Nitrate Movement Research Articles

Zeolite intervention in soil nitrate dynamics: insights from column experiments and modelling

ABSTRACT This study aims to address the harmful effects of excessive nitrogen fertilizer by investigating the mobility retardance effect of zeolite on nitrate movement in loam soil columns. Disturbed and undisturbed soil columns, treated with zeolite, as well as control soil columns, were analysed over a span of three years. Breakthrough curves generated from the experiments were evaluated using the HYDRUS1D code with mobile–immobile water (MIM) and dual-permeability (DP) models. Our findings highlight that zeolite application significantly reduced nitrate mobility, with recovery rates decreasing by 8% in disturbed and 11% in undisturbed columns. The DP model, which accurately reflects real soil water flow conditions, outperformed the MIM model in predictive accuracy. This research offers a novel long-term perspective on the benefits of zeolite in enhancing soil properties and mitigating nitrate leaching, recommending the DP model for superior prediction of contaminant transport in structured soils within the vadose zone.

Unveiling the dynamic of nitrogen through migration and transformation patterns in the groundwater level fluctuation zone of a different hyporheic zone sediment

This study investigates the impact of water levels and soil texture on the migration and transformation of nitrate (NO3−-N) and ammonium (NH4+-N) within a soil column. The concentrations of NO3−-N gradually decreased from an initial concentration of 34.19 ± 0.86 mg/L to 14.33 ± 0.77 mg/L on day 70, exhibiting fluctuations and migration influenced by water levels and soil texture. Higher water levels were associated with decreased NO3−-N concentrations, while lower water levels resulted in increased concentrations. The retention and absorption capacity for NO3−-N were highest in fine sand soil, followed by medium sand and coarse sand, highlighting the significance of soil texture in nitrate movement and retention. The analysis of variance (ANOVA) confirmed statistically significant variations in pH, dissolve oxygen and oxidation–reduction potential across the soil columns (p < 0.05). Fluctuating water levels influenced the migration and transformation of NO3−-N, with distinct patterns observed in different soil textures. Water level fluctuations also impacted the migration and transformation of NH4+-N, with higher water levels associated with increased concentrations and lower water levels resulting in decreased concentrations. Among the soil types considered, medium sand exhibited the highest absorption capacity for NH4+-N. These findings underscore the significant roles of water levels, soil texture, and soil type in the migration, transformation, and absorption of nitrogen compounds within soil columns. The results contribute to a better understanding of nitrogen dynamics under varying water levels and environmental conditions, providing valuable insights into the patterns of nitrogen migration and transformation in small-scale soil column experiments.

Simulation analysis of the preventative effects of planting sweet corn on nitrate leaching in a cherry greenhouse soil.

To ensure higher productivity, fertilizers have been excessively applied to the fruit greenhouse soil yearly, thus resulting in the increasing risks of residual nitrate leaching in the North China Plain. In this study, a water and solute transport HYDRUS-1D model was used to evaluate the effects of using sweet corn as a catch crop on deep water drainage and nitrate leaching in a sweet cherry greenhouse soil. A three-year (2019-2021) field experiment was conducted during the rainfall season from July to September in the post-harvest of sweet cherry, when the plastic cover was removed each year. In the experiment, the five treatments were designed. The three nitrate residue levels denoted by CKR, N1R, and N2R, represented nitrate residue amounts in the soil profile of three nitrogen fertilizer levels(0, 280 and 420kg ha-1) before the harvest of sweet cherry(March to June). Two other treatments with and without sweet corn as a catch crop based on the treatments of N1R and N2R were denoted by N1RC and N2RC, respectively. The data of both the spatial and temporal distribution of water and nitrate content during the rainy seasons of 2019, 2020 and 2021 in the field experiment were collected to calibrate and validate the model. The simulated results have showed that using sweet corn as a catch crop increased the evapotranspiration rate, the upward flux of water and nitrate at a 100cm soil depth reached a maximum of 1.5mm d-1 and 1.0kg N ha-1d-1, respectively, and the downward movement of water and nitrate leached to deeper soil layers was reduced. Compared with CKR, the treatments with catch crops (N1RC and N2RC) reduced the amount of water drainage by 16.4% -47.7% in the 0-180cm soil profile. The average amounts of nitrate leaching in the 1.8m soil profile during the three-year experiment were 88.1, 113.3, and 58.2kg N ha-1 for the treatment without catch crop (N1R and N2R) and 32.3, 54.8, and 31.4kg N ha-1 for the treatment with catch crop (N1RC and N2RC), respectively. The treatments (N1RC and N2RC) with catch crops decreased the amount of nitrate leaching by 29.6%-69.1% compared with the treatments without catch crops (N1R and N2R). Sweet corn as summer catch crop can reduce nitrate leaching in the sweet cherry greenhouses. Our study has provided an effective method to reduce the risk of nitrate leaching for sweet cherry greenhouses in the North China Plain.

