Introduction of Organic Eprints

Organic Eprints is an open, on-line archive for research in organic food and farming with more than 10,000 publications - and growing rapidly. All use of the archive is free of charge. There are 15,000 registered users of Organic Eprints, and the archive has more than 175,000 visits each month. The archive contains scientific and popular articles, reports, presentations, project descriptions, books and other research publications. For each publication there is a short summary along with information about authors and contacts, publishing details, peer review status, subject area and research affiliation. In most cases, the full articles are freely available for download

Sowing time, false seedbed, row distance and mechanical weed control in organic winter wheat.

In organic farming, mechanical weed control in winter wheat is often difficult to carry out in the fall, and may damage the crop, and weed harrowing in the spring is not effective against erect, tap-rooted weeds such as Tripleurospermum inodorum, Papaver rhoeas, Brassica napus and others which have been established in the autumn. Some experiments concerning sowing strategy and intensity of mechanical weed control, which included row distance, were conducted. The results underline the importance of choosing weed control strategy, including preventive measures, according to the weed flora in the field. In the experiment with low weed pressure and without erect weeds, there was very little effect of sowing strategy and row distance. In such a case, the winter wheat might as well be sown early, in order to avoid possible yield loss by later sowing, and at normal row distance to enhance the competitiveness of the crop. In the experiments with high weed pressure and erect weeds, the weed control was better with late sowing and large row distance (high intensity control), even though this was not always reflected in the yield. However, the trade-off for lower input to the soil seed bank in organic systems should be enough to balance off the risk of smaller yield

Organic bread-wheat in New England, USA

In October 2010, researchers, farmers and millers from Maine and Vermont, USA, organized a trip to Denmark, in order to learn about local bread wheat production, milling and use from their more experienced counterparts with climates similar to their own. They have received a grant over four years for the project antitled Enhancing Farmers’ Capacity to Produce High Quality Organic Bread Wheat in which they will carry out research, development and education to improve the production and quality of organic bread wheat in the two states

Integration of Elymus repens control and post-harvest catch crop growing in organic cropping systems

In Northern Europe, Elymus repens (L.) Gould infestations are traditionally controlled by repeated stubble cultivation in the period from harvest to ploughing in autumn. However, in organic farming, post-harvