Lysimeter Study Research Articles

Sowing a winter catch crop can reduce nitrate leaching losses from winter‐applied urine under simulated forage grazing: a lysimeter study

AbstractGrazing of winter forage crops is a common management option used in the dairy industry of New Zealand, particularly in the South Island, where they are used to feed nonlactating, pregnant dairy cows prior to calving. However, there is concern that the large crop yields per hectare grazed, combined with a high stocking density of cows, lead to large amounts of urinary nitrogen (N) deposited on bare, wet soil that, in turn, could lead to large nitrate leaching losses. We report the results of a simulated winter forage grazing event using field lysimeters planted with a kale (Brassica oleracea L.) crop. The effect of sowing a ‘catch crop’ of oat (Avena sativa L.) following the simulated winter forage grazing on nitrate leaching losses from urine applied at different times throughout the winter was measured. A catch crop sown between 1 and 63 days after the urine deposition in early winter reduced N leaching losses from urine patches by ~34% on average (range: 19–49%) over the winter–spring period compared with no catch crop. Generally, the sooner the catch crop was sown following the crop harvest, the greater the uptake of N by the catch crop and the greater the reduction in nitrate leaching losses. The results indicate that sowing of a catch crop following winter crop grazing could be an effective management strategy to reduce nitrate leaching as well as increase the N‐use efficiency of dairy winter forage grazing systems.

Fate of carbamazepine, its metabolites, and lamotrigine in soils irrigated with reclaimed wastewater: Sorption, leaching and plant uptake

Irrigation with reclaimed wastewater may result in the ubiquitous presence of pharmaceutical compounds (PCs) and their metabolites in the agroecosystem. In this study, we focused on two highly persistent anticonvulsant drugs, lamotrigine and carbamazepine and two of its metabolites (EP-CBZ and DiOH-CBZ), aiming to elucidate their behavior in agricultural ecosystem using batch and lysimeter experiments. Sorption of the studied compounds by soils was found to be governed mainly by the soil organic matter level. Sorption affinity of compounds to soils followed the order lamotrigine > carbamazepine > EP-CBZ > DiOH-CBZ. Sorption was reversible, and no competition between sorbates in bi-solute systems was observed. The results of the lysimeter studies were in accordance with batch experiment findings, demonstrating accumulation of lamotrigine and carbamazepine in top soil layers enriched with organic matter. Detection of carbamazepine and one of its metabolites in rain-fed wheat previously irrigated with reclaimed wastewater, indicates reversibility of their sorption, resulting in their potential leaching and their availability for plant uptake. This study demonstrates the long-term implication of introduction of PCs to the agroecosystem.

Effect of highly processed calcined kaolin residues on apple water use efficiency

Processed calcined kaolin particle films (PKPF) have been shown to repel some insects and reduce various environmental stresses often resulting in improved yield and quality of horticultural crops. PKPF studies in the literature have various water use efficiency (WUE) responses. The purpose of this study was to evaluate 2 application rates of PKPF (3% and 12%) on the whole tree water use efficiency and compare gas exchange values with carbon isotopic discrimination and seasonal water use efficiency in order to determine if there are consistent effects on WUE in apple and infer the mechanisms of action. Fruit yield and total biomass influence WUE whether WUE is measured directly in whole plant chambers, estimated by biomass/unit evapotranspiration, or Δ13C. Δ13C analysis of WUE generally found that the untreated control had lower values and therefore higher WUE than PKPF treatments. Whole plant gas exchange analysis of WUE generally lacked the sensitivity to identify the treatment differences observed using Δ13C analysis and those treatment differences identified were contrary to Δ13C analysis. A lysimeter study supported the reduced WUE of PKPF treated plants by demonstrating increased E with a range of PKPF residue amounts. The lysimeter results suggest that for well-watered and presumably non-stressed conditions, gas exchange is limited by leaf temperature and the concomitant leaf-air vapor pressure deficit that influence stomatal conductance. When leaf temperature is reduced by PKPF, the response results in increased stomatal conductance and gas exchange, as measured by increased E. The reduction in WUE by PKPF treatment is balanced by an increase in overall gas exchange and increased yield and quality.

