Soil Mineral Nitrogen Dynamics Research Articles

Short-Term Nitrous Oxide Emissions from Cattle Slurry for Silage Maize: Effects of Placement and the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP)

Cattle slurry is an important nitrogen source for maize on dairy farms. Slurry injection is an effective measure to reduce ammonia emissions after field application, but with higher risk of nitrous oxide emission than surface application. This study compared soil mineral nitrogen dynamics and nitrous oxide emissions with two ways of application. First, traditional injection at 25 cm spacing between rows followed by ploughing (called “non-placed slurry”), and second, injection using a new so-called goosefoot slurry injector that placed the slurry in ploughed soil as a 30 cm broad band at 10 cm depth below maize crop rows with 75 cm spacing (named “placed slurry”). Furthermore, the effect of treating slurry with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in Vizura® was tested with both application methods. The field experiment was conducted on a sandy loam soil in a temperate climate. Both nitrous oxide emissions, and the dynamics of soil mineral nitrogen, were monitored for eight weeks after slurry application and seeding of maize using static chambers. The level of nitrous oxide emissions was higher with non-placed compared to placed slurry (p < 0.01), mainly due to higher emissions during the first four weeks. This might be due to higher rates of nitrification and in turn stimulation of denitrification. In both placed and non-placed slurry treatments, Vizura® caused higher soil ammonium concentrations and lower nitrate concentrations (p < 0.001), particularly from 3 to 8 weeks after slurry application. The final level of soil nitrate was similar with and without the nitrification inhibitor, but higher with placed compared to non-placed slurry. Adding Vizura® to non-placed slurry reduced nitrous oxide emissions by 70% when compared to untreated slurry. Surprisingly, there was a non-significant trend towards higher cumulative emissions from placed slurry with the nitrification inhibitor compared to untreated slurry, which was due to higher emissions in the last part of the monitoring period (5–7 weeks after slurry application). Possibly, degradation of the nitrification inhibitor and nitrification activity inside the slurry band as the soil dried promoted nitrous oxide emissions by this time. In summary, placement of untreated slurry in a broad band under maize seeds reduced nitrous oxide emissions compared to non-placed slurry with more soil contact. A comparable reduction was achieved by adding a nitrification inhibitor to non-placed slurry. The pattern of nitrous oxide emissions from placed slurry treated with the inhibitor was complex and requires more investigation. The emission of nitrous oxide was highest when nitrate accumulated in soil around decomposing cattle slurry, and mitigation strategies should aim to prevent this. This study demonstrated a potential for mitigation of nitrous oxide emission by placement of cattle slurry, which may be an alternative to the use of a nitrification inhibitor.

Nitrification inhibitor and management of liquid hog manure: the effect on soil mineral nitrogen dynamics and wheat yield

Management is of fundamental importance in increasing the efficiency of liquid hog manure (LHM) when used as a source of nitrogen (N) and minimizing its impact on the environment. This paper evaluates the effect of surface application and injection of LHM and the use of dicyandiamide (DCD) on the dynamics of mineral N in the soil and on the components of yield in wheat crops. An experiment was conducted at the Federal University of Santa Maria, Frederico Westphalen Campus, Rio Grande do Sul state, Brazil, involving the following treatments: T0 - Control; T1 - surface application of LHM (Sup); T2 - subsurface injection of LHM (Inj); T3 - surface application of LHM + DCD (Sup+DCD); T4 - subsurface injection of LHM + DCD (Inj+DCD), and T5 - application of N, phosphorus (P), and potassium (K) in mineral form (NPK) in 2014 and 2015. The mineral N recovered with the injection of LHM was superior to surface application, and DSD reduced the speed with which anionic forms of mineral N appear. There was a greater increase in the number of ears of wheat with LHM injection. In 2014, the number of grains per ear was higher with the injection of LHM + DCD, whereas in 2015 all the treatments were higher than the control. There was no difference in 1,000-grain weight between treatments with LHM. Hectoliter weight was higher with the injection of LHM + DCD and the yields observed in this treatment were also higher, not differing from mineral fertilization. It is concluded that LHM injection provides lower losses of N and DCD and reduces the speed with which anionic forms of mineral N appear. In addition, the final yield of wheat grains does not differ when comparing LHM + DCD with mineral fertilization.

