NO3 Leaching Research Articles

Oxyanions Enhancing Crystallinity of Reconstructed Phase for Oxygen Evolution Reaction.

The catalysts were always undergoing continuous amorphization and dissolution of active structure in operating condition, hindering the compatibility between stability and activity for oxygen evolution reaction (OER). Herein, we propose the selective adsorption of leached NO3- to strengthen the crystallinity and activity of surface reconstructed layer with amorphous and crystalline (a-c) heterojunction. Taking a-c Ni doped Fe2O(OH)3NO3·H2O (Ni-FeNH) as a model precatalyst, we uncover that the leached NO3- are readily adsorbs on the crystalline phase in the formed a-c Fe(Ni)OOH during OER, lowering the disorder degree and further activating Ni and Fe ion of the crystalline Fe(Ni)OOH on a-c heterojunctions. Accordingly, Ni-FeNH deliver a low overpotential of 303 mV and high durability of 500 hours at 500 mA cm-2 for OER. Particularly, constructing industrial water electrolysis equipment exhibits high stability of 100 hours under a high operating current of 8000 mA.

Oxyanions Enhancing Crystallinity of Reconstructed Phase for Oxygen Evolution Reaction

The catalysts were always undergoing continuous amorphization and dissolution of active structure in operating condition, hindering the compatibility between stability and activity for oxygen evolution reaction (OER). Herein, we propose the selective adsorption of leached NO3‐ to strengthen the crystallinity and activity of surface reconstructed layer with amorphous and crystalline (a‐c) heterojunction. Taking a‐c Ni doped Fe2O(OH)3NO3·H2O (Ni‐FeNH) as a model precatalyst, we uncover that the leached NO3‐ are readily adsorbs on the crystalline phase in the formed a‐c Fe(Ni)OOH during OER, lowering the disorder degree and further activating Ni and Fe ion of the crystalline Fe(Ni)OOH on a‐c heterojunctions. Accordingly, Ni‐FeNH deliver a low overpotential of 303 mV and high durability of 500 hours at 500 mA cm‐2 for OER. Particularly, constructing industrial water electrolysis equipment exhibits high stability of 100 hours under a high operating current of 8000 mA.

Spatial-temporal patterns of foliar and bulk soil 15N isotopic signatures across a heterogeneous landscape: Linkages to soil N status, nitrate leaching, and N2O fluxes

The natural abundance of plant and bulk soil 15N isotopic signatures provides valuable insights into the magnitude of nitrogen cycling and loss processes within terrestrial ecosystems. However, 15N isotopic signatures are highly variable in space due to natural and anthropogenic factors affecting N cycling processes and losses. To date, most studies on foliar and bulk soil 15N isotopic signatures have focused on N-limited forest ecosystems at relatively large spatial scales, while similar studies in N-enriched ecosystems at finer spatial scales are lacking. To address this gap and evaluate links between soil 15N isotopic signatures and ecosystem N cycling and loss processes (plant N uptake, N leaching, and gaseous loss), this study quantified foliar and bulk soil 15N isotopic signatures, soil physicochemical parameters, gaseous (N2O), and hydrological (NO3) N losses at 80 sites distributed across a heterogeneous landscape (∼5.8 km2). To account for the spatial-temporal heterogeneity, the measurements were performed in four campaigns (March, June, September 2022, and March 2023) at sites that considered different land uses, soil types, and topography. Results indicated that foliar and bulk soil 15N isotopic signatures were significantly (P < 0.05) more enriched in arable and grassland ecosystems than forests, suggesting a more open N cycle with significant N cycling and losses due to higher N inputs from fertilizers. Similar to soil inorganic N, N2O fluxes, and NO3 leaching rates, landscape-scale foliar and soil 15N isotopic signatures varied widely spatially, particularly at grassland and arable land (−3 to 9.0‰), with bivariate and multivariate analyses also showing significant relationships between landscape-scale soil 15N isotopic signatures and the aforementioned parameters (r2: 0.29 to 0.82). Based on these relationships, our findings suggested that foliar and bulk 15N isotopic signatures may capture fine-scale areas with persistently high and low environmental N losses (N2O fluxes and NO3 leaching) within a heterogeneous landscape.

Vermicompost and flue gas desulfurization gypsum addition to saline-alkali soil decreases nitrogen losses and enhances nitrogen storage capacity by lowering sodium concentration and alkalinity

Saline-alkali soils have poor N storage capacity, high N loss and inadequate nutrient supply potential, which are the main limiting factors for crop yields. Vermicompost can increase organic nutrient content, improve soil structure, and enhance microbial activity and function, and the Ca2+ in flue gas desulfurization (FGD) gypsum can replace Na+ and neutralize alkalinity in saline-alkali soils though chemical improvement. This study aimed to determine if vermicompost and FGD gypsum addition could improve the N storage capacity through decreasing NH3 volatilization and 15N/NO3− leaching from saline-alkali soils. The results indicate that the combined application of vermicompost and FGD gypsum led to the displacement and leaching Na+ in the upper soil layer (0–10 cm), as well as the neutralization of HCO3− by the reaction with Ca2+. This treatment also improved soil organic matter content and macroaggregate structure. Also, these amendments significantly increased the abundance of nifH and amoA genes, while concurrently decreasing the abundance of nirK gene. The structural improvements and the lowering of Na + concentration in and alkalinity decreased cumulative NH3 volatilization, and leaching of 15N and NO3− to the deep soil layer (20–30 cm). FGD gypsum increased the 15N stocks and inorganic N stocks of saline-alkali soil, whereas vermicompost not only increased the 15N and inorganic N stocks, but also increased the total N stocks, the combination of vermicompost and FGD gypsum can not only increase the available N storage capacity, but also enhance the potential for N supply. Therefore, vermicompost and FGD gypsum decrease N loss and increase N storage capacity through structural improvement, and lowering of Na+ concentration and alkalinity, which is crucial for improving the productivity of saline-alkali soil.

Quantification of nitrogen leaching losses by paddy cultivation under controlled and continual runoff conditions

In Asia, paddy is an important food crop that requires a high level of nitrogen, which is provided by straight chemical fertilizers that contribute a single nutrient, mainly urea. A study was conducted to quantify the leaching loss of nitrogen (as NO3--N) under two water management practices: controlled runoff and continual runoff in paddy cultivation at Low Country Intermediate Zone, Sri Lanka from 2015 to 2016 for four consecutive cropping seasons. Urea (N 46%) was applied as a sole source of Nitrogen at the rate of 225 kg ha-1. A randomized complete block design was employed with triplicates by two factors and two levels (cropping seasons; Yala, Maha, gradients; upper, lower). Lysimeters were arranged to collect leached water. The leachate from the study plots was collected weekly throughout the cropping period and the total amount of leached NO3--N for each cropping season was quantified. The leaching losses of NO3--N accounted under controlled runoff and continual runoff conditions were 8.6 kg ha-1 and 3.0 kg ha-1 respectively throughout the cropping period. It contributed to 8% and 3% of Nitrogen out of the total amount of applied N fertilizers in the same order. The water management practices and gradient effects were significant with respect to nitrogen leaching losses from paddy fields while cropping season had no effect on nitrogen leaching. A significant amount of nitrogen leaching losses could occur under the root zone, even though a controlled runoff situation posing possible threats of surface and groundwater pollution.

Electromagnetic Water Treatment and Soil Compost Incorporation to Alleviate the Impact of Soil Salinization

