The single-point P sorption index (PSI), which is defined as the ratio of sorbed P (S) to the log P concentration in soil solution following a single P addition, is often used to estimate maximum soil P sorption capacity (S-max). Although studies have found good correlations between PSI and S-max as determined from fitting the Langmuir model to complete sorption isotherm data, a thorough analysis of the role of added P concentration on this relationship is needed. Our first objective was to investigate the effect of added P concentration on the correlation between PSI and S-max as determined by the Langmuir equation. Our second objective was to determine if S was better than PSI for predicting S-max. Using numerical simulations, we tested the correlation between S-max and PSI for added P concentrations of 75, 100, 150, and 200 mg P L-1. Results of the simulations show that the strength of the correlation between S-max and PSI increases with increasing P concentration. Our results also show that PSI was a better predictor of S-max than S for added concentrations of 75 and 100 mg P L-1, whereas at the higher rates S was a slightly better predictor of S-max and gave a direct estimate of S-max rather than the relative estimate obtained from PSI. Results from P sorption data measured on soils from Maryland and Sweden were consistent with our results from the numerical simulations. Our findings highlight important limitations of using PSI for estimating S-max.

In response to concerns over the translocation of P from soils to P-sensitive water bodies, there is high demand for developing simple indicators for evaluating a soil's risk of releasing P into solution. Many studies have shown that the degree of soil phosphorus saturation (DPS), calculated as the ratio of soil P concentration to soil P sorption capacity (PSC), is good predictor of a soil's risk of releasing Pin solution. In this study we compared four different DPS indices in how well they predicted dissolved P following extraction with either a 0.01 M caCl2 (P-caCl2) solution or deionized water (P-w). The first two indices were calculated from the ratio of extractable P to extractable Al and Fe using either acid ammonium oxalate (Al-OX + Fe-OX) or ammonium lactate solutions (Al-AL + Fe-AL). The second two DPS indices were calculated from the ratio of either Olsen-extractable P or AL-extractable P with sorption capacity estimated from the single point P sorption index (PSI). On a subset of 11 soils, we compared the different methods for estimating PSC with fitted Langmuir sorption maximum (Smax) using data from complete sorption isotherms. Both (Al-OX + Fe-OX) and PSI were well correlated with Smax and hence regarded as good estimates for P sorption capacity. Conversely, (Al-AL + Fe-AL) was not significantly correlated with Smax. P saturation calculated from PSI together with P-AL or P-O1s predicted P-caCl2 and P-w, best, whereas P saturation calculated from ammonium oxalate predicted P-caCl2 and P-w the least. We did not find notable improvements in the regression models when we added a second explanatory variable (clay content, pH or total carbon) to the models. Our results show that multiple measures of P saturation provide similar predictions of a soils potential for releasing dissolved P into soil solution. This provides flexibility in how P saturation indices are calculated to identify leaching prone hotspots.

Most phosphorus (P) modeling studies of water quality have focused on surface runoff loses. However, a growing number of experimental studies have shown that P losses can occur in drainage water from artificially drained fields. In this review, we assess the applicability of nine models to predict this type of P loss. A model of P movement in artificially drained systems will likely need to account for the partitioning of water and P into runoff, macropore flow, and matrix flow. Within the soil profile, sorption and desorption of dissolved P and filtering of particulate P will be important. Eight models are reviewed (ADAPT, APEX, DRAINMOD, HSPF, HYDRUS, ICECREAMDB, PLEASE, and SWAT) along with P Indexes. Few of the models are designed to address P loss in drainage waters. Although the SWAT model has been used extensively for modeling P loss in runoff and includes tile drain flow, P losses are not simulated in tile drain flow. ADAPT, HSPF, and most P Indexes do not simulate flow to tiles or drains. DRAINMOD simulates drains but does not simulate P. The ICECREAMDB model from Sweden is an exception in that it is designed specifically for P losses in drainage water. This model seems to be a promising, parsimonious approach in simulating critical processes, but it needs to be tested. Field experiments using a nested, paired research design are needed to improve P models for artificially drained fields. Regardless of the model used, it is imperative that uncertainty in model predictions be assessed.

Den mangd naringsamnen som transporteras fran Sveriges yta och belastar havet utgor ett viktigt beslutsunderlag for nationell och internationell vattenforvaltning. Den mest omfat-tande berakningen ...

