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Nutrient leaching from clay soils can show extreme temporal and spatial variation. Using an optical sensor (hourly data storage), a Swedish field with vermiculite clay was monitored for water flow (Q expressed in mm), turbidity values (TURB), and nitrate-nitrogen concentrations (CNO3N, mg L-1) in four hydrological years representing different cropping/soil management regimes. Mean TURB-Q slope (1300) decreased in the order: ploughed soil > winter wheat > unfertilized fallow > winter wheat after drainage system renovation + structure-liming of topsoil and backfill, estimated in the initial phase from 16 selected autumn events. A similar ranking was found for variability in turbidity relative to that in discharge (CVT/CVQ) in the entire autumn. Mean CNO3N-Q slope (=2) was significantly lower under fallow than in the three cropping systems (7-32), confirming results from adjacent experimental plots. A spring-period had no snow cover or intensive rain, but in situ monitoring revealed that nutrient leaching was still substantial. Particulate- and dissolved reactive phosphorus, and nitrate-nitrogen leaching was estimated reasonably well (less than 8% difference) based on in situ high-frequency resolution measurements, compared with laboratory analysis of weekly composite samples. Accurate assessment of C-Q relationships in agricultural drainage water across temporal and spatial scales is therefore important. [ABSTRACT FROM AUTHOR]

Leaching losses of nitrogen (N), phosphorus (P) and potassium (K) from arable land can be high, with N and P contributing significantly to the eutrophication of lakes and coastal waters. This study examined whether agriculture management and drain repair changed the chemical properties of shallow groundwater and affected nutrient leaching in the field. The hydrology of a subsurface-drained agricultural observation field included in the Swedish water quality monitoring programme was simulated for the period 1976–2006 using the process-based, field-scale model DRAINMOD. On the assumption that the drainage system operated similarly before and after repair, 54% more water was assigned to low-moderate flow events. Measured concentrations of sulphate-sulphur (SO4-S), sodium (Na), chloride (Cl) and potassium (K) were significantly lower in shallow groundwater in the period before drainage system repair (1980–1998) than afterwards (1998–2010). The concentrations were also significantly correlated with the corresponding concentrations in near-simultaneously sampled drain water. A similar connection was not observed for Na and Cl in the period before drain repair. Elevated concentrations of nitrate-nitrogen (NO3-N) were recorded both in shallow groundwater and in drainage water from 1998 to 2010, especially after incorporation of chicken manure into the soil in 1998. Based on simulated discharge (assuming a functioning measuring station throughout), estimated flow-weighted mean NO3-N concentration in drainage water increased from 5.6 mg L−1(1977–1998) to 15.7 mg L−1in the period 1998–2000. Simultaneously, mean NO3-N concentration in shallow groundwater increased from 0.2 to 4.0 mg L−1, and then to 4.8 mg L−1in the period 2000–2012. It was estimated that after drain repair, a greater proportion of infiltrated NO3-N entered the receiving stream directly via the outlet of the tile drainage system close to the field's monitoring station than was the case before repair. [ABSTRACT FROM PUBLISHER]

Overall, arable soils in Sweden are currently generally close to phosphorus (P) balance, but excessive P accumulation has occurred on animal fur farms, i.e., those rearing mink ( Mustela vison) and foxes ( Alopex lagopus and Vulpes vulpes). Manure P from these farms has sometimes regarded as sparingly soluble. Laboratory lysimeter topsoil trials with simulated rain demonstrated that potential leaching of P in dissolved reactive form (DRP) can be very high, even for heavy clay (50%-65%) soils. The Swedish/Norwegian soil test P-AL (soil P extracted with acid NH4 lactate, AL) proved useful as a potential indicator of DRP leaching risk (regression coefficient [ R2] = 0.89) from fur farms. The upper 5-cm soil layer, with 190% higher (median) soil P status than the 5-20 cm layer, was the major source of potential DRP leaching through soil columns at the site, despite having been under grass or green fallow for the past 8 y. In percolate from topsoil lysimeters, DRP concentration increased by 0.29 mg L-1 after the long-term manure application but only by 0.14 mg L-1 after the single slurry application when compared to no addition of slurry. Therefore, the build-up to a high soil P status due to the long-term application of mink manure was more important than a single application of pig slurry at a rate corresponding to 22 kg P ha-1 with respect to soil leachate DRP losses in this lysimeter study. The study stresses the importance of precision farming, in which the amount of slurry-P applied is based on testing the already existing soil P content. [ABSTRACT FROM AUTHOR]