This study explores the effects of alternating current-induced electromagnetic field (EMF) on mitigating brackish water irrigation and soil salinization impacts. Greenhouse experiments were conducted to evaluate the effect of EMF on plant growth, soil properties, and leaching of ions under different conditions, including using brackish water and desalinated water for irrigation and soil compost incorporation. The experiment was performed with four types of irrigation water using soil columns representing field soil layers. EMF-treated brackish water maintained a sodium adsorption ratio of 2.7 by leaching Na+ from the soil. EMF-treated irrigation columns showed an increase in soil organic carbon by 7% over no EMF-treated columns. Compost treatment reduced the leaching of NO3− from the soil by more than 15% using EMF-treated irrigation water. EMF-treated brackish water and compost treatment enhanced plant growth by increasing wet weight by 63.6%, dry weight by 71.4%, plant height by 22.8%, and root length by 115.8% over no EMF and compost columns. EMF-treated agricultural water without compost also showed growth improvements. The findings suggest that EMF treatment, especially combined with compost, offers an effective, low-cost, and eco-friendly solution to mitigate soil salinization, promoting plant growth by improving nutrient availability and soil organic carbon.

Critical loads for alkalization in terrestrial ecosystems

Critical loads are a risk assessment approach that has supported large decreases in atmospheric acidic deposition globally. In Canada, SOx emissions fell by approximately 70 % between 1990 and 2021, whereas total particulate matter (TPM) emissions increased by about 40 %, mostly after 2010. Base cations are a major component of TPM, and critical load models consider base cation deposition as beneficial to ecosystems insomuch as it reduces the risk of acidification. However, close to point sources, high levels of alkaline dust deposition have altered soil chemistry and caused an undesirable shift in ecosystem state; something that critical loads are designed to prevent. In this study, the simple mass balance model (SMB) was modified with the objective of preventing base cation accumulation in soil above an acceptable threshold. The concept was applied to a forested site close to large emission sources of sulphur, nitrogen, and base cations in the Oil Sands region of Alberta, Canada. At this site, base cation leaching measured at 25 cm was approximately three times higher than estimated background leaching and exceeded combined SO4 + NO3 leaching. The critical load for alkalization was exceeded under each scenario considered in this study, although the exceedance was marginal if all N in current deposition was assumed to leach from soil. While this framework can easily be applied to regional and national critical load efforts, the main uncertainties of the proposed approach include base cation deposition estimates, assumptions regarding the behavior of N in soil, the selection of an appropriate Alkle(crit) and the long-term immobilization of deposited base cations in soil.

Coping with groundwater pollution in high-nitrate leaching areas: The efficacy of denitrification

The Ningxia Yellow River irrigation area, characterized by an arid climate and high leaching of NO3--N, exhibits complex and unique groundwater nitrate (NO3--N) pollution, with denitrification serving as the principal mechanism for NO3--N removal. The characteristics of N leaching from paddy fields and NO3--N removal by groundwater denitrification were investigated through a two-year field observation. The leaching losses of total nitrogen (TN) and NO3--N accounted for 10.81–27.34% and 7.59–12.74%, respectively, of the N input. The linear relationship between NO3--N leaching and N input indicated that the fertilizer-induced emission factor (EF) of NO3--N leaching in direct dry seeding and seedling-raising and transplanting paddy fields was 8.2% (2021, R2 = 0.992) and 6.7% (2022, R2 = 0.994), respectively. The study highlighted that the quadratic relationship between the NO3--N leaching loss and N input (R2 = 0.999) significantly outperformed the linear relationship. Groundwater denitrification capacity was characterized by monitoring the concentrations of dinitrogen (N2) and nitrous oxide (N2O). The results revealed substantial seasonal fluctuations in excess N2 and N2O concentrations in groundwater, particularly following fertilization and irrigation events. The removal efficiency of NO3--N via groundwater denitrification ranged from 42.70% to 74.38%, varying with depth. Groundwater denitrification capacity appeared to be linked to dissolved organic carbon (DOC) concentration, redox conditions, fertilization, irrigation, and soil texture. The anthropogenic-alluvial soil with limited water retention accelerated the leaching of NO3--N into groundwater during irrigation. This process enhances the groundwater recharge capacity and alters the redox conditions of groundwater, consequently impacting groundwater denitrification activity. The DOC concentration emerged as the primary constraint on the groundwater denitrification capacity in this region. Hence, increasing carbon source concentration and enhancing soil water retention capacity are vital for improving the groundwater denitrification capacity and NO3--N removal efficiency. This study provides practical insights for managing groundwater NO3--N pollution in agricultural areas, optimizing fertilization strategies and improving groundwater quality.

