Slurry Tanker Research Articles

Traffic induced compaction and physical quality of grassland soil under different soil moisture deficits

Soil compaction is widely recognised as one of the key contributors to soil degradation in Europe. Information is needed for farmers and land managers to guide management decisions and prevent traffic-induced soil compaction. Predicted soil moisture deficit (SMD) from the hybrid SMD model may provide information on when soil conditions are suitable for machinery trafficking. The objective of this study was to investigate the relationship between soil water content and traffic induced soil compaction and if a predicted SMD threshold level could be identified, above which soils can be trafficked without significant soil compaction occurring. The study also evaluated the capacity of selected soil physical indicators such as soil bulk density and water stable aggregates to indicate soil physical degradation across a range of soil water contents. The experiment was carried out on grassland with moderately drained soil, located in Wexford, Ireland. Machinery trafficking of the soil with a tractor equipped with a fully loaded slurry tanker, was assessed in the field across the four seasons of the year. Traffic was imposed at target predicted SMD + 10 mm (relatively dry soil), 0 mm (relatively moist soil), and −10 mm (relatively wet soil). After each traffic event, samples were taken in the middle of the wheel track at three depths (0–10, 10–20 and 20–30 cm) to assess soil bulk density. Water aggregate stability was evaluated at the same three depths following the fourth traffic event. Results showed that when planning field machinery operations, especially repeated trafficking events, soil becomes prone to physical degradation when predicted SMD ≤ 0 mm. Traffic on soil at predicted SMD 0 mm (close to field capacity) lead to compaction after two traffic events. However, when predicted SMD was −10 mm, soil bulk density indicated no significant difference from the non-trafficked soil. When water-stable aggregates were measured on the predicted SMD 0 mm and −10 mm trafficked soils, it indicated physical degradation of soil. Hence, bulk density alone did not give an accurate indication of soil structural quality when soils where trafficked under relatively wet or saturated conditions (SMD −10 mm). These results indicate that avoiding machinery trafficking of grassland soils at predicted SMD ≤ 0 mm will help protect soil physical structure. On soils where multiple machinery operations are likely to occur over the year, trafficking when the predicted SMD > 0 mm is recommended to minimise loss of soil physical quality.

On-farm use of recycled liquid ammonium sulphate in Southwest Germany using a participatory approach

AbstractFor political and environmental reasons, there is an urgent need for alternatives to energy-intensive synthetic fertilizers. One solution is the targeted recycling of nutrients within agriculture. In this study, liquid ammonium sulphate (LAS) as a recycling product derived from digestate treatment was compared to calcium ammonium nitrate, manure and original digestates in an on-farm experiment using a participatory approach. Based on regular meetings with the farmers involved, a flexible experimental design was developed which integrated the fertilization legislation and the farmers’ operational structures already in place, such as crop rotation, available application techniques and manure management demands. The aim was to achieve both implementation practicability and acceptance of the study results by the farmers. Results from the year 2020 showed that LAS applied with three-jet nozzles in barley and wheat had significantly lower yields than the other fertilizers. Applied with a slurry tanker trailing shoe applicator in 2021, LAS had comparable yields to the other fertilizers in maize (51.2 t ha−1) and comparable yields to digestate in rapeseed (4.4 t ha−1). Application techniques that minimize environmental impacts and lower the LAS pH could potentially increase the effectiveness of the fertilizer. We recommend that farmers use this fertilizer not as a single solution but as a mineral compensatory fertilizer in addition to organic fertilizers following local fertilizer legislation. In this case, LAS could potentially substitute calcium ammonium nitrate (CAN).

Life cycle assessment of Parmigiano Reggiano PDO cheese with product environmental footprint method: A case study implementing improved slurry management strategies

The environmental impact of Parmigiano Reggiano PDO cheese was quantified using the Product Environmental Footprint Category Rules (PEFCRs) in a Traditional System (TS) and in an Improved Management System (IMS). The TS differs from IMS with respect to slurry management (raw slurry storage vs anaerobic digestion and storage of the liquid fraction of digestate) and application of nutrients to the field (by slurry tanker with a diverter plate vs soil injection at pre-sowing and side dressing).Two additional scenarios were evaluated by considering the possible environmental enhancement achievable by reducing enteric methane production and by using soybean grain produced in Italy as the protein source for animals' diets. The environmental impact was quantified both for 1 kg of fat and protein corrected milk (FPCM) and for the production of 10 g dry matter equivalent of cheese as single score. For the first assessment, the environmental impact results were 124 and 112 μPt kg FPCM−1 for TS and IMS, respectively. In the second case, it was 10.8 μPt and 9.9 μPt 10 g dry matter equivalent−1 of cheese, for TS and IMS, respectively. The specific cost for reducing the GHG emissions in this production chain was equal to 34 € Mg−1 milk produced. Finally, although specific studies should consider the reduction of enteric methane emissions and the use of soybean grain nationally produced as feed source, the scenarios evaluated in this study highlighted some potential for environmental improvements. Even small environmental improvements to the Parmigiano Reggiano PDO cheese supply chain can bring substantial improvements to the sustainability of the food market, because of the widespread demand on the global market of Parmigiano Reggiano and of its chance of attracting consumers who are sensitive to environmental problems.

Effect of Cover Crop, Slurry Application with Different Loads and Tire Inflation Pressures on Tire Track Depth, Soil Penetration Resistance and Maize Yield

Agricultural soils can be affected in their ecological functions by in-field traffic of agricultural machinery. A three-factorial research design was carried out in a field experiment to test the effect of slurry tanker filling level (filled, half-filled, empty), tire inflation pressure of the slurry tanker (high: 300 kPa, low: 100 kPa), and ground covering (+cover crop, −cover crop) on tire track and soil penetration resistance (averaged, 0–20 cm, 21–40 cm) after application on the fields in spring. Additionally, the effect on grain yield of the subsequent culture was considered. The total weight of the tractor slurry tanker combination was 16,470 kg (empty), 25,940 kg (half-filled), and 34,620 kg (filled). The low tire inflation pressure of the slurry tanker increased the mean tire–soil contact area by 75% (filled), 38% (half-filled), and 16% (empty tanker). The results obtained show a significant effect of tire inflation pressure and ground covering on the measured parameters. The tire inflation pressure reduction effect on track depth was highest in the filled slurry tanker (−17.8%). With increasing wheel load, the effect of reduced tire inflation pressure on soil penetration resistance (0–20 cm) increased. In the subsoil (21–40 cm), the effect of tire inflation pressure was much lower, indicating that a reduction of tire inflation pressure preserves the upper layers rather than the lower ones. Furthermore, cover crops are linked to a higher degree of soil deformation after traffic with the tractor–slurry combination due to their loosening effect on the topsoil. Tire tracks were 15.0% deeper in the cover crop field than in the field without a cover crop. It is assumed that cover crop mixtures with different types of root mass can influence the mitigation of soil compaction in an ameliorative way.

Optimizing Treatment of Cesspool Wastewater at an Activated Sludge Plant

The purpose of this work was to determine the optimal percentage of wastewater from cesspool in the mixture of wastes subjected to treatment processes, which will not have a negative impact on the functioning of the collective treatment plant. The study was carried out over a period of two years, with 48 samples of wastewater flowing in from the sewage network and delivered with the slurry tanker collected and subjected to physical and chemical analysis. The analysis included: Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and Total Nitrogen (TN). In addition, the study defined the daily balance of the amount of inflowing and transported wastewater. Based on the analysis carried out, it was found that the unit loads of BOD5, COD and TN in the mixture of wastewater subjected to the treatment process will be at the level of loads assumed in the project, when the share of supplied wastewater, i.e., from cesspool, will be at the level of 5% of the total amount of wastewater. Considering that in the analysed period the total average daily amount of wastewater subjected to the treatment process was 253.5 m3·d−1, the optimal amount of wastewater delivered should be 12.7 m3 in each day of the week.

Ocena racjonalności działań inwestycyjnych w powiecie suwalskim w ramach wsparcia młodych rolników

Celem badań była ocena racjonalności doboru maszyn w ramach działań inwestycyjnych podejmowanych przez młodych rolników. Analizie poddano wyposażenie techniczne 54 losowo wybranych gospodarstw, których właściciele uzyskali wsparcie w ramach działań „Ułatwianie startu młodym rolnikom” lub „Premie dla młodych rolników”. Z przeprowadzonych rozważań wynika, że prawie połowa zakupów wozów asenizacyjnych była nieracjonalna pod względem ekonomicznym. Bardziej racjonalne pod względem organizacyjnym i technologicznym były inwestycje w ciągniki rolnicze i kosiarki dyskowe.

