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| Petersen, B.M.; Berntsen, J.; Jensen, L.S.; Hansen, S.. |
| In order to achieve predictive abilities for both short- and long-term simulations, SOM models should be developed on the basis of as large and diverse a data-set as possible. Many soil organic matter (SOM) models have parameters, where the criteria for estimating their values do not seem transparent, and few have been subject to a formal sensitivity analysis regarding the influence of parameter settings. One of the major problems in most SOM models is to estimate the soil content of very slowly decomposing or perhaps even inert organic matter ("refractory" SOM). In view of these possible limitations of present SOM models, the following model development criteria were chosen for this study: 1) use of a comprehensive data-set from both laboratory and... |
| Tipo: Conference paper, poster, etc. |
Palavras-chave: Soil biology. |
| Ano: 2003 |
URL: http://orgprints.org/4660/1/4660.doc |
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| Hansen, J.P.; Eriksen, J.; Jensen, L.S.. |
| Forecasting crop nitrogen (N) demand is important for maximising productivity and minimising losses to the environment and includes taking into account residual effects. The residual N effect was estimated in a dairy crop rotation (spring barley undersown with grass-clover, 1st and 2nd year ley, spring barley/pea undersown with ryegrass, oats undersown with ryegrass and fodder beets) with different management (grazed/cut) and manure type (slurry/deep litter) by anaerobic incubation and plant N-uptake in a pot experiment and in the field. For comparison a 10-year-old grass-clover was included. Type of animal manure did not affect the residual N effect. Crop rotations with grazed grassland had a residual effect that on average was 13% higher than the same... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover. |
| Ano: 2005 |
URL: http://orgprints.org/4572/1/4572.doc |
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| Petersen, B.M.; Berntsen, J.; Hansen, S.; Jensen, L.S.. |
| A computer model is presented that describes the flow of C and N in the soil. It employs a structure with conceptual compartments. Organic matter is represented by seven different compartments, two for added matter, two for soil microbial biomass, one for microbial residues, one for native organic matter, and one for inert organic matter. The latter pool probably represents both truly inert matter, and matter with a very slow turnover. This paper describes the parameterisation and performance of this model on selected long-term field data from United Kingdom, Sweden and Denmark. Statistical methods were employed to optimise parameters, and obtain proximate confidence intervals for these parameters. Very satisfactory simulations could be acquired, using the... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover. |
| Ano: 2005 |
URL: http://orgprints.org/87/1/87.pdf |
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| Petersen, B.M.; Jensen, L.S.; Berntsen, J.; Hansen, S.; Pedersen, A.. |
| Carbon (C) and nitrogen (N) transformations are highly interdependent, driven by the C metabolism. Though many details of the transformations of C and N forms in soil are well known, basic knowledge about the mechanisms determining substrate availability, and the chemical and physical properties determining the stabilisation of organic matter are still lacking. The soil biota furthermore constitutes an extremely complex food web, consisting of a vast number of bacteria, fungi and fauna species, each having their own feeding preferences and characteristic life cycle. A good quantitative description of the main processes involved is required. This involves both the long-term build-up and degradation of soil organic matter, and the more short-termed N... |
| Tipo: Conference paper, poster, etc. |
Palavras-chave: Soil biology. |
| Ano: 2003 |
URL: http://orgprints.org/4662/1/4662.doc |
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| Petersen, B.M.; Jensen, L.S.; Berntsen, J.; Hansen, S.; Pedersen, A.; Henriksen, T.M.; Sørensen, P.; Trinsoutrot, I.. |
| A computer model is presented, which describes the transformations of C and N in the soil. The development has been divided into two interdependent tasks, the first being development of long-term SOC simulation capabilities, and the second being short-term simulations of C and N, as described in this paper. A number of existing, independent laboratory experiments, covering a range of amendments, have been used for this task. The amendments includes a variety of different crop residues and animal manure. These experiments have included measurements of 13C, 14C and 15N in various pools, and the model facilitates the simulation of these isotopes. Non-linear, automated optimisation procedures were utilised wherever feasible. The model generally yielded good... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover. |
| Ano: 2005 |
URL: http://orgprints.org/88/1/88.pdf |
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| Oelofse, Myles; Jensen, L.S.; Magid, Jakob. |
| Soil fertility management in organic systems, regulated by the organic standards, should seek to build healthy, fertile soils and reduce reliance on external inputs. The use of nutrients from conventional sources, such as animal manures from conventional farms, is currently permitted, with restrictions, in the organic regulations. However, the reliance of organic agriculture on the conventional system is considered problematic. In light of this, the organic sector in Denmark has recently decided to gradually phase out, and ultimately ban, the use of conventional manures and straws in organic agriculture in Denmark. Core focal areas for phasing out conventional nutrients are as follows: (1) amendments to crop selection and rotations, (2) alternative... |
| Tipo: Journal paper |
Palavras-chave: Soil quality Nutrient turnover Soil Values; Standards and certification Farm nutrient management. |
| Ano: 2013 |
URL: http://orgprints.org/24655/1/Oelofse_et_al_Journal%20of%20Organic%20Agriculture.pdf |
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| Eriksen, J.; Jensen, L.S.. |
| Soil tillage was studied as a strategy to synchronise N mineralization with plant demand following ploughing of two types of grazed pastures (ryegrass/white clover [Lolium perenne/Trifolium repens] and pure ryegrass). The swards were either rotovated and ploughed or only ploughed. Soil respiration, as determined by a dynamic chamber method, was related to net N mineralization and to plant N uptake in a subsequent spring barley crop (Hordeum vulgare). Diurnal variations in temperature were important for the CO2 flux and care must be taken that temperatures during measuring periods are representative of the daily mean. Soil tillage increased the CO2 flux considerably compared to untilled soil with total emissions of 2.6 and 1.4 t carbon ha-1, respectively,... |
| Tipo: Journal paper |
Palavras-chave: Nutrient turnover. |
| Ano: 2001 |
URL: http://orgprints.org/153/1/10330139.pdf |
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