Effect of soil texture and wheat plants on N2O fluxes: A lysimeter study

Agricultural soils are a major source of nitrous oxide (N2O) emissions and an understanding of factors regulating such emissions across contrasting soil types is critical for improved estimation through modelling and mitigation of N2O. In this study we investigated the role of soil texture and its interaction with plants in regulating the N2O fluxes in agricultural systems. A measurement system that combined weighing lysimeters with automated chambers was used to directly compare continuously measured surface N2O fluxes, leaching losses of water and nitrogen and evapotranspiration in three contrasting soils types of the Riverine Plain, NSW, Australia. The soils comprised a deep sand, a loam and a clay loam with and without the presence of wheat plants. All soils were under the same fertilizer management and irrigation was applied according to plant water requirements. In fallow soils, texture significantly affected N2O emissions in the order clay loam>loam>sand. However, when planted, the difference in N2O emissions among the three soils types became less pronounced. Nitrous oxide emissions were 6.2 and 2.4 times higher from fallow clay loam and loam cores, respectively, compared with cores planted with wheat. This is considered to be due to plant uptake of water and nitrogen which resulted in reduced amounts of soil water and available nitrogen, and therefore less favourable soil conditions for denitrification. The effect of plants on N2O emissions was not apparent in the coarse textured sandy soil probably because of aerobic soil conditions, likely caused by low water holding capacity and rapid drainage irrespective of plant presence resulting in reduced denitrification activity. More than 90% of N2O emissions were derived from denitrification in the fine-textured clay loam—determined for a two week period using K15NO3 fertilizer. The proportion of N2O that was not derived from K15NO3 was higher in the coarse-textured sand and loam, which may have been derived from soil N through nitrification or denitrification of mineralized N. Water filled pore space was a poorer predictor of N2O emissions compared with volumetric water content because of variable bulk density among soil types. The data may better inform the calibration of greenhouse gas prediction models as soil texture is one of the primary factors that explain spatial variation in N2O emissions by regulating soil oxygen. Defining the significance of N2O emissions between planted and fallow soils may enable improved yield scaled N2O emission assessment, water and nitrogen scheduling in the pre-watering phase during early crop establishment and within rotations of irrigated arable cropping systems.

Cadmium losses from a New Zealand organic soil

ABSTRACTCadmium (Cd) losses from acidic organic soils amended with phosphate fertiliser are potentially important for the assessment of Cd accumulation, but are currently poorly understood. This study investigated the effect of soil pH and single superphosphate (SSP) fertiliser at application rates of 0, 50, 100 and 200 kg P ha−1 on Cd leaching and plant uptake from an organic soil in a lysimeter study. Average leaching losses ranged from 0.14–0.39 g Cd ha−1. The greatest leaching losses were from soils at pH 4.5 at the highest rates of P application (100 and 200 kg P ha−1). In comparison, there was no significant difference in the amounts of Cd lost at pH 5.5 or 6.5 at any rate of P application. Losses equated to <1% of the Cd added to the soil from an application of 200 kg P ha−1. Average ryegrass Cd concentrations ranged from 0.03–0.09 mg kg−1 dry weight. Soil pH had no significant effect on concentrations for the two lowest SSP application rates, whereas at the two high SSP treatments, Cd concentrations increased between pH 4.5 and 5.5, but decreased between pH 5.5 and 6.5. Cadmium losses from both leaching and plant uptake are low in this organic soil, highlighting the important role that organic matter and pH provide in retaining Cd.

Effectiveness of the nitrification inhibitor dicyandiamide and biochar to reduce nitrous oxide emissions

ABSTRACTAnimal urine from grazing animals is responsible for the majority of New Zealand’s nitrous oxide (N2O) emissions. A field lysimeter study was conducted to determine the ability of the combination of the nitrification inhibitor dicyandiamide (DCD) and biochar to mitigate N2O emissions from a winter grazing forage crop soil. The results showed that over a 4 month period, applying cow urine at a rate of 700 kg N ha−1 increased N2O emissions from 0.7 kg N2O-N ha−1 to 14.7 kg N2O-N ha−1. The application of DCD at 20 kg ha−1 reduced total N2O emissions by 65%. The application of biochar at 5 t ha−1 had no significant effect on N2O emissions. The combination of DCD with biochar did not lead to greater N2O reductions than DCD alone. These results indicated that DCD was highly effective whereas biochar was ineffective in reducing N2O emissions in the winter forage soil.