Coupled Dynamics of Soil Water and Nitrate in the Conversion of Wild Grassland to Farmland and Apple Orchard in the Loess Drylands

Understanding the dynamics of soil water and nitrate in response to typical agricultural crops in dryland ecosystems are crucial for assessing ecological consequences and informing land use planning. This study was conducted in the Changwu tableland, a representative area for agricultural crop cultivation in the Loess Plateau of China. Fifteen soil profiles, including grassland, farmland, and young, mature, and old apple orchards, were sampled to investigate the effects of different land uses on soil water and nitrate dynamics using a “space-for-time” substitution approach. The results showed that the soil water content and nitrate content in farmlands were comparable to those in wild grassland. However, significant differences in soil water were observed below a depth of 2 m in apple orchards, with mature and old orchards experiencing water deficits compared to grassland of 624.9 mm and 690.0 mm, respectively. Moreover, a dried soil layer formed below a depth of 5 m in these orchards. In terms of soil nitrate, the concentration in the 0–5 m depth of apple orchards was significantly higher than that in agricultural land and grassland, and it increased with the age of the orchards. However, below 5 m, the residual nitrate stock per unit depth in apple orchards decreased to levels comparable to grassland and farmland, primarily due to the inhibitory effect of the dried soil layer on downward migration and leaching processes. Furthermore, the relationship between nitrate and soil water at 0–5 m soil depths differed during the conversion from grassland to farmland and apple orchard, with positive and negative correlations observed, respectively. This indicates that water plays a key role in influencing nitrate movement, and distinct hydrological processes occur for soil water and nitrate nitrogen under different land use change conditions. In conclusion, converting grassland and farmland to apple orchards can lead to soil water decline and nitrate accumulation in the vadose zone, posing potential threats to ecosystem sustainability and security in dryland regions. Therefore, implementing appropriate water-fertilizer management practices is crucial for promoting sustainable land use in loess drylands, with potential implications for similar areas worldwide.

Withdrawal: Enhanced efficiency fertilizers decrease nitrate movement while maintaining yield in sugarcane production system

Withdrawal: Enhanced efficiency fertilizers decrease nitrate movement while maintaining yield in sugarcane production system

Groundwater Depth and Nitrogen Application Amount Jointly Regulate the Water and Residual Soil Nitrate Accumulation in Agricultural Soil Profile

Despite the known influence of groundwater conditions and nitrogen application on crop growth and the soil microenvironment, less information is available on the influence of groundwater depth and nitrogen application amount on the movement and accumulation of soil water and residual nitrate in deep soil in summer maize–winter wheat rotation systems. Therefore, a large lysimeter experiment was conducted to examine how groundwater depth and nitrogen application amount influence the transport and accumulation of soil water and nitrate in the summer maize (Zea mays L.)–winter wheat (Triticum aestivum L.) rotation system. The results showed that nitrogen reduction increased soil water storage both in the summer maize and winter wheat fields. The residual soil nitrate accumulation in the entire soil profile of summer maize and winter wheat under deeper groundwater depth treatment was higher than that of shallow groundwater depth treatment. Hence, the deeper the groundwater depth, the longer the nitrate transport path, and the nitrate that would have entered the groundwater accumulates in deep soil. The residual soil nitrate accumulation in the whole soil profile of winter wheat was 76.05–130.11 kg ha−1 higher than that of summer maize. Structural equation models (SEMs) showed that the nitrogen application amount not only exhibited a directly positive effect on the residual soil nitrate accumulation but also indirectly influenced it by regulating total soil nitrogen; groundwater depth only exhibited a directly negative effect on residual soil nitrate accumulation; and soil depth had an indirect positive effect on residual soil nitrate accumulation through the regulation of soil water storage. Together, our findings prove that groundwater depth and nitrogen application amount jointly regulate the residual soil nitrate accumulation in agricultural soil rotated with winter wheat and summer maize. Therefore, in formulating a fertilization strategy for regional agricultural green development, it is necessary to consider the fertilizer application amount rate and the groundwater depth.