Sodium accumulation vs. nitrate leaching under different fertigation regimes in greenhouse soils in South Uruguay

In greenhouse conditions, soil salinity and N leaching depend on the provision of irrigation, the irrigation water quality and the application of fertilizers and organic amendments. The objective of this study was to quantify and analyze the accumulation and/or leaching process of NO3- and Na+ in greenhouse tomato production in the south region of Uruguay in fine-textured soil under different fertigation regimes. The study was conducted in four tomato crops during 2019/20/21 seasons. Three fertigation regimes were applied. Irrigation volume was the same for all treatments. Drainage was determined by using free drainage lysimeters. Concentration in soil solution and leaching of NO3- and Na+ was measured by monitoring soil solution and drainage solution. Yield, N uptake and N utilization efficiency were determined for each treatment. Soil total drainage was the main factor explaining N and Na+ leaching. The leaching of N ranges from 0 to 23.4 kg N ha-1 per tomato crop with total drainage between 0 and 46.2 % of total irrigation. Drainage necessary to avoid Na+ accumulation was 13 % of total irrigation. This drainage produced 8.4 kg of N leaching per ha-1 during tomato cropping period. Optimizing irrigation is the key factor to the salinity-nitrogen leaching paradox. Irrigation amount and timing should attempt: (1) to avoid excessive irrigation when NO3- concentration in soil solution is high, and (2) to apply leaching irrigation when Na+ concentration in soil solution is high. Soil solution monitoring with suction probes and rapid chemical analysis systems could be a useful tool to identify periods of high risk of N leaching and the right time for leaching irrigation.

Conversion of biobased substances into biochar to enhances nutrient adsorption and retention capacity.

Reducing the environmental issues brought on by nutrients especially nitrogen pollution and loss is important. Owing to its unique composition and physico-chemical characteristics, biomass-derived biochar exhibits varying degrees of adsorption and interception for all types of soil nutrients. Thus, a novel way to improve nutrient absorption in the soil is to include biomass derived biochar into it. Various biomass-derived biochar from locally available biobased substances was synthesized through low-cost portable charring kiln. It has been quantified the influence of four biobased substances and three pyrolysis temperature on different morphomineralogical characteristics of biochar for utilizing as low-cost sorbent to manage nutrient adsorption and retention capacity. The morphomineralogical characteristics were principally manipulated by feedstocks rather than pyrolysis temperature. Higher porosity and surface area of biomass-derived biochar illustrated its soil structural modification and nutrient retention capacity along with their utilization for adsorbents. With increase in pyrolysis temperature, the adsorption capacity of biochar for NH4+-N and NO3--N was gradually weakened and gradually enhanced respectively. The adsorption process of ammonia nitrogen and nitrate nitrogen conformed to the Langmuir model and the fitted KL value was less than 1 indicating that the adsorption process was uniform monolayer adsorption and the adsorption of biochar was favorable adsorption. With increase in biochar application rate the leaching of NO3--N decreased having higher at 2.5 t ha-1 application rate followed by 5 t ha-1 and lower at 7.5 t ha-1. In packed soil column, the NH4+-N in leachate was maximum in T7 (18.6), followed by T4 (17.9), T13 (17.3) and minimum in T10 (17.2) at same application rate of manures and biochar. Finally, results also revealed that packed soil column performed better as compared with intact soil column to retain soil nutrient and hence, leaching potential of nutrient was less in packed column than intact soil column. In conclusion, biomass-derived biochar can enhance the amount of nutrient that is absorbed into the soil while decreasing the loss of nutrient from the soil in the form of ammonia and nitrate. To sum up, biomass-derived biochar can increase the adsorption amount of the nitrogen and reduce the loss of ammonia nitrogen and nitrate nitrogen in the soil, thus retaining the nitrogen.

Potential Secretory Transporters and Biosynthetic Precursors of Biological Nitrification Inhibitor 1,9-Decanediol in Rice as Revealed by Transcriptome and Metabolome Analyses

Biological nitrification inhibitors (BNIs) are released from plant roots and inhibit the nitrification activity of microorganisms in soils, reducing NO3‒ leaching and N2O emissions, and increasing nitrogen- use efficiency (NUE). Several recent studies have focused on the identification of new BNIs, yet little is known about the genetic loci that govern their biosynthesis and secretion. We applied a combined transcriptomic and metabolomic analysis to investigate possible biosynthetic pathways and transporters involved in the biosynthesis and release of BNI 1,9-decanediol (1,9-D), which was previously identified in rice root exudates. Our results linked four fatty acids, icosapentaenoic acid, linoleate, norlinolenic acid, and polyhydroxy-α,ω-divarboxylic acid, with 1,9-D biosynthesis and three transporter families, namely the ATP-binding cassette protein family, the multidrug and toxic compound extrusion family, and the major facilitator superfamily, with 1,9-D release from roots into the soil medium. Our finding provided candidates for further work on the genes implicated in the biosynthesis and secretion of 1,9-D and pinpoint genetic loci for crop breeding to improve NUE by enhancing 1,9-D secretion, with the potential to reduce NO3‒ leaching and N2O emissions from agricultural soils.

Unexpectedly high nitrate levels in a pristine forest river on the Southeastern Qinghai-Tibet Plateau

River nitrate (NO3–) pollution is a global environmental issue. Recently, high NO3– levels in some pristine or minimally-disturbed rivers were reported, but their drivers remain unclear. This study integrated river isotopes (δ18O/δ15N-NO3– and δD/18O-H2O), 15N pairing experiments, and qPCR to reveal the processes driving the high NO3– levels in a nearly pristine forest river on the Qinghai-Tibet Plateau. The river isotopes suggested that, at the catchment scale, NO3– removal was prevalent in summer, but weak in winter. The pristine forest soils contributed more than 90 % of the riverine NO3–, indicating the high NO3– backgrounds. The release of soil NO3– to the river was “transport-limited” in both seasons, i.e., the NO3– production/stock in the soils exceeded the capacity of hydrological NO3– leaching. In summer, this regime and the NO3–-plentiful conditions in the soils associated with the strong NO3– nitrification led to the high riverine NO3– levels. While the in-soil nitrification was weak in winter, the leaching of legacy NO3– resulted in the consistently high NO3– levels. This study provides insights into the reasons for high NO3– levels in pristine or minimally-disturbed rivers worldwide and highlights the necessity to consider NO3– backgrounds when evaluating anthropogenic NO3– pollution in rivers.

PENGARUH PEMBERIAN PUPUK BOKASHI DAN ZEOLIT SEBAGAI BAHAN PEMBENAH TANAH TERHADAP KETERSEDIAAN NITROGEN TANAH REGOSOL

Regosol has been widely used for agricultural production despite its low nutrient availability and adsorption. This research aimed to know the effects of bokashi and zeolite on the availability of nitrogen (N) in Regosol. The experiment was carried out with a completely randomized 2-factors design. The first factor was bokashi, with three levels: 0 t ha-1 (B0), 20 t ha-1 (B1), and 30 t ha-1 (B2). The second factor was zeolite with three levels: 0 t ha-1 (Z0), 5 t ha-1 (Z1), and 10 t ha-1 (Z2). Each treatment was repeated three times. Each treatment was incubated for 30 days. The parameters before being treated were texture, bulk density, pH H2O, N-totals, C-organic, available N, and CEC in soil, pH H2O, N-totals, available N, and C-organic in bokashi, also CEC in the zeolite. The parameters after being treated were pH H2O, N-totals, C-organic, C/N, available N, and CEC in soil, also leached NH4+ and leached NO3- in water. The data were analyzed with ANOVA followed by the DMRT at a 5% level. The results showed that bokashi significantly affected the available N, pH H2O, N-total, leached NO3-, and CEC, meanwhile zeolite did not significantly affect the available N but significantly affected the N-totals, C/N in soil, and leached NO3-. The combination of bokashi and zeolite did not significantly affect the available N in the soil. The best dose of bokashi increasing available N of Regosol was at a dose of 20 t ha-1 (B1).