High‐resolution accurate mass spectrometry as a technique for characterization of complex lysimeter leachate samples

Lysimeter studies can be used to identify and quantify soil degradates of agrochemicals (metabolites) that have the potential to leach to groundwater. However, the apparent metabolic profile of such lysimeter leachate samples will often be significantly more complex than would be expected in true groundwater samples. This is particularly true for S-metolachlor, which has an extremely complex metabolic pathway. Consequently, it was not practically possible to apply a conventional analytical approach to identify all metabolites in an S-metolachlor lysimeter study, because there was insufficient mass to enable the use of techniques such as nuclear magnetic resonance. Recent advances in high-resolution accurate mass spectrometry, however, allow innovative screening approaches to characterize leachate samples to a greater extent than previously possible. Leachate from the S-metolachlor study was screened for accurate masses (±5 ppm of the nominal mass) corresponding to more than 400 hypothetical metabolite structures. A refined list of plausible metabolites was constructed from these data to provide a comprehensive description of the most likely metabolites present. The properties of these metabolites were then evaluated using a principal component analysis model, based on molecular descriptors, to visualize the entire chemical space and to cluster the metabolites into a number of subclasses. This characterization and principal component analysis evaluation enabled the selection of suitable representative metabolites that were subsequently used as exemplars to assess the toxicological relevance of the leachate as a whole. Environ Toxicol Chem 2016;35:1401-1412. © 2015 SETAC.

Nitrate Leaching from Soluble Nitrogen Applied to ‘Floratam’ St. Augustinegrass and Common Centipedegrass during Dormancy

Fertilizer bans in Florida prevent turf managers from applying nitrogen (N) fertilizers during periods of active turf growth and may encourage fertilization in fall and winter. Nutrient applications during fall or winter may pose an increased risk to nitrate N (NO3–N) leaching. A 3‐yr field lysimeter study was conducted in Jay, FL, to determine the effect of N rates on NO3–N leaching from ‘Floratam’ St. Augustinegrass (SA) [Stenotaphrum secundatum (Walter) Kuntze] and common centipedegrass (CE) [Eremochloa ophiuroides (Munro) Hack.] during turfgrass dormancy. Treatments consisted of urea applied as a foliar spray every 45 d beginning in October at rates of 0.0, 6.0, 12.5, 24.0, or 49.0 kg N ha−1. Leachate was collected weekly and analyzed for NO3–N. Elevated NO3–N levels were observed for 105 d after initiation (DAI). No differences in NO3–N leached were detected among N rates until the late winter cycle of 2008 when rainfall exceeded historic levels by 268 mm. The 49.0 kg N ha−1 treatment resulted in more NO3–N leached than untreated turf during 2008, with 12.5 and 1.3 kg NO3–N ha−1 leached, respectively. These findings suggest that N rates ≤24.0 kg ha−1 applied to dormant or semidormant warm‐season turf do not pose an increased threat of NO3–N leaching even when rainfall is excessive. Soluble N rates &gt;24.0 kg ha−1 should be avoided during dormancy when excessive rainfall is imminent. The benefits, if any, need to be investigated further before fertilization of dormant warm‐season turf is recommended.

