhizal fungi, nano humus, and fertilizer; root biomass increased 4 times, and shoot biomass and seed production increased 3 times. Combined applications generally provided greater benefits than sole applications, which could be a useful practice in heavy metal contaminated reclamation sites.

Synergic Effect of Microorganism and Colloidal Biochar-Based Organic Fertilizer on the Growth and Fruit Quality of Tomato

It is well known that carbon-based organic fertilizer can effectively promote crop growth and improve nutrient utilization efficiency. However, little is known about the effect of microorganisms on the nutrient availability of carbon-based organic fertilizer. To elucidate the contribution of microorganisms to the agricultural benefit of colloidal biochar-based fertilizer, a 5-month pot experiment was conducted to study the effect of different combinations of Methyltrophic bacillus, colloidal biochar, and organic fertilizer on physical–chemical properties of soil, plant growth, physiological-biochemical reactions, yield, and quality of tomato. The results show that the addition of Methyltrophic bacillus effectively promoted the availability of soil nutrients (such as nitrate nitrogen and available potassium) and increased soil cation exchange capacity; meanwhile, it significantly increased the content of chlorophyll-a (9.42–27.41%) and promoted the net photosynthetic rate (10.86–13.73%) and biomass of tomato fruit (17.84–26.33%). The contents of lycopene, vitamin C, total sugar, and soluble sugar in the fruits treated by the ternary combination of Methyltrophic bacillus, colloidal biochar, and organic fertilizer increased by 58.40%, 46.53%, 29.45%, and 26.65%, respectively. The above results demonstrate that the addition of beneficial microorganisms could further improve the performance of biochar-based fertilizer on plant growth, yield, and fruit quality of tomato. This information provides evidence for the promising performance of microorganism-supported biochar organic fertilizer in agricultural applications.

Physicochemical Changes in Loam Soils Amended with Bamboo Biochar and Their Influence in Tomato Production Yield

Soil degradation and water stress in Costa Rica challenge the production of highly sensitive crops. This work is aimed at evaluating the physical and chemical changes in sandy loam (SL) and a silt loam (SiL) soil when amended with bamboo biochar while estimating the enhancement of tomato productivity. Biochar, obtained from Guadua Angustifolia bamboo feedstock, was mixed into sieved bulk soil substrate from the topsoil, from Andosol and Umbrisol groups, at application rates of 1, 2.5, and 5% (dry mass). Physicochemical and morphological properties of biochar such as pH, hydrophobicity, scanning electron microscopy images, helium picnometry, specific surface area by the Brunauer–Emmett–Teller (BET) method, CHNS, and ash content were determined. Soil hydrophobicity, acidity, electrical conductivity, cation exchange capacity and water retention, available water content, and air capacity were analyzed for the amended soils. Tomato yield was quantified after a harvest period of two months. The admixture of biochar did not significantly increase soil cation exchange capacity but increased water retention in the range of available water content. Class A (>200 g) tomato yield increased 350% in the SL and 151% in the SiL. Class B (100–200 g) tomato yields increased 27% in the SL but decreased about 30% in the SiL. Tomato yield response seems attributable to variation of water retention capacity, available water content, and air capacity. These results support the use of adapted water management strategies for tomato production based on soil physical changes of biochar.

Availability of soil base cations and micronutrients along soil profile after 13-year nitrogen and water addition in a semi-arid grassland

Alteration in the availability of soil base cations and micronutrients is critical to maintain stable ecosystem functioning under the predicted global change scenarios. However, changes in these soil cations and their relationships with soil physiochemical properties along soil profile remain unclear under the combined increasing N deposition and precipitation changes. In this study, the concentrations of soil exchangeable base cations (Ca, Mg, K and Na) and available micronutrients (Fe, Mn, Cu and Zn) were determined along an 80-cm soil profile after 13-year continuous N and water manipulation in a semi-arid grassland. Our results showed that N addition significantly decreased exchangeable Ca (− 25.4%, averaging across the three N addition rates) and Mg (− 7.8%) at the depth of 10 cm while increased available Fe (+ 70.5%), Mn (+ 64.7%), and Cu (+ 26.0%). Besides, the magnitude of the increase or decrease escalated with the rates of additional N. Such pattern was also true for the concentrations of available Fe, Mn and Cu in the 10–20 cm soil layer, but the magnitude of changes was much smaller than in the top 10-cm soil layer. Nevertheless, N addition increased the concentrations of the three available micronutrients across the entire profile, indicating that Fe, Mn and Cu were more sensitive to N addition in subsoils than surface soils. Nitrogen addition significantly reduced soil cation exchange capacity (CEC) in the top 10-cm and soil base saturation (BS) ratio in the top 20-cm soil, while water addition significantly increased soil CEC and BS ratio in the top 20-cm soil. Water addition significantly increased Na (+ 75.1%) in the entire soil profile and increased Ca (+ 14.8%), Mg (+ 12.7%) at the 0–10, 10–20 and 40–60 cm soil layers. Soil pH positively correlated with soil exchangeable Ca, Mg and Na, but negatively with available Fe, Mn and Cu in the upper 20 cm. Soil base cations and CEC positively correlated with clay and silt contents, but negatively with sand content along the profile. These results can extend our understandings on soil cation dynamics to deep soil profile under long-term N and water addition and suggest that precipitation effects should be considered when assessing N deposition effects on these soil cations.

Effects of nitrogen fertilizer reduction and biochar application on paddy soil nutrient and nitrogen uptake of rice

We explored the impacts of nitrogen (N) reduction and biochar application on soil fertility and nutrient uptake of rice in early and late seasons of 2018 with a field experiment. There were six treatments, including control (no N application, CK), conventional N application (N100), 20% N reduction (N80), 20% N reduction plus biochar application (N80+BC), 40% N reduction (N60), 40% N reduction plus biochar application (N60+BC). Our results showed that 20% and 40% N reduction and/or with biochar application did not affect soil pH, organic matter, total N, total phosphorous (P), total potassium (K), ammonium N, available P and K in comparison with N100 treatment. N80+BC and N60+BC substantially increased soil cation exchange capacity (CEC) at tillering stage and electrical conductivity (EC) at heading stage in late season, respectively. Compared with the treatment with single N reduction, N80+BC significantly increased soil available K in early and late seasons and soil pH and total N in late season, while N60+BC increased soil total K at mature stage in early season. Soil nitrate content was decreased along with the growth stages for all treatments in early season. Compared with tillering stage, soil nitrate N content in conventional N application at heading stage and mature stage was decreased by 50.0% and 71.6%, respectively. Soil nitrate content in biochar treatment only was decreased by 6.3%-45.5%. N application along with biochar application had no significant effects on plant N uptake and utilization in early season. However, N reduction with biochar application significantly increased plant N uptake and N utilization rate by 34.8%-52.4% in late season, compared to conventional N application and single N reduction. Our findings suggest that adequate N reduction along with biochar application could maintain soil health and improve plant N uptake and utilization efficiency.

Arbuscular Mycorrhizal Fungi Mitigate Nitrogen Leaching under Poplar Seedlings

The leaching of soil nitrogen (N) has become one of the most concerning environmental threats to ecosystems. Arbuscular mycorrhizal (AM) fungi have important ecological functions, however, their influence on soil N leaching and the mechanism of action remain unclear. We conducted a two-factor (N application level × AM inoculation) experiment on poplar, and for the first time, comprehensively analyzed the mechanism by which AM fungi influence soil N leaching. The results showed that, under optimum (7.5 mM) and high (20 mM) N levels, the nitrate (NO3−) and ammonium (NH4+) concentrations of leachate in the AM inoculated treatment (+AM) were lower than in the non-inoculated treatment (−AM), with significant reductions of 20.0% and 67.5%, respectively, under high N level, indicating that AM inoculation can reduce soil N leaching and that it is more effective for NH4+. The arbuscular and total colonization rates gradually increased, and the morphology of spores and vesicles changed as the N level increased. Under optimum and high N levels, +AM treatment increased the root N concentration by 11.7% and 50.7%, respectively; the increase was significant (p < 0.05) at the high N level, which was associated with slightly increased transpiration and root activity despite reductions in root surface area and root length. Additionally, the +AM treatment increased soil cation exchange capacity (CEC), soil organic carbon (SOC), and significantly (p < 0.05) increased the proportions of macroaggregates (but without significant change in microaggregates), causing soil total nitrogen (TN) to increase by 7.2% and 4.7% under optimum and high N levels, respectively. As the N levels increased, the relative contributions of AM inoculation on N leaching increased, however, the contributions of plant physiological and soil variables decreased. Among all of the variables, SOC had important contributions to NH4+ and total N in the leachate, while root N concentration had a higher contribution to NO3−. In conclusion, AM fungi can mitigate soil N leaching and lower the risk of environmental pollution via enhancing N interception by the inoculated fungi, increasing N sequestration in plant roots, and by improving soil N retention.

Vermikompostun Farklı Tekstürlü Toprakların Agregat Stabilitesi, Hacim Ağırlığı ve Bazı Kimyasal Özelliklerine Etkisi

This study was conducted to investigate the effects of vermicompost treatments on physical and chemical characteristics of two soils with different textures. Experiment was conducted in 30 pots with two different soil types, 5 vermicompost doses and 3 replications. Vermicompost doses were placed into 5 kg pots in dry bases and soil-vermicompost mixtures were incubated under laboratory conditions for about 90 days. Vermicompost treatments had significant effects on organic matter content, pH, electrical conductivity (EC) and cation exchange capacity (CEC) of both soils. Increasing organic matter contents and salinity values were observed with increasing vermicompost doses. As compared to the control treatment, soil salinity greatly increased with the greatest vermicompost dose (16 t da-1). With vermicompost treatments, pH of acidic loamy soils increased and pH of clay soils with relatively high pH levels decreased. Since vermicompost has high organic matter content, it increased soil CEC values significantly. There were significant positive correlations between organic matter content and CEC values of the soils. Vermicompost treatments had positive effects also on soil physical characteristics, increased aggregate stability (AS) and decreased bulk density (BD) of the soils. While vermicompost treatments increased aggregate stability of loamy soils remarkably, such effects were not remarkable in clay soils.

15N Natural Abundance, Nitrogen and Carbon Pools in Soil-Sorghum System Amended with Natural and NH4+-Enriched Zeolitites

The use of rocks containing high amounts of natural zeolites (zeolitites) as soil amendment has been found as a valuable method for increasing agriculture sustainability. However, the potentialities and the effects of zeolitites on the biogeochemical cycles of nitrogen (N) and carbon (C) have still not been clearly addressed in the literature. The objective of this study was therefore to investigate the N and C pools and 15N distribution in an agricultural soil amended with both natural and NH4+-enriched zeolitites with the aim of understanding their effects on the soil-plant system, during sorghum cultivation, under fertilization reductions. Zeolitites were applied to an agricultural soil both at natural state (5 and 15 kg m−2) and in an enriched state with NH4+ ions from pig slurry (7 kg m−2). Both zeolitites at natural and enriched state increased soil cation exchange capacity and affected microbial biomass, causing an initial decrease of microbial C and N and then a possible increase of fungal population. N-NO3− content was lower in natural zeolitite treatments, that lead to a lower NO3− availability for denitrifying bacteria. Zeolitites slightly affected the fixed N-NH4+ pool. δ15N turnover indicated that N from NH4+-enriched zeolitites remained in the soil until the growing season and that fertilizers partially substituted the fixed pool. Leaf δ15N content indicated that plants assimilated N from NH4+-enriched zeolitites and evidenced a higher fertilization recovery in natural zeolitite treatments. Organic C tended to be higher in all zeolitite treatment rhizospheres. In soils amended with zeolitites at natural state (at both application rates) sorghum yield was similar (+3.7%) to that obtained in the control while it was higher (+13.9%) in the plot amended with NH4+-enriched zeolitites.