Investigating Nitrate with Other Constituents in Groundwater in Two Contrasting Tropical Highland Watersheds

Nitrate is globally the most widespread and widely studied groundwater contaminant. However, few studies have been conducted in sub-Saharan Africa, where the leaching potential is enhanced during the rainy monsoon phase. The few monitoring studies found concentrations over drinking water standards of 10 mg N-NO3− L−1 in the groundwater, the primary water supply in rural communities. Studies on nitrate movement are limited to the volcanic Ethiopian highlands. Therefore, this study aimed to evaluate the transport and fate of nitrate in groundwater and identify processes that control the concentrations. Water table height, nitrate, chloride, ammonium, reduced iron, and three other groundwater constituents were determined monthly in the groundwater in over 30 wells in two contrasting volcanic watersheds over two years in the Ethiopian highlands. The first watershed was Dangishta, with lava intrusion dikes that blocked the subsurface flow in the valley bottom. The water table remained within 3 m of the surface. The second watershed without volcanic barriers was Robit Bata. The water table dropped rapidly within three months of the end of the rain phase and disappeared except near faults. The average nitrate concentration in both watersheds was between 4 and 5 mg N-NO3− L−1. Hydrogeology influenced the transport and fate of nitrogen. In Dangishta, water was blocked by volcanic lava intrusion dikes, and residence time in the aquifer was larger than in Robit Bata. Consequently, nitrate remained high (in several wells, 10 mg N-NO3− L−1) and decreased slowly due to denitrification. In Robit Bata, the water residence time was lower, and peak concentrations were only observed in the month after fertilizer application; otherwise, it was near an average of 4 mg N-NO3− L−1. Nitrate concentrations were predicted using a multiple linear regression model. Hydrology explained the nitrate concentrations in Robit Bata. In Dangishta, biogeochemistry was also significant.

Importance of snowmelt on soil nitrate leaching to groundwater – A model study

The movement of nitrate to surface water bodies during snow accumulation and melting has been extensively studied, but there are only limited studies on the influence of snow processes on nitrate leaching to groundwater. The present study investigated the impact of snow processes on nitrate leaching to groundwater based on a simulation modeling approach using HYDRUS-1D. HYDRUS-1D model has a temperature threshold-based snow model in addition to water, solute, and heat simulation components. The snow component in HYDRUS-1D was previously not applied to snow simulation studies since the method does not consider a detailed physical and process-based representation of snow accumulation and melting. In the present study, HYDRUS-1D was used to simulate snow accumulation and melting over 30 years for a location in Waverly, Lancaster County, Nebraska, USA. From the simulations, it was observed that the calibrated temperature threshold based snow module in HYDRUS-1D is effective in simulating snow accumulation and melting, as shown by the index of agreement and root mean squared error of 0.74 and 2.70 cm for calibration (15 years) and 0.88 and 2.70 cm for validation (15 years), respectively. The impact of snow melt on nitrate leaching was studied based on a study area with corn cultivation (Waverly, Nebraska, USA). A long-term (60 years) analysis was carried out for irrigated and non-irrigated agriculture with and without precipitation as snow. A higher nitrate leaching to groundwater was observed in the order of irrigated–with snow (54,038 kg/ha), irrigated-without snow (53,516 kg/ha), non-irrigated-with snow (7,431 kg/ha), and non-irrigated-without snow (7,090 kg/ha). This displays a 0.98% and 4.81% increase in nitrate leaching due to snow in irrigated and non-irrigated conditions, respectively. When extrapolated over the corn cultivated regions in Nebraska, this resulted in a difference of 1.2E+09 kg and 6.1E+08 kg of nitrate when considering snow in irrigated and non-irrigated areas over 60 years. This is the first study that has analyzed the long-term impact of snow on nitrate transport to groundwater based on a simulation modeling approach. The results show that snow accumulation and melting plays a vital role in the nitrate leaching into the groundwater and indicates the importance of considering snow components in similar studies.