Biochar increases availability and uptake of phosphorus to wheat under leaching conditions

Phosphorus (P) fertilisers have long been applied to sandy soils in south-western Australia to enhance agricultural production. However, significant P leaching is experienced which decreases P availability to crops. The aim of this study was to determine if biochar could be used as a soil amendment to decrease P leaching and increase P uptake by wheat plants. A lysimeter study was designed where two types of biochar, derived either from chicken manure (CM) or wheat chaff (WC) at 0, 1 and 2 % (w/w) and three P fertiliser rates at 0, 25 and 50 kg/ha, were applied to a loamy sand soil where wheat (Triticum aestivum L. var. Wyalkatchem) was grown under glasshouse conditions. Leaching events were conducted over a period of 8 weeks at two weekly intervals. Leachate volume was less in the biochar-amended soil compared to non-amended soil. Biochar increased plant shoot P uptake but also P leaching, which was attributed to P derived from both the applied fertiliser and the biochar. Biochar also increased available P and microbial biomass P in soil, although the extent of increase with WC biochar was less pronounced than for that with CM biochar. Biochar application increased mycorrhizal colonisation in wheat roots which was higher (up to 70 %) at the P application rate of 25 kg/ha but declined with P application rate of 50 kg/ha (to 35 %). Increase in soil pH and mycorrhizal colonisation from biochar application might be contributing to the increase in plant P uptake and shoot growth. However, biochar was not a mitigation strategy to decrease P leaching on these sandy soils.

Lysimeter study of nitrogen losses and nitrogen use efficiency of Northern Chinese wheat

A study was conducted in the lysimeters and rain-out shelter facility at Shandong Agricultural University to investigate the impact of nitrogen (N) fertilization management practices and irrigation on the losses of N and N use efficiencies of winter wheat in the Huang Huai Hai Plains of northern China. 4 factors, each with two levels, including wheat varieties (SM15 and JM19), irrigation level (well water and deficit water), N fertilizer type (manure fertilizer and urea), N fertilizer rates (90 and 180kg Nha−1) were applied in duplicate over three wheat growing seasons from 2009 to 2012. Ammonia volatilization rates (AVR) were highest immediately following fertilizer application and declined over 20 days after fertilization, AVR following urea is significantly greater than following manure application and is largely affected by soil NH4+-N concentrations. Cumulative ammonia volatilization (CAV) from urea was approximately three times that from manure. AV accounts for most of N losses and may account for 25% or more of applied N. Leaching losses increased with N fertilization concentration. Pre-winter leaching losses accounted for 69.6–100% of total leaching loss. Total N losses through AV and leaching during the whole wheat growing season were estimated to range from 30 to 60% of applied N. Nitrogen use efficiency (NUE), and N uptake efficiency (NUpE) of the cultivar SM15 is 10.1 and 19.8% greater than JM19 by average under well watered conditions, respectively, but NUE and N utilization efficiency (NUtE) of JM19 were 17.5% and 21.8% higher than SM15 under water stress condition, respectively. In addition, the difference of crop N use efficiency (NUEc) and crop N uptake efficiency (NUpEc) between two varieties was inconsistent to NUE and NUpE. The following results were implicated from this study: (1) ammonia volatilization could be reduced by 66.6% through manure application instead of urea application; (2) reducing fertilizer and irrigation supply during pre-winter stage could be a effective method to reduce N loss in the region; (3) all treatments in this study lead to progressively lower soil fertility except for the 180kg Nha−1 manure which is able to maintain soil fertility; (4) wheat variety, N fertilizer level, irrigation amount and their interactions have obviously impact on NUE parameters.

Crop Co-efficient Values of Sunflower for Different Growth Stages by Lysimeter Study

Crop Co-efficient Values of Sunflower for Different Growth Stages by Lysimeter Study

Identification of nitrate leaching loss indicators through regression methods based on a meta-analysis of lysimeter studies.

This study presents a meta-analysis of 12 experiments that quantify nitrate-N leaching losses from grazed pasture systems in alluvial sedimentary soils in Canterbury (New Zealand). Mean measured nitrate-N leached (kg N/ha × 100 mm drainage) losses were 2.7 when no urine was applied, 8.4 at the urine rate of 300 kg N/ha, 9.8 at 500 kg N/ha, 24.5 at 700 kg N/ha and 51.4 at 1000 kg N/ha. Lismore soils presented significantly higher nitrate-N losses compared to Templeton soils. Moreover, a multiple linear regression (MLR) model was developed to determine the key factors that influence nitrate-N leaching and to predict nitrate-N leaching losses. The MLR analyses was calibrated and validated using 82 average values of nitrate-N leached and 48 explanatory variables representative of nitrogen inputs and outputs, transport, attenuation of nitrogen and farm management practices. The MLR model (R (2) = 0.81) showed that nitrate-N leaching losses were greater at higher urine application rates and when there was more drainage from rainfall and irrigation. On the other hand, nitrate leaching decreased when nitrification inhibitors (e.g. dicyandiamide (DCD)) were applied. Predicted nitrate-N leaching losses at the paddock scale were calculated using the MLR equation, and they varied largely depending on the urine application rate and urine patch coverage.

