Comparing conventional and improved organic vegetable rotations, yields and nitrogen husbandry

During 2005 to 2009 three approaches to organic vegetable rotations were compared to a conventional rotation in an interdisciplinary project. The organic rotations differed in their reliance on animal manure vs. cover crops and intercrops, but the rotation of main vegetable and cereal crops were identical in the four rotations. One organic rotation (O1) relied on import of manure for supply of nutrients, in another (O2) cover crops were used to replace most of the manure import, and in (O3) also intercrops were grown to improve natural pest regulation. The yearly import of nitrogen were on average 149, 94, 28, and 28 kg N.ha-1 in C, O1, O2, and O3 respectively. On average the yield in the O1 system was 83% of the yield in the conventional system. In the O2 rotation the yield was the same, though the nutrient import was much lower, whereas the intercrops in O3 reduced the yield to 70% of the conventional fotation. The effect on single crops varied with organic yields ranging from 60% (onion) to almost 100% (carrots, oats) of conventional yields. Crop root growth varied strongly among crops with rooting depths of less than 0.4 m (onions) to more than 2 m (cabbage, rye, fodder radish catch crop). Root growth was unaffected by cropping system, but the inclusion of deep rooted catch crops and green manures in O2 and O3 increased the total root exploitation of the soil strongly. Thus, while the O1 and O2 systems had almost identical yields and N uptake there were large differences in their effects on soil N; e.g. the subsoil (1-2.5 m) N content was on average 18 kg N.ha-1 in the O2 compared 61 and 53 kg N.ha-1 in the C and O1 respectively, indicating strongly reduced N leaching losses in O2

Cauliflower and leeks to have company in the field

Organic vegetables may benefit from the growing of living mulch crops between crop rows. Scientists from four EU countries are looking for potential positive effects

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&

Self-sufficiency with vitamins and minerals on organic dairy farms

Self-sufficiency of nutrients is a central element in the organic farming principles. In a project involving five private organic dairy farms, we aimed to achieve self-sufficiency in vitamins and minerals at farm level. All the herds are fed 100% organically grown feed, but so far supplements of minerals and vitamins based on inorganic and synthetic products are imported to all farms. The same level and type of supplement was used for the cows all year round, even though all cows were on grass for at least 150 days during the summer period. The average daily intake from the supplement for a lactating cow was 751 mg E vitamin, 111 mg Cu, and 558 mg Zn. The content of vitamin and minerals in the home-grown feeds was modelled taking into account the effect of choice of crops; conservation method; season, plant development and climate conditions at harvest; quality of the silage production, and duration of storage. The modelled contents of vitamins in the main ingredients in the feed ration were verified by measuring the actual vitamin content in the silage at harvest as well as losses during storage. As an example, at one of the farms, where the feed intake was based on 85% grass clover crops during the summer but only 68% during the winter, the home-grown feed could supply the cows with enough vitamin E according to the requirement (800 mg/day) during the summer feeding but not during the winter period. The Cu requirement (10 mg/kg DM) could not be met from home-grown feed during any season. However, supplements of vitamins and minerals secure that requirement was met. The final outcome of the project will result in strategies for achieving self-sufficiency in vitamins and minerals at individual farms through optimization of the choice of forage crops and management of feed production

Vegetable quality in a conventional and three organic cropping systems

Differences in nutrient availability and methods of pest management may affect crop growth and product quality. The question is if conventional and organic cropping systems, which differ clearly in strategies for nutrient and pest management, influence the harvest and sensory quality of the products? Lettuce and onion were grown in a conventional and three organic vegetable cropping systems with different levels of external inputs and use of cover- and inter-crops for nutrient re-cycling and natural pest management in the period of 2007-2009 (VegQure project). The crop rotation consisted of 8 fields of vegetables and cereals. Onion was grown after a year of oat and iceberg lettuce after winter rye. There were 3 replicates of each cropping system each year. Sensory analysis of samples of iceberg lettuce was performed as quantitative descriptive analysis by a trained sensory panel of 10 assessors. A sensory profile of 9 attributes was evaluated on a 15-cm non-structured continuous scale. Harvest and sensory quality were not affected by the clear differences in nutrient and pest management between the four cropping systems

Blomkål og porrer får selskab i marken

Økologiske grønsager kan få gavn af, at der dyrkes ledsagerafgrøder imellem rækkerne. Forskere fra fire EU-lande undersøger de potentielt gavnlige effekter

Origin of the wide-angle hot H2 in DG Tauri: New insight from SINFONI spectro-imaging

We wish to test the origins proposed for the extended hot H2 at 2000K around the atomic jet from the T Tauri star DGTau, in order to constrain the wide-angle wind structure and the possible presence of an MHD disk wind. We present flux calibrated IFS observations in H2 1-0 S(1) obtained with SINFONI/VLT. Thanks to spatial deconvolution by the PSF and to accurate correction for uneven slit illumination, we performed a thorough analysis and modeled the morphology, kinematics, and surface brightness. We also compared our results with studies in [FeII], [OI], and FUV-pumped H2. The limb-brightened H2 emission in the blue lobe is strikingly similar to FUV-pumped H2 imaged 6yr later, confirming that they trace the same hot gas and setting an upper limit of 12km/s on any expansion proper motion. The wide-angle H2 rims are at lower blueshifts than probed by narrow long-slit spectra. We confirm that they extend to larger angle and to lower speed the onion-like velocity structure observed in optical atomic lines. The latter is shown to be steady over more/equal than 4yr but undetected in [FeII] by SINFONI, probably due to strong iron depletion. The H2 rim thickness less/equal than 14AU rules out excitation by C-shocks, and J-shock speeds are constrained to 10km/s. We find that explaining the H2 wide-angle emission with a shocked layer requires either a recent outburst (15yr) into a pre-existing ambient outflow or an excessive wind mass flux. A slow photoevaporative wind from the dense irradiated disk surface and an MHD disk wind heated by ambipolar diffusion seem to be more promising and need to be modeled in more detail