Audun Korsaeth - Profile on Academia.edu (original) (raw)

Papers by Audun Korsaeth

Long-term effects of cropping systems on the earthworm populations in a loam soil

Relations between a Commercial Soil Survey Map Based on Soil Apparent Electrical Conductivity (ECa) and Measured Soil Properties on a Morainic Soil in Southeast Norway

The aim of this study was to compare production and policy risk of organic, integrated and conven... more The aim of this study was to compare production and policy risk of organic, integrated and conventional cropping systems in Norway. Experimental cropping system data (1991-1999) from eastern Norway were combined with budgeted data. Empirical distributions of total farm income for different cropping systems were estimated with a simulation model that uses a multivariate kernel density function to smooth the limited experimental data. Stochastic efficiency with respect to a function (SERF) was used to rank the cropping systems for farmers with various risk aversion levels. The results show that the organic system had the greatest net farm income variability, but the existing payment system and organic price premiums makes it the most economically viable alternative.

Synthesis of the Apelsvoll Cropping System Experiment in Norway – Nutrient Balances, Use Efficiencies and Leaching

Organic Crop Production – Ambitions and Limitations, 2008

In this overview, a synthesis of the first 10 years of the Apelsvoll cropping system experiment, ... more In this overview, a synthesis of the first 10 years of the Apelsvoll cropping system experiment, located in southeast Norway, is given. All major flows of N, P and K in six different cropping systems, each covering 0.18 ha of separately tile-drained plots, were either measured or estimated. The effects of the cropping system on the soil nutrient pools (total-N,

Stepwise chemical digestion, near-infrared spectroscopy or total N measurement to take account of decomposability of plant C and N

Soil Biology & Biochemistry, 2007

Mechanistic, multi-compartment decomposition models require that carbon (C) and nitrogen (N) in p... more Mechanistic, multi-compartment decomposition models require that carbon (C) and nitrogen (N) in plant material be distributed among pools of different degradability. For this purpose, measured concentrations of C and N in fractions obtained through stepwise chemical digestion ...

Comments on the recently published study: "Compositional differences in soybeans on the market: glyphosate accumulates in Roundup Ready GM soybeans", by T. Bøhn, M. Cuhra, T. Traavik, M. Sanden, J. Fagan and R. Primicerio (Food Chemistry 2014, 153: 207-215)

Food chemistry, 2015

Soil Biology and Biochemistry, 2002

Economical and ecological criteria for optimal N fertilization are inherently in con¯ict, largely... more Economical and ecological criteria for optimal N fertilization are inherently in con¯ict, largely due to lack of precise predictions of nitrogen availability as a function of agronomic practice and weather conditions. This problem is particularly pronounced in organic farming, where plant N supply depends on microbial mineralization of organic N such as`green manure'. In the present paper, N dynamics after incorporation of a mixture of a green manure material (undersown white clover) and barley straw was investigated in laboratory and ®eld experiments. Nitrogen¯ows in the soil±plant system were further analyzed with simulation models (COUP: heat and water transport model, SOILN_NO: soil nitrogen model). Our laboratory experiments showed that the incorporation of a mixture of N-rich white clover material and N-poor barley straw created a transient accumulation of clover derived inorganic N during the ®rst period. Thereafter, microbial N demand during straw C utilization resulted in net immobilization of most of the clover derived inorganic N. As a consequence, the synchronization between net N mineralization and plant N uptake would be better by spring than autumn incorporation. This was largely con®rmed both by measurements and simulations. However, the expected bene®t of spring incorporation (ploughing) was counteracted by a large loss (36%) of clover material due to freeze/thaw damage and subsequent surface runoff during the winter. Such winter loss is likely to be a rare phenomenon, however.

