Nutrient losses by surface run-off following the application of organic manures to arable land. 2. Phosphorus

Phosphorus (P) surface run-off losses were studied following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farm yard manure (FYM) and inorganic nitrogen (N) and P fertiliser were compared, over a 4-year period (1993-97). N losses from the same studies are reported in a separate paper. The application of cattle FYM and, especially slurry, to the silty clay loam soil increased both particulate and soluble P loss in surface water flow. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increased application of slurry solids increased all forms of P loss via surface run-off; the results suggested that a threshold for greatly increased risk of P losses via this route, as for N, occurred at ca. 2.5-3.0 t/ha solids loading. This approximates to the 50 m3/ha application rate limit suggested for slurry within UK 'good agricultural practice'. The studies also provided circumstantial evidence of the sealing of the soil surface by slurry solids as the major mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Losses of total and soluble P, recorded for each of the 4 years of experiments, reached a maximum of only up to 2 kg/ha total P (TP), even after slurry applications initiating run-off. Whilst these losses are insignificant in agronomic terms, peak concentrations of P (up to 30,000 micrograms/l TP) in surface water during a run-off event, could be of considerable concern in sensitive catchments. Losses of slurry P via surface run-off could make a significant contribution to accelerated eutrophication on entry to enclosed waters, particularly when combined with high concentrations of NO3(-)-N. Restricting slurry application rates to those consistent with good agronomic practice, and within the limits specified in existing guidelines on good agricultural practice, offers the simplest and most effective control measure against this potentially important source of diffuse pollution.     

Nutrient losses by surface run-off following the application of organic manures to arable land. 1. Nitrogen

Research was conducted on nitrogen (N) surface run-off losses following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farmyard manure and inorganic N and phosphorus (P) fertiliser were compared, over a 4-year period (1993-97). P losses from the same studies are reported in a separate paper. The application of cattle slurries to the silty clay loam soil increased the loss of solids and NH4(+)-N in surface water flow compared to control plots receiving inorganic fertiliser only, or no treatment, but had little effect on NO3(-)-N losses by this route. Results were consistent with other observations that rainfall events immediately after manure applications are particularly likely to be associated with nutrient run-off losses. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increasing slurry application rate and, in particular, slurry solids loading, increased solids and NH4(-)-N losses via surface run-off. The threshold, above which the risk of losses via surface run-off appeared to be greatly increased, was ca. 2.5-3.0 t/ha slurry solids, which approximates to the 50 m3/ha limit suggested for slurry within UK 'good agricultural practice'. Sealing of the soil surface by slurry solids appears to be a possible mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Total losses of NH4(+)-N and NO3(-)-N during the 4-year monitoring period were insignificant in agronomic terms, but average soluble N concentrations (NH4(+)-N + NO3(-)-N) in run-off, ranging from ca. 2.0 mg/l, up to 14.0 mg/l for the higher rate slurry treatments. Peak concentrations of NH4(+)-N > 30 mg/l, are such as to be of concern in sensitive catchments, in terms of the potential for contribution to accelerated eutrophication and adverse effects on freshwater biota.     

Agronomic measures of P, Q/I parameters and lysimeter-collectable P in subsurface soil horizons of a long-term slurry experiment

Soils from a long-term slurry experiment established in 1970 at Hillsborough, Northern Ireland, were used in the experiment. The site has a clay loam soil overlying Silurian shale. Seven treatments were used with three replicate plots per treatment under the following manurial regimes: (1) mineral fertiliser supplying 200 kg N, 32 kg P and 160 kg K ha(-1) yr(-1); (2)-(4) pig slurry applied at 50, 100 or 200 m3 ha(-1) yr(-1); (5)-(7) cow slurry applied at 50, 100 or 200 m3 ha(-1) yr(-1). Agronomic measures of P determined on subsurface layers down to 90 cm were compared with sorption isotherm data and rates of desorption. Adsorption isotherms were fitted using a standard Langmuir model. Data were compared with soluble (molybdate-reactive) P levels in soil water collected at 35 and 90 cm using PTFE suction cup lysimeters. Agronomically available P was concentrated in the top 30 cm of soil in all treatments. The accumulation of P in surface layers of the plots was significantly greater in the pig slurry treatments compared to the cow slurry, reflecting the history of P amendments. Nevertheless, over a period of a year, molybdate-reactive phosphorus (MRP) concentrations in lysimeter collections was consistently higher at 35 cm depth in the highest cow slurry treatment (7) compared to the equivalent pig slurry treatment (4). Either the movement of soluble P down the profile is facilitated by the higher organic content of cow slurry or P movement is not directly related to P accumulation in the soils. In addition, it is hypothesised that P movement down the soil profile depends upon two separate mechanisms. First, a 'break' point above which the accumulated P in the surface horizons is less strongly held and therefore amenable to dissolution and movement down the profile. Second, a mechanism by which some solute P from the surface horizons can travel rapidly through horizons of low P status to greater depth in the soil, i.e., by preferential flow.     