Soil mineral nitrogen dynamics in fallow periods in a rainfed semiarid Mediterranean agricultural system

Rainfed agricultural systems in semiarid Mediterranean environments are subject to erratic but often heavy rainfall events. As an agronomic practice, fallow periods can be included even within the existing EU common policy for crop diversification. This research aimed to quantify the effects of a previous mineral fertilization on the soil mineral nitrogen (N min ) content and on potential nitrate leaching during no-tilled fallow periods of a crop rotation. Water and N min soil measurements obtained during three fallow seasons were used. Data were also used to check if the Leaching Estimation and Chemistry Model (LEACHM) can be used for the soil N min prediction after fallow. During these periods, the N min measured in the soil profile increased on average by 125 kg N ha -1 , while the model averaged an increase of 95 kg N ha -1 . The estimate of N leached ranged from 11 to 38 kg N ha -1 . The N balance simulated using LEACHM might differ from the actual processes. After a drought period followed by a soil water replenishment, the calibrated LEACHM underestimated soil N min probably due to the “Birch effect”. After occasional rainy spells when soil quickly became saturated, LEACHM overestimated soil N min probably due to occasional N 2 O emissions not being fully accounted by the model and to specific preferential water flow, which might produce a greater nitrate leaching than that simulated by LEACHM using the convection-dispersion equation . The results show that soil N min measurements by sampling after the fallow period cannot be replaced by LEACHM simulations. These samplings are of interest in fallow established inside a rotation and to avoid over-fertilization in the following cropping season, while reducing N environmental impacts.

Soil Properties for Predicting Soil Mineral Nitrogen Dynamics Throughout a Wheat Growing Cycle in Calcareous Soils

A better understanding of the capacity of soils to supply nitrogen (N) to wheat can enhance fertilizer recommendations. The aim of this study was to assess the soil mineral N (Nmin) dynamics throughout the wheat growing season in crucial stages for the plant yield and grain protein content (GPC). To this aim, we evaluated the utility of different soil properties analyzed before sowing: (i) commonly used soil physicochemical properties, (ii) potentially mineralizable N or No (aerobic incubation), and (iii) different extraction methods for estimating No. A greenhouse experiment was established using samples from 16 field soils from northern Spain. Wheat N uptake and soil Nmin concentrations were determined at following growing stages (GS): sowing, GS30, GS37, GS60, harvest, post-harvest, and pre-sowing. Pearson’s correlation analysis of the soil properties, aerobic incubations and chemical extractions with the soil Nmin dynamics and N uptake, yield and GPC was performed. In addition, correlations were performed between Nmin and the N uptake, yield, and GPC. The dynamics of soil Nmin throughout the cropping season were variable, and thus, the crop N necessities were variable. The soil Nmin values in the early wheat growth stages were well correlated with the yield, and in the late stages, they were well correlated with GPC. N0 was correlated with the late N uptake and GPC. However, the chemical methods that avoid the long periods required for N0 determinations were not correlated with the N uptake in the late wheat growth stages or GPC. Conversely, clay was positively correlated with the late Nmin values and GPC. Chemical methods were unable to estimate the available soil N in the later stages of the growing cycle. Consequently, as incubation methods are too laborious for their widespread use, further research must be conducted.

N2O emissions and nitrogen dynamics of winter rapeseed fertilized with different N forms and a nitrification inhibitor

Winter oilseed rape is one of the most important crops in Germany. However, due to intensive nitrogen (N) fertilization, nitrous oxide (N2O) emissions can occur, which may negatively affect the greenhouse gas (GHG) balance of biodiesel produced from rapeseed oil. Therefore, various field experiments were performed during 2013 to 2016 to investigate the influence of different N forms (ammonium sulphate nitrate and urea) as well as the use of a nitrification inhibitor (NI) on the harvest yields, N uptake, soil mineral nitrogen (SMN) dynamics and N2O emissions during the cultivation of winter rapeseed. At a N fertilization level of 220 kg ha−1 and seed yields of up to 6.0 Mg ha−1, the N2O-N emissions during the crop growing period were relatively low, i.e., within the range of 200 and 2300 g ha−1. The oil yield of the various N forms did not differ significantly. Concerning SMN dynamics, the nitrate values in the urea treatments were mostly lower than in the ammonium sulphate nitrate (ASN) plots. Although being on a relatively low level, the bulk of N2O emissions occurred between flowering and maturity of plants. N surpluses in plants fertilized with urea were highest, but in contrast these treatments showed the lowest measured N2O emissions within the fertilized plots. N2O-N emissions during the different seasons averaged 360 g ha−1 in the unfertilized control treatment. In the fertilized treatments, 770 g N2O-N emitted in the single schedule treatment with urea + NI, respectively 790 g ha−1 N2O-N in the urea + NI treatment with a split fertilization, moreover 1110 g ha−1 in the urea treatment without NI and 1450 g ha−1 in the plots fertilized with ammonium sulphate nitrate. The results show that the choice of the form of N and use of nitrification inhibitors at this site represent an approach for the abatement of nitrous oxide fluxes. This potential should be enhanced to fulfil the sustainability requirements of the European Union (EU RED) concerning the use of biofuels.

Effects of urease and nitrification inhibitors on the soil mineral nitrogen dynamics and nitrous oxide (N2O) emissions on calcareous soil.

Urease inhibitors and nitrification inhibitors can reduce nitrogen (N) loss in agriculture soil. However, the effect of inhibitors on soil N2O emissions under the drip irrigation system remains unclear. A pot and a field experiment with two inhibitors were conducted to explore how inhibitors regulate soil nitrogen transformation and N2O emissions. In the pot experiment, three treatments included control, urea, and urea + N-(n-butyl)thiophosphoric triamide (NBPT, urease inhibitor). In the field experiment, three treatments included control, urea, and urea + NBPT + 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin, nitrification inhibitor). The urease inhibition rate in the treatment of urea + NBPT was 27.5% at the 14th day of incubation (pot experiment), and NH4+-N was significantly decreased by 37-64% compared with urea alone treatment. In the field experiment, the nitrification inhibition rate in the treatment of urea + NBPT + nitrapyrin was 47.7 and 63.9% on the 3rd day after fertilization at the wheat heading and filling stages, respectively. Compared to urea treatment, NO3--N concentration in the double-inhibitor-added treatment was significantly decreased by 32 and 20% on the 5th day after fertilization at the heading and filling stages, respectively; N2O fluxes were also decreased by 30.9 and 33.3% at the two stages of wheat, respectively. In total, adding an inhibitor reduced N loss by 7.39 and 7.44% at the 14th and 35th day in the pot experiment and by 10.53 and 6.65% at the two growing stages of wheat in the field experiment, respectively. Path and correlation analysis showed that N2O emissions were significantly correlated with soil NO3- in both pot and field experiments.

Soil mineral nitrogen dynamics following repeated application of dairy slurry

Repeated applications of animal slurry to soil can lead to residual nitrogen (N) effects from mineralization of organic N carried over from the previous year and from remineralization of previously immobilized N. We studied the effect of repeated slurry applications on soil mineral N (SMNt: nitrate‐N plus soluble, exchangeable and non‐exchangeable ammonium‐N) dynamics in a simplified, aerobic laboratory incubation. The experiment evaluated the effects of up to four applications (84‐day intervals) of two different liquid cow slurries, ammonium sulphate and water (unfertilized control, CON) to sandy loam and clay loam soils. The slurries came from heifers (HEI) and lactating dairy cows (COW). Both soil types showed net N mineralization in HEI during each 84‐day interval after application (3–6% of slurry‐N), whereas decomposition of COW induced net N immobilization at 16% of slurry‐N. The effect observed for COW might have come from its larger C to organic‐N ratio. After each application to the clay loam soil, 36–64% of the ammonium applied was not recoverable at day 0 because of ammonium fixation by clay minerals, and an average of 20% of fertilizer‐N was measured as non‐exchangeable ammonium at day 84. Recovery of N applied with both HEI and COW at day 84 increased significantly with subsequent applications to clay loam soil, but not to sandy loam soil. Residual effects in clay loam soil ranged from 2 to 11% of applied N, which probably resulted from slow mineralization of recalcitrant organic fractions in the slurry and partial stabilization of microbial by‐products within the soil.HighlightsA novel incubation approach was used to study residual N effects of ammonium sulphate and slurries. Fertilizers were applied one, two, three or four times to a sandy loam (SL) and a clay loam (CL) soil. Residual N effects were small; less slurry NH4‐N was available in CL than SL because of clay fixation. Mineralization of residual slurry‐N and stabilization of microbial by‐products were slow.