Improving fertigation efficiency by numerical modelling in a lettuce subsurface drip irrigation farm

Management strategies that lead to efficient fertigation are essential to minimize nitrate (N) leakage and environmental issues and to optimize crop yield. A helpful way for agricultural water and nutrient management is studying the water and solute movement by models. The objective of this study is to use the Hydrus-2D model to evaluate different nitrate fertigation strategies for improving fertigation management efficiency. The model was calibrated and validated for 2-years field unpublished data with Iceberg Lettuce (Lactuca sativa L.) for Subsurface Drip Irrigation (SDI) system under wastewater strategies. The validation of the water content model showed that the maximum and average of RMSE are equal to 1.2 and 0.7 cm3/cm3, respectively. Also, the Hydrus model performance was acceptable to simulate soil water content. The results of the soil Nitrate movement model showed the average RMSE is 2.77 mg/l with R2 = 0.97. Different scenarios in fertigation intervals, fertigation time, replacement of drip line, nitrate concentration of wastewater, different nitrate concentrations, and times of fertigation through the growing season were defined. The results of these scenarios analyze to find maximum water uptake and minimum deep percolation, which help to achieve a drip irrigation design with minimal losses and the best efficiency. Scenario results showed that reducing fertigation time by 60% and halving the fertigation interval increase the uptake of water and nitrate by 3.89% and 11.55%, while the rate of deep percolation decreased by 27%. The results of dripline replacement scenarios showed that the depth of 12 cm, without moving in the horizontal direction, has created more favorable conditions. The result of increasing nitrate concentration shows that up to 24.2 mg/l nitrate concentration, increment the plant nitrate uptake by 63.25%, however increasing more than 36.6 mg/l of nitrate concentration had no significant effect on plant nitrate uptake. For finding the best time of fertigation through the growing season, 42 scenarios were defined. All applied nitrate injected into 1, 2, 3, 4, 6, and 11 irrigation events equally, form 6 fertigation strategies of F, B, T, Q, E, and C respectively. Based on which irrigation number, fertigation strategies start, indices 1–11 are assigned to these 6 fertigation strategies. Based on the results, the best fertigation strategies in this study, were F5, B4, T3, and Q3, which have minimum nitrate leaching losses of 17.79%, 19.9%, 20.8%, and 20.0%, respectively, while had high root nitrate uptake equal to 25.1%, 26.3%, 26.6%, and 26.6%, respectively. Therefore, fertigation of lettuce is most efficient at 22–30 days after planting, equal to 30–38 days before harvesting for the silty clay loam lettuce farm, under SDI at 12 cm depth conditions.

Assessing transport and retention of nitrate and other materials through the riparian zone and stream channel with simulated precipitation

Abstract Riparian zones, the interfaces between land and stream, perform vital ecosystem functions including transformation and retention of nutrients and sediment moving across the landscape. Although many studies assess transport through and transformation of materials in riparian zones, less is known about the direct influence of precipitation falling on these zones on material retention and transport. Additionally, few experiments can compare riparian retention to stream‐channel retention. We present a novel experimental approach to assess retention of nitrate entering as precipitation in riparian zones and compare riparian retention and movement of nitrate, other ions, sediments to and within the adjacent stream channel. We simulated an intense precipitation event with 15N‐labelled nitrate as a bioactive solute and bromide as an inert tracer. This method extends tracer release approaches applied to streams worldwide and links it to processes at the aquatic/ terrestrial interface. It further allows determination of movement of materials into streams from bankside precipitation. The riparian zone removed or retained a greater proportion of nitrate than the stream relative to bromide; over half the added bromide reached the stream through a few metres of riparian zone, compared to only 0.2% of the added nitrate. Of the 0.2% that reached the stream, 30% of that nitrate was removed or retained by instream processes after travelling 60 downstream. Roughly 10% of the total 15N addition ended up sequestered in the above‐ground portions of the riparian grasses by the end of the growing season, and very little of it was recovered from the soil. We saw little evidence of bulk transport of other ions or sediment from this riparian soil to the stream. Our data are consistent with the concept of high nitrate retention in vegetated riparian zones, even for nitrate falling directly upon them in the form of atmospheric deposition in precipitation.