Measurement of ammonia volatilization from a field,in upland Japan,spread with cattle slurry

Ammonia volatilization from livestock manure is one of the most important pathways of nitrogen loss from agricultural cultivated fields. In this paper, we report the measurement of ammonia emission from cattle slurry manure applied to upland in Miyazaki, Japan. It has been determined that after the cattle slurry was sprayed on the upland surface, the emission flux of the first day was 110 microg N ha(-1) s(-1). The loss of NH4(+) -N in the applied slurry was 60% after 5 days following the spraying of cattle slurry.     

Phosphorus quantity-intensity relationships and agronomic measures of P in surface layers of soil from a long-term slurry experiment

Soils from a long-term slurry experiment established in 1970 at Hillsborough, Northern Ireland, were used in the experiment. The site has a clay loam soil overlying Silurian shale. Seven treatments were used with three replicate plots per treatment. Control plots were treated with mineral fertiliser supplying 200 kg N, 32 kg P and 160 kg K ha(-1) yr(-1). Slurry treatment plots were in two blocks and treated with either pig or cow slurry supplied at 50, 100 or 200 m3 ha(-1) yr(-1). Agronomic measures of P determined on 10-cm soil cores were compared with measured P quantity/intensity (Q/I) parameters from fitted sorption and desorption isotherms. Phosphorus affinity constant was found to be significantly and negatively correlated with P loading of soils. Desorption rate coefficient also increased significantly with increase in P loading from slurry, although there was no significant difference between slurry types (cow vs. pig). In contrast, while agronomic measures of P (water-soluble P, Olsen P, calcium chloride-extractable P, degree of P saturation (DPS)) also correlated significantly with P loading and total P (TP) in the soils, there was a separation and significant differences between the cow and pig slurry treatment blocks, with the former being much lower. Phosphorus inputs to pig slurry treated plots were much higher than to equivalent cow slurry plots over the first 15 years of the study but declined sharply over the most recent 10 years to more or less par. Conventional measures of agronomic P such as Olsen P and DPS, measure only P accumulation over the longer term and indicated only the higher content of P accumulating in soil of pig slurry treatments. Risk of P loss estimated by Q/I parameters appeared to show very similar behaviour between the two slurry types in line with more recent manurial additions but in contradiction of P accumulation statistics.     

Ammonia emissions from cattle, pig and poultry wastes applied to pasture

In four field experiments, carried out in The Netherlands, small wind-tunnels were used to make direct measurements of ammonia (NH(3)) volatilization from different types of slurry and manure applied to the surface of grassland. During periods of up to six days following application, losses of NH(3)-N often amounted to more than 40% of the NH(4)-N applied. Percentage loss was highest (83%) from a poultry slurry and least (21%) from an air-dried poultry manure. Losses of NH(3)-N were generally greater from pig slurry (36-78%) than from cattle slurry (41%). In most cases 80% or more of the total NH(3)-N loss occurred within 48 h of application. Estimates were made of total annual NH(3) emissions from four systems of poultry housing. The highest total loss (50% of the N voided in droppings) occurred with a battery house producing a slurry with a low content of dry-matter; most of the loss took place after spreading. With a second battery house, in which the droppings were air-dried, the total loss was only 12%, with much lower emissions from the housing and during spreading.     

The ability of Azolla caroliniana to remove heavy metals (Hg(II), Cr(III), Cr(VI)) from municipal waste water

The aim of this paper was to investigate the capacity of a small water fern, Azolla caroliniana Willd. (Azollaceae), to purify waters polluted by Hg and Cr. Many plants are capable of accumulating heavy metals (called hyperaccumulators) and one of them is the water fern A. caroliniana. During 12 days of the experiment the fern was grown on the nutrient solution containing Hg2+, Cr3+ and CrO4(2-) ions, each in a concentration 0.1, 0.5 and 1.0 mg dm(-3). The presence of these ions caused a 20-31% inhibition of A. caroliniana growth, the highest in the presence of Hg(II) ions, in comparison to the control. After day 12 of the experiment, metal contents the solution decreased to 0-0.25 mg dm(-3), and this decrease comprised between 74 (Cr3+ 1.0 mg dm(-3) treatment) and 100% (CrO4(2-) 0.1 mg dm(-3) treatment). The fern took a lesser quantity of the metals from 0.1 mg dm(-3) treatments compared to 0.5 and 1.0 mg dm(-3) treatments. In the A. caroliniana tissues the concentration of heavy metals under investigation ranged from 71 to 964 mg kg(-1) dm; the highest level being found for Cr(III) containing nutrient solution.     

The dissipation and transport of veterinary antibiotics in a sandy loam soil

The environmental fate of the antibiotics sulfachloropyridazine and oxytetracycline was investigated in a sandy loam soil. Liquid pig manure was fortified with the compounds and then applied to soil plots to investigate leaching, dissipation and surface run-off under field conditions. Additionally, as the macrolide antibiotic tylosin had been administered to the pigs from which the slurry had been sourced, this was also analysed for in the samples collected. Sulfachloropyridazine dissipated rapidly with DT(50) and DT(90) values of 3.5 and 18.9 days but oxytetracycline was more persistent with DT(50) and DT(90) values of 21.7 and 98.3 days. Both sulfachloropyridazine and oxytetracyline were detected in surface run-off samples at maximum concentrations of 25.9 and 0.9microg/l respectively but only sulfachloropyridazine was detected in soil water samples at a maximum concentration of 0.78microg/l at 40cm depth 20 days after treatment. Tylosin was not detected in any soil or water samples. The results indicated that tylosin, when applied in slurry, posed very little risk of accumulating in soil or contaminating ground or surface water. However, tylosin may pose a risk if used to treat animals on pasture and risks arising from transformation products of tylosin, formed during slurry storage, cannot be ruled out. Oxytetracycline posed a very low risk of ground or surface water contamination but had the potential to persist in soils and sulfachloropyridazine posed a moderate risk of contaminating ground or surface water but had low potential to accumulate in soils. These findings were consistent with the sorption and persistence characteristics of the compounds and support a number of broad-scale monitoring studies that have measured these antibiotic classes in the environment.     

Residues of phosphamidon in rice fields

Thirty-day-old seedlings of rice plants (IR-20 variety) from the nursery were transplanted into experimental plots and after 52 days were sprayed with phosphamidon (Dimecron 85% EC) at two dose-rates (0.38 kg a.i. ha(-1) and 0.76 kg a.i. ha(-1)). Residues of phosphamidon in the plant, soil and water were analysed by GLC, at various time intervals, and were found to decrease steadily up to 15 days. A second application of the pesticide was made on day 113 and grains harvested on day 138. The residue level in the plants was 0.12 microg g(-1) and in the grains 0.04 microg g(-1) with the high dose. This is slightly below the EPA prescribed tolerance level of 0.05 microg g(-1). The residues in both soil and water were very low, 24 h after spraying.     

Transport of veterinary antibiotics in overland flow following the application of slurry to arable land

The environment may be exposed to veterinary medicines administered to livestock due to the application of organic fertilisers to land. Slurry is often spread on to fields following the harvest of the previous crop. Despite recommendations to do so, the slurry may not be ploughed into the soil for some time. If precipitation occurs before incorporation then it is likely that the slurry and any antibiotic residues in the slurry will be transported towards surface waters in overland flow. This phenomenon has been investigated in a plot study and transport via 'tramlines' has been compared to that through crop stubble. Three veterinary antibiotics, from the tetracycline, sulphonamide and macrolide groups, were applied to the plots in pig slurry. Twenty four hours after the application the plots were irrigated. Following this the plots received natural rainfall. Sulphachloropyridazine was detected in runoff from the tramline plot at a peak concentration of 703.2 microgl(-1) and oxytetracycline at 71.7 microgl(-1). Peak concentrations from the plot that did not contain a tramline were lower at 415.5 and 32 microgl(-1), respectively. In contrast, tylosin was not detected at all. Mass losses of the compounds were also greater from the tramline plot due to greater runoff generation. These did not exceed 0.42% for sulphachloropyridazine and 0.07% for oxytetracycline however.     