Feasibility for use of digested slurry by the pouring method in paddy fields of Southern Vietnam

In this study, we evaluated the feasibility for the use of digested slurry from livestock manure (hereafter, slurry) in paddy fields through field experiments conducted in Southern Vietnam. The pouring method for slurry was used, and a vacuum truck was used for transportation and pouring of the slurry. A prototype slurry tanker was manufactured for transportation and application of slurry, because vacuum trucks are rarely available in rural areas of Vietnam. For evaluation of feasibility, costs and labor for application of slurry and rice production were examined and compared with conventional cultivation methods using chemical fertilizers. As the results, rice production with the use of slurry was 485 g m−2, which is within the range of on-site conventional cultivation, so slurry may be a good substitute for chemical fertilizers in rice production. Costs for slurry fertilization with a prototype slurry tanker and a vacuum truck were estimated at 0.13 USD m−2 and 0.10 USD m−2, respectively. These costs were higher than for conventional cultivation of 0.06 USD m−2 under the present conditions with T-N concentrations of approximately 400 mg L−1 in the slurry. However, we clarified that the cost for slurry fertilization can be lower than conventional cultivation when the concentrations of nitrogen in slurry increase from 400 to 2000 mg L−1. These results show that an increase in nitrogen concentrations in slurry make slurry fertilization feasible if the amounts of water for washing livestock sheds that enter into the biogas digesters are reduced.

A Retrofit Variable-Rate Control System for Pressurized Slurry Tankers

<abstract> <b><i>Abstract. </i></b> In the last several decades, livestock effluent management practices and field slurry spreading operations have received increasing attention due to their economic and environmental implications. In this study, a variable-rate control system for pressurized slurry tankers was developed according a retrofit approach (i.e., as a self-standing module that can be adapted and mounted on existing slurry tanker equipment). The system provides farmers with a useful tool for achieving compliance with environmental protection regulations and for developing good practices for livestock and nitrogen management. This system is suitable for new and used pressurized tanker equipment. For field-testing purposes, this system was mounted on a double-axis 10 m³ slurry tanker equipped with a crawling nozzle distribution unit. Field experiments were conducted at two typical forward speeds (2 and 3 km h^-1) and three different nitrogen application rates (170, 250, and 340 kg ha^-1). Based on the experimental results, the system was generally capable of limiting the differences between the nominal and measured application rates to less than 9%. In addition, the data analysis indicated that the slurry spreading was not significantly affected by the forward speed of the tanker. The uniformity of nitrogen spreading was evaluated according to the UNI EN 13406:2002 standard. The results showed that the transverse field distribution was uniform throughout the working width of the machine and at all tested operating conditions, with maximum deviations that were limited to less than 15%.

Simulation of field NH3 and N2O emissions from slurry spreading

Land application of manures and slurries are a major source of pollution such as water contamination by nitrates and greenhouse gas emissions. NH3 and N2O emissions can be lowered by suitable spreading techniques. However, a comprehensive review of the impact of slurry spreading techniques is lacking. For that we developed a model, named OSEEP, that simulates the effect of slurry incorporation, slurry spatial distribution, and soil compaction on NH3 and N2O emissions. OSEEP integrates a soil compaction model, a hydraulic pedotransfer function, a NH3 volatilization model, and a crop model. We ran OSEEP for five sites in France for 7 years. Four techniques were simulated: broadcast spreading, band spreading, incorporation after surface spreading, and injection. We tested various sizes of slurry tankers and tractors. We calculated NH3 and N2O relative emissions from various spreading techniques with respect to band spreading. Results show good agreement between model calculation and published field data. We found that slurry applied by a self-propelled 15-m3 tanker with extra large tires led to an increase of 20 % in N2O emission, by comparison with a 15-m3 tanker trailed by a tractor. Hence, we show that soil compaction should be taken into account to optimize trade-offs between NH3 and N2O emissions.

Verification of traffic-induced soil compaction after long-term ploughing and 10 years minimum tillage on clay loam soil in South-East Norway