The lagging movement of soil nitrate in comparison to that of soil water in the 500-cm soil profile

The combination of forage-crop rotation with conservation tillage has long been known to result in proven productivity and sustainability, but less information is available on the influence of long-term conservation tillage practices on the movement of soil water and residual nitrate at deep soil depths in forage-crop rotation systems. In this study, we measured the changes in soil water storage, residual soil nitrate accumulation and their relationship to study the long-term effects of tillage and mulching practices on regional nitrogen management in maize (Zea mays L.)-wheat (Triticum aestivum L.)-common vetch (Vicia sativa L., annual legume forage) rotation system. Soils were collected from the 500-cm soil profile at the harvest stage of the maize and common vetch after 19 years of continuous conventional tillage (T), conventional tillage followed by straw mulching (TS), no tillage (NT), and no tillage followed by straw mulching (NTS) on the Loess Plateau, China. The results showed that the NT practices increased soil water storage by 3.07% compared with the T practices in the maize field, mulching practices increased soil water storage by 3.47% compared with no mulching practices in the common vetch field, and the improvement effect was mainly concentrated in the deep soil layer (150–500 cm). When compared with no mulching, straw mulching practices increased residual soil nitrate accumulation by 51.20 kg ha−1 at shallow soil depths (0–120 cm) but decreased this accumulation by 206.09 kg ha−1 at deep soil depths (120–500 cm) in the maize field; however, straw mulching decreased nitrate accumulation by 16.25 kg ha−1 throughout the whole profile (0–500 cm) in the common vetch field. The NT practices decreased residual soil nitrate accumulation by 131.65 kg ha−1 compared with the T practices in the maize field but had no effects on the common vetch field in the 0–500-cm soil profile. Greater changes in soil residual nitrate accumulation appeared at depths of 200–500 cm than at other depths. Moreover, according to structural equation model, nitrite accumulation was limited by soil water storage. Soil nitrate peaked at deeper soil depths in the NT (90–120 cm) and TS (250–300 cm) treatments than in the T treatment (60–90 cm), whereas the NTS treatment resulted in no nitrate accumulation peak across the whole soil profile. Soil water recharge and depletion were deeper in the NT and TS treatments than in the T treatment, and this effect could limit the further leaching of soil nitrate into deep soil. The depth of soil water recharge was deeper than the depth of nitrate accumulation, and the vertical movement speed of soil residual nitrate was slower than that of soil water. Therefore, the downward movement of soil nitrate lagged behind that of soil water. Together, these results demonstrated that the NTS treatment exerted the strongest effect on maintaining soil water and decreasing residual nitrate accumulation at deep soil depths, which will be favorable for improving regional N management and assessing N budgets in agroecological systems on the Loess Plateau.

A hypothesis concerning the nitrate ion

ABSTRACT The global electric circuit and the marine layer in coastal regions result in the presence of atmospheric negative polarity ions within the canopy of plants. This leads to the hypothesis: In the presence of negative polarity atmospheric ions plants activate a plant wide system to absorb and utilize these negative polarity ions. This plant wide system, termed Extracellular Transport System (ETS), is focused on nitrate movement. The object of this paper is to verify the existence of ETS by characterizing 1) how ETS absorbs ion from the atmosphere and 2) within the plant how ETS moves ions from source to destination. Over the past 2-years characteristics of ETS were examined in pecans, pistachios, lemons, wine grapes, cotton, corn, avocados and chili peppers in production agriculture fields in Arizona and California. Nitrate movement was separated into three physical locations: Location I, in the atmosphere outside the plant; Location II, in the interfacial volume between the atmosphere and the plant surface; Location III, in the plant itself. The paper is divided into three parts. Each part is concerned with a particular location of nitrate movement. The major tool of verification is presentation of simultaneous patterns of nitrate ion arrival rate on a simulated plant surface and subsequent movement of nitrate within the extracellular region of the plant. Use of this tool is illustrated in corn, lemons, chili peppers and avocados. A base functionality of ETS has been developed: ETS is a transient, plant wide system wherein 1) nitrate ions are putatively absorbed by a variety of epidermal structures including trichomes and transferred into the extracellular region, 2) hydrated pathways are produced in the extracellular region through which these nitrate ions pass 3) electrical potential gradients are created in the extracellular region which provide a force field to provoke movement of nitrate ions through these pathways. Anthropomorphic climate has three dimensions: light, temperature and moisture. Phytomorphic climate has five dimensions: light, temperature, moisture, earth tides and atmospheric ion presence. ETS is a natural adaptation of plants to the transient nature of atmospheric negative polarity ion presence. It provides a mechanism for plants to utilize this ubiquitous and renewable source of nitrate.