Soil nitrogen dynamics after slurry injection in field trials: Evaluation of a soil sampling strategy

AbstractSlurry injection below maize seeds is a rather new application technique developed to improve the nitrogen use efficiency of liquid organic manure. To enable the characterization of the spatial and temporal soil mineral nitrogen (SMN) dynamics after slurry injection, the present study aims to develop an appropriate soil sampling strategy. Three consecutive experiments were conducted. The first testing of the soil sampling approach was conducted in an existing field trial where the slurry was injected down to a depth of 12 cm (upper rim) below the soil surface. The soil profile (75 cm wide) centered below the maize row was sampled grid‐like to a depth of 90 cm. Around the injection zone, soil monoliths (SM) were sampled using a purpose‐built soil shovel. Below the SMs and in the interrow space (15 and 30 cm distance to the row) a standardized auger procedure was performed. The second experiment aimed at improving the sampling strategy with a focus on sample homogenization quality and necessary sample sizes per pooled sample. Furthermore, the risk of a carryover of slurry components along the soil core due to drilling an auger through a slurry band was analyzed. In the third experiment this improved sampling strategy was validated. Results from the first testing of the sampling procedure showed that the strategy is suitable, although some problems occurred (especially the high spread in values among the replications causing high coefficients of variation (CV) of mostly 40–60%). The improvement trial revealed that due to the high gradient of SMN concentration in the direct range of the injection zone an intensive homogenization of these samples is required. Suitable sample sizes (twelve auger samples and six soil monolith samples per pooled sample) have to be collected to obtain reliable SMN values. Drilling an auger through a slurry band to sample subjacent soil layers has to be avoided. Following this enhanced sampling strategy, in the final validation trial the spread in values were considerably reduced and resulted in CV values of mostly < 20%. The developed sampling strategy enables the characterization of the spatial and temporal SMN dynamics when slurry has been band‐injected below a maize row. The method can be transferred to other row crops and different slurry injection spacing.

Influence of Nitrogen Form Supply on Soil Mineral Nitrogen Dynamics, Nitrogen Uptake, and Productivity of Sugarcane

Current limitations on the use of conventional N fertilizers on sugarcane (Saccharum spp.) in Brazil require the search for alternative sources with adequate N use efficiency. Field experiments were conducted in Typic Hapludox (TH) and Typic Eutrustox (TE) soils in São Paulo State, Brazil, to evaluate the dynamics of soil mineral N, N uptake, and sugarcane yield in response to N amendments including Ajifer‐8, ammonium chloride, ammonium nitrate, calcium ammonium nitrate (CAN), and urea applied on sugarcane ratoon at 100 kg N ha−1. The experiments were arranged in randomized complete block design, with four replications. The treatments were applied at 105 and 122 days after harvest of plant cane (DAH) in the TH and TE soil. Ajifer‐8 exhibited higher NH4+–N availability in the 0‐ to 20‐cm soil layer 139 DAH in the TH soil. Ammonium nitrate and CAN resulted in the highest NO3−–N values in the soil within the same period. In the TE soil, the soil mineral N content remained unaltered during all of the sampling dates. The high values of accumulated N uptake by sugarcane in both soils indicates that a good portion of the soil mineral N was take up by the plants. The Ajifer‐8 and CAN fertilizers resulted in higher sugarcane yield in both experiments, and may be used as replacement for conventional N sources. In contrast, the use of ammonium chloride resulted in low values of soil mineral N and accumulated N uptake.