Abstract: In order to explore the influence of site-specific soil properties on nitrogen (N) and phosphorus (P) losses between individual fields and crop sequences, 16 drained fields with clay soils were investigated in a four-year study. Mean total N (TN) loss was 6.6–11.1 from a conventional, 14.3–21.5 from an organic and 13.1–23.9kgha−1 year−1 from an integrated cropping system across a 4year period, with 75% in nitrate form (NO3–N). Mean total P (TP) loss was 0.96–3.03, 0.99–4.63 and 0.76–2.67kgha−1 year−1, from the three systems respectively during the same period, with 25% in dissolved reactive form (DRP). Median N efficiency was calculated to be 70% including gains from estimated N fixation. According to principal component factor (PCA) analysis, field characteristics and cropping system were generally more important for losses of N and P than year. Accumulation of soil mineral N in the autumn and (estimated) N fixation was important for N leaching. No P fertilisers were used at the site in either cropping system. Total P concentration in drainage water from each of the fields was marginally significantly (p<0.05) correlated to TP concentration in the topsoil (r=0.52), measured in hydrochloric acid extract (P-HCl). Mean DRP concentrations were significantly (p<0.01) correlated to degree of P saturation (DPS-AL) and soil carbon (C) content in the topsoil (r=0.63). Good establishment of a crop with efficient nutrient uptake and good soil structure was general preconditions for low nutrient leaching. Incorporation of ley by tillage operations in the summer before autumn crop establishment and repeated operations in autumn as well, increased N leaching. Crop management in sequences with leguminous crops needs to be considered carefully when designing cropping systems high efficiency in N utilisation and low environmental impact. [Copyright &y& Elsevier]

Phosphorus (P) leaching from agricultural soils is a serious environmental concern. Application of aluminium water treatment residuals (Al-WTR5) at a rate of 20 Mg ha-1 to clay soils from central Sweden significantly increased mean topsoil P sorption index (PSI) from 4.6 to 5.5 imol kg-1 soil. Mean degree of P saturation in ammonium lactate extract (DPS-AL) significantly decreased from 17 to 13%, as did plant-available P (P-AL). Concentrations of dissolved reactive P (DRP) decreased by 10-85% in leaching water with Al-WTR treatments after exposure of topsoil lysimeters to simulated rain. Soil aggregate stability (AgS) for 15 test soils rarely improved. Three soils (clay loam, silty loam and loam sand) were tested in greenhouse pot experiments. Aluminium-WTR application of 15 or 30 ton ha-1 to loam sand and a clay loam with P-AL values of 80-100mg kg-1 soil significantly increased growth of Italian ryegrass when fertilised with P but did not significantly affect growth of spring barley on any soil. Al-WVR should only be applied to soils with high P fertility where improved crop production is not required. [ABSTRACT FROM AUTHOR]

Leaching of nutrients and major ions from a tile-drained arable field was evaluated over a 25-year period (1980-2005). The soil, classified as a Gleyic Cambisol, received moderate applications of fertilizers. During later years the soil was more frequently under ley, and since 2002, an area of ravine (29% of the total field) has been managed as a permanent fallow with annual cutting without removing the grass material. A decrease in the concentration of nitrate nitrogen (NO3-N) in the drainwater was estimated in 1980-2005, based on non-parametric tests on concentrations flow-normalized with a robust fitting curve procedure. The average concentration of soluble reactive phosphorus after pre-filtration (RPf) of 0.030 mg l-l corresponded to a calculated degree of phosphorus saturation (DPS) of 6% in acid extract of ammonium lactate from the topsoil. Between 1995 and 2005, concentrations of suspended solids (SS), RP and total organic carbon (TOC) decreased significantly in the drainage water from the entire field. Throughout the entire period, there was a negative net accumulation of the major ions to the soil. The order of decrease in relative terms was calcium (Ca2+)>magnesium (Mg2+)>sulphate (SO42-)>chloride (Cl-)>potassium (K+). In addition, the soil phosphorus (P) balance was negative. A significant reduction in ion concentrations in the drainwater, including sodium (Na+) and hydrogen carbonate HCO3 -, was estimated. The order of reduction in relative terms was: SO4 2->Mg2+>Ca2+>HCO3->Cl->NO3->Na+>HPO4. Altogether these trends were equal to approximately 0.1 mmolc l-1. yr-1 of positively and negatively charged ions. Based on measured concentrations, decreasing trends in SO4 2- and Ca2+ were also observed in the shallow groundwater (3.6 m below the soil surface), while K+, Na+ and HCO3- tended to increase. Trends of cations in deeper groundwater (5.8 m below the soil surface) were in some cases the opposite of the trends in the drainwater. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the long-term (1977-2004) effects of new agricultural practices and reduced acid rain on drainwater and groundwater chemistry for an intensely cultivated arable field with sandy soil in south-west Sweden. Trends in chemical composition of the drainwater were compared with those of atmospheric deposition and groundwater. A modified crop rotation including catch crops significantly decreased the average concentration of nitrate nitrogen (NO3-N) in drainwater from 13.0 to 7.2 mgL-1. This rotation was also found to be a very effective measure against high NO3-N concentrations in shallow groundwater (1.7 m below the soil surface). The degree of phosphorus saturation (DPS) in the subsoil, calculated to be 10% and 9% by two different laboratory methods, corresponded to an average and constant concentration of dissolved reactive phosphate (DRP) in drainwater of 0.006 mg l-1. Generally lower inputs of acid deposition to the soil were confirmed by a decreasing SO4-S trend (by 3% over 24 years) in drainwater. Changes in cropping had reduced the acid load to the soil, while drainwater alkalinity showed a slow but significant positive trend amounting to 0.4% over 24 years. [ABSTRACT FROM AUTHOR]