Soil Biology and Biochemistry, 2001

Plant±microbe competition for inorganic N is a common phenomenon in soils, and the traditional vi... more Plant±microbe competition for inorganic N is a common phenomenon in soils, and the traditional view is that microorganisms are much stronger competitors than are plant roots. We challenged this view, hypothesizing that the balance between the two competitors is strongly dependent on the spatial heterogeneity of the soil. We constructed a model to explore this hypothesis. The model was structured to simulate a laboratory experiment where N-limited plants were grown in a soil containing two types of microbial ªhotspotsº; with high potential for either net N-immobilization (straw particles) or net N mineralization (clover particles). In this experiment (Wang and Bakken, 1997), plant roots appeared to compete successfully with microorganisms for inorganic N, and their competitiveness depended strongly on the distance (3, 6, 9 or 12 mm) between the layers of straw and clover material. Most model parameters were taken from the literature, whilst some parameters were estimated by least square model optimization using selected treatments within the experiment. The parameterized model was then statistically evaluated against treatments not used in the parameterization. The model ef®ciently simulated the observed transient inorganic N accumulation in unplanted soil and its dependency on distance between hotspots (modelling ef®ciency, EF 0.611). It also captured very well the plant N uptake and its dependency of the distance between hotspots (EF 0.860). The modelling exercise underscored the importance of soil heterogeneity in determining the outcome of the competition between plant roots and microorganisms for inorganic N in soil. Spatial segregation of hotspots with net N-immobilization and net N mineralization is likely to be the rule rather than the exception in natural soils. This has a profound impact on the N dynamics of soil plant systems, and it should be taken into account for the interpretation of experiments (such as 15 N pool dilution experiments) as well as in general models for the C and N dynamics of soil±plant systems. q

Precision Agriculture, 2006

Spring barley was grown for 4 years (2001)(2002)(2003)(2004) in field trials at two sites on mora... more Spring barley was grown for 4 years (2001)(2002)(2003)(2004) in field trials at two sites on morainic soil in central SE Norway, with five N level treatments: 0, 60, 90, 120 and 150 kg N ha -1 . Regression analyses showed that a selection of soil properties could explain 95-98% of the spatial yield variation and 47-90% of the yield responses (averaged over years). A strategy with uniform fertilizer application of 120 kg N ha )1 (U N120 ) was compared with two variable-rate (VR) strategies, with a maximum N rate of either 150 kg N ha )1 (VR N150 ) or 180 kg N ha )1 (VR N180 ). These strategies were tested using either Norwegian prices (low price ratio of N fertilizer to yield value; P N /P Y ), or Swedish prices (high P N /P Y ). The VR N180 strategy had the highest potential yield and net revenue (yield value minus N cost) at both sites and under both price regimes. Using this strategy with Norwegian prices would increase the profit of barley cropping as long as at least 40 and 31% of the estimated potential increase in net revenue was realized, respectively. Using Swedish prices, uniform application appeared to be as good as or even better economically than the VR methods, when correcting for extra costs of VR application. The environmental effect of VR compared with uniform application, expressed as N not accounted for, showed contrasting effects when using Norwegian prices, but was clearly favourable using Swedish prices, with up to 20% reduction in the amount of N not accounted for.

Zeitschrift für Pflanzenernährung und Bodenkunde, 1997

Prediction of wheat yield and protein using remote sensors on plots–Part I: assessing near infrared model robustness for year and site variations