Cropping systems with high phosphorus (P) inputs may constitute a risk of P leaching, which contributes to eutrophication. The main objective of this study was to identify P leaching risks associated with three long-term fertilization regimes in separately tile-drained plots on a sandy soil in southwest Sweden. The three regimes resulted in different annual P surpluses of, on average, 16 kg P ha−1 (14 lb P ac−1) in mineral form and 18 kg P ha−1 (16 lb P ac−1) and 37 kg P ha−1 (33 lb P ac−1) as pig slurry. The importance of different soil characteristics (soil P, iron, aluminum, and calcium content, and degree of P saturation [DPS]) and processes (water flow and P sorption/desorption) was examined using 15 years (1989 to 2003) of P leaching measurements and simulations with the ICECREAM model. Measurements of high soil P content and DPS values in the topsoil, in combination with high precipitation and rapid water flow, indicated a high potential for P losses, which was confirmed by the model simulations. However, the model considerably overestimated total P leaching by a factor of 5 to 9 since measured P leaching was small for all treatments. Measured mean annual total P leaching and total P concentration ranged respectively from 0.14 kg ha−1 (0.12 lb ac−1) and 0.06 mg L−1 (3.75 × 10−6 lb ft−3) at a high rate of slurry application to 0.20 kg ha−1 (0.18 lb ac−1) and 0.08 mg L−1 (4.99 × 10−6 lb ft−3) in the mineral P treatment. The differences in concentration were statistically significant (p < 0.001). A main conclusion from this 15-year study was that annual pig slurry application rates of 37 to 58 kg P ha−1 (33 to 52 lb P ac−1) did not increase P leaching. High sorption capacity of the subsoil, caused by Fe, Al, and Ca, was obviously very important for controlling P losses. Thus, information on soil P content and fertilization must be supplemented with estimates of soil P sorption capacity when evaluating the risk of P leaching for different soils. This must also be considered in models used for assessment of P leaching from arable land. The current ICECREAM model does not include appropriate functions for describing P sorption/desorption processes in this type of soil and needs further development.

I samband med retentionsberakningar i vissa avrinningsomraden med aker pa ler-jordar har problem uppstatt med laga bruttobelastningar. Detta skulle kunna bero pa for laga kvavehalter for lerjordar ...

The ability of demand-driven fertilization, based on the growth potential provided by solar radiation and temperature, to regulate golf turf characteristics such as growth rate, leaf nitrogen (N) concentration, carbohydrate storage and playing quality was investigated in a 2-year field experiment at Landvik, Norway. Three N regimes (100, 60 and 40% of the estimated N requirement for maximum growth) were applied on a sand-based green with a turf cover consisting of creeping bentgrass, colonial bentgrass, velvet bentgrass, slender creeping red fescue or chewings fescue. In the 100% treatment, this corresponded to 3 (creeping bentgrass), 2.1 (colonial and velvet bentgrass) and 1.5 (chewings and slender creeping red fescue) kg N 100 m(-2) yr(-1). The weekly liquid fertilizer dose basically followed the potential growth curve provided by solar radiation and temperature from early April to late October. The turf was exposed to artificial wear and daily maintenance followed conventional standards. Growth, leaf N concentration, carbohydrate storage in clippings, green appearance and playing quality were determined once per month. The results indicated that solar radiation and temperature can successfully be used as driving variables when quantifying turf fertilizer requirements from early spring to late autumn. The desired leaf N concentration, i.e. growth rate, and the resulting effects on fructan content and playing quality can be achieved by raising or lowering the seasonal fertilizer curve. A leaf N level of 3.1-3.5% was indicated as the lower limit for producing healthy-looking turf with high playing quality.

I samband med retentionsberakningar i vissa avrinningsomraden med aker pa ler-jordar har problem uppstatt med laga bruttobelastningar. Detta skulle kunna bero pa for laga kvavehalter for lerjordar ...

The effect of four nitrogen (N) availabilities on growth, leaf N concentration, N productivity (dry matter production per unit time and unit N taken up), shoot: root ratio and carbohydrate storage was studied in velvet bentgrass (Agrostis canina 'Legendary'), creeping bentgrass (A. stolonifera 'Independence'), slender creeping red fescue (Festuca rubra ssp. trichophylla 'Cezanne') and chewings fescue (F. rubra ssp. commutata 'Center'). In growth chamber experiments, plants were grown for 3 weeks in sand with 12.5, 25, 50 or 200 mg N L-1 in the irrigation water and at two mowing intensities, cut at 5 mm twice per week or uncut. It proved possible to control important turf grass traits such as shoot growth rate, shoot: root ratio, leaf morphology and carbohydrate storage through leaf N concentration. The relationship between leaf N concentration and aboveground growth was linear for both cut and uncut turf. The relative N demand of the studied species, based on their N productivity, was 1: 0.67: 0.67: 0.37 for creeping bentgrass, velvet bentgrass, chewings fescue and slender creeping red fescue, respectively. Clipping significantly reduced N productivity, and hence turf N demand. The lowest possible leaf N concentration without adverse effects on plant health and appearance was between 3.1 and 3.5% of dry matter (DM) in both bentgrasses and fescues. This value can be used as a target in minimizing fertilizer usage and N leaching losses. In conclusion, fertilization based on the influence of leaf N concentration on growth-related processes offers possibilities to control growth in a predictable and desirable manner under varying climate and growth conditions. This could provide more environmentally friendly and economic fertilization regimes and also better playing quality.

