Soil Nitrate Dynamics 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.

Crop diversification and digestate application effect on the productivity and efficiency of irrigated winter crop systems

Irrigated winter crops can reduce input demands when compared with irrigated summer cropping systems in the Mediterranean area. The sustainability of these systems can be further improved resorting to diverse rotations, but also to fertilisation with digestate, a by-product from anaerobic digestion of organic waste. Post-treatments such as drying and acidifying can improve the fertiliser value of this product. In this study, we compare wheat performance in a three-year full cereal rotation or in a diverse rotation, with pea and canola. Besides, untreated and dried acidified digestates are tested as fertilisers for all crops, comparing to mineral fertilisation at a rate of 140 kg N ha−1 and a control with no fertilisation. To assess productivity and efficiency of the different systems, grain yield and N concentration, N uptake efficiency (NUpE) and water use efficiency (WUE) were determined, along with soil nitrate dynamics and total N at the end of the experiment. Results showed an average wheat yield increase of 1.79 t ha−1 by the last year of the diverse crop rotation rather than the cereal rotation (p < 0.001). Although there was no yield increase in the previous year, wheat after pea showed higher grain N concentration (p < 0.001). However, the NUpE of wheat remained steady due to a higher soil N availability after pea, which suggests that fertilisation can be adjusted. Although wheat WUE increased due to canola and pea precedents (p < 0.001), the cereal rotations should be more adapted to systems with low water availability. Nonetheless, both rotations required about 30% of irrigated water than the typical irrigated summer crops of the Ebro valley region. Fertiliser effect on yields was variable according to the tested crop mainly due to differences in N demand along each growing cycle. Overall, dried acidified digestate application resulted in similar soil nitrate levels than the mineral fertiliser. The diverse rotation raised soil nitrates content compared to the cereal rotation at sowing and harvesting times (p = 0.002 and p < 0.001, respectively). Higher soil nitrate levels were found when associating these two practices, while nitrate levels after mineral fertilisation showed to be less dependent on the implemented rotation. The diverse rotation also raised soil total N at the end of the experiment (p = 0.023). Similarly, the dried acidified digestate application resulted in higher soil total N than mineral fertilisation (p = 0.011). These findings show how these management practices should allow for a chemical fertilisation reduction in irrigated winter crop systems.

Nitrogen balances of innovative cropping systems for feedstock production to future biorefineries

Future biorefineries will prefer crops with high biomass yields, thus may precipitate fundamental changes to the agricultural landscape and the biomass production systems. Understanding the fate of nitrogen (N) in novel agricultural land uses is vital for product optimisation and environmental protection. This work reports and investigates the first multi-annual N balances for novel cropping systems optimised for high biomass production compared to traditional systems under North European climate and soil conditions.In a three-year study, two types of novel systems, i) a rotation of annual crops optimised for maximum biomass production (maize, beet, hemp/oat, triticale as main crops, and winter rye and winter oilseed rape as “second” - cover crops), and ii) perennial grasses (intensively fertilised (festulolium, reed canary grass, tall fescue and cocksfoot), low-fertilised (miscanthus) and unfertilised (grass-legume mixtures)), were compared with iii) traditional systems (continuous maize or triticale, and a cereal crop rotation) at two sites in Denmark varying in temperature, rainfall and soil type (sandy loam and coarse sand). Harvested biomass N and soil nitrate dynamics, as well as model-supported nitrate leaching and field surface N balance (input minus output) of the systems were compared.At each study site, the fertilised perennial grasses outperformed all other systems by doubling biomass N and reducing nitrate leaching by 70–80% compared to the traditional systems. Compared to continuous maize monoculture, the optimised rotation supplied 70% more biomass N and 40% less nitrate leaching on coarse sandy soil, whereas on sandy loam soil it yielded about 10% less biomass N with 50% less nitrate leaching. Field surface N balances were overall neutral/positive, except for festulolium and continuous maize monoculture that slightly mined the soil for N. When N losses by leaching, denitrification and volatilisation were included, soil total N stocks were estimated to decline for the majority of the systems at both sites.

