Kristian Kristensen

Aarhus University | AU · Department of Agroecology

Free-range pig production is typically associated with high risks of nitrogen (N) leaching due to the pigs excretory behaviour creating nitrogen ‘hotspots’ and rooting behaviour destroying the grass sward. This challenge is reinforced at high animal densities causing high nitrogen deposition. A combined production of pigs and perennial energy crops...

The Olsen phosphorus (P) soil test, known in Denmark as “Ptallet” or “fosfortallet”, has been used for decades for P fertilizer recommendations. Today it is also used to device legislative thresholds for application of P to farmers fields. It is therefore unfortunate that the test results of this method vary significantly and systematically between...

Drought is a great challenge to agricultural production, and cultivation of drought-tolerant or water use-efficient cultivars is important to ensure high biomass yields for bio-refining and bioenergy. Here, we evaluated drought tolerance of four C3 species, Dactylis glomerata cvs. Sevenop and Amba, Festuca arundinacea cvs. Jordane and Kora, Phalari...

Weed harrowing is an alternative to herbicides but it may have negative effects on epigaeic arthropods. We assessed the effects of frequent (four) versus two harrowings during the growing season on the density and diversity of generalist arthropods and the weed flora. Collection by flooding was used to estimate arthropod densities, after collection...

Cropping practice can affect pests and natural enemies. A three-year study of the strawberry tor-tricid, Acleris comariana (Lienig and Zeller) (Lepidoptera: Tortricidae), its parasitoid Copidosoma aretas Walker (Hymenoptera: Encyrtidae), and its entomopathogenic fungi was conducted in seven pairs of organic and conventional farms to test the hypoth...

Since 10 years, EU-legislation states that ‘pigs must have permanent access to sufficient quantity of material to enable proper investigation and manipulation activities’. While much research has focused on which materials ‘enable proper investigation and manipulation activities’, little has been done to determine what constitutes ‘sufficient quant...

To establish a national inventory of soil organic carbon (SOC) stocks and their change over time, soil was sampled in 1986, 1997 and 2009 in a Danish nation-wide 7-km grid and analysed for SOC content. The average SOC stock in 0–100-cm depth soil was 142 t C ha−1, with 63, 41 and 38 t C ha−1 in the 0–25, 25–50 and 50–100 cm depths, respectively. Ch...

Green open access link: http://rdcu.be/zdef. Potatoes (Solanum tuberosum L.) are drought‐sensitive and more efficient water use, while maintaining high yields is required. Here, water‐use efficiency (WUE) of a mapping population comprising 144 clones from a cross between 90‐HAF‐01 (Solanum tuberosum 1 ) and 90‐HAG‐15 (S. tuberosum 2 × S. sparsipilu...

Elytrigia repens is a rhizomatous perennial weed prevalent in organic cropping systems in Scandinavia. This study analysed the population dynamics of E. repens in a long-term crop rotation experiment on coarse sand in Denmark in order to gain insights into the factors influencing its population changes, especially those important for outbreaks of E...

Over the past century phosphorus (P) has accumulated in Danish agricultural soils. We examined the soil P content and the degree of P saturation in acid oxalate (DPS) in 337 agricultural soil profiles and 32 soil profiles from deciduous forests sampled at 0-0.25, 025-0.50, 0.50-0.75 and 0.75-1.00 m in the nationwide 7 km Grid System in Denmark. Cha...

The strawberry tortricid, Acleris comariana Lienig and Zeller (Lepidoptera: Tortricidae) is an important pest in Danish strawberry production. Its most common parasitoid is Copidosoma aretas (Walker) (Hymenoptera: Chalcidoidea: Encyrtidae). To identify selective flowering plants that could be used to increase functional biodiversity, the longevity...

This paper presents a survey of grass weeds in grass seed crops in Denmark. The survey is based on an analysis of data from a database containing monitoring of grass weeds in the period from 2004 to 2009 on an acreage of approximately 400,000 ha. The survey is based on weed monitoring carried out during a mandatory field inspection of grass seed cr...

Abstract The parasitization capacity of 3 parasitoids and the predation capacity of 3 predators towards the shallot aphid, Myzus ascalonicus Doncaster (Homoptera: Aphididae), on strawberry, Fragaria x ananassa Duchesne (Rosales: Rosaceae) cv. Honeoye, were examined in laboratory experiments. In Petri dish assays, both Aphidius colemani Viereck (Hym...

Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long-term mean. The experiment was initiated in a 4-yr-old...

The effect of different autumn and spring nitrogen (N) application rates on plant establishment, plant development, and seed yield were tested in a field experiment using tall fescue (Festuca arundinacea Schreb.). Results clearly showed that the optimum distribution of N between autumn and spring to achieve the highest seed yield and economical ben...

The natural field margin ecotone from the field border and into a cropped field hosts a diversity of plant species. In conventional cropped fields, biodiversity suffers from fertilizer and pesticide application. In our study at Danish conventional spring-barley fields, we laid out bufferzones with no pesticide application spraying after sowing, wit...

The paper shows how the α-design (also known as generalised lattice) may be used for constructing incomplete split-plot designs and describes four different methods (A, B, C and D) of construction. Intra-block efficiency factors and theoretical considerations are used to compare the methods. Based on those considerations method B was considered to...

The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (Reco), from eight organic soils managed by agriculture. The sites were located in three regions rep...

Crop production must continuously be adjusted according to economic return and fluctuating prices on inputs versus harvested plant products and calls for continuous revision of the crop rotation and flexible management systems. This study describes grass seed production of three different types, respectively, of perennial ryegrass (Lolium perenne L...

The house fly (Musca domestica L.) may transmit Campylobacter to broiler flocks. We assessed the retention time of house flies for Campylobacter jejuni at five temperatures and three doses. Flies were inoculated individually at their proboscis with 1.6 x 10(7) CFU (colony forming units) of C. jejuni and incubated at 15, 20, 25, 30, and 35 degrees C...

The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (Reco), from eight organic soils managed by agriculture. The sites were located in three regions rep...

Two main challenges facing organic arable farming are the supply of nitrogen (N) to the crop and the control of perennial weeds. Nitrate leaching from different organic arable crop rotations was investigated over three consecutive four-year crop rotations in a field experiment at three locations in Denmark (12 years in total). The experimental trea...

Several studies have identified optima in soil water content for aerobic microbial activity, and this has been ascribed to a balance between gas and solute diffusivity as limiting processes. We investigated the role of soil structure, as created by different tillage practices (moldboard ploughing, MP, or shallow tillage, ST), in regulating net nitr...

In order to obtain a high and stable yield of organic spring barley, production should be optimized according to the specific environment. To test the performance of spring barley varieties under varying cropping conditions, a field experiment was carried out in 2003 and 2004 in a six-field mixed organic crop rotation. We investigated the choice of...

M elander B, M athiassen SK, N ørremark M, K ristensen EF, K ristensen JK & K ristensen K (2011). Physical destruction of the sprouting ability of Elytrigia repens rhizome buds. Weed Research 51 , 469–477. Summary Elytrigia repens is a perennial grass that spreads mainly by rhizomes. It is controlled by repeated post‐harvest cultivations in organi...

The effect of restricted randomisations on the validity and efficiency of using spatial model as well as more common analysis of variance methods for analysing field trials was examined by simulating yields in agricultural fields with known spatial variation and analysing those using eight different statistical models. Some of the models took into...

Data on grain yield from field trials on winter wheat under conventional farming, harvested between 1992 and 2008, were combined with daily weather data available for 44 grids covering Denmark. Nine agroclimatic indices were calculated and used for describing the relation between weather data and grain yield. These indices were calculated as averag...

Effect of machinery wheel load on grass <p class=Author style=margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; text-indent: 0cm> <p class=Author style=margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; text-align: justify; text-indent: 0cm> Ole Green<sup>1, Rasmus N. Jørgensen²,...

A radical shift in our approach to crop production is needed to ensure food security and to address the problems of soil degradation, loss of biodiversity, polluted and restricted water supplies, coupled with a future of fossil fuel limitations and increasingly variable climatic conditions. An interdisciplinary network of European scientists put fo...

In pursuit of a biological disease and stress management strategy for ornamentals, a three-factorial experiment was performed to examine the effects of plant darkness stress, Ulocladium atrum and Glomus mosseae on gray mold caused by Botrytis cinerea and plant vigour in potted roses. While darkness stress significantly enhanced gray mold, U. atrum...

Enhanced biological control of weed seeds may improve sustainability of agricultural production. Biological control due to seed predation may be higher in organic fields because organic production generally supports more seed predators. To investigate such a difference, weed seed predation was studied in autumn in eight organic and eight convention...

Stripe rust (yellow rust) of wheat, caused by Puccinia striiformis f. sp. tritici, has become more severe in eastern United States, Australia, and elsewhere since 2000. Recent research has shown that this coincided with a global spread of two closely related strains that were similar based on virulence phenotype and amplified fragment length polymo...

Traffic intensities have been shown to have a negative influence on the yield of grass and clover. A full scale grass-clover field trial was established to estimate the effect on clover-grass yields as a function of different wheel loads and tire pressures. The trial comprised 16 different traffic intensities with 35 replicates and 1 traffic free t...

For low-input crop production, well-characterised varieties increase the possibilities of managing diseases and weeds. This analysis aims at developing a framework for analyzing grain yield using external varietal information about disease resistance, weed competitiveness and yield potential and quantifying the impact of susceptibility grouping and...

In crop experiments measurements are often made by a judge evaluating the crops' conditions after treatment. In the present paper an analysis is proposed for experiments where plots of crops treated differently are mutually ranked. In the experimental layout the crops are treated on consecutive plots usually placed side by side in one or more rows....

SummaryA screening programme for crop variety competitiveness would ideally be based on only a few, non-destructive measurements of key growth traits. In this study we measured the weed suppressive ability of 79 varieties of spring barley in two ways: (i) directly, by weed coverage assessments under weedy conditions at three Danish locations in 200...

The interest in organic grown cereals has increased the need for variety tests under organic growing systems and/or the knowledge on whether growth characteristics describe yield differently under conventional and organic conditions. This paper is a contribution to that question by examining the relationships between some important growth character...

max. 1200 words. (Presently 782 words) Session 1: Management of field experiments SICAT – Satellite, internet and computer aided trials for plant production Abstract Plot trials are standardized methods for investigating different treatments of plants and/or soil in both scientifical and commercial applications within agriculture and horticulture....

It is possible to design and perform plot trials of high quality using conventional farming machinery equipped with AutoFarm RTK Autosteer™ The Least Significant Differences (LSD) for yield and TGW were in the lower end of what is normally seen in plot trials with 2-5 replicates

Experiments were conducted to clarify the optimal dose and timing of single applications of Ulocladium atrum for control of gray mold on pot rose and pelargonium under conditions similar to those found in commercial greenhouses. In general, application of the antagonist 1-d prior to infestation with conidia of Botrytis cinerea was more effective th...

The occurrence and magnitude of variation of selected characters in clones derived from meristem tips of four potato cultivars in field trials in three countries was assessed. Recorded were: the number of plants per plot; maturity of plants; skin and flesh colour; tuber deformity; time of emergence; flowering; number of stems and tubers per plant;...

The aim of this paper is a methodological proof of concept for a labour extensive and semiautomated field trial design using auto-guidance and conventional machinery. A modified strip plot design was created involving two principal treatments, soil tillage and plant density. The different tillage treatments were randomized to columns within groups...

The concept of structural and functional hierarchy prevails in studies on the turnover of organic matter (OM) in soil. We examined the degree of structural hierarchy in arable soils sampled at six locations along a naturally occurring texture gradient (11 to 45% clay, 12.9 to 15.8 mg C g− 1 soil). One set of samples was incubated with 14C labeled r...

Nutrient load and distribution on pasture were investigated with fattening pigs that: (1) spent a proportion of or their entire life on pasture; (2) were fed either restrictively or ad libitum; and (3) were weaned at different times of the year. N and P retention in pigs decreased the longer they were kept on pasture. The contents of soil inorganic...

Conversion to shallow (non-inversion) tillage (ST) from moldboard ploughing (MP) alters soil properties as pore size distribution, pore tortuosity and soil organic matter distribution. This in turn influences the conditions for soil aeration and thus for turnover of soil organic matter. Intact soil cores (100 cm 3) were taken at 0-4 and 14-18 cm de...

Single-node leaf-bud cuttings of Schefflera arboricola Hayata and Stephanotis floribunda Brongn. were set and root formation, onset of axillary bud growth and plant height were measured. An increase in the number of roots in Schefflera, which was achieved with increasing cutting position on the stock plant (measured from top to base) or with increa...

We investigated the effects on annual weeds of location, weed control, manure application and catch crops and their interactions in a crop rotation with cereals and pulses for grain during conversion to organic farming in order to better understand the combined effects of management. An experiment with a 4-year crop rotation (spring barley/undersow...

In a 2 year experiment, residues in field-grown strawberries were investigated from the fungicides fenhexamid, pyrimethanil, tolylfluanid, and kresoxim-methyl resulting from different strategies, as regards the dose, number, and time of fungicide applications. Kresoxim-methyl was only used the first year and in full or no dose to control powdery mi...

Nitrate leaching from crop rotations supporting organic grain production was investigated from 1997 to 2000 in a field experiment at three locations in Denmark on different soil types. Three experimental factors were included in the experiment in a factorial design: (1) proportion of N2-fixing crops in the rotation (crop rotation), (2) catch crop (...

Four management systems combining high and low livestock densities (0.7 and 1.4 livestock units ha−1) and different types of organic manure (slurry and straw based FYM) were applied to an organic dairy crop rotation (undersown barley – grass–clover – grass–clover – barley/pea – oats – fodder beet) between 1998 and 2001. The effects of the managemen...

Perennial ryegrass (Lolium perenne L.) was grown for seed infield trials in order to investigate the temporal variation in plant nitrogen (N) concentration during ontogeny. Crops were sown in three successive years and grown with five N fertiliser rates applied in the autumn and in the spring (autumn-spring): 0-0, 0-50, 0-100, 30-120 or 60-140 kg N...

Fifty spring barley varieties grown under organic as well as conventional growing conditions in experimental fields in four combinations of year and site were studied. The yield varied much within and between environments (years and sites) and systems. Further, the variation between varieties was substantially and it differed between different envi...

Data from five 3-year experiments comparing different strategies of non-chemical weed control were analysed in order to set up a model that could be used for simulating further strategies. The treatments included different frequencies and effects of weed control using flaming, steaming and weed brushing. Each plot consisted of about 100 m of sidewa...

To be proactive in minimizing pesticide use, the public authorities in Denmark agreed in 1998 to phase out the use of pesticides on publicly owned areas by the end of 2002. A part of the agreement was an increasing focus on research into and development of new methods and implements for non-chemical weed control on paved areas. Due to a large incre...

Miscanthus is a perennial rhizomatous warm-season grass with C4-photosynthesis. It shows considerable production potentials (10– dry matter ha−1) under NW European growth conditions and plantations of Miscanthus are established to provide biomass for energy. The plant senesces in the autumn in response to adverse climatic conditions, but harvest is...

One to four applications of the antagonist Ulocladium atrum 302 were made to determine the effective timing and frequencies of applications needed to reduce the sporulation of Botrytis cinerea on potted roses under conditions conducive to development of gray mold. Potted rose foliage is maximally susceptible to B. cinerea infection when cuttings ar...

The possibilities for increasing total grain yield in organic cereal production through manipulation of crop rotation design were investigated in a field experiment on different soil types in Denmark from 1997 to 2000. Three experimental factors were included in the experiment in a factorial design: (1) proportion of grass-clover and pulses in the...

This is the first reported study of the interactions between indigenous arbuscular mycorrhizal fungi (AMF) and Aphanomyces euteiches in pea under field conditions. A. euteiches was applied to the soil by adding oospores produced in vitro. Attempts were made to create a non-mycorrhizal control by incorporating carbendazim (Derosal Fl) in the topsoil...

The design of a prototype decision support system (DSS) for growing malting barley (Hordeum vulgáre L.) without use of pesticides is described. The system comprises a main module and two sub modules. The main module predicts the yield and some quality parameters, assuming no problems with weeds, fungal diseases, insect pests and harvest/post harves...

Animal welfare considerations have stimulated the development of outdoor piglet (Sus scrofa) production systems, but the high levels of nutrients excreted suggest that nutrient losses from this system may be high. This study first described the spatial distribution of denitrification activity in a 5- x 5-m grid within and outside a paddock immediat...

Animal welfare considerations have stimulated the development of outdoor piglet (Sus scrofa) production systems, but the high levels of nutrients excreted suggest that nutrient losses from this system may be high. This study first described the spatial distribution of denitrification activity in a 5- × 5-m grid within and outside a paddock immediat...

An increasing number of breeding sows is kept outdoors in Europe. Outdoor pig production has benefits in terms of animalwelfare but may have hidden costs through nutrient losses. We investigated the distribution of nutrients in sow paddocks and the consequence for losses and utilization in the succeeding crop. Significant correlation between soil i...

A 24-yr-old permanent field trial on coarse sand (Orthic Haplohumod) under temperate coastal climate conditions was used to determine (i) the effect of introducing perennial ryegrass (Lolium perenne L.) as a catch crop on plots with a history of low input of organic matter, and (ii) the residual effect of long-term use of ryegrass as a catch crop o...

A 24-yr-old permanent field trial with spring-sown crops was used in a nitrate N leaching study to determine (i) the effect of long-term cover crop use compared with the introduction of perennial ryegrass (Lolium perenne L.) as a cover crop on plots with a history of no previous cover crop use and (ii) the effect of discontinuing long-term use of r...

The high number of cases where pesticide residues have been found in groundwater during the last decade has enhanced the need for more knowledge about the fate of pesticides in soil. The purpose of the present study was to extend the knowledge of pesticide mineralisation in soil. Many publications have described the difficulties of finding a useful...

In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (ba...

To evaluate the effect of soil texture and soil water content on decomposition of organic carbon (OC), turnover of partially stabilized -labelled ryegrass residues was studied at four matric potentials in twelve differently textured soils of similar origin and cropping history. Six soils were from a naturally occurring clay gradient and had 11, 16,...

Soil type effects on organic matter turnover are most often ascribed directly to differences in soil clay content. Since soil texture determines the physical characteristics of soil, aggregation and water holding capacity may be more relevant to address in the search for controls of organic matter turnover. Most studies of microbial processes in so...

The mineralization of 14C‐ETU was measured by the evolution of 14CO2 and described with a mathematical model consisting of two terms — one term describing the immediate mineralization of 14C‐ETU and another term describing the first order degradation of humus and/or biomass, where 14C had been built in. The influence of pesticide concentration, dep...