A tradeoff between denitrification and nitrate leaching into the subsoil in nitrate-rich vegetable soils treated by reductive soil disinfestation

Intensive vegetable cultivation often leads to substantial accumulation of nitrate (NO3−-N) in the topsoil, thus posing serious threat to groundwater safety by NO3−-N leaching and food safety by excessive uptake of NO3−-N by vegetables. Reductive soil disinfestation (RSD) may remove over-accumulated NO3−-N in the topsoil due to its water-saturated, strongly reductive, and carbon-rich characteristics that favor the removal of NO3−-N via denitrification, immobilization, and leaching. However, how RSD affects the fates of NO3−-N of the topsoil in intensive vegetable lands remains largely unknown. Here, a soil column experiment using 15N tracing technique was conducted to quantify the fates of NO3−-N in the topsoil under RSD in six representative intensive vegetable soils in China. The results showed that an average of 99.7% of the added 15NO3−-N in the topsoil was removed by RSD in all intensive vegetable lands. Denitrification in the entire soil profile and leaching of NO3−-N into the subsoil were responsible for 21.8–78.3% and 14.9–68.4% of the removed 15NO3−-N, respectively, whereas microbial NO3−-N immobilization and dissimilatory nitrate reduction to ammonium in the topsoil played a negligible role in removing 15NO3−-N. A tradeoff was found between denitrification and leaching of NO3−-N into the subsoil among the six soils under RSD. The structural equation modeling demonstrated that the positive effects of RSD on topsoil pH, dissolved organic carbon, and bacterial abundance decreased the leaching of NO3−-N into the subsoil by enhancing denitrification. Overall, the results provided the first direct evidence for complete removal of NO3−-N in the topsoil by RSD. Such an evidence has implications for controlling NO3−-N accumulation through implementing RSD in intensive vegetable soils.

Environmental aspects of mineral fertilizing of perennial grass mixtures on drained organic soils

Environmental protection and effective use of floodplain organic soils of river valleys in the humid zone is associated with the development of sustainable agrosystems, in which 65–75% of the sown area is allocated to perennial grasses. The main measure in the technology of growing perennial grass mixtures is the introduction of mineral fertilizers. The conducted studies show that the highest yield of perennial grass mixtures on average for 2016–2019 was obtained with the introduction of recommended doses of fertilizers obtained on the basis of perennial studies (N45P45K120) — 8.9 t/ha, and with the addition of 2 l/ha Organic Balance — 9.4 t/ha of dry mass; for the yield of 8.5 t/ha for the calculated dose of fertilizers to increase the yield of herbs N45P84K150 and 8.3 t/ha for the calculated dose for the planned yield taking into account the content of nutrients in the soil N45P138K293. Therefore, the most economically profitable and scientifically justified application of mineral fertilizers to crops of perennial grasses obtained on the basis of long-term scientific data, taking into account soil, climatic and weather conditions. In addition, the introduction of different doses of mineral fertilizers led to their corresponding leaching into the drainage waters, the leaching of NO3 during the growing season in the version with the recommended dose of fertilizers was 12.3 mg/l, and in the version with the introduction of mineral fertilizers for crop growth (N45P84K150) increased leaching into groundwater up to 17.2 mg/l of water. Thus, the economic and ecological evaluation of determination of doses of mineral fertilizers calculated by various methods showed that it is most expedient to determine calculations based on data obtained in long-term studies on crops of perennial grasses.

Alfalfa in rotation with annual crops reduced nitrate leaching potential.