Effects of organic fertilizers on soil physicochemistry and on the yield and botanical composition of forage over 3 years

Organic wastes have been reported to reduce saturation of the exchange complex by Al in Al-rich acid soils. For 3 years, the main soil fertility properties were studied in plots sown with mixed pasture species. These plots were fertilized with cattle slurry, dairy sludge (DS), or granulated broiler litter (BL) in comparison with mineral fertilizer. Al saturation levels were low after the initial inorganic liming treatment (19.00-33.71%) but tended to rise under all treatments (21.09-61.37%) except BL (8.45-30.98%), which was also associated with the highest average soil pH and the highest average levels of exchangeable Ca2+, Mg2+, and K+. Treatment DS performed similarly to mineral fertilizer in most respects, but it led to greater available P levels. Under the dry conditions of the second and third years of the study, BL and DS treatments were associated with significantly greater forage yields than the other treatments. Under DS treatment, available P levels were too low to allow the maintenance of mixed pasture, clover being eliminated by the less P-dependent species.     

Effect of phosphate fertilizer application on phosphorus (P) losses from paddy soils in Taihu Lake Region. I. Effect of phosphate fertilizer rate on P losses from paddy soil

A field plot study was conducted on two types of paddy soils in the Taihu Lake Region, during the rice season of year 2000 in order to assess phosphorus (P) losses by runoff and vertical leaching, which are considered the two main pathways of P movement from paddy soil into its surrounding water course. Commercial NPK compound fertilizer and single superphosphate fertilizer were applied to furnish 0, 30, 150, and 300 kg applied P ha m(-2). The experiments consisted of three replicates of each treatment in Changshu site and four replicates in Anzhen site, with a plot size of 5 x 6 m2 in a randomized block. Results revealed that the average concentration range for total P (TP) in runoff was 1.857-7.883, 1.038-5.209, 0.783-1.255 and 0.572-0.691 mg P l(-1) respectively for P300, P150, P30 and P0 in Anzhen, while it was 2.431-2.449, 1.578-1.890, 1.050-1.315 and 0.749-0.941 mg P l(-1) respectively in Changshu. In all treatments, particulate P (PP) represented a major portion of the TP lost in runoff, it was 80% in Anzhen, and it was even more (>90%) in Changshu. Phosphate fertilizer treatments significantly affected P concentrations and P loads in the runoff. The mean concentration and average seasonal TP load from the P150 plots were 1.809 mg P l(-1) and 395 g P ha m(-2) season(-1) respectively, and lower than that from the P300 plots (2.957 mg P l(-1) and 652 g P ha m(-2) season(-1)). These were obviously higher than from the P30 (0.761 mg P l(-1) and 221 g P ha m(-2) season(-1)) and P0 (0.484 mg P l(-1) and 146 g P ha m(-2) season(-1)) respectively. There was no significant difference found between the P30 and the P0 in both sites. Under usual P application rate, there were total 31.7 and 20.6 tones P removed by runoff from permeable (Anzhen site) and waterlogged (Changshu site) paddy soils in the southern Jiangsu region (major part of the TLR) in the rice season of the year 2000. But if the P application rate is unusual high, or the Olsen P in soil accumulates to above a certain level, then this could sharply increase in the future. The average concentration of molybdate reactive phosphorus (MRP) in the vertical leachate from the four different P treatments ranged from 0.058 to 0.304 mg P l(-1) in Anzhen and from 0.048 to 0.394 mg P l(-1) in Changshu. P application rate significantly affected the MRP concentration at each depth in both sites, except for the 90 cm in Anzhen. The average MRP loads during the rice season moved by vertical leaching from the four treatments ranged from 163 to 855 g P ha m(-2) season(-1) in Anzhen and 208-1,825 g P ha m(-2) season(-1) in Changshu. Vertical leachate movement does not necessarily mean that it moves towards surface water and contaminate the watercourses in this flat plain paddy soil region, it does, however, imply that P can move down from surface layers of soil to deeper levels.     

