Integrated forage and livestock production

Integrated forage and livestock production can be considered at the farm level and at the herd or animal level. At the farm level it is relevant to consider the overall utilization of N in the system in relation to crops and livestock. It is demonstrated that in organic dairy production a high transformation efficiency of N from input to edible products can be achieved compared, with conventional production. In addition, combining dairy and pig production allows an even higher N utilization. At the herd level the quality of grass or clover-grass based forage is extremely important. This holds for the overall intake and milk production in dairy cows and for the intake of clover-grass by grazing sows. In addition the composition of the sward should be considered in relation to the influence of specific plant species on the development of endoparasitic infections in ruminants and on the wear strength in relation to free-range pig production. For dairy production it is proposed that a strategy including only 20% concentrates (or cereals) of the dry matter in a total diet based on clover-grass and clover-grass silage represenst an efficient milk production without impairing the health of the cows

Protostellar half-life: new methodology and estimates

(Abridged) Protostellar systems evolve from prestellar cores, through the deeply embedded stage and then disk-dominated stage, before they end up on the main sequence. Knowing how much time a system spends in each stage is crucial for understanding how stars and associated planetary systems form, because a key constraint is the time available to form such systems. Equally important is understanding what the spread in these time scales is. The most commonly used method for inferring protostellar ages is to assume the lifetime of one evolutionary stage, and then scale this to the relative number of protostars in the other stages, i.e., assuming steady state. This method does not account for the underlying age distribution and apparent stochasticity of star formation, nor that relative populations are not in steady state. To overcome this, we propose a new scheme where the lifetime of each protostellar stage follows a distribution based on the formalism of sequential nuclear decay. The main assumptions are: Class 0 sources follow a straight path to Class III sources, the age distribution follows a binomial distribution, and the star-formation rate is constant. The results are that the half-life of Class 0, Class I, and Flat sources are (2.4+/-0.2)%, (4.4+/-0.3)%, and (4.3+/-0.4)% of the Class II half-life, respectively, which translates to 47+/-4, 88+/-7, and 87+/-8 kyr, respectively, for a Class II half-life of 2 Myr for protostars in the Gould Belt clouds with more than 100 protostars. The mean age of these clouds is 1.2+/-0.1 Myr, and the star formation rate is (8.3+/-0.5)x10^-4 Msun/yr. The critical parameters in arriving at these numbers are the assumed half-life of the Class II stage, and the assumption that the star-formation rate and half-lives are constant. This method presents a first step in moving from steady-state to non-steady-state solutions of protostellar populations.Comment: Accepted for publication in A&

Temperature dependent deviations from ideal quantization of plateau conductances in GaAs quantum point contacts

We present detailed experimental studies of the temperature dependence of the plateau conductance of GaAs quantum point contacts in the temperature range from 0.3 K to 10 K. Due to a strong lateral confinement produced by a shallow-etching technique we are able to observe the following unexpected feature: a linear temperature dependence of the measured mid-plateau conductance. We discuss an interpretation in terms of a temperature dependent, intrinsic series resistance, due to non-ballistic effects in the 2D-1D transition region. These results have been reproduced in several samples from different GaAs/GaAlAs heterostructures and observed in different experimental set-ups.Comment: 7 pages, 6 figures; to appear in proceedings of ICPS 2002, Edinburg

Utilization of nitrogen in legume-based mobile green manures stored as compost or silage

The utilization of nitrogen (N) in green manure leys can be improved by harvesting, storage and spreading of the plant material as manure in other crops. By green manure storage as silage, storage losses of N are lower than by composting. Also, a relatively high fertilizer value of silage N is achievable depending on the C/N ratio of the material. Nitrogen availability in green manure leys is higher after storage as silage compared to composting. Use of mobile green manures is mainly relevant in arable cropping systems without livestock where utilization of the roughage for animal feed or biogas production is impossible, as costs for ley/roughage harvest and transport can be relatively high. Our study showed that surface application of green manure silage to growing crops can damage plants and is therefore not recommended, whereas incorporation of silage before sowing has significant positive effects on crop yields

Ecological modernisation in the public catering sector. Danish experiences with use of organic food

The paper is part of the proceedings of an iPOPY seminar. The authors reflect on whether and how organic food in schools and kindergartens can be described as a part of an ecological modernization strategy in Denmark. They discuss how it has merged with more economically and technically approach in public catering policy. They discuss how it has merged with more economically and technically approaches in public catering policy