Nitrate distribution pattern under conventional and trickle irrigation system

Nitrate is a highly mobile ions that moves with water. So that nitrate distribution around the driplines is strongly affected by irrigation and fertigation strategy. Nitrate movement under conventional flood irrigation system was observed 2 to 3.5 times faster as compared with trickle irrigation as well as NO3 "-N concentrations exceeded the threshold limit (i.e. 10 mg l-1) under traditional irrigation method, while stayed below the threshold limit under micro irrigation methods. Nitrate distribution was influenced by hydraulic properties, drip discharge rate, soil layering, timing of nutrient application and irrigation frequency. To maintain larger amounts of nutrient nearby emitter in highly permeable coarse-textured soils, nutrients must be applied at the starting of an irrigation cycle so that it is less susceptible to leaching losses. Study revealed that higher transpiration raised the NO3-N uptake by the plats. The study also revealed that urea moves promptly with irrigation water and urea–ammonium–nitrate fertilizer increased the nitrate concentration, near the drip line immediately after the drip fertigation due to the nitrification, while low concentrations was found near the periphery of the wetting zone.

Contemporary systematics of vadose zone nitrate capture by speleothem carbonate

The movement of nitrate through the vadose zone has major implications for environmental and human health. This issue is particularly prevalent in karst terrain where agricultural activity, thin soils and dual permeability compound the problem of high nitrate loading to the overlying ecosystem. However, a paucity of records which document vadose zone nitrate concentrations prior to the 21st century render legacy nitrate dynamics, source attribution and baseline conditions to be poorly parameterised. Speleothems growing within karst cave settings may provide an opportunity to obtain records of vadose zone nitrate contamination which extend throughout the anthropogenic era. Here, we use dual isotope analysis of δ15NNO3 and δ18ONO3 in a contemporary study at Cueva-cubío del Llanío, N. Spain, designed to examine the transformation of nitrate between surface to cave environment, taking account of biogeochemical transformation, karst hydrology and partitioning as controls on the delivery of nitrate to the speleothem record. Concentrations of nitrate within speleothem calcite are low (measured range of 0.05 mM to 0.37 mM) due to partitioning (DNO3) across the dripwater-calcite interface. Values of δ15NNO3 extracted from cave waters in Cueva-cubío del Llanío (range +2.0 to +7.0‰) are shown to be excellent indicators of nitrate source and demonstrate no fractionation during incorporation into speleothem carbonate (range of δ15NNO3 in speleothem carbonate +1.6‰ to +6.4‰). Values of δ18ONO3 contained within cave waters (range −2.5‰ to +6.0‰) and speleothem carbonate (range +12.3‰ to +32.3‰) reflect a mixed signal of source, biogeochemical processing and hydrological pathway, providing critical insight into the behaviour of the karst aquifer. Contemporary systematics at Cueva-cubío del Llanío therefore confirm speleothem carbonate contains an excellent record of vadose zone nitrate. Analysis of nitrate contained within speleothem carbonate from other regions confirms the ubiquitous nature of partitioning across the water‑carbonate interface and the use of speleothem nitrate isotopes for recording surface ecosystem processes and vadose zone behaviour. Application of these principles to dated speleothem records should provide critical timeseries of nitrate loading, enabling understanding and remediation against the presence of vadose zone legacy nitrate.