Runoff of trifluralin,metolachlor, and metribuzin from a clay loam soil of Louisiana

Trifluralin[2,6-dinitro-N,N-dipropyl-4-(trifluormethyl)benzenamine], metolachlor[2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] and metribuzin[4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)one] were applied as pre-emergent herbicides to soybean plots in Louisiana (LA) at the rate of 1683 g/ha, 2759 g/ha and 609 g/ha, respectively. The concentrations of trifluralin in the runoff water ranged between 0.09 ng/mL and 0.02 ng/mL, which is lower than the 2 ng/mL US Environmental Protection Agency (EPA) advisory level for trifuralin in drinking water. Metolachlor concentrations in the runoff water ranged from 9.0 ng/mL to 221.5 ng/mL, which is both lower and higher than the 175 ng/mL EPA advisory level for metolachlor. Similarly, metribuzin concentrations in the runoff water ranged between 1.5 ng/mL and 56.2 ng/mL, which is also lower and higher than the 10 ng/mL EPA advisory level for metribuzin. Accordingly, from the field plots located on a Commerce clay loam soil in LA, although the concentration of trifluralin in runoff water were substantially lower than the EPA advisory level, metolachlor and metribuzin concentrations are likely to exceed the EPA advisory levels early on in the application season with a subsequent rapid decrease to safe levels. The total loss of trifluralin in runoff water was 0.005% of the applied amount over an 89 day period after application. The total loss of metolachlor and metribuzin in the runoff water was 4.67% and 5.36% of the applied amount, respectively, over a 22 day period after application. As such, there was almost no movement of trifluralin in the runoff water, whereas metolachlor and metribuzin were much more easily moved.     

Runoff of pesticides from rice fields in the Ile de Camargue (Rhône river delta, France): field study and modeling

A field study on the runoff of pesticides was conducted during the cultivation period in 2004 on a hydraulically isolated rice farm of 120 ha surface with one central water outlet. Four pesticides were studied: Alphamethrin, MCPA, Oxadiazon, and Pretilachlor. Alphamethrin concentrations in runoff never exceeded 0.001 microg L(-1). The three other pesticides were found in concentrations between 5.2 and 28.2 microg L(-1) in the runoff water shortly after the application and decreased thereafter. The data for MCPA compared reasonably well with predictions by an analytical runoff model, accounting for volatilization, degradation, leaching to groundwater, and sorption to soil. The runoff model estimated that runoff accounted for as much as 18-42% of mass loss for MCPA. Less runoff is observed and predicted for Oxadiazon and Pretilachlor. It was concluded that runoff from rice paddies carries important loads of dissolved pesticides to the wetlands in the Ile de Camargue, and that the model can be used to predict this runoff.     

Winter runoff losses of phosphorus from paddy soils in the Taihu Lake Region of South China

A winter wheat field plot experiment was conducted on two types of paddy soils, from November, 2000 to June, 2001 to assess P losses to its surrounding watercourses by runoff in the Taihu Lake Region. Commercial NPK compound fertilizer and single superphosphate fertilizer were applied to furnish 0, 20, 80, and 160 kg P ha(-1). The experiments consisted of six replicates of each treatment in Changshu site and four replicates in Anzhen site, with a plot size of 5x6 m2 in a randomized block design. Results revealed that the average concentration of dissolved P (DP), particulate P (PP), and total P (TP) in runoff water during the winter season was 0.13, 0.90 and 1.04 mg P l(-1) respectively, from P20 plots in Anzhen site. While it was 0.67, 1.08 and 1.75 mg P l(-1) respectively, from P20 plots in Changshu site. The seasonal TP load (mass loss) from P20 plot ranged from a low of 290.88 g P ha(-1)season(-1) to a high of 483.54 g P ha(-1)season(-1), with a mean of 382.29 g P ha(-1)season(-1) in Anzhen, but from 444.92 to 752.21 g P ha(-1)season(-1), with a mean of 539.13 g P ha(-1)season(-1) in Changshu. Both in Anzhen and Changshu PP represented a major portion of the TP lost in runoff, the average PP/TP was about more than 80% in P0 and P20 plot, but it was decreased with the increase of P rate. The average seasonal P loads (DP, PP, and TP) in Changshu were greater than in Anzhen although runoff volume in Anzhen (45 mm season(-1)) was more than in Changshu (36 mm season(-1)). This was probably associated with the differences of soil physical and chemical properties between the two sites. Phosphate fertilizer rate significantly affected P concentrations and P loads by runoff. Both the mean concentrations and the average seasonal P loads from the P80 plots were lower than from the P160 plots, but obviously higher than from the P20 and P0 plots. There was no significant difference found between the P20 plots and the P0 plots both in Anzhen and Changshu sites. It indicated that P loads by runoff would be greatly increased in 5-10 years due to the accumulation of soil P if 20 kg P ha(-1) applied each wheat season in this area.     

