An improved understanding of potential soluble phosphorus (P) loss in run-off and leachate from agriculturally managed soils presents practical and theoretical challenges. Our study aimed to discover whether modified Morgan extractable P (MMP) can be used to predict water-soluble P (WSP). We first addressed the relationship between MMP and WSP, and whether MMP is useful for predicting the WSP concentrations demanded by water quality regulations. Secondly, we applied novel soil chemical models to explain why the relationship between MMP and WSP depends upon soil properties. Thirdly, we explain how soil properties relate to potential soluble P loss in situations in which soil is subjected to a wide liquid-to-soil ratio (e.g. run-off and rivers) compared with those with a narrow ratio (e.g. soil porewater). To address these P loss scenarios, 60 agricultural topsoils (0-10 cm) were collected from a mixed-farming catchment (Lunan catchment, northeast Scotland) and chemically characterized. Theoretical understanding of P solubility was obtained with a P sorption model. The data showed variability in the relationship between MMP and WSP. Modelling shows the MMP versus WSP relationship is nonlinear, depending on several confounding factors (P sorption capacity (PSC), Ca, pH) and the liquid-to-soil ratio (L:S) employed for WSP determination. Consequently, the slope of the relationship is not unique but depends subjectively on the set of soils surveyed. MMP versus WSP at large L:S (e.g. in run-off or rivers) is positively correlated to PSC, whereas at narrow L:S (e.g. porewater) there is a negative correlation with PSC. The study provides new ideas for the interpretation and extrapolation of agronomic soil test data for soils of varied properties and highlights the need to utilize insights from soil chemistry.

Four geographically distinct regions of Scotland are used to describe temporal and spatial trends in soil phosphorus (P) using ca. 180 000 routine advisory samples which included information on previous and next crop. Regional differences in Modified Morgan's extractable P concentrations exist primarily in response to differences in land use and particularly the greater role of livestock in the west compared to arable cropping in the east. No obvious or consistent temporal trend in extractable P was apparent, but a very wide range of soil properties and extractable P concentrations was evident. The current (since 2010) target soil P status is moderate (M) for cereal-based arable rotations and the upper half of moderate (M+) for rotations with potatoes, and more than half the samples fell into this range (with 40% M-). Some ca. 30% of samples fell below this, while 14% had high or very high P status, most noticeably where the previous crop was either potatoes, vegetables or berries. Half (ca. 13 000) of the samples with a low soil P status also had a below optimum pH. An apparent contradiction between the regularly reported long-term declines in agricultural P surplus not being matched by a drop in extractable soil P status is discussed. This 'lag effect' means many Scottish agricultural soils have the capability to buffer change in extractable soil P. We make the first attempt to link advisory P data with information from the National Soil Database of Scotland and explore the value of introducing 'soil type' into the P fertilizer recommendation system.

Concentrations of six elements copper (Cu), molybdenum (Mo), cobalt (Co), boron (B), sulphur (S) and zinc (Zn) are summarized for Scottish advisory soil samples collected during the period 19962008. Accompanying cropping information indicated that the majority of samples collected for Co analysis were from grassland compared with B, S and Zn where sampling was predominantly prior to either potatoes or vegetables. The proportion of samples measured as potentially deficient [very low (VL) or low categories] were 80% for Co, compared with 50, 40, 38, 25 and 18% for Mo, S, Zn, Cu and B, respectively. Only S displayed a significant decline (ca. 2 mg S/kg) over this 13-year period. However, comparison of Cu and Co data with some collected from an earlier time period (19731980) suggested little difference for Cu but a smaller number of VL and low Co status samples. A predicted risk assessment using soil parent material, texture and drainage status suggested that 22, 38 and 40% of the agricultural area of Scotland were at a high, medium and low risk of Cu deficiency; comparable numbers for Co were 48, 30 and 22%. The reliability of the risk assessment was tested using a sub-set of advisory samples with specific information on soil series. Of the soils predicted to have a high risk of Cu deficiency, 52% actually fell into the deficient status. A similar comparison for Co indicated 90% of the samples predicted as having a high risk of deficiency were measured as VL or low.

Summary This paper describes some aspects of a project whose objective is to develop sustainable strategies for local produce, with an emphasis on organic systems and trace element cycling. It aims to provide knowledge on soil management and crop species/variety selection in order to optimise trace element use in such systems. A range of trace elements have been considered, including B, Co, Cu, Fe, Mo, Mn, Ni, Se and Zn. Agricultural activities in Sweden and Scotland are the main project focus, with identification of areas and soil types in these countries with contrasting parent material and trace element concentrations a core aim. Linkages between these and potential trace element deficiencies of crops and livestock are being sought. The potential of common and novel forage species to provide components of ruminant diets based on their ability to take up/concentrate trace elements on contrasting soils are being investigated. This paper concentrates on the Scottish component of the project, and highlights information collated as part of the project’s reviewing process as well as the presentation of previously unpublished data.

