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Highlights • NO 3 -N leaching was two orders of magnitude less below a perennial grain than maize. • Soil solution NO 3 -N was lower beneath a perennial grain than maize and switchgrass. • N fertilizer increased perennial grain yield without increasing NO 3 -N leaching. Abstract Global expansion of high-input annual grain crops and associated nitrogen (N) fertilizer use can have negative consequences for the environment and human health. Nitrate nitrogen (NO 3 -N) leaching from fertilized annual crops can contaminate groundwater and pollute natural aquatic ecosystems and rural drinking water sources. Intermediate wheatgrass (IWG; Thinopyrum intermedium) is a perennial grass being domesticated to serve as the world's first widely available perennial grain crop. Our objective was to measure water quality variables and crop yields in order to model NO 3 -N leaching beneath IWG, maize, and switchgrass under three N fertilizer treatments; low N (0 kg N ha−1), medium N (maize = 80, switchgrass and IWG = 40 kg N ha−1), and high N (maize = 160, switchgrass and IWG = 120 or 160 kg N ha−1). The switchgrass and IWG medium N treatments also included alfalfa as an intercrop. The NO 3 -N concentration in soil solution 50 cm below the surface was one and two orders of magnitude lower in high N fertilized IWG compared to switchgrass and maize, respectively. Soil solution NO 3 -N increased with N fertilizer in all crops. Soil water content was less at 50 and 100 cm depths in IWG compared to switchgrass and maize but was unaffected by N fertilizer treatment. Using the Denitrification and Decomposition (DNDC) model, average annual NO 3 -N leaching estimates in the high N treatments were 21.7 kg N ha−1 for maize and 3.7 and 0.2 kg N ha−1 for switchgrass and IWG, respectively. Despite consistent biomass yields through time, IWG grain yields decreased with stand age at all N fertilizer treatments. Alfalfa did not persist in the IWG and switchgrass medium N treatments, thus other legumes should be tested for intercropping with perennial grain crops. Intermediate wheatgrass has great potential to provide food-quality grain and biomass while preventing NO 3 -N leaching. [ABSTRACT FROM AUTHOR]

Quantitatively ascertaining and analyzing long-term responses of crop yield and nitrate leaching on varying irrigation and fertilization treatments are focal points for guaranteeing crop yield and reducing nitrogen loss. The calibrated agricultural-hydrological RZWQM2 model was used to explore the long-term (2003–2013) transport processes of water and nitrogen and the nitrate leaching amount into groundwater in summer maize and winter wheat rotation field in typical intensive plant area in the North China Plain, Daxing district of Beijing. Simulation results showed that application rates of irrigation and nitrogen fertilizer have couple effects on crop yields and nitrogen leaching of root zone. When both the irrigation and fertilizer for summer maize and winter wheat were 400 mm and 400 kg N ha − 1 , respectively, nitrate leaching into groundwater accounted for 47.9% of application amount of nitrogen fertilizer. When application amount of irrigation is 200 mm and fertilization is 200 kg N ha − 1 , NUPE (nitrogen uptake efficiency), NUE (nitrogen use efficiency), NPFP (nitrogen partial factor productivity), and W pi (irrigation water productive efficiency) were in general higher than that under other irrigation and fertilization condition (irrigation from 104–400 mm, fertilizer 104–400 kg N ha − 1 ). Irrigation bigger than 200 mm could shorten the response time of nitrate leaching in deeper soil layer in different irrigation treatment. [ABSTRACT FROM AUTHOR]

The cost and time involved in frequent field observations pertaining to quantification of nitrate leaching below the crop root zone leads to the use of simulation models, which is a more plausible approach. Nitrate leaching below the root zone of a maize-wheat cropping system under surface irrigation was assessed. The model's predicted results pertaining to water percolation and nitrate leaching were in line with the observed data, with root mean square error (RMSE) values close to zero, and index of agreement values close to 1. The seasonal percolation of water below 120 cm soil depth in maize and wheat were 36.5 and 27.5% of applied water, respectively. Similarly, nitrate leaching below 120 cm soil depth was 18.1 and 14.3% of the applied nitrogenous fertilizer in maize and wheat, respectively. Under similar conditions, the nitrate leaching under a maize-wheat cropping system was 6.8 kg NO3 ha-1 less than in a rice-wheat cropping system. Furthermore, nitrate leaching below the crop root zone under different fertilizer application rates was estimated and best-fit second-order polynomial equations were developed. The equations can be used for estimation of nitrate leaching under different fertilizer input scenarios of maize-grown and wheat-grown areas under similar hydro-agro-climatic regions. [ABSTRACT FROM AUTHOR]

This paper aimed to confirm the hypothesis that rates of ammonification and net mineral-N production in soils under grass in summer are low and this, rather than nitrate uptake by plants, reduces mineral leaching from soils in summer. Six sets of soil samples were collected from under mown grass on the University of York campus in the UK. Samples were taken from two depths in late summer (August) and late autumn (November) to compare seasonal differences in N species transformations when field-moist soils were incubated for a week at ambient outdoor temperatures after prior removal of vegetation. Ammonification and net mineral-N production rates were low in August in spite of warm temperatures. Net mineral-N production rates were also low in November. The results agreed with those of an earlier study in a different year after considering weather differences between years. They support the hypothesis that litter accumulated over autumn/winter will be minimally mineralised and retain N before the temperature rises in spring. The study shows the merit of measuring concentrations of mineral-N species in both fresh soils and soils incubated at ambient outdoor temperatures after removing plant material to eliminate plant N uptake effects. The results suggest that soil C% and N% are more important than soil C:N ratio alone in understanding controls on N transformations. [ABSTRACT FROM PUBLISHER]

Mowing and grazing studies over 3 years were used to examine the effects of application of the nitrification inhibitor dicyandiamide (DCD) on pasture production, soil nitrogen (N) transformations, nitrous oxide (N2O) emissions and nitrate leaching from dairy pastures in the Waikato region (northern North Island) of New Zealand. In all cases, DCD inhibited nitrification and reduced the amount of nitrate production. Emissions of N2O from pastoral soil receiving cow urine in autumn were reduced by 18%–71% due to DCD application. Lysimeter studies showed a decrease in nitrate leaching from urine due to DCD by up to 74%, but it was dependent on timing and frequency of DCD application. DCD applications between April and June were most effective for reducing nitrate leaching, but timing of applications needs to account for the temperature profile effects on DCD longevity in soil and three applications may be necessary to achieve greatest benefits. In the mowing trial in one year there was a 4% (P< 0.05) increase in pasture growth during the winter/spring period. Otherwise, there was no significant effect of DCD applications (two to five applications per year) on seasonal or annual pasture production. This study indicates that DCD can provide valuable reductions in N emissions to the environment, making it an effective N mitigation option for use on dairy farms in northern North Island regions. [ABSTRACT FROM AUTHOR]

A 3-year study was carried out in Canterbury, New Zealand, to determine the effect of a nitrification inhibitor dicyandiamide (DCD) on N2O emissions, nitrate () leaching and pasture yield. In all 3 years, DCD was highly effective in reducing N2O emissions from urine-nitrogen (N) applied in autumn (April and May), decreasing the N2O emission factor by 41%–82%. In addition, DCD consistently reduced-N leaching losses by 48%–69% from the animal urine applied in April. Pasture yield responses to DCD application varied from 0%–17%, probably due to other growth limiting factors and/or the methodology used in the pasture yield measurement. The reductions inleaching are of particular value at this point in time due to the increasingly strict regional council regulations that are being imposed on farmers to reduce N leaching losses. [ABSTRACT FROM AUTHOR]

The water movement and soil nitrogen cycle of the Baiyangdian Basin were simulated, and the risk of nitrate leaching and nitrate runoff loss from intensive farmland was assessed by using the distributed hydrological soil and water assessment tool (SWAT) in this study. The model assessment showed that SWAT was able to simulate water and nitrate movement in the region with satisfactory results. The modeling analysis indicated that fertilizer application was the overriding source of soil nitrogen and might result in a large amount of nitrate accumulation in soils; this nitrate might be lost by leaching or runoff driven by water movement. In 2009, nitrate nitrogen leaching represented 19.5 % of the total amount of nitrogen fertilizer application, while nitrate nitrogen runoff represented 1.7 % only. Thus, it showed that the nitrate leaching was the main approach of soil nitrogen movement in farmland because of strong percolation. It also showed a significant variation of nitrate leaching from different soil depths, with the largest amount leached from surface soil layers and the smallest amount leached from lower soil layers. Therefore, it could be further revealed that the nitrate concentration was very low at soil layers lower than the root zone of crops (1.2 m). Validated by groundwater observations, groundwater pollution by nitrate derived from fertilizers was not serious because of the deep groundwater level in the study plain. However, the risk of groundwater pollution would increase significantly if precipitation increased. [ABSTRACT FROM AUTHOR]

Abstract: Cropland derived nitrate leaching was a major reason for groundwater pollution. The objective of this study was to on-farm investigate the behavior of nitrate leaching affected by N fertilization rates, rainfall, and temperature in a rainfed winter wheat field in Taihu watershed. The experiment had five urea-N rates (0–360kgNha−1 in 90-kg increments), and nitrate-N in leachate was daily collected by wedge-shaped fiberglass wick lysimeters during four stages (seeding stage, SS; tillering stage, TS; booting stage, BS; harvesting stage, HS). Results showed that: (1) higher potential of leachate would be engendered when the rainfall intensity was over 5.9mmd−1; (2) variations of nitrate concentrations in leachate were well responsed to three split fertilizations, which increased with the increase of urea-N applied rates. A similar variation pattern of nitrate concentrations was observed in −0.3m and −0.6m soil leachate. Besides, the nitrate concentrations in leachate could be raised with the sharply increase of air temperature, especially in the SS and TS stages; (3) the fluxes of nitrate leaching were significantly affected by N rates (P <0.05) with the loss ratio varied from 4.0% to 8.5% for five treatments, and the fluxes in four wheat growing stages followed the order of TS>HS>BS>SS. The N application rate of 180kgNha−1 optimized wheat production, but N application over that rate greatly increased nitrate leaching potential. Therefore, options other than lowering the N application rate need to be considered to reduce environmental impacts while maintain winter wheat production. [Copyright &y& Elsevier]

Maize production is affected by water and nitrogen (N) deficit either separately or joined, but this fact is not completely defined. The aim was to evaluate the fate of N in maize fertilized and subjected to water stress in controlled conditions. A greenhouse experiment was carried out at the University of Buenos Aires campus. The design was a 2 × 2 factorial with four replications. The factors were N: 70 and 140 kg N ha-1 as labeled urea (15N), and water: 100% or 50% of the potential evapotranspiration. The harvest of aerial and root biomass was carried out at R1 stage. Nitrogen in plants, soils nitrate, ammonia volatilization, and 15N percentage were determined. Obtained results only partially agree with previous research. Water stress depressed aerial biomass production independently of N doses. When water was limiting, the uptake of N from fertilizer was independent of N. When water was not limiting, N uptake increased with the higher N doses. Volatilization losses were 3.7 to 7.8% of N applied as fertilizer. Plant N recovers was around 45% of the N applied, except in treatment water stressed with high N rate (19%). Nitrate-N from the fertilizer in the soil at harvest and accumulated N from the fertilizer in plant were lineally related (r2 = 0.54; p < 0.001). Important destinations of N were accumulation in plant, volatilization and incorporation into soil organic matter. However, residual nitrate was a main fate in heavily fertilized and water deficit treatment. This process could lead to the eventual nitrate leaching. [ABSTRACT FROM AUTHOR]

Nitrogen (N) biogeochemistry of a mature Scots pine ( Pinus sylvestris L.) stand subjected to an average total atmospheric N deposition of 48 kg ha−1 year−1 was studied during the period 1992–2007. The annual amount of dissolved inorganic nitrogen (DIN) in throughfall (TF) averaged 34 kg ha−1 year−1 over the 16-year monitoring period. The throughfall fluxes contained also considerable amounts of dissolved organic nitrogen (DON) (5–8.5 kg N ha−1 year−1), which should be incorporated in the estimate of N flux using throughfall collectors. Throughfall DIN fluxes declined at a rate of −0.9 kg N ha−1 year−1, mainly due to the decreasing TF fluxes of ammonium (NH4), which accounted for 70% to TF DIN. The decrease in TF DIN was accompanied by a decrease in DIN leaching in the seepage water (−1.6 kg N ha−1 year−1), which occurred exclusively as nitrate (NO3 −). Nitrate losses in the leachate of the forest floor (LFH) equalled the TF NO3 − delivered to the LFH-layer. On the contrary, about half of the TF NH4 + was retained within the LFH-layer. Approximately 60% of the TF DIN fluxes were leached indicating that N inputs were far in excess of the N requirements of the forest. For DON, losses were only substantial from the LFH-layer, but no DON was leached in the seepage water. Despite the high N losses through nitrate leaching and NO x emission, the forest was still accumulating N, especially in the aggrading LFH-layer. The forest stand, on the contrary, was found to be a poor N sink. [ABSTRACT FROM AUTHOR]

An integrated model system has been developed to estimate the impact of nitrogen reduction measures on the nitrogen load in groundwater and in river catchment areas. The focus lies on an area-wide, regionally differentiated, consistent link-up between the indicator "nitrogen balance surplus" and nitrogen charges into surface waters. As a starting point of the analysis actual nitrogen surpluses in the soil were quantified using the agro-economic RAUMIS-model, which considers the most important N-inputs to the soil and N-removals from the soil through crop harvest. The most important pathways for diffuse nitrogen inputs into river systems are modelled with the water balance model GROWA. Additionally, the time-dependent nitrogen degradation along the nitrogen pathways in soil and groundwater are modelled using the WEKU- model. The two selected river basins in Germany cover a variety of landscape units with different hydrological, hydrogeological and socio-economic characteristics. The results indicate a wide range of annual nitrogen surpluses for the rural areas between than 10 kg N ha-1⋅a-1 and 200 kg N ha-1⋅a-1 or more, depending on the type and intensity of farming. The level of nitrogen inputs into the surface waters is reduced because of degradation processes during transport in soil and groundwater. Policy impact analyses for a nitrogen tax and a limitation of the livestock density stress the importance of regionally adjusted measures. [ABSTRACT FROM AUTHOR]