A Field experiment to investigate nutrient leaching was established in 2011 on a clay loam. The field site is located about 15 km south of Uppsala in eastern Sweden (59°43'0" N; 17°41'21" E). The experimental field is about 0.42 ha (72 × 50 m), with a slope in the north-south direction of about 1%. At the lower part of the field, grassed buffer strips were established as follows: A) Control, which is managed in the same way as the main field; B) Grass buffer strips; C) As B, but the grass harvested once a year. Each treatment was 6 m by 6 m, and is replicated in four blocks. Each plot is drained with a central 6-m long drain pipe at 1 m depth. The rest of the field is not drained. Surface runoff and drainage water are led to an automated measuring and sampling station. The samples were analyzed for phosphorus, nitrogen and organic carbon. On average, the leaching of particulate phosphorus via drainage tiles was reduced by 17 % in the grass buffer strips but the effect of harvesting the grass on reducing leaching was very little. Nitrate leaching was reduced by 28 %. Surface runoff was scarce during the experimental years and its data was insufficient to draw conclusions. [ABSTRACT FROM AUTHOR]

Diffuse phosphorus losses from arable land contribute significantly to eutrophication in many regions. To enable the most efficient measures for reducing P losses to be identified, it is important to quantify the contributions from different sources and the effects of various scenarios aimed at reducing these losses. To account for transport to tile-drains through macropores, we extended the field-scale simulation model ICECREAM with descriptions based on mixing layer and dual porosity concepts. For losses of particulate phosphorus (PP) to tile-drains, a new description of particle generation and detachment was included. The model was applied on a 6-year field experiment on a structured clay soil in south-west Sweden and simulation results were compared with measured water flow and losses of suspended particles (SP), PP and dissolved reactive phosphorus (DRP) to tile-drains. After calibration of parameters related to macropore flow and transport, and to particle generation and detachment, the model could describe the extremely episodic losses of SP, PP and DRP reasonably accurately. However, some short-term fluctuations were not captured (model efficiency during the validation period −2.1 for PP and 0.43 for DRP). Thus, further development and testing are required before the model can be used with confidence for predictive applications or management purposes. Based on this application, we suggest that direct leaching from non-decomposed plant material and infiltration in partly frozen soil be included in the ICECREAM model. We also suggest that the controls on the sorption distribution coefficient for partitioning between DRP and labile phosphorus (P L) and the effects of using the ‘storage routing’ equation for calculation of soil water content instead of the Richards equation be further investigated. [Copyright &y& Elsevier]

Abstract: The use of biochar as a soil amendment has recently increased because of its potential for long-term soil carbon sequestration and its potential for improving soil fertility. The objective of this study was to quantify the effects of biochar soil incorporation on pesticide adsorption and leaching for two Swedish topsoils, one clay soil and one loam soil. We used the non-reactive tracer bromide and the pesticides sulfosulfuron, isoproturon, imidacloprid, propyzamid and pyraclostrobin, substances with different mobility in soil. Adsorption was studied in batch experiments and leaching was studied in experiments using soil columns (20cm high, 20cm diameter) where 0.01kgkg−1 dw biochar powder originating from wheat residues had been mixed into the top 10cm. After solute application the columns were exposed to simulated rain three times with a weekly interval and concentrations were measured in the effluent water. The biochar treatment resulted in significantly larger adsorption distribution coefficients (Kd ) for the moderately mobile pesticides isoproturon and imidacloprid for the clay soil and for imidacloprid only for the loam soil. Relative leaching of the pesticides ranged from 0.0035% of the applied mass for pyraclostrobin (average Kd =360cm3 g−1) to 5.9% for sulfosulfuron (average Kd =5.6cm3 g−1). There were no significant effects of the biochar amendment on pesticide concentrations in column effluents for the loam soil. For the clay soil concentrations were significantly reduced for isoproturon, imidacloprid and propyzamid while they were significantly increased for the non-mobile fungicide pyraclostrobin suggesting that the transport was facilitated by material originating from the biochar amendment. [Copyright &y& Elsevier]