Tradeoffs between Maize Silage Yield and Nitrate Leaching in a Mediterranean Nitrate-Vulnerable Zone under Current and Projected Climate Scenarios.

Future climatic changes may have profound impacts on cropping systems and affect the agronomic and environmental sustainability of current N management practices. The objectives of this work were to i) evaluate the ability of the SALUS crop model to reproduce experimental crop yield and soil nitrate dynamics results under different N fertilizer treatments in a farmer’s field, ii) use the SALUS model to estimate the impacts of different N fertilizer treatments on NO3- leaching under future climate scenarios generated by twenty nine different global circulation models, and iii) identify the management system that best minimizes NO3- leaching and maximizes yield under projected future climate conditions. A field experiment (maize-triticale rotation) was conducted in a nitrate vulnerable zone on the west coast of Sardinia, Italy to evaluate N management strategies that include urea fertilization (NMIN), conventional fertilization with dairy slurry and urea (CONV), and no fertilization (N0). An ensemble of 29 global circulation models (GCM) was used to simulate different climate scenarios for two Representative Circulation Pathways (RCP6.0 and RCP8.5) and evaluate potential nitrate leaching and biomass production in this region over the next 50 years. Data collected from two growing seasons showed that the SALUS model adequately simulated both nitrate leaching and crop yield, with a relative error that ranged between 0.4% and 13%. Nitrate losses under RCP8.5 were lower than under RCP6.0 only for NMIN. Accordingly, levels of plant N uptake, N use efficiency and biomass production were higher under RCP8.5 than RCP6.0. Simulations under both RCP scenarios indicated that the NMIN treatment demonstrated both the highest biomass production and NO3- losses. The newly proposed best management practice (BMP), developed from crop N uptake data, was identified as the optimal N fertilizer management practice since it minimized NO3- leaching and maximized biomass production over the long term.

Response of nitrogen use efficiency and soil nitrate dynamics to soil mulching in dryland maize (Zea mays L.) fields

Plastic film (FM) and gravel mulching (GM) have been used extensively to increase dryland agricultural productivity. Understanding mulching effects on nitrogen (N) use efficiency (NUE) and soil nitrogen dynamics is important for optimizing N management strategies. A 3-year field experiment was performed on the Loess Plateau of China to investigate the GM and FM effects on plant N accumulation, N translocation, N harvest index (NHI), NUE and soil NO3 −-N dynamics in dryland maize fields. Compared with the control (CK, non-mulching), the mulching treatments markedly promoted plant N accumulation and especially maintained higher N uptake rates during the post-silking stage. At harvest, the total N accumulation was 12.8–41.2 and 33.2–55.8 % higher in the GM and FM treatments, respectively, than in the CK treatment. The NHIs of the mulching treatments were significantly higher by 9.6–32.4 % than the CK treatment, primarily due to greater N translocation and N accumulation post-silking. Overall, compared with the CK treatment, the GM and FM NUEs increased significantly by 17.1 and 28.3 % in 2010, 70.3 and 87.6 % in 2011, and 16.7 and 38.2 % in 2012, respectively. In the wet years of 2010 and 2011, the increased amount of soil NO3 −-N in the 100–200 cm layer after harvest was 27.1–57.1 and 47.9–85.7 % lower in the GM and FM treatments, respectively, than in the CK treatment, indicating a lower NO3 −-N leaching loss. These results suggest that mulching (especially FM) is an effective measure for increasing NUE and grain yield and decreasing N leaching loss in dry farmland.