Application of the Bayesian calibration methodology for the parameter estimation in CoupModel

Abstract. This study provides results for the optimization strategy of highly parameterized models, especially with a high number of unknown input parameters and joint problems in terms of sufficient parameter space. Consequently, the uncertainty in model parameterization and measurements must be considered when highly variable nitrogen losses, e.g. N leaching, are to be predicted. The Bayesian calibration methodology was used to investigate the parameter uncertainty of the process-based CoupModel. Bayesian methods link prior probability distributions of input parameters to likelihood estimates of the simulation results by comparison with measured values. The uncertainty in the updated posterior parameters can be used to conduct an uncertainty analysis of the model output. A number of 24 model variables were optimized during 20 000 simulations to find the "optimum" value for each parameter. The likelihood was computed by comparing simulation results with observed values of 23 output variables including soil water contents, soil temperatures, groundwater level, soil mineral nitrogen, nitrate concentrations below the root zone, denitrification and harvested carbon from grassland plots in Northern Germany for the period 1997–2002. The posterior parameter space was sampled with the Markov Chain Monte Carlo approach to obtain plot-specific posterior parameter distributions for each system. Posterior distributions of the parameters narrowed down in the accepted runs, thus uncertainty decreased. Results from the single-plot optimization showed a plausible reproduction of soil temperatures, soil water contents and water tensions in different soil depths for both systems. The model performed better for these abiotic system properties compared to the results for harvested carbon and soil mineral nitrogen dynamics. The high variability in modeled nitrogen leaching showed that the soil nitrogen conditions are highly uncertain associated with low modeling efficiencies. Simulated nitrate leaching was compared to more general, site-specific estimations, indicating a higher leaching during the seepage periods for both simulated grassland systems.

Organic amendment effects on tuber yield, plant N uptake and soil mineral N under organic potato production

AbstractThe market for certified organic potatoes in Canada is growing rapidly, but the productivity and dynamics of soil N under commercial organic potato systems remain largely unknown. This study examined, at two sites in Atlantic Canada (Winslow, PEI, and Brookside, NS), the impacts of organic amendments on Shepody potato yield, quality and soil mineral nitrogen dynamics under organic management. Treatments included a commercial hog manure–sawdust compost (CP) and pelletized poultry manure (NW) applied at 300 and 600 kg total N ha−1, plus an un-amended control (CT). Wireworm damage reduced plant stands at Brookside in 2003 and those results are not presented. Relatively high tuber yields (~30 Mg ha−1) and crop N uptake (112 kg N ha−1) were achieved for un-amended soil in those site-years (Winslow 2003 and 2004) when soil moisture was non-limiting. Compost resulted in higher total yields than CT in one of three site-years. Apparent recovery of N from CP was negligible; therefore CP yield benefits were attributed to factors other than N availability. At Winslow, NW300, but not NW600, significantly increased total and marketable yields by an average of 5.8 and 7.0 Mg ha−1. Plant available N averaged 39 and 33% for NW300 and NW600, respectively. Soil (0–30 cm) NO3−-N at harvest was low (<25 kg N ha−1) for CT and CP, but increased substantially both in season and at harvest (61–141 kg N ha−1) when NW was applied. Most leaching losses of NO3−-N occur between seasons and excessive levels of residual soil NO3-N at harvest, as obtained for NW600, must be avoided. Given current premiums for certified organic potatoes, improving yields through application of amendments supplying moderate rates of N or organic matter appears warranted.

Influence of root zone nitrogen management and a summer catch crop on cucumber yield and soil mineral nitrogen dynamics in intensive production systems

Nutrient and water management is crucially important in shallow-rooted vegetable production systems characterized by high input and high environmental risk. A 2-year field experiment on greenhouse cucumber double-cropping systems examined the effects of root zone nitrogen management and planting of sweet corn as a catch crop in the summer fallow period on cucumber yield and soil Nmin dynamics compared to conventional practices. Cucumber fruit yields were not significantly affected by root zone N management and catch crop planting despite a decrease in N fertilizer application of 53% compared to conventional N management. Soil Nmin content to a depth of 0.9 m decreased markedly and root zone (0–0.3 m) soil Nmin content was maintained at about 200 kg N ha−1. Root zone N management efficiently and directly reduced apparent N losses by 44% and 45% in 2005 and 2006, respectively. Sweet corn, the summer catch crop, depleted Nmin residue in the soil profile of 1.8 m at harvest of winter–spring season cucumber by 304–333 kg N ha−1, which contributed 19–22% reduction in N loss. Compared to conventional N management, N loss was reduced by 56% under root zone N management and catch crop planting.