This paper provides a brief review and assessment of the key environmental, regulatory and technical issues facing the turfgrass sector with specific reference to the European context. It considers the range of externalities or 'drivers for change' facing the industry, and the challenges and opportunities available for promoting and achieving more sustainable turfgrass management within the sports, landscape and amenity sectors. The analysis confirms that there are a number of key areas where a concerted research and industrial effort is required. These include responding to the pressures from government demands for greater environmental regulation, the increasing pressure on natural resources (notably water, energy and land), the emerging role of turf management in supporting ecosystem services and enhancing biodiversity, the continued need to promote integrated pest management, and the looming challenges posed by a changing climate, and urgent need to adapt. Whilst many of these externalities appear to be risks to the sports turf industry, there will also be significant opportunities, for those where the labour, energy and agronomic costs are minimized and where the drive to adopt a multifunctional approach to sportsturf management is embraced.

Pa uppdrag av Naturvardverket har SMED genomfort berakningar av kvave- och fosforbelastningar pa vatten och hav i Sverige for ar 2009. Berakningarna har ge-nomforts med PLC5-metodik och underlag fo ...

The aim of the project was to find a method to predict the potential growth and winter hardeness of three turf grass species as a function of different light and temperature conditions. Good knowledge of the potential growth is the basis for planning of a sound sustainable maintenance program, both regarding turf grass quality and economical and environmental concerns. A simulation model for grass growth and winter mortality was used to estimate growth curves and winter survival for three different turf grass species (Agrostis stolonifera, Festuca rubra and Poa annua) for different climatic conditions. Four locations in the Nordic countries (Umeå, Västerås and Lund in Sweden and Særheim in Norway) were modeled. The three different places in Sweden represented different light and temperature conditions due to different latitudes. Særheim in Norway was selected to represent a more maritime climate. The effect of different climate change scenarios was also tested. Field data from Fullerö GK, Västerås was sampled during 2007 and 2008 to be used for calibration of the model. The established model could reproduce growth pattern of turfgrass (Agrostis stolonifera) within the range of measurements several years when compared to independent data of grass clippings. However, there are still many uncertainties in the parameterization of the model, and especially with the winter mortality part, because the lack of physiological knowledge of the grass species studied and a lack of observations to test the model against. The results on winter mortality showed very interesting results and identified the complexity between the two opposite processes of hardening and dehardening and the interaction with the climatic conditions during winter to determine the effects on plant mortality. The model showed that although a milder climate reduced the risk for temperatures below the minimum temperatures for grass tolerance at maximum hardening, mild autumns can lead to a less effective hardening so that maximum hardening never is reached. The weaker hardening made the grass more sensitive to low temperatures. A milder climate also decreased the number of days during winter with snow cover. The number of days with snow cover and the depth of snow are very important parameters for the soil surface temperature and thus for the survival of the turf.

SummaryPrevious comparisons of measured phosphorus (P) losses and simulatedresults obtained using the ICECREAMDB model revealed certainsystematic deviations that could be attributed to soil texture in the studyareas. In the previous investigation, simulations were performed with thestandard parameterisations for different soil textures that are used for thePLC5 calculations. Before the next set of PLC we therefore deemed itimportant to review the generality of soil texture-related parameterisationand to make an assessment of its site-specificity. This report describespreliminary work in which soil texture-related PLC5 parameterisation andmore site-specific parameterisation were tested in three different fieldsincluded in the environmental monitoring programme ‘Observation fieldson arable land’. The soil texture in these fields consists of sandy loam andloam and the fields were chosen because they represent soils that occur inall leaching regions of Sweden, corresponding to over 50% of theagricultural area in 12 of the 22 regions, and therefore play an important rolein calculation of the regional leaching coefficients.The results showed that the standard parameterisations from the PLC5calculations used for the ICECREAMDB model generally functioned wellas regards capturing the run-off pattern in the three observation fields forsimulation of 5-9 year periods. Starts and stops of run-off events werecaptured but the size of the peak flows as well as the accumulated run-offwere underestimated. In contrast, the simulated results of P losses, bothtotal-P and dissolved-P, were overestimated with the standardparameterisations.The site-specific parameterisation further underestimatedrun-off, while overestimation of total-P losses decreased.In the tests on site-specific parameterisation, the value given to the waterstorage capacity in the soil, i.e. porosity, field capacity and wilting point,was critically important for total run-off and for the distribution of flowsbetween surface run-off, macropore flow and flow in the micropore region.Since water flows in turn control P flows in the model, these parameterswere also highly important for the P flows. Small changes in clay contentand pH both had a large impact on simulated P losses. Not in any of thecases did the site-specific parameterisation improve the simulated resultscompared to parameterisation according to PLC5.The study presented was an introductory test of a few of the standardparameterisations used for the PLC5 calculations. A continued study,financed by the SLU Environmental mentoring and assessment program willbe performed during 2009 to cover more soil types and a broader spectrumof climatic variations.