Journal of Near Infrared Spectroscopy, 2013

ABSTRACT Validation of reflectance-based prediction models for plant properties is often performe... more ABSTRACT Validation of reflectance-based prediction models for plant properties is often performed on just one or two years of data. Hence, we aimed to perform a more comprehensive study regarding the validation of prediction models for grain yield and protein concentration. A FieldSpec3 portable field spectroradiometer was used to measure canopy reflectance in spring wheat. Spectral reflectance data were collected from three different experimental locations in up to four different years during the period 2007-2010, so that seven unique site years were included, comprising, altogether, 976 individual plots. Several datasets had moderate to severe lodging, which had a markedly negative influence on the prediction results. To correct for this problem, a classification model for the classes "lodging" and "standing crop" was calibrated from the spectral data. The model gave a total classification accuracy of 98.3%. Prediction models for grain yield and grain protein concentration were computed by means of the recent statistical method powered partial least squares (PPLS). Models were calibrated and validated on several combinations of the spectral datasets in order to reveal spatial and temporal effects on the prediction performance. The model performance generally increased with increasing variation in the calibration data, both in time (i.e. more years included) and space (i.e. more sites included). The best model for grain yield explained 94% [root mean square error of prediction (RMSEP)=156 g m(-2)] of the variance and the predictions of grain protein concentration explained 67% [RMSEP=1.51 g dry matter (DM) 100 g(-1)] of the variance. The performance of the grain yield PPLS models was compared with that of models based on some widely used vegetation indices [normalised difference vegetation index (NDVI), modified soil adjusted vegetation index (MSAVI), red edge inflection point (REIP) and d-chl-ab]. The explained variance of the models based on vegetation indices did not exceed 55%, indicating that these models were inferior to full spectrum models. This study shows that one or two years of spectral measurement are insufficient for building fully operational models for cereal property predictions.

$Research paper thumbnail of Near infrared reflectance spectroscopy for quantification of crop residue, green manure and catch crop C and N fractions governing decomposition dynamics in soil$

Near infrared reflectance spectroscopy for quantification of crop residue, green manure and catch crop C and N fractions governing decomposition dynamics in soil

Journal of Near Infrared Spectroscopy, 2004

ABSTRACT For environmental, as well as agronomic reasons, the turnover of carbon (C) and nitrogen... more ABSTRACT For environmental, as well as agronomic reasons, the turnover of carbon (C) and nitrogen (N) from crop residues, catch crops and green manures incorporated into agricultural soils has attracted much attention. It has previously been found that the C and N content in fractions from stepwise chemical digestion of plant materials constitutes an adequate basis for describing a priori the degradability of both C and N in soil. However, the analyses involved are costly and, therefore, unlikely to be used routinely. The aim of the present work was to develop near infrared (NIR) calibrations for C and N fractions governing decomposition dynamics. Within the five Nordic countries, we sampled a uniquely broad-ranged collection representing most of the fresh and mature plant materials that may be incorporated into agricultural soils from temperate regions. The specific objectives of the current study were (1) to produce NIR calibrations with data on C and N in fractions obtained by stepwise chemical digestion (SCD); (2) to validate these calibrations on independent plant samples and (3) to compare the precision and robustness of these broad-based calibrations with calibrations derived from materials within a narrower quality range. According to an internal validation set, plant N, soluble N, cellulose C, holocellulose (hemicellulose + cellulose) C, soluble C and neutral detergent fibre (NDF) dry matter were the parameters best predicted (r2=0.97, 0.95, 0.94, 0.91, 0.90 and 0.94, respectively). However, the calibrations for soluble C and NDF were regarded as unstable, as their validation statistics were substantially poorer than the calibration statistics. The calibrations for all structural N fractions and lignin C were considered poor (r2=0.47-0. 70). By comparing our broad-based calibrations for plant N and NDF with similar calibrations for a sample set representing a commercial forage database, it was evident that the broad-based calibrations predicted a narrow-based sample set better than vice versa. For plant N, the residual mean squared error of prediction (RMSEP), when testing the broad-based calibration with the narrow-based validation set, was substantially smaller than the RMSEP obtained when validating the broad-based calibration internally (1.8 vs 2.7 mg N g -1 dry matter). Overall, the calibrations that performed best were those concerning the parameters most strongly influencing C and N mineralisation from plant materials.