Soil water and nitrogen interaction effect on residual soil nitrate and crop nitrogen recovery under maize–wheat cropping system in the semi-arid region of northern India

Over fertilization of nitrogen (N) in the premise of higher crop yield has sometimes led to build up of residual soil nitrate and pollution of ground water. Though, maize and wheat are two heavy feeders of N, studies on soil nitrate dynamics under maize–wheat cropping system in the Indo-Gangetic Plains of northern India, are limited. Hence, the present study was carried out at the research farm of Indian Agricultural Research Institute, New Delhi with maize–wheat cropping sequence grown for four consecutive cropping seasons, during 2002–2004. The treatments consisted of three levels of water regimes and five N levels taken in split plot design. Three levels of water regime, namely, W1, W2 and W3 referred to as limited, medium and maximum number of recommended irrigation. The five N levels were T1 (0% N), T2 (75% N), T3 (100% N), T4 (150% N) and T5 (100% N from organic source). For both the crops, 100% N corresponded to the recommended dose of 120kgNha−1 from inorganic source. Irrespective of crop, N recovery was higher under T2 and W3 treatment combination, though yield and biomass were highest under T4 and W3 treatments. Nitrogen recovery from organic treatment gradually increased from 8.8% in the first crop season (maize, 2002) to 26.1% in the last crop season of the experiment (wheat, 2004). Peak NO3− concentration was observed at 15–30cm soil depth in W1 and W2 treatments and at 30–60cm in W3 water regime. The NO3− buildup was higher in W1 as compared to W3 treatment and was to the extent of 62kgha−1 in the 0–120cm soil profile under W1T4 treatment after four crop seasons. Across water treatments, soil NO3− was higher under T4 (150% N), followed by T3 (100% N) throughout the experiment period. Despite a trend of soil NO3− buildup, application of N (150%) maximized crop productivity (maize and wheat) under W3. The study revealed that maize–wheat cropping system grown under higher N application levels beyond the recommended dose, would reduce N use efficiency and enhance soil nitrate buildup.

Post-harvest soil nitrate dynamics in aspen- and spruce-dominated boreal forests

It has been suggested that clear-cutting boreal forests shifts the soil N environment from ammonium-domination to nitrate-domination, which encourages aspen regeneration but inhibits spruce regeneration. We assessed nitrate production and availability in clear-cut and uncut aspen- and spruce-dominated forests in a boreal mixedwood forest in northern Alberta, Canada, 4 years after harvesting. We hypothesized that nitrate production and availability would be higher in aspen than spruce-dominated forests, and higher in clear-cuts than in uncut forests. Nitrate production occurred in all forest types, but ammonium was the dominant inorganic N form and at all sites. Clear-cutting did not increase nitrate production and neither was it higher in aspen-dominated forests. Nitrate consumption was also unaffected by harvesting. Thus clear-cutting does not appear to convert boreal forest soils into “nitrate environments”. Nitrate was produced by both autotrophic and heterotrophic soil organisms, but heterotrophic activity dominated. Nitrification was responsive to manipulation of available C levels in laboratory, but changes in soil C availability in the field treatments were not associated with significant changes in nitrate production and consumption.

Nitrous Oxide Emission from No‐Till Irrigated Corn

Field experiments were conducted to determine optimal time during the day for N2O flux determination and to evaluate the effects of wheel traffic and soil parameters on N2O fluxes following urea ammonium nitrate (UAN) injection and summer UAN fertigations. The experiments were located on silty clay loam soils under no‐till irrigated continuous corn of eastern Nebraska. Three approaches were used. First, near‐continuous N2O flux measurements were made in non‐wheel‐tracked (NWT) interrows in four 24‐h periods during the growing season of 2002. Second, point measurements of N2O flux were made in the wheel‐tracked (WT) and NWT interrows at five dates during the growing season of 2002. Third, point measurements of N2O fluxes and soils (nitrate, ammonium, moisture, and temperature) were made in the NWT interrows from 2001 to 2004. The differences between point vs. continuous flux measurements (&lt;8 g N2O‐N ha−1 d−1) and between the WT vs. the NWT (&lt;3.7 g N2O‐N ha−1 d−1) were not significant. The means of N2O daily flux within 60 d after injection (period of high soil N) in the first, second, and third year were 26.8, 21.2, and 28.0 g N2O‐N ha−1 d−1, respectively. The means during low soil N were 9.24, 4.05, and 7.50 g N2O‐N ha−1 d−1, respectively. Summer fertigations did not increase N2O flux. Under the conditions of this study, optimal point measurement for N2O daily flux can be made any time during the day at the NWT interrows. Among the soil parameters, soil nitrate dynamics in the injection zone correlates best with N2O fluxes.