Two contrasting phases of work are described that help inform the development and requirements of a soil monitoring system: firstly, the development and application of a multi‐criterion analysis of soil quality indicators grounded in the basic natural sciences; and secondly, scrutiny of the outcome of that process by a wide range of non‐specialist but key stakeholders at a workshop. This process ensures that the final monitoring design meets both the scientific rigour expected from a monitoring system and as far as possible meets the aspirations of policy and regulatory stakeholders. Individual indicators of soil quality were evaluated in terms of their applicability against a number of important environmental and logistical parameters and therefore their overall fitness for purpose. These included relevance to different soil types, functions, habitats and threats to soil, the inherent variability of soil, and a range of technical aspects such as analytical complexity, precision and reproducibility of analytical results and whether a standard operating procedure (SOP) existed for the technique. A tiered approach to soil monitoring was supported by workshop delegates. This will require indicators that are suitable and effective at national, site‐specific and process‐level scales. In addition, the opportunities for synchronizing soil monitoring with air and water quality monitoring should be considered and the potential for integrating on‐site measurements with remote methods should be researched further. It was considered by workshop attendees that soil monitoring should be rooted in pedological principles (i.e. recognizing defined soil horizons) to ensure that results can be extrapolated from individual sites and to retain flexibility.

The entry of Pb into the food chain is of concern as it can cause chronic health problems. The concentration of Pb was determined in cereal grain samples collected representatively from British Cereal Quality Surveys in 1982 and 1998 (n=176, 250 and 233 for wheat collected in 1982 and 1998, and barley in 1998, respectively). In addition, paired soil and grain samples were collected from 377 sites harvested across Britain in 1998–2000. Wheat grain Pb ranged from below the analytical detection limit (0.02mgkg−1 dry weight, DW) to 1.63mgkg−1 DW, and barley grain Pb from <0.02 to 0.48mgkg−1 DW. The vast majority of samples (>99% for both wheat and barley, excluding Scottish barley samples collected in 2000) were well below the newly introduced EU limit for the maximum permissible concentration of Pb in cereals (0.2mgkg−1 fresh weight, equivalent to 0.235mgkg−1 DW). There was a significant reduction in wheat grain Pb in the 1998 survey compared with the 1982 survey. However, 40 barley samples collected from Scotland in 2000 in the paired soil and crop survey showed anomalously high concentrations of Pb, with 10 samples exceeding the EU limit. Washing experiments demonstrated that surface contamination, introduced during grain harvest and/or storage, was the main reason for the high concentrations in these samples. In the paired soil and crop surveys, there were no significant correlations between grain Pb concentrations with total soil Pb and other soil properties, indicating low bioavailability of Pb in the soils and limited uptake and transport of Pb to grain. The Pb in cereal grain is likely to originate mainly from atmospheric deposition and other routes of surface contamination during harvest and storage.

The EC Nitrate Directive (91/676), agreed by the EC Environment Council in 1991, is an environmental measure designed to protect water against pollution caused by nitrate from agriculture. In 2000, the River Ythan catchment, a 68 000 ha area of predominantly agricultural land in NE Scotland, was designated a nitrate vulnerable zone (NVZ) by the Scottish Executive. A combination of reasons for designation was suggested, including evidence of elevated nitrate concentrations in the surface waters of the catchment together with the criteria set out at Annex IA(3) of the EC Nitrates Directive, i.e. that the estuary is eutrophic or in the near future may become eutrophic. Evidence from the Scottish Environment Protection Agency surface water monitoring sites has revealed several tributaries of the Ythan with nitrate concentrations exceeding the maximum permitted level of 50 mg l(-1) (11.3 mg l(-1) NO3-N) and a rising trend in the main river channel. There has been an approximate threefold increase in surface water nitrate concentrations since the early 1960s to a current value of similar to 35 mg l(-1) (8 mg l(-1) NO3-N). There is separate evidence of elevated nitrate concentrations in groundwater. The amounts of fertiliser N applied annually has also increased substantially and in 1994 these were estimated to be similar to 60% of the total N (equivalent to 194 kg ha(-1)) added to the catchment. Various stages have been involved in the decision to designate including documents for public consultation and a proposed Action Programme. However, several issues remain to be resolved, especially the extent to which a causal relationship actually exists between the increased loss of nitrate to the estuary and algal growth. Being able to accurately apportion sources of N 'supply' with periods of 'uptake' within the aquatic system is complicated. Here we suggest that an estimated 70% of the terrestrially derived nitrate input to the estuarine system actually occur out with the main period of algal growth. This emphasises the need for a greater understanding of the spatial and temporal linkages that exist between N cycling in terrestrial and aquatic ecosystems particularly as this will directly influence the likely success and cost effectiveness of remedial measures taken to relieve the symptoms of eutrophication. (C) 2003 Elsevier B.V. All rights reserved.