Journal of Arachnology, 2013

The fauna of surface-active spiders was studied in 12 cereal fields, with two types of subcrop, a... more The fauna of surface-active spiders was studied in 12 cereal fields, with two types of subcrop, and in four young (17 months old) perennial leys (grass/clover). The fields were located in the southeastern (A), central (B) and western (C) parts of Norway. In total, 3945 spiders were caught from May to September 2004, using pitfall traps. Linyphidae was the most numerous family, with Erigone atra Blackwall 1833 representing 56% of all trapped individuals. The total numbers of spider species and individuals were significantly higher in leys than in barley at sites where both crops were present (sites A and B), with on average 11 species and 93 specimens in barley, and 20 species and 393 specimens in leys. Thus, young perennial leys appeared to provide a better habitat for spiders than did cereal fields, as has previously been documented for older perennial leys. The use of multi-species crops instead of a single crop species undersown in cereals, tended to result in higher spider species diversity, but it did not influence the total number of specimens. An ordination (DCA) showed a clustering of the spider fauna from the same site, but no clear separation between main crop types (ley vs. barley) was apparent. The main crops, subcrops, and the surrounding environs of the cropped field seem to affect the diversity and abundance of spiders.

Nutrient Cycling in Agroecosystems, 2003

Nitrate leaching is often low from grasslands, primarily due to their long period of N uptake com... more Nitrate leaching is often low from grasslands, primarily due to their long period of N uptake compared to arable crops. In the present paper we explore the combined effects of N input regime, soil type and climatic conditions through a combination of field lysimeter studies and simulation modeling of temporary grassland. A lysimeter consisting of eight 10 × 4 ×

Agriculture, Ecosystems & Environment, 2008

In order to assess long-term effects on productivity, environmental impacts and soil fertility of... more In order to assess long-term effects on productivity, environmental impacts and soil fertility of contrasting farming practices, six cropping systems, ranging from conventional arable without livestock to organic mixed dairy farming with few arable crops, have been compared since 1989 on a loam soil. A decline in soil structure quality was found in a conventional arable system with annual ploughing with no rotational grass. This system had higher bulk density and mean aggregate size than other systems, and lower levels of plant available water and aggregate stability. Opposite trends were related to the proportion of grass leys in the other systems and to their levels of soil organic matter. The latter declined markedly over 15 years in the conventional arable system, and there were smaller declines in most other systems. In an arable system without ploughing, but with rotary tillage in spring, organic matter was maintained and high structural stability was found. This system had high bulk density, but the proportion of small aggregates equalled that found in systems with ley. There were overall increases in earthworm density (84%), earthworm biomass (80%) and the density of earthworm channels (132%) in the topsoil between 1994 and 2004. Most of these increases were found in systems with 1-3 years of ley in the 4-year rotation. Low values of all earthworm parameters, and only minor changes over the period studied, were found in two non-organic arable systems without ley, indicating high pressure on soil fauna. Lower earthworm activity was found in the non-organic arable system with reduced tillage as compared to the non-organic arable system with annual ploughing. Thus, 50% leys in the rotation appeared desirable for the maintenance of satisfactory soil structure and earthworm activity. Though the deterioration of soil structure in the conventional arable system was not extreme, as the soil was well structured initially, the results may have implications for the sustainability of stockless arable systems on soils with a less favourable initial structure. #

Agriculture, Ecosystems & Environment, 2000

For a cropping system to be sustainable, should not only the soil nitrogen (N) content be preserv... more For a cropping system to be sustainable, should not only the soil nitrogen (N) content be preserved but also the N runoff be minimised. Finding a simple but robust way to estimate N runoff would thus be a great advantage when evaluating cropping systems. In this study all major N flows in six different cropping systems, each covering 0.18 ha of a separately pipe drained field lysimeter, located in southeast Norway, were either measured or estimated over a period of 8-years. The effect of the cropping system on the soil N content was evaluated using mass balances of total N, and the usefulness of such N balances to predict N runoff (total N losses via drainage and surface water) was investigated. The experiment included systems with conventional arable cropping (CON-A), integrated arable-cropping (INT-A), ecological arable cropping (ECO-A), conventional forage cropping (CON-F), integrated forage cropping (INT-F), and ecological forage cropping (ECO-F). All the arable cropping systems resulted in a net reduction in the calculated soil N pool, and the reduction increased with decreasing N input. The only system, which did not alter the soil N content, was CON-F. The largest net reduction was estimated for ECO-A and ECO-F, which averaged 45 and 43 kg N ha −1 per year, respectively. The N runoff from the systems was in the range of 18-35 kg N ha −1 per year, with highest losses from the two conventional and lowest from the two ecological systems and INT-F. The forage systems had lower N runoff than the arable systems. The INT-F system appeared to be the most favourable system in terms of both soil N balance and N runoff.