Leaching of trifluralin,metolachlor, and metribuzin in a clay loam soil of Louisiana

Trifluralin[2,6-dinitro-N,N-dipropyl-4-(trifluormethyl)benzenamine], metolachlor[2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and metribuzin[4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)one] were applied in field plots located on a Commerce clay loam soil near Baton Rouge, Louisiana at the rate of 1683 g/ha, 2759 g/ha and 609 g/ha, respectively. The half-lives of trifluralin, metolachlor, and metribuzin in the top 0-15 cm soil depth were found to be 54.7 days, 35.8 days and 29.8 days, respectively. The proportion of trifluralin, metolachlor, and metribuzin in the top 0-15 cm soil depth was 94.7%, 86.6%, and 75.4%, respectively of that found in the top 0-60 cm soil depth 30 days after application. Trifluralin concentrations were within a range of 0.026 ng/mL to 0.058 ng/mL in 1 m deep well water, and between 0.007 ng/mL and 0.039 ng/mL in 2 m deep well water over a 62 day period after application. Metolachlor concentrations in the 1 m and 2 m wells ranged from 3.62 ng/mL to 82.32 ng/mL and 8.44 ng/mL to 15.53 ng/mL, respectively. Whereas metribuzin concentrations in the 1 m and 2 m wells ranged from 0.70 ng/mL to 27.75 ng/mL and 1.71 ng/mL to 3.83 ng/mL, respectively. Accordingly, trifluralin was found to be strongly adsorbed on the soil and showed negligible leaching. Although metolachlor and metribuzin were also both readily adsorbed on the soil, their leaching potential was high. As a result, in the clay loam soil studied, metribuzin concentration in groundwater with shallow aquifers is likely to exceed the 10 mg/L US Environmental Protection Agency (EPA) advisory level for drinking water early in the application season, whereas trifluralin and metolachlor concentrations are expected to remain substantially lower than their respective 2 ng/mL and 175 ng/mL EPA advisory levels.     

The dynamics of dissolved nitrogen in a blanket peat dominated catchment

Precipitation, soil solution and drainage water were collected from a blanket peat catchment at Moor House National Nature Reserve in the Northern Pennine Uplands, UK, an area of moderately high N deposition. Two tributaries of the main stream were also sampled. Between 1993 and 1995 samples were analysed for NH4+ and NO3- and for part of the period for organic N. Inputs of N in precipitation exceeded outputs in stream water. Organic N represented a small proportion of N inputs while inputs of inorganic N averaged 10.2 kg ha(-1) a(-1). Soil solution from 10 cm depth in the peat was dominated by organic N whereas at 50 cm NH4+ slightly exceeded organic N. NO3- was rarely detected at either depth except during a period of exceptionally warm and dry weather in 1995. Output fluxes in stream water of organic N (5.7 to 6.5 kg ha(-1) a(-1)) were much greater than those of inorganic N (0.6 to 2.2 kg ha(-1) a(-1)). Inorganic N in streams was predominantly NO3- except in the smallest stream which had the largest concentrations of NH4+. This suggests that N transformations, particularly nitrification, may be taking place in the mineral soils adjacent to the streams or within the stream channel of the larger catchment.     

Contamination of wild-grown edible mushrooms by heavy metals in a former mercury-mining area

The aim of this study was to evaluate the contamination of six edible wild species of mushrooms (Boletus pulverulentus, Cantharellus cibarius, Lactarius quietus, Macrolepiota procera, Russula xerampelina and Suillus grevillei) by heavy metals (Hg, Cd, Pb, Zn, Cu, Ni, Cr, Co, Mn and Fe). Mushroom samples were collected from sites contaminated by emissions from mining and processing of polymetallic ores in operation during the period 1969–1993 in Rudňany, southeast Slovakia. The four study sites spanned up to a 5-km distance from the emission source. The collected mushroom samples were analyzed using Flame Atomic Absorption Spectrophotometry and/or Flame Atomic Absorption Spectrophotometry with graphite furnace. Mercury, Cd and, in some samples, also Pb present the highest risks in terms of contamination of the food chain following subsequent consumption. The content of two metals in the dry matter (dm) of the mushrooms exceeded the limits set by the European Union (EU; Cd: 0.5 mg/kg dm, Pb: 1.0 mg/kg dm). The highest mean contents of the eight metals recorded for S. grevillei were 52.2, 2.15, 107, 104, 2.27, 2.49, 81.6 and 434 mg/kg dm for Hg, Pb, Zn, Cu, Ni, Cr, Mn and Fe, respectively. The highest content of Cd was recorded in M. procera (3.05 mg/kg dm) and that of Co in L. quietus (0.90 mg/kg dm). The calculated weekly intake for Hg, Pb and Cd shows that regular consumption of mushrooms from the studied area poses risks to human health.     

Nitrate leaching in an Andisol treated with different types of fertilizers

Nitrate (NO3) leaching was studied in an Andisol treated with four N fertilizers (SC: swine compost, CU: coated urea, AN: ammonium N, or NF: no fertilizer) for 7 years. Sweet corn (Zea mays L.) was grown in summer, followed by Chinese cabbage (Brassica rapa L. var. amplexicaulis) or cabbage (Brassica oleracea L. var. capitata) in autumn each year. In chemical fertilizer plots treated with AN or CU, NO(3)-N concentrations in soil water at 1-m depth increased markedly in the summer of the second year and fluctuated between 30 and 60 mg l(-1). In the SC plot, NO(3)-N concentration started increasing in the fourth year, reaching the same level as in the AN and CU plots in the late period of the experiment. In the NF plot, NO(3)-N concentration was about 10 mg l(-1) for the first 4 years and decreased to 5 mg l(-1). The potential NO(3)-N concentrations by an N and water balance equation satisfactorily predicted NO(3)-N concentration in the AN and CU plots, but substantially overestimated that in the SC plot, presumably because a large portion of N from SC first accumulated in soil in the organic form. Our results indicate that, under the Japanese climate (Asian monsoon), excessive N from chemical fertilizers applied to Andisols can cause substantial NO3 leaching, while compost application is promising to establish high yields and low N leaching during a few years but would cause the same level of NO3 leaching as in chemically fertilized plots over longer periods.     

Cadmium in cereal grain and herbage from long-term experimental plots at Rothamsted, UK

Crop samples harvested and stored from three long-term agricultural experiments started in the 1840-1850s at Rothamsted Experimental Station (UK) have been analysed recently for Cd. Increased Cd burden in the soils of the experiments, which have had a range of treatments, originates mainly from atmospheric deposition. Soils treated with farmyard manure (FYM) or, in some cases, applications of phosphate fertilisers, have increased Cd levels. Herbage, wheat and barley grain from the three experiments were analysed by neutron activation analysis (NAA) and graphite furnace atomic absorption spectrometry (GFAAS). Samples were bulked for groups of years between 1860 and 1986, from variously treated plots in each experiment (control or 'nil' treatment, P-fertilised, FYM-amended, NPK-fertilised-limed and unlimed). There were marked differences in Cd concentrations between treatments. For example, uptake of Cd into herbage was greater where P fertiliser had been applied than not, and was greater from unlimed than limed soils. Offtake of Cd (mg ha(-1) year(-1)) was affected by large differences in yield and probably also by other factors. These include changes in botanical composition in the permanent grassland experiment; cultivar changes in the wheat and barley experiments; changes in soil organic matter and soil pH of some plots; changes in atmospheric deposition of Cd through time. All of these potentially confounding factors make the interpretation of results complicated. It is concluded, however, that, with one exception, there is little evidence of a long-term increase in crop Cd concentrations at Rothamsted.