Rotation of perennial alfalfa (Medicago sativa L.) with annual crops has the potential to reduce nitrate-nitrogen (NO3 -N) in the vadose zone and increase soil organic carbon (SOC) sequestration. The objective of this study was to determine the long-term effects on SOC, NO3 -N, ammonium-N (NH4 -N), and soil water in the 7.2m depth with an alfalfa rotation compared with continuous corn (Zea mays L.). Soils from six pairs of alfalfa rotation versus continuous corn observation points were sampled to 7.2m depth in 0.3m increments. The uppermost 0.3m was divided into 0-0.15 and 0.15-0.30m. For the 0-7.2m depth, the alfalfa rotation compared with continuous corn had 26% less soil water (0.29vs. 0.39g cm-3 ) and 55% less NO3 -N (368vs. 824kg ha-1 ). The cropping system and NO3 -N concentration did not affect NH4 -N in the vadose zone. The alfalfa rotation compared with continuous corn had 47% higher SOC (105.96 Mg ha-1 vs. 72.12 Mg ha-1 ) and 23% higher total soil nitrogen (TSN) (11.99 Mg ha-1 vs. 9.73 Mg ha-1 ) in the 0-1.2m depth. The greater depletion of soil water and NO3 -N with alfalfa rotation was primarily below the rooting zone of corn, suggesting no negative implications for corn following alfalfa but greatly reduced potential of NO3 -N leaching to the aquifer with the alfalfa rotation. Alfalfa rotation compared with continuous corn is a means to greatly reduce the leaching of NO3 -N to the aquifer and improve the surface soil with the potential to increase SOC sequestration.

Effect of Nitrogen Application and Fertigation Scheduling On Potato Yield Performance Under Drip Irrigation System

The drip irrigation method offers the potential of higher application efficiency of water and allows precise placement of fertilizer directly in the root zone. The use of drip irrigation also facilitates the frequent application of fertilizer via injection in the irrigation system, which allows the conjunction between nutrient application and time of crop needs. The effect of nitrogen (N) rate and drip fertigation scheduling were evaluated on yield, N uptake, and recovery of potato grown on sandy soil. The N was applied at two rates under regular irrigation (control) or through drip irrigation along with four fertigation schedules including: equal doses applied at the weekly or biweekly intervals and different doses based on growth curve characters (12.5, 25, 50, and 12.5% of the total N amount) at the same intervals, for initial, developmental, mid, and mature stages, respectively. The N rate and wise fertigation scheduling significantly affected yield and yield components except for the tuber number per plant. The higher tuber yield was associated with a higher N rate when the respective nutrient was stage wise scheduled and typically responded to growth curve character than equal scheduling at any time intervals. The increase in yield was higher with wise weekly by 13 and 22% than with equal weekly or biweekly intervals, respectively. For this scenario, the modeled crop uptake at the weekly interval was 16% higher than equal applied at the same interval or even greater by 31% than equal applied at the biweekly interval. Similarly, the higher N rate and wise weekly scheduling increased N recovery and N use efficiency (NUE). Soil N movement with wise scheduling resulted in lesser leaching of NO3−-N to deeper soil layers, particularly with wise weekly scheduling. The framework presented in this study regarding the rate and N scheduling to copy with plant growth curve can sustain high crop yield while reducing NO3−-N leaching, increasing N uptake and recover.

Microplastics change the leaching of nitrogen and potassium in Mollisols

Nowadays, the dynamics of nutrients leaching from the soils and their driving mechanism have been focused on, however, it is still unclear how microplastics (MPs) influence the nutrients' leaching in soils. In this study, five concentrations (w/w, 0.0 %, 0.5 %, 1 %, 2 %, 3 %) and three sizes of MPs of polyethylene (PE) (0.15–0.36 mm, 0.36–0.60 mm and 0.60–1.00 mm) influencing the leaching of NO3−-N and water-soluble potassium (WSK) was simulated by a column method in Mollisols, and both the pre-fertilization and post-fertilization were considered. The results showed that, before KNO3 addition, there was a negative power function relationship between the NO3−-N concentration and the leaching solution volume/leaching time. The amount and concentration of NO3−-N leaching was higher in the early leaching stage. Compared with the CK, PE0.5% significantly reduced the leaching amount of WSK, while increased the leaching amount of NO3−-N but not significantly. The leaching amount of WSK decreased with the increasing size of PEMP when the PEMP concentration was the same, while NO3−-N was opposite. PE0.60–1.00 increased the leaching amount of NO3−-N, while reduced the leaching amount of WSK. After KNO3 addition, compared with CK, PE1% significantly reduced the leaching amount of NO3−-N, and PE1% had the lowest leaching amount of WSK. However, when the PEMP concentration in the soil reached a certain threshold (w/w, >1 %), the leaching amount of NO3−-N and WSK increased gradually with PEMP increasing. PE0.60–1.00 reduced the leaching amount of NO3−-N and WSK most obviously. In general, low concentrations (w/w, <1 %) and large sizes (0.60–1.00 mm) of PEMP promoted NO3−-N leaching and inhibited the WSK leaching from the soil before the addition of KNO3, however, they both inhibited the leaching of NO3−-N and WSK from the soil after addition of KNO3.