Agriculture, Ecosystems & Environment, 2002

Development of environmentally and economically sound agricultural production systems is an impor... more Development of environmentally and economically sound agricultural production systems is an important aim in agricultural policy and has a high priority in agricultural research worldwide. The present work uses results from the first complete crop rotation period (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997) of the Apelsvoll cropping system experiment in south-eastern Norway to discuss the effect of cropping systems and their management practices on environment, soil fertility, crop yields and the farm economy, and how this knowledge may be used to develop a more sustainable agriculture. The experiment includes conventional arable (CON-A), integrated arable (INT-A), ecological arable (ECO-A), conventional forage (CON-F), integrated forage (INT-F) and ecological forage (ECO-F) cropping systems which were established on model farms of 0.2 ha. On the basis of nutrient runoff, soil erosion and pesticide contamination, the following ranking from the most to the least favourable was made for environmental effects:

The influence of system boundaries on life cycle assessment of grain production in central southeast Norway

Agricultural Systems, 2012

ABSTRACT This study assesses the environmental impacts from production of 1 kg barley, oat and sp... more ABSTRACT This study assesses the environmental impacts from production of 1 kg barley, oat and spring wheat, in central southeast Norway by means of life cycle assessment. The results were given for twelve impact categories, selected based on relevance to the system. These categories are climate change, fossil depletion, freshwater ecotoxicity, freshwater eutrophication, human toxicity, marine ecotoxicity, marine eutrophication, ozone depletion, particulate matter formation, photochemical oxidant formation, terrestrial acidification and terrestrial ecotoxicity. The assessment covers processes from cradle to farm gate, including all farm activities related to grain cultivation, as well as the production and acquisition of machinery, equipments and buildings, diesel and oil, fertilizer, lime, seeds and pesticides.In order to reveal the importance of system boundaries, factors that are included in this study and often excluded in other studies, such as machinery manufacturing, buildings, pesticide production and use, humus mineralization and NOX loss from use of mineral fertilizer were systematically individually omitted. The sensitivity of the LCA results to several selected parameters governing greenhouse gas emissions and climate change (CC) was evaluated by varying the parameters ±50% of the default value.The assessment gave a CC impact of 0.79, 0.77 and 0.74 kg CO2-eq for production of 1 kg barley, oat and spring wheat, respectively. The choice of system boundaries were found to have great impact on the results, and CC impact was reduced by more than 40% when factors that are not commonly reported in literature were excluded. This clearly demonstrates the need of comprehensive documentation of system boundaries in order to perform meaningful comparisons of environmental impact caused by grain production under different conditions.The sensitivity analysis revealed that most of the impact categories were not particularly sensitive to the parameters selected. A 50% change in the emission factor for N2O emissions from N inputs had highest effect on CC with 11–13%. The highest overall impacts were found for the fraction of mineral fertilizer volatilized as NH3 and NOX, with 32–53% change in photochemical oxidant and particular matter formation, and terrestrial acidification impact categories.

Effects of regional variation in climate and SOC decay on global warming potential and eutrophication attributable to cereal production in Norway

Agricultural Systems, 2014

Height above ground corrections of EM38 readings of soil apparent electrical conductivity

Acta Agriculturae Scandinavica, Section B - Plant Soil Science, 2006