Water Use Dynamics of Peach Trees under Postharvest Deficit Irrigation

Postharvest deficit irrigation is a potential strategy for conserving valuable fresh water for production of early season tree fruit crops such as peaches. However, water use dynamics under deficit irrigation conditions that can be described as seasonal changes in crop evapotranspiration (ETc) and crop coefficient (Kc) are largely unknown. A three-year field study was carried out in a 1.6 ha peach orchard to determine seasonal ETc and Kc characteristics. The orchard was divided equally into 72 plots, in which 12 randomly selected plots received deficit irrigation and the remaining 60 plots received full irrigation. A Bowen ratio flux tower was installed in the orchard to make meteorological measurements for estimating an integrated ETc for the orchard. The study showed that from July to August 75-85% of the daily net radiation was used by latent heat or partitioned into ETc. The average monthly cumulative ETc was 151 mm in June, 162 mm in July, and 155 mm in August. Kc values under deficit irrigation conditions or termed as Deficit_Kc was computed as ratios of the ETc over potential evapotranspiration or ETo, and were compared with Kc derived from a lysimeter study under non-water stressed conditions or termed as Lysimeter_Kc. The maximum Deficit_Kc values were 0.90, 1.03, and 1.07 for the three field seasons but all were smaller than 1.20, the maximum Lysimeter_Kc. The study demonstrated that water stress under deficit irrigation can be characterized in Kc values. The approach may be used to detect if portions of an orchard or the entire orchard are under water stress. Conversely, the method may provide guidance on deploying deficit irrigation practices with pre-determined Deficit_Kc.

Effect of defatted oilseed meals applied as organic fertilizers on vegetable crop production and environmental impact

Defatted oilseed meals from sunflower (Helianthus annuus L.), and some Brassica species have a well known economic value as feed for animals, whilst their value as organic nitrogen fertilizers has been not fully explored so far. Compared to sunflower, the seed meals of Brassica species are reported to have a potentially higher capacity of nutrient supply, due to their lower content of indigestible fiber. The high content of glucosinolates may conversely reduce the availability of nitrogen, because of their inhibitory effect on nitrification processes.In this lysimetric study we compared the effect of the application of three seed meals: partially defatted meals of sunflower and of Ethiopian mustard (Brassica carinata A. Braun), and completed defatted meal of sunflower on the yield and N utilization of three vegetable crops (lettuce, chard and spinach), compared to an unfertilized control and one fertilized with ammonium nitrate. Furthermore, we also investigated the residual effect of fertility of oilseed meal application on winter barley and fallow. Both sunflower meals revealed a fertilization effect comparable to that of the mineral fertilizer, whilst B. carinata meal reduced the yields of chard and spinach, due to low N availability as shown by the lower N use efficiency index. We argue that this lower efficacy of B. carinata meal was due to the technique of the application of the meal, that might have produced a high concentration of glucosinolates in the soil layer explored by roots, concurrently determining a significant impact on soil biota and direct phytotoxicity phenomena.A relevant part of the N applied with fertilizers was not absorbed by the three vegetables and hence accumulated in the soil. Despite the high values of unabsorbed soil N in the plots fertilized with oilseed meals, nitrate leaching was lower than with ammonium nitrate. The impact on global warming potential of fertilization with defatted oilseed meals was assessed and shown to be lower than or comparable to the impact of the synthetic fertilizer. In particular, defatted sunflower meals caused a lower impact per hectare and total biomass, and a similar impact per fresh marketable product.Overall, our findings confirmed the high value of oilseed meals as a sustainable alternative to mineral fertilizers. However, their efficacy strongly depends on the technique of application to the soil.

Salt as a mitigation option for decreasing nitrogen leaching losses from grazed pastures.

The main source of nitrogen (N) leaching from grazed pastures is animal urine with a high N deposition rate (i.e. per urine patch), particularly between late summer and early winter. Salt is a potential mitigation option as a diuretic to induce greater drinking-water intake, increase urination frequency, decrease urine N concentration and urine N deposition rate, and thereby potentially decrease N leaching. This hypothesis was tested in three phases: a cattle metabolism stall study to examine effects of salt supplementation rate on water consumption, urination frequency and urine N concentration; a grazing trial to assess effects of salt (150 g per heifer per day) on urination frequency; and a lysimeter study on effects of urine N rate on N leaching. Salt supplementation increased cattle water intake. Urination frequency increased by up to 69%, with a similar decrease in urine N deposition rate and no change in individual urination volume. Under field grazing, sensors showed increased urination frequency by 17%. Lysimeter studies showed a proportionally greater decrease in N leaching with decreased urine N rate. Modelling revealed that this could decrease per-hectare N leaching by 10-22%. Salt supplementation increases cattle water intake and urination frequency, resulting in a lower urine N deposition rate and proportionally greater decrease in urine N leaching. Strategic salt supplementation in autumn/early winter with feed is a practical mitigation option to decrease N leaching in grazed pastures.

Effects of tillage practices on drainage and nitrate leaching from winter wheat in the Northern Atlantic Coastal-Plain USA

Management strategies for winter wheat (Triticum aestivum L., cultivar Pioneer “2548”) in the Northern Atlantic Coastal-Plain region of the USA must balance agronomic production with practices to reduce nitrate-N (NO3-N) leaching, because much of this region lies within the Chesapeake Bay watershed. Winter wheat in this region is commonly grown using no-tillage (NT), but few studies have evaluated the effects of NT on NO3-N leaching for winter wheat. A four-year lysimeter study was conducted in Beltsville, Maryland by growing winter wheat in eight tension-drained undisturbed soil-column lysimeters (41cm diameter by 100cm deep) configured to exclude runoff, to compare the effects of NT vs. simulated plow-tillage (PT) and N fertilization practices on drainage volumes and NO3-N leaching. Additional data documented wheat total N uptake and bromide leaching. The temporal pattern of drainage showed that NT produced significant, but modestly higher, drainage volumes than PT during fall establishment (mid-Oct. to mid-Dec.), which increased the potential for NO3-N leaching, especially following high rainfalls. However, the greater risk of NO3-N leaching with NT during establishment decreased in the spring as tillage effects subsided and wheat water-use and N uptake became dominant. The increased fall leaching risk with NT can be managed by reducing fall-N applications, but both NT and PT can benefit from reduced NO3-N leaching resulting from spring split-N applications. The final NO3-N leaching losses depend on the interactions of precipitation timing and amount, fertilizer-N rate and timing, and initial soil water status. Additional winter-wheat NO3-N leaching research is needed to study to a wider range of soils, to assess high-residue vertical-tillage implements, and to evaluate precision application of spring fertilizer-N.

Indirect nitrogen losses of managed soils contributing to greenhouse emissions of agricultural areas in Austria: results from lysimeter studies

A considerable share of greenhouse gas emissions, especially N2O, is caused by agriculture, part of which can be attributed to indirect soil emissions via leaching and runoff. Countries have to report their annual emissions, which are usually calculated by using the default value of 0.3 for FracLEACH, a factor that represents the fraction of nitrogen losses compared to total nitrogen inputs and sources. In our study we used 22 lysimeters, covering a wide range of soils, climatic conditions and management practices in Austria, to evaluate nitrogen losses through leaching and to calculate FracLEACH. The terms of the nitrogen mass balance of the lysimeters were directly measured for several years. Both grassland and arable land plots gave significantly smaller values of FracLEACH than the default value. For grassland, FracLEACH values of only 0.02 were found which varied very little over the entire observation period. For arable sites, FracLEACH values were higher (around 0.25) and showed significant variability between years due to variations in crop rotation, fertilization rates, and yields.

Urine patch and fertiliser N interaction: Effects of fertiliser rate and season of urine application on nitrate leaching and pasture N uptake

Urine patches are the primary source of N loss from pastoral systems due to the high N loading that occurs over a relatively small area. However, few studies have sought to determine the effect of concurrently deposited urine and fertiliser on the fate of N in pastoral systems, even though the application of fertiliser soon after grazing is commonly practised, while no studies have examined seasonal effects of any interaction.The objective of this study was therefore, to understand how the combination of fertiliser-N and urine affected fertiliser-associated NO3− leaching losses and plant uptake of N. A two year lysimeter study was undertaken with urine (800kg Nha−1) applied in either autumn or spring. Urea fertiliser enriched with 15N was applied to these lysimeters at rates equivalent to 200 or 400kg Nha−1 per year according to the standard regional practice.Urine and fertiliser at the 400kg Nha−1 rate increased total NO3− leaching by up to 58kgha−1 (P<0.001), from urine applied in either autumn or spring. Fertiliser applied at 200kg Nha−1 did not increase N leaching from urine patches. Fertiliser 15N recovery in drainage was <2.2% and was not affected by fertiliser rate. Pasture uptake accounted for up to 52% of the fertiliser 15N recovery and this increased with increasing fertiliser rates, even in the presence of urine. Recovery of fertiliser 15N in the soil at the end of the experiment averaged 22% with the majority of this in the top 10cm soil.These results indicate that the potential for leaching of fertiliser N, applied to a urine patch, is low, and that avoiding fertiliser application over urine patches, reduces leaching losses of fertiliser-N by <2%, which is minimal in terms of total N loss mitigation. However, at high fertiliser application rates to urine patches (i.e. 400kg Nha−1), the total N leaching from non-fertiliser (non 15N-enriched) sources can increase. Further work is required to quantify these effects at the paddock scale. The results also show that NO3− leaching losses were greater from autumn applied urine compared to spring applied urine by up to 306kg NO3−-Nha−1.

Effects of fertiliser N and slurry on nitrate leaching – lysimeter studies on 5 soils

The results of a two-year lysimeter investigation into the effects of fertiliser nitrogen (N) combined with pig or cattle slurry applied in winter or early spring on nitrate (NO3-N) leaching are presented. Soil type, fertiliser N and a combination of fertiliser plus slurry N affected concentrations of NO3-N in the drainage water. Peak concentrations were recorded usually in the December-February period. In the drainage water the maximum admissible concentration (MAC) of NO33-N for drinking water was breached to the greatest degree by pig slurry (Year 2) applied in November (117 kg per hectare) combined with fertiliser N (300 kg per hectare).

Concentrations of dissolved organic carbon in peat soils as influenced by land use and site characteristics — A lysimeter study

The release of dissolved organic carbon (DOC) from peatlands implies a loss of sequestered carbon. During the last two decades, an increase of DOC exports in Europe and North America has been reported. The influence of land use on DOC has been contradictorily discussed and a lack of knowledge exists particularly for fens in Northeastern Germany. Therefore, we aimed to investigate DOC release from fen soils with differing land use intensity. To exclude climatic influences and water level fluctuations, a lysimeter study was performed. The lysimeter vessels contained three histosols from Northeastern Germany and varied in peat quantity, substrate quality, water table depth, pH and vegetation, as these factors are strongly influenced by land use intensity. Water for DOC analysis was sampled biweekly over a two year period. DOC release ranged from 4 to 123mg/L−1 with a median of 32±22mg/L−1. Lowest DOC concentrations were found at deeply drained gleysols and at relatively slightly decomposed, acidic histosols. Highest concentrations were measured in the most degraded histosols. Degree of decomposition and pH were found to be the major driving factors for DOC release. Long-lasting rewetted lysimeters were not observed to release a lower amount of DOC than drained ones, which may be of importance when restoration of degraded peatlands is intended. As lysimeters from the same site released relatively similar amounts of DOC despite their varying management during the last 50years, it appears that peatlands have an individual potential for DOC release.