Real-time monitoring of rhizosphere nitrate fluctuations under crops following defoliation

BackgroundManagement regime can hugely influence the efficiency of crop production but measuring real-time below-ground responses is difficult. The combination of fertiliser application and mowing or grazing may have a major impact on roots and on the soil nutrient profile and leaching.ResultsA novel approach was developed using low-cost ion-selective sensors to track nitrate (NO3−) movement through soil column profiles sown with the forage crops, Lolium perenne and Medicago sativa. Applications of fertiliser, defoliation of crops and intercropping of the grass and the legume were tested. Sensor measurements were compared with conventional testing of lysimeter and leachate samples. There was little leaching of NO3− through soil profiles with current management practices, as monitored by both methods. After defoliation, the measurements detected a striking increase in soil NO3− in the middle of the column where the greatest density of roots was found. This phenomenon was not detected when no NO3− was applied, and when there was no defoliation, or during intercropping with Medicago.ConclusionMowing or grazing may increase rhizodeposition of carbon that stimulates soil mineralization to release NO3− that is acquired by roots without leaching from the profile. The soil columns and sensors provided a dynamic insight into rhizosphere responses to changes in above-ground management practices.

The ability of layered double hydroxides for nitrate absorption and desorption in crop and fallow rotation

BACKGROUND AND OBJECTIVES: This study aims down to evaluate the ability of chloride magnesium- aluminium- layered double hydroxides (4:1) for nitrate adsorption from the soil solution in successive cropping periods. METHODS: The study was conductedunder long-term cropping periods, including first crop): bell pepper; second crop: mentheae; third crop: cherry tomato; and fort h crop: wheat), absorption of soil mineral nitrate in fallow periods and nitrate absorption from plants by layered double hydroxides. The effect of layered double hydroxides on qualitative and quantitative characteristics of plants was also studied. FINDING: Results indicated that layered double hydroxides were able to induce long-term nitrate exchange in crop and fallow sequences. Layered double hydroxides can adsorb soil excessive nitrates in cropping periods and reduce nitrate concentration in the soil solution. Compared to control, the treatment with 16 gram layered double hydroxide/kilogram soil could reduce nitrate concentration in the soil solution by 95%. During two-week fallow periods, the amount of nitrates mineralized in the soil solution was increased, but layered double hydroxides treatments could adsorb them well and maintained the N-nitrate concentration in the soil solution at a low level. Additionally, Results indicated that application of 2, 4, 8 and 16 gram layered double hydroxides/kilogram soil led to 34%, 44%, 58% and 69% reduction in N-nitrate concentration of soil leachates, respectively, compared to control. By increasing nitrogen availability, layered double hydroxides improved the quantitative and qualitative properties of plants. Application of 2, 4, 8 and 16 gram layered double hydroxides/ kilogram soil increased the plant height (cherry tomato) by 14%, 26%, 50% and 80%, respectively. CONCLUSION: It is concluded that the layered double hydroxides has a potential to be used as a long-term nitrate exchanger to control the movement of nitrate in soil, and thereby reduce risks of nitrate leaching in crop production in sensible areas.

Short-lived Effects of Olive Pomace Biochar Produced at Different Temperatures on Nitrate (NO3 -), Bromide (Br-), Sulfate (SO4 2-) and Phosphate (PO4 3-) Leaching from Sandy Loam Soils

ABSTRACT Biochar is a product of organic origin, which can be used in agriculture to improve primarily the physical and chemical properties of soil. In this study, olive pomace (OP) was used for biochar production. Olive pomace biochar (OB) was produced at two different pyrolysis temperatures as 350°C and 700°C (OB350 and OB700). OB was mixed at the rates of 1% (w/w) with sandy loam (SL) soil (Hypereutric Fluvisols) and the effect of OB350 and OB700 treatments on selected anions leaching was investigated using column study. Fertilizers were applied to the soil at the rate of 400 kg nitrogen (N), 100 kg phosphorus (P), 50 kg sulfur (S) ha−1. The bromide (Br−) tracer (KBr2) was added for monitoring nitrate (NO3 −) movement within the soil. Nitrate (NO3 −), phosphate (PO4 3-), sulfate (SO4 2-), and bromide (Br−) concentrations in the leachates were measured 12 times (LN) during the study. Biochar produced at two different temperatures did not have significant effects on anion leaching from the SL soil. There was no PO4 3- anion detected in leachates of all treatments over 12 leaching periods. Recovery of NO3 − content was about 30% higher than that of Br− at the end of the last leaching period however NO3 − and Br− leaching showed similar trends during the study. As a conclusion application of 1%, OB produced at 350°C and 700°C temperatures did not have any effect on NO3 −, Br−, and SO4 2- leaching from SL soils.