Agro-Industrial Waste Biochar Abated Nitrogen Leaching from Tropical Sandy Soils and Boosted Dry Matter Accumulation in Maize

This study was conducted to assess the effects of amending tropical sandy soils with biochar derived from agro-industrial wastes on the leaching and utilization of nitrogen (N) by maize. The experiment was conducted in pots in a greenhouse with two sandy soil types and two different biochars. The biochars used in this experiment were preselected in a preliminary column experiment that assessed the N retention capacities of the different biochars and those that exhibited the best retention capacities chosen for experimentation. The biochars evaluated included saw dust, rice husk and corncob pyrolyzed at 500 °C and the results from the column leaching experiment showed that sawdust biochar had superior retention capacities for both NO3− and NH4+, followed by rice husk biochar. The pot experiment utilized sawdust and rice husk biochars applied at rates of 0, 20 and 40 t/ha to the soil treated with different N sources including cow dung and ammonium sulfate and growing maize on the amendments for two seasons with each season lasting for five weeks. The soils were leached on the 14th and 28th days after planting to determine the amount of leachable N. Biochar amendments reduced the leaching of NO3−N and NH4+N with no significant differences observed between biochar types, but between soil types. The abatement of leaching by biochar amendments consequently enhanced N uptake by maize and dry matter production and thus, agro-industrial waste biochar amendment is recommended for reducing leaching in tropical sandy soils.

Nitrogen retention potentials of magnesium oxide- and sepiolite-modified biochars and their impacts on bacterial distribution under nitrogen fertilization

Mitigating the loss and negative impacts of reactive N from fertilized soils remains a global environmental challenge. To optimize N retention by biochar, bamboo and pig manure biochars were modified as MgO- and sepiolite-biochar composites and characterized. Novel soil application of the modified biochars and their raw forms were comparatively evaluated for N-retention in a fertilized soil leached for 90 days in a column experiment. Changes in N-cycling-related enzyme and bacterial structure were also reported after 90 days. Results revealed low leaching losses of NH4+, which reduced over time across all the treatments. However, while sole fertilizer (F) increased the initial and cumulative NO3− leached from the soil, the MgO-bamboo biochar (MgOBF) and sepiolite-bamboo biochar (SBF) treatments reduced leachate NO3− by 22.1 % and 10.5 % compared to raw bamboo biochar (BBF) treatment. However, 15.5 % more NO3− was leached from the MgO-pig manure biochar-treated soil (MgOPF) compared to its raw biochar treatment (PMBF) after 90 days. Dissolved organic N leached was reduced by 9.2 % and 0.5 % in MgOBF and SBF, as well as 15.4 % and 40.5 % in MgOPF and SPF compared to their respective raw forms. The total N of the biochars, adjustment of surface charges, cation exchange capacity, surface area, pore filling effects, and the formation of potential MgN precipitates on the modified-biochar surfaces regulated N leaching/retention. In addition, the modified biochar treatments reduced the hydrolysis of urea and stimulated some nitrate-reduction-related bacteria crucial for NO3− retention. Hence, unlike the raw biochar and MgOPF treatments, MgOBF, SBF, and SPF hold promise in mitigating inorganic-N losses from fertilized soils while improving the soil's chemical properties.