Karin Blombäck

Modelling C, N, water and heat dynamics in winter wheat under climate change in southern Sweden

Abstract The possible consequences of climate change on carbon and nitrogen budgets of winter wheat were examined by means of model predictions. Biomass, nitrogen, water and heat dynamics were simulated for long-term climatic conditions in central and southern Sweden for a clay soil and a sandy soil. The effects of elevated atmospheric CO2 and changed climate as predicted for 2050 were simulated daily with two linked process orientated models for soil and plant (SOIL/SOILN). The models had previously been calibrated against several variables at the sites under present conditions, and the long-term predictions at present climate were shown to correspond reasonably well with measured soil C and N trends in long-term experiments. The climate and CO2 conditions for the year 2050 were represented by climatic scenarios from a global climate model, and the elevated atmospheric CO2 concentration was assumed to change plant parameter values in accordance with literature data. For the year 2050, winter wheat production was predicted to increase by 10–20% (depending on soil type) compared with the present value. Plant N concentration decreased although N mineralisation increased by 18%. Drainage was predicted to increase which resulted in increased N leaching by 17%, and the decrease in soil C became larger. The predictions were found to be most sensitive to assumptions concerning changes of radiation use efficiency, stomatal conductance, air temperature and precipitation. Hence, the load of N and C to surrounding ecosystems and the atmosphere, on a ground surface basis, was predicted to increase under climate change. However, because the harvest will increase, these negative effects of climate change on a yield basis will be almost zero, except that N leaching from the sandy soil will still increase.

Simulations of soil carbon and nitrogen dynamics during seven years in a catch crop experiment

Abstract This study aimed, with the use of simulation models, to quantify the effect of several years incorporation of catch crop material into the soil on soil organic matter storage, N mineralisation capacity and risk for N leaching. C and N dynamics in crop and soil were simulated with the SOILN model (Version 9.2). The simulated results were compared with measurements of crop and soil N, crop biomass and N-leaching from a catch crop field experiment situated in southwestern Sweden. The generality of parameter values determining the long-term turnover of soil organic matter was tested. To reproduce measured soil mineral N and crop N, mineralisation had to be favoured by high C mineralisation. After 6 years of catch crop treatment, simulated soil organic matter content had increased by less than 2%, but the N-mineralisation capacity had increased by 25%, corresponding to 37 kg N ha−1. With a continuous annual use of catch crops only a few per cent of the extra mineralised N was leached. Without a succeeding catch crop, however, 30% of N from the increased mineralisation was leached. The results indicated that the decomposition rate increased immediately after frost events.

Applicability of models to predict phosphorus losses in drained fields: a review.

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.

Simulation of water and nitrogen flows and plant growth for a winter wheat stand in central Germany

Abstract Two linked simulation models were applied to an experimental loam site at Neuenkirchen, Germany, for the years 1989 and 1991, using a data set with soil and plant properties for winter wheat. Simulations of soil water and heat dynamics were performed with the SOIL model. Both years were rather dry. For the first year, soil water content and soil water tension were calibrated by tuning the saturated hydraulic conductivity. The simulations showed good correspondence with the measurements during the first six months down to 130 cm depth. However, the dynamics of the simulated water tension in deeper layers was poor compared to the measurements. Using the same parameterization for 1991, the model simulated soil moisture dynamics reasonably well in the upper 70 cm. Below this depth, the water content was underestimated. Soil and plant nitrogen dynamics, litter decomposition and plant biomass production were simulated with the SOILN model. The model was tested against measurements of leaf, stem and grain biomass and nitrogen, leaf area and soil nitrate and ammonium content. It was calibrated for the first year (1989) and validated in 1991. Parameters related to translocation of assimilates and nitrogen from different tissues to grain were estimated by calibration. The simulated plant properties in 1989 explained about 95% of the variations in measured values. A similar agreement was obtained for the validation year. The corresponding value for soil mineral nitrate in 1989 was only 38%, mainly due to problems in reproducing the dynamics in the upper 30 cm in connection to fertilization applications. In deeper layers up to 90% of the variation was explained. For nitrate in 1991 and ammonium the agreement between simulated and measured values was poor.

Simulated growth and nitrogen dynamics of a perennial rye grass

Abstract The growth and nitrogen uptake of Italian Rye Grass ( Lolium multiflorum Lam.) used as a catch crop were studied in 1988/1989 and 1990/1991 with the aim of determining the extent to which differences between the two years could be explained by variation in climatic conditions. The experimental field was situated about 50 km south of Halmstad close to the Swedish west coast (56°30′N; 13°00′E, 10 m elevation). The SOILN model, which considers the major flows of nitrogen and carbon in both plant and soil, was used to evaluate the importance of three growth factors, i.e., solar radiation temperature and nitrogen status, under autumn and winter conditions. The model was calibrated against measured total plant biomass ( r 2 = 96%) and nitrogen ( r 2 = 95%) together with soil mineral nitrogen in 1988/1989 and validated on an independent dataset in 1990/1991. Measured increases in biomass and nitrogen were much lower in 1990 than in 1988 (79% and 68% lower, respectively). The simulations were able to explain 90% of the observed between-year variation in relative growth rate. The higher maintenance respiration in 1990 was the main factor responsible for the differences observed. In 1990, plant N was well simulated ( r 2 = 89%), whereas estimates of plant biomass was high ( r 2 = 76%).

Demand-driven fertilization. Part I: Nitrogen productivity in four high-maintenance turf grass species

Abstract 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.

Priorities for sustainable turfgrass management: a research and industry perspective

Abstract 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.

Demand-driven fertilization. Part II: Influence of demand-driven fertilization on shoot nitrogen concentration, growth rate, fructan storage and playing quality of golf turf

Abstract 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.