Effects of straw mulch on soil nitrate dynamics, weeds, yield and soil erosion in organically grown potatoes

The application of straw mulch to organic seed potatoes ( Solanum tuberosum L.) has been shown to reduce virus incidence. In order to determine the associated agronomic effects of straw mulch, applied at 2.5–5 t ha −1, on soil nitrate dynamics, weed development, tuber yield and soil erosion, 12 field experiments were evaluated. Experiments were conducted on organic farms over 3 years at two locations in a temperate climate (635–709 mm precipitation/year; 8.1 °C mean air temperature) on loamy silt soils. Tuber yield and tuber size distribution were not influenced significantly by mulching. However, the risk of undesirable post harvest N-leaching was significantly reduced due to the immobilization of nitrate–N after harvest at 6.8–7.0 kg N t −1 straw in two experiments (18–34 kg NO 3–N ha −1). There was no consistent effect of straw mulch on number of weeds, weed cover and above ground biomass of weeds. The fact that yield and weed development were not significantly affected by straw mulch is mainly attributed to the relatively low amounts of straw applied. Soil erosion was reduced by >97% in a rain simulation experiment on a potato field of 8% slope with 20% crop cover. Soil loss was greatest (1606 g m −2) in the unmulched treatment, and 31, 42 and 26 g m −2 in treatments with chopped straw at 1.25, 2.5 and 5 t ha −1, respectively.

Differential N uptake by maize cultivars and soil nitrate dynamics under N fertilization in West Africa

Nitrate is prone to leaching in the sandy soils of the West African moist savannas. Better management of nitrogen (N) resources and maize cultivars with enhanced genetic capacity to capture and utilize soil and fertilizer N are strategies that could improve N-use efficiency. In two field experiments conducted at Zaria, northern Nigeria, five maize ( Zea mays L.) cultivars planted early in the season were assessed under various N levels for differences in N uptake, soil N dynamics, and related N losses. Cultivar TZB-SR accumulated more N in the aboveground plant parts in both years than the other cultivars. All, except the semi-prolific late (SPL) variety, met about 50–60% of their N demand by the time of silking (64–69 DAP). In both years, SPL had the greatest capacity to take up N during the grain filling period, and it had the highest grain-N concentration and the least apparent N loss through leaching in the second year. There were no significant differences in soil N dynamics among cultivars in both years. At harvest, the residual N in the upper 90 cm of the profile under all the cultivars ranged from 56 to 72 kg ha −1 in the first year and from 73 to 83 kg ha −1 in the second year. Apparent N loss from 0 to 90 cm soil profile through leaching ranged from 35 to 122 kg ha −1 in both years. N application significantly increased N uptake by more than 30% at all sampling dates in the second year of the experiment, but had no effect on apparent N loss. Results indicate that the use of maize cultivars with high N uptake capacity during the grain filling period when maximum leaching losses occur could enhance N recovery and may be effective in reducing leaching losses of mineral N in the moist savanna soils.