Grain yields are presented from a 10-year field trial with four tillage regimes (annual ploughing, harrowing only, ploughing/harrowing alternate years and minimum tillage) on clay loam. We also present soil physical analyses and use the compaction verification tool (CVT) to assess compaction on plots with annual ploughing and minimum tillage, after using slurry tankers with contrasting wheel loads (4.1 Mg, 6.6 Mg) and wheeling intensities (1×/10×) in the 11th trial year, and yields monitored two years after compaction. Winter wheat yields in the period before compaction were strongly affected by tillage, with annual ploughing giving on average 24% higher yield than direct drilling. Both wheat and oats were far less affected in treatments with harrowing only or ploughing/harrowing alternate years, on average within 6% of annual ploughing. Yields after compaction were affected by both previous tillage and compaction intensity. In the first year, single wheeling after annual ploughing gave 23% yield reduction with 4.1 Mg wheel load and 28% reduction with 6.6 Mg wheel load, whilst multiple wheeling gave 14% reduction at 6.6 Mg wheel load. Yield reductions after minimum tillage ranged from 63% (single wheeling with 4.1 Mg) to 100% (multiple wheeling with 6.6 Mg). Similar trends were found in the second year. The soil physical data indicated that all wheeling led to changes in bulk density, pore sizes and permeability in both topsoil and subsoil on both sampled tillage plots. However, effects in the subsoil were partly masked by the soil's high initial bulk density, partly due to its high clay content. The CVT, which plots air capacity against hydraulic conductivity, suggested some harmful compaction on both plots, with the minimum tillage plot being less affected than the ploughed plot. However, yield results did not support this conclusion, indicating that other factors limited yields on the minimum tilled plot.

Traffic-induced soil compaction during manure spreading in spring in South-East Norway

The objective of this study was to evaluate long-term effects of two tillage regimes (ploughing and minimum tillage) on the bearing capacity of a clay rich soil, by using two different slurry tankers (4.1 and 6.6 Mg wheel load) and contrasting wheeling frequencies (1 and 10 passes). The soil strength was assessed by laboratory measurements of the precompression stress (Pc) at −6 kPa in topsoil (20 cm) and subsoil (40 and 60 cm) samples. Stress propagation, elastic and plastic deformation during wheeling were measured in the field with combined stress-state-transducer and displacement transducer system. Results presented in this study show that minimum tilled soil had 74% higher Pc than ploughed soil in the upper soil layer, whilst differences were less distinct in subsoil. Wheeling increased Pc at all soil depths. Compared to ploughing, higher strength in the upper layer of minimum tilled soil led on average to 60% and 48% reductions in the major principal stress with the use of the light and heavy slurry tanker, respectively. The extent of the major principal stress was dependent on the ground pressure in the topsoil. The first pass of a wheel caused the greatest damage in some cases, but all wheelings led to accumulative plastic deformation in both vertical and horizontal directions. Wheeling with high intensity would have exceeded Pc in all cases when soil was at a matric potential of −6 kPa. The results show that soil water content is an important factor influencing bearing capacity. Drier soil (−100 kPa), in combination with minimum tillage, limited the occurrence of stresses exceeding Pc in the upper soil layer.

Band application of slurry in orchards using a prototype spreader with an automatic rate controller

A prototype slurry spreader for band application in orchards was designed, constructed, and tested. The spreader comprised several components: 1) 5 m3 tank, 2) distribution device of trailing hoses to reduce ammonia emissions during application, 3) automatic rate controller to apply nitrogen per crop requirements, and 4) low-pressure, wide-section tyres to mitigate soil compaction and sward damage. The slurry tanker design fitted between tree row spacings accounting for tree shape differences. The spreading system consists of two groups of six trailing hoses; each hose group distributes slurry into two 1.0 m wide bands alongside the machine and 0.5 m from tree rows. Operator input of slurry total nitrogen content, determined by onboard hydrometer in the field, and target application rate in the control unit ensured that nitrogen was applied at a constant rate based on metering pump rotational speed as a function of machine forward speed. The rate control system was tested at different application doses and with rapid changes in machine forward speed (range of 3–9 km h−1). The machine responded promptly (<2 s) to forward speed changes, and the spreader evenly distributed slurry in both application bands (Dave < 2.5% on the treated surface). Band application of slurry by the trailing hose device reduced ammonia emissions by 63% compared to the common broadcast application system by splash plate.

Field evaluation of soil moisture deficit thresholds for limits to trafficability with slurry spreading equipment on grassland

AbstractThis study investigated the extent of soil damage caused by field traffic associated with different levels of soil moisture deficit (SMD). The hybrid SMD model was used for computing temporal patterns of SMD which can be accurately predicted for a range of soil types in Ireland. The aim of this study was to determine SMD threshold limits to trafficability for incorporation into a decision support system for safe slurry spreading. A tractor and a fully loaded single‐axle slurry tanker (total weight ca. 18 tonnes) were driven over well, moderate and poorly drained soils at SMD values of 0, 5, 10 and 20 mm during drying phases. The change in soil bulk density (SBD) was used as an indicator of soil compaction, and rut profile measurements were taken to determine soil deformation indicative of surface damage. The effect of traffic on the grass crop was determined by measuring dry matter yield at 30 and 60 days posttraffic in the wheel‐rut and nontrafficked area. Results showed that the SMD at the time of traffic had a significant (P &lt; 0.05) effect on the magnitude of the changes in SBD on soils of different drainage status, and on rut dimensions following traffic. DMY was significantly (P &lt; 0.05) reduced on the wheeled compared with the nonwheeled soil. No differences in the magnitude of DMY loss were identified between the sites having different drainage status. An SMD value of 10 mm was suggested as an SMD threshold for trafficability for safe slurry spreading purposes.

Repair and Maintenance Costs for Nine Agricultural Machine Types

<abstract><title><italic>Abstract. </italic></title> On the basis of a farm survey conducted in Switzerland, annual repair and maintenance cost functions are estimated for nine agricultural machine types (wagon, harrow, rotary harrow, seed drill, single seeder, field sprayer, solid-manure spreader, hydraulic loader, and slurry tanker). In a second step, the annual costs are aggregated to indicate the accumulated repair and maintenance costs for the machine’s estimated service life, information that is crucial for machinery cost calculation. Assuming full utilization of the estimated service life, measured in work units such as hectares or barrels, the analysis reveals a strong influence of annual utilization. High annual utilization combined with short length of service measured in years has the effect of reducing the accumulated repair and maintenance costs. Despite limited comparison of the obtained results for repair and maintenance costs with the existing literature, there is some evidence of a reduction in these costs over time.

Q value for calculation of pressure propagation in arable soils taking topsoil stability into account

Reliable recommendations for practice are required, to enable farmers themselves to decide whether or not it is acceptable to drive over the soil under the prevailing conditions. To this end, the pressure propagation has to be calculated by means of easily recorded parameters. The TASC program (Tyres/Track And Soil Compaction) makes a contribution to this. The risk of soil compaction may be evaluated with reference to six parameters (tyre size, wheel load, tyre inflation pressure, topsoil stability, soil type and maximum tillage depth). The program uses these parameters to evaluate the soil stress caused by tyres and tracks. The aim of the study is on the basis of field measurements to derive a regression equation for calculation of the q value (as a measurement of soil hardness when calculating the pressure propagation in the soil) as a function of the penetration resistance. The topsoil stability can then be taken into account when calculating the compressive stress. Locations ranging from high (ley on dry clay soil) to very low soil stability (shortly after ploughing) were selected for the purpose of the study. Soil pressure measurements were made at plough pan level at a total of nine sites (cropland and pasture) with light to heavy soils. Different machine weights were used, producing wheel loads varying from the empty slurry tanker (wheel load 1432 daN) to the 6-row sugar beet harvester (wheel load 10,678 daN). The q value is a measure of topsoil stability (penetration resistance). The q value is determined by the compressive stress at a particular depth, by the depth itself, by the contact area and by the wheel load. The so-called equivalent contact pressure can be recalculated on the basis of the compressive stress values measured at a depth of 20 cm. The ratio of the equivalent contact area pressure to the measured contact area pressure (wheel load/measured contact area) gives the q value. This value increases as the soil stability decreases. For the purpose of the regression calculation a logarithmic function was derived for mineral soils from the upper quartiles on the one hand and from the medians of the q value and the medians of the penetration resistance on the other. The coefficient of determination is 0.71. The function applies to mineral soils. First measurements on organic soils indicate that mineral and organic soils react differently to pressure propagation. No direct correlation was found here between penetration resistance and soil moisture.

An automatic depth control system for shallow slurry injection, Part 2: Control design and field validation

Shallow slurry injection is considered to be the most efficient way to reduce the ammonia emission by agriculture, but its performance is highly dependent on the injection depth. An automatic electro-hydraulic depth control system was developed to maintain the injection depth within narrow margins around the desired value. It utilised the hydraulic system of the four-point linkage of the slurry tanker to change the position of the injector with respect to the tanker in order to minimise the difference between the desired height of the supporting frame of the injector and the height measured by means of an ultrasonic sensor. Based on a grey-box model, the performance of different control algorithms was compared by simulation with this model. Although the bandwidth of the system with a lead compensator was slightly larger than with a proportional controller for a linearised model structure, the performance of both controllers was comparable when actuator saturation was taken into account. Because of its simplicity, the proportional controller was implemented. Comparison of the performance of the depth control system with the commercially available pressure control system on two fields with a high and a low soil penetration resistance showed that the depth control system outperforms the pressure control system in terms of overall mean error (51–78% more accurate) and standard deviation (16–44% less variation) for all parallel runs.

Development of an In-line Nutrient Sensing System for Livestock Slurries

An in-line nutrient sensing system was designed, built and fitted to a slurry tanker of 7 m3capacity. The system measured particular physical and chemical properties of the tanker contents to derive estimates of their ammoniacal nitrogen, total phosphorus and total potassium concentrations. The complete system was tested in the UK and Ireland using seven cattle slurries and 11 pig slurries. The nutrient estimates were based on calibration coefficients which related the nutrient concentrations to the measured physical and chemical properties. Results proved that most of these coefficients, which had been determined previously using a different sensing system, could be transferred directly to the tanker-mounted system.In the cases where the coefficients could be transferred, the overall standard errors per observation for estimation of ammoniacal nitrogen, phosphorus and potassium concentrations were ±0·29, ±0·29, and ±0·79 kg/m3, respectively. The respective ranges over which these values were determined were 0·63–5·29, 0·12–0·71 and 0·81–6·49 kg/m3. It was also demonstrated that re-calibration could improve the accuracy of estimation, particularly in instances where the system was used to determine the effects of aqueous dilution of slurries. In practice, the nutrient content of each tanker load of slurry was estimated within a period of 2 min, and thus could be completed whilst the tanker was moving from a slurry store to a spreading site, so that the target application rate could be adjusted to achieve a desired nutrient application. Therefore, it did not reduce the normal work rate of the tanker.

Estimation of the Nutrient Value of Agricultural Slurries by Measurement of Physical and Chemical Properties

Abstract A prototype nutrient sensing system was used to investigate relationships between the nutrient status of agricultural slurries and a range of physical and chemical properties. These properties were all measured using devices suitable for possible installation in full-scale slurry handling systems. The prototype system was tested on a total of 160 slurries, comprising approximately 20 cattle and 20 pig slurries from each of four European countries. Linear relationships were identified between ammoniacal nitrogen concentration and the electrical conductivity of the slurries and between total phosphorus and the density of the slurries. Generally, regressions for total potassium were weaker than those identified for either ammoniacal nitrogen or total phosphorus. The results show that a practical nutrient sensing system is feasible for farm use. For example, such a system could be used on a slurry tanker to estimate the nutrient status of the whole tanker contents, thus eliminating the sampling errors associated with sub-sampling from a large store.

Development of a Prototype Nutrient Sensing System for Livestock Slurries

The scientific literature has shown good relationships between the nutrient (nitrogen, phosphorus and potassium) status and the physical/chemical properties of both cattle and pig slurries. In particular, the ammoniacal nitrogen and the potassium contents of the slurries correlated with their electrical conductivities. The best indication of the available phosphorus was given by total solids and specific gravity. Based on these findings, a prototype sensing system to measure the physical and chemical properties was designed, built and tested on 41 slurries. The system was able to detect the effect of dilution on any given slurry; and to estimate ammoniacal nitrogen in all slurries and phosphorus in cattle slurries. It established the feasibility of the approach and provided a basis for the development of subsequent versions for installation on slurry tankers.

Practice to avoid contamination of drainflow and runoff from slurry spreading in spring

Abstract. Use of either three or six occasions to spread similar total amounts of slurry was investigated over the late winter/early spring period in two years, on plots with underdrainage. Slurry was spread on four 7 m by 25 m plots which were instrumented to allow collection of drainflow and runoff. The ‘mobile water’ pore space allowed transport of a small proportion of applied slurry through the 0.75 m soil profile. Evidence of a polluted ‘mobile water’ pulse occurred after periods of up to 48 hours following spreading, suggesting subsurface rather than overland flow. Timing of the pulse depended on whether subsequent rainfall accelerated the flow The contaminated flow persisted for 6–12 hours. The worst contamination of 39 mg/l NH4+ ‐N occurred under ‘bypass flow’ conditions, when 52 mm of rain fell during the 48 hours after a 5.2 mm application. Two contributory factors appeared important. The first was the long duration of the high intensity storm and the second was an extended period of severe frost believed to have created fissures associated with frost heave. Making several applications of slurry in amounts less than 35 m3/ha is preferable to fewer larger applications during spring, for cereals on medium to heavy soils. This recognises the likelihood of there being underdrainage on arable land and the optimal use of well‐drained, partially frozen ground to avoid compaction by slurry tankers.