Responses of soil water, nitrate and yield of apple orchard to integrated soil management in Loess Plateau, China

The managements of fertilization and surface mulching in apple orchards have both potential positive environmental and productive effects due to their benefits of water infiltration and soil nitrate movement in field ecosystem. However, the research to date had tended to focus on single measure rather than both together. The aims of this study were to determine how integrated management for apple orchards influenced spatial and temporal changes of soil water content (SWC) and soil water storage (SWS), illustrate the effects on reducing soil nitrate accumulation (SNA) and promoting N uptake, determine the impacts of water use efficiency (WUE) and apple yield. We applied three treatments for demonstration contrast experiments, traditional farming measure (chemical fertilizer, FM), existing management measure (chemical fertilizer plus manure, plastic film mulch in-row, EM) and optimized management measure (chemical fertilizer plus manure, plastic film mulch in-row and cover crop inter-row, OM). We found that the SWC in 3 m soil layers was influenced by the tree growth period, the clearly benefits of OM to invariably increase SWS in 3 m soil layer were observed in different period, especially in dry year. During the tree growth, the OM treatment significantly increased rainwater retention in deep soil (below 1 m) and received a maximum value of SWS in 3 m soil layers. Apple yield was significantly enhanced in OM, but the water consumption in each treatment had no obvious difference, and consequently WUE was elevated compared with EM and FM. The SNA after the apple harvest was significantly decreased under the OM, especially in 2−3 m soil depth. Meanwhile, total N in fruits and leaves in OM were significant higher than FM, indicating that the risk of N leaching was reduced, and the N was effectively used by trees. Regression relationships between SNA and SWS were significantly negative in the dry year, means that the OM would perform better in mitigating soil desiccation and soil nitrate leaching in dry climatic condition. This study highlights integrated soil management is a considerable practice for apple orchards in Loess Plateau and the rain-fed area around the world.

Impact of various irrigation practices on nitrate movement in soil profile and wheat productivity

Nitrate is important for plant nutrition and is considered as an index of soil fertility. Its leaching to underground water not only poses severe threat to environment but also to human health. Amount of water supplemented to crops have significant role in yield and nitrate distribution in soil. An experiment was carried out to evaluate the effect of different irrigation rates on nitrate movement, soil properties and wheat yield. Experiment was laid out in randomized complete block design with three replicates. Three irrigation levels applied were I1 (0.5 ET0 deficit irrigation), I2 (1.0 ET0; according to farmer’s practice) and I3 (1.5 ET0; over irrigation). Wheat (Sehar-2006) was used as test crop. Irrigation levels had significant effects on most of growth and yield parameters of wheat. Maximum number of leaves per plant, 1000-grain weight and grain yield were observed in second irrigation level. Irrigation rates had significant effect on infiltration rate and soil saturated hydraulic conductivity, and a decrease in value of these parameters was observed in I3 that was mainly due to higher moisture contents. Bulk density and porosity of the soil remained unchanged under various treatment applied.

Effects of agricultural plastic film residues on transportation and distribution of water and nitrate in soil

Residual plastic film in soil destroys the soil structure and changes the normal transportation and distribution of water and nutrient. In this work, we compared experiments on soil containing residual plastic film with a control experiment to investigate how residual film affects the transportation and distribution of water and nitrate (NO3-) in wetted soil. The experiment used Mariotte bottle, water tube, and soil tank to test six levels of residual-film concentration varying from 0 to 720 kg/hm2 in the soil. The wetting front, soil water content, and nitrate concentrations were all measured, and the results showed that when the concentration of residual-film was less than 360 kg/hm2, more water and nitrate remained in the upper part of the wetted volume due to block of residual film. Excessive residues (>360 kg/hm2) resulted in obvious phenomenon of preferential flow, which increased the wetting distance, wetted volume, and water content in the lower part of the wetted volume and the concentration of nitrate at the boundary of the wetted volume. These results not only help us to understand the consequences of plastic-film-residues pollution in terms of water and nitrate movement, but also provide scientific support to the development and establishment of reasonable irrigation, fertilization and management systems for polluted farmland with differential mulch residual concentrations.