Soil nitrate dynamics in relation to nitrogen source and landscape position in Malawi

Nitrogen is normally the nutrient most limiting production of maize (Zea mays) — the main staple food crop — in southern Africa. We conducted a field study to determine the effect of N sources on soil nitrate dynamics at three landscape positions in farmers' fields in southern Malawi. The landscape positions were dambo valley or bottomland, dambo margin, and steep slopes. The N sources were calcium ammonium nitrate fertilizer applied at 120 kg N ha−1, biomass from Sesbania sesban, and no added N. Sesbania biomass was produced in situ in the previous season from sesbania relay cropped with maize. Nitrate in the topsoil (0 to 15 cm depth) increased to 85 days after maize planting (mean = 48 kg N ha−1) and then decreased markedly. Application of N fertilizer and sesbania biomass increased soil nitrate, and nitrate-N in topsoil correlated positively with amount of incorporated sesbania biomass. The strongest correlation between sesbania biomass added before maize planting and topsoil nitrate was observed at 85 days after maize planting. This suggests that the sesbania biomass (mean N content = 2.3%) mineralized slowly. Inorganic N accumulated in the subsoil at the end of the maize cropping season when N fertilizer and sesbania were applied. This study demonstrated the challenges associated with moderate quality organic N sources produced in smallholder farmer's fields. Soil nitrate levels indicated that N was released by sesbania residues in the first year of incorporation, but relay cropping of sesbania with maize may need to be supplemented with appropriately timed application of N fertilizer.

Seasonal Soil Nitrate Dynamics in Corn as Affected by Tillage and Nitrogen Source

AbstractA better understanding of seasonal soil NO−3 dynamics in corn (Zea mays L.) as affected by different tillage and N sources is essential to refine N management options for more profitable production and less negative impact on water resources. We conducted an experiment in central Pennsylvania to study seasonal soil NO−3 dynamics in corn managed with conventional tillage (CT) or no‐till (NT) and supplied with commercial N fertilizer or legume green manures of red clover (Trifolium pratense L.) or hairy vetch (Vicia villosa Roth) double‐cropped with winter wheat (Triticum aestivum L.). The legume cover crops and winter fallow after the wheat harvest were followed by two corn crops. Soil samples taken biweekly during the corn growing seasons were analyzed for NO−3 concentrations in the 0‐ to 25‐ (Ap horizon) and 25‐ to 45‐cm (upper B horizon) soil layers. In the first corn crop, soil NO−3 concentrations peaked about 4 wk after planting in all treatments. Where no broadcast N fertilizer was applied, mid‐ to late‐season soil NO−3‐N concentrations in the Ap horizon averaged 6, 25, and 1.3 mg kg−1 in the clover CT, vetch CT, and fallow CT treatments, respectively, while the NO−3‐N concentrations in all NT 0 N treatments were similar (1.3–1.9 mg kg−1). After the first corn harvest, the clover and vetch CT 0 N treatments had 113 and 124 kg NO−3‐N ha−1 in the 120‐cm soil profile, slightly higher than that estimated for the fallow treatment with N fertilizer at the economic optimum rate (99 kg NO−3‐N ha−1). No‐tillage also reduced the amount of NO−3 accumulated in the 0‐ to 120‐cm soil profile to one‐half of the NO−3 levels in the corresponding CT treatments, regardless of N source. Both tillage and N source strongly affected seasonal soil NO−3 dynamics in the first corn season, with the major difference appearing in the Ap horizon.

Simulation of Nitrate Leaching from Arable Land in Southern Sweden

Abstract Soil nitrate dynamics and nitrate leaching were simulated for a nine-year period. Hydrological time-series, previously simulated with a soil water and heat model were used as driving variables. Parameter values were derived from measurements and management practices or adapted from other comparable applications. Model outputs were tested against measurements of leaching and nitrate content of the soil. Dominating crops were spring wheat, barley and sugar beets but also winter wheat and winter rape were grown. Predictions of nitrate in the soil were good on six of eight occasions. Simulated yearly leaching was close to measured values in most years. The deviations could be explained by model failure in predicting surface runoff and uncertainties in the nitrogen harvest. The between-year variation in the leaching magnitude during years with ‘normal' discharge rates could largely be explained by the amount of nitrate remaining in the soil profile in the beginning of September and the litter minerali...