In situ ion exchange resin membrane (IEM) technique to measure soil mineral nitrogen dynamics in grazed pastures

This paper explored the potential of application of in situ ion exchange resin membrane (IEM) technique for assessing soil nitrogen (N) availability and spatial distribution in New Zealand grazed pastures. Field and incubation experiments conducted to test the technique proved IEM technique to be a useful approach to monitoring the continuous changes in soil mineral N in pasture soils. The field testing showed that the IEM technique reflects both differences in pool size and mineral N flux, while 2-M KCl extraction reflects only pool size at the sampling. Testing the effects of residence time, temperature, soil inorganic N content, and soil water content through diffusion modeling offers further support for using IEM to explore the complex dynamics of nitrogen availability in pasture soils.

Impact of harvest residues on soil mineral nitrogen dynamics following clearfall harvesting of a hoop pine plantation in subtropical Australia

An alternative management strategy allowing post-harvest residues to remain as a blanket cover instead of being incorporated into windrows may prevent problems associated with lack of soil fertility in the inter-windrow space. Parallel, 2-year, in situ nitrogen (N) mineralisation studies were undertaken during the inter-rotation period following clearfall harvesting of a first-rotation hoop pine ( Araucaria cunninghamii Aiton ex D. Don) plantation in subtropical Australia. We investigated the dynamics of ammonium N, nitrate N and nitrite N in the top 20 cm soil under a residue retention situation and under normal, operational conditions. Initially, ammonium N was the dominant form of soil mineral N but declined to <10 kg N ha −1 at both sites after 12 sampling cycles of 28-day duration. Nitrate N levels remained at approximately 30 kg N ha −1 despite seasonal fluctuations, throughout the 2-year sampling period. At the residue site there was no net N mineralisation in the soil until the 20th sampling cycle; approximately 110 kg N ha −1 was mineralised at the end of the sampling period. This compared with approximately 300 kg N ha −1 mineralised at the operational site for the same period. Approximately 100 and 220 kg N ha −1 were lost through leaching at the residue and operational sites, respectively. Residue retention promoted N immobilisation, reducing the potential for N losses through leaching and denitrification in the critical inter-rotation and early establishment period.

Soil mineral nitrogen dynamics under bare fallow and wheat in vertisols of semi-arid Mediterranean Morocco

The evoluion of NH4+-N and NO3–-N was monitored during three growing seasons, 1992–1993, 1993–1994, 1994–1995 in the soil profile (0–60 or 0–90 cm) under bare fallow and wheat on a vertisol site of the Sais plateau, Morocco. The aim of this study was to relate the soil mineral N dynamics to crop N uptake and soil N transformation processes. The efficacy of the current N fertilisation rate (100 kg N ha–1) for wheat production in the region was evaluated. The high level of residual mineral N in the soil profile resulted from a low N plant uptake relative to the soil N supply and N fertilisation, and masked the effect of N fertilisation on dry matter accumulation. NH4+-N was present in considerable amounts, suggesting a low nitrification rate under the given pedo-climatic conditions. An artefact due to the sampling procedure was encountered shortly after the application of N fertiliser. Losses through leaching and denitrification occurred after heavy rainfall, but were limited. At least part of the exchangeable NH4+-N seemed to be barely taken up by the crop. NO3–-N was therefore considered to be a better indicator of plant-available N than total mineral N for this type of soil. The low N fertiliser use efficiencies demonstrated clearly that the current fertilisation rate (100 kg N ha–1) for wheat production in this region is unsustainable. The maximum N uptake ranged from 40 kg N ha–1 to 180 kg N ha–1. The estimation of the seasonal production potential is considered to be the main prerequisite for the determination of the best rates and timing of N fertiliser application in this region.

Effects of artificial drainage on soil mineral nitrogen dynamics in winter wheat on the southern piedmont

Abstract Excess soil moisture is believed to cause reduced levels of soil mineral N and crop production in winter wheat on the Southern Piedmont. Artificial subsurface drainage was used to relieve excess soil moisture and soil mineral N levels, mineralization, nitrification, denitrification and a group of soil properties were analyzed in both drained and undrained treatments. Drainage increased rates of mineralization and nitrification and decreased rates of denitrification, leading to higher levels of soil mineral N in drained plots than in undrained plots. Wheat yields were not affected by drainage, probably because the rate of N applied in spring (80 kg‐N/ha) was high enough to counteract the effects of decreased soil mineral N levels in undrained treatments.