.............................................................................................................................................. 5 INTRODUCTION ..................................................................................................................................... 6 MATERIALS AND METHODS............................................................................................................ 1

Use of fertilizers and manures during 1994 were studied at the farm and catchment scale in the largely agricultural Ythan catchment, north-east Scotland, using farm level census data supplemented by questionnaire data. Grassland accounted for 40% of the agricultural land, and seven farm types represented 87% of the total land, having an average size of 90 ha. The average livestock density of 1·2 livestock units/ha was high compared to Scotland as a whole (0·5). Rates of inorganic fertilizer applied to individual crops in the area corresponded with the national average and current advisory recommendations. At the catchment scale, most fertilizer N was applied to grassland (47%), whereas spring crops received the greatest proportion of the fertilizer P (35%). The annual manure production equated to an average over the catchment of 63 and 16 kg/ha of N and P, respectively. When calculated for farm types these figures ranged from 27 and 6 kg/ha on ‘cereal’ farms to 384 and 163 kg/ha on ‘pig’ farms. The ratio of applied fertilizer N and P varied from 4[ratio ]1 for ‘general cropping’ to 10[ratio ]1 for ‘cattle and sheep (lowground)’ farms. There was no significant compensatory reduction in inorganic fertilizer applications on crops, which also had received manures.

Farm nutrient budgets related to 1994 were calculated for seven farm types, accounting for similar to 90% of the agricultural land in the River Y han catchment, NE Scotland. The magnitude offIuxes of nitrogen (N) and phosphorus (P) at the catchment scale in relation to these farm types was also assessed. Positive budgets were calculated for all farm types, with the largest surpluses estimated for intensive Livestock units. Nutrient efficiency, defined as a percentage of outgoing over incoming nutrients, ranged from 11% (N) and 21% (P) on 'cattle and sheep' farms in less favoured areas to 54% (both N and P) on 'cereal' farms. The contribution from cropping versus Livestock farming in the total efficiency varied widely between farm types. At the catchment scale the surplus associated with grassland and Livestock (225 and 37kg ha(-1) of N and P) clearly exceeded that associated with arable crops (44 and 19kg ha(-1) of N and P). (C) 2000 Society of Chemical Industry.

A suggested increase in the growth of macrophytic algae within the Ythan estuary (N.E. Scotland) over recent years has been linked to the increased amounts of nitrogen in the form of NO3–N entering the estuary from the river. The increased NO3 concentration in the river has been associated with recent changes in farming practices in this predominantly agricultural catchment. Terrestrially derived phosphorus is also considered to contribute increasingly to eutrophication of fresh waters. Historical agricultural census data together with appropriate surveys of fertilizer practice were used to calculate the total quantities of fertilizer and manure derived N and P applied annually over the wholeYthan catchment during the period 1960 – 1990. While the total agricultural land area has remained similar, significant changes in cropping practice have occurred. In particular, a greater proportion of land is given to autumn sown crops while the area of grassland has declined. These changes in farming practice are associated with differences in both the total amounts and timing of fertilizer applied. The use of inorganic N in the catchment has trebled since 1960 and is currently approximately 6400 tonnes (104 kg N/ha). The use of P has decreased by more than a quarter to 1274 tonnes (21 kg P/ha) over a similar time period. There has been no obvious change in total quantity of N and P derived from animal manures, estimated to be 44 and 11 kg per ha, respectively, when averaged over the area of agricultural land. Cattle and sheep numbers have remained relatively constant and together account for approximately 80% of the manure N and 70% of the manure P produced annually. However, poultry have declined by 70% since 1960 while pig numbers have increased six-fold. The average annual application rate of manure derived N over the whole catchment (44 kg/ha) is considerably below that proposed at the farm scale in the EC Nitrate Directive (210–170 kg/ha). However, on a local scale difficulties may arise for large manure producing concerns such as dairy or pig units.

A pot experiment was carried out in order to test the hypothesis that manganese nutrition of wheat was dependent on the phosphorus status of soil as well as on its pH and manganese status. An arable mineral soil whose lime and phosphorus status had been massively adjusted more than 18 years previously was compared with identical soil not so adjusted. Wheat plants were grown to maturity in these soils. Analyses were carried out on both soil and plant samples at intervals. Data for soil pH, soil solution concentrations of manganese and phosphorus, plant dry weight and tissue concentrations of manganese and phosphorus are presented. Concentrations of manganese were depressed in leaf tissue of plants from limed soils and also in high phosphorus soils. The depressed values for limed treatments were explained in terms of depressed soil solution manganese concentrations resulting from elevated pH. The results for high phosphorus soils could not be related to soil solution composition. It was suggested that high soil phosphorus resulted in elevated plant phosphorus which interfered in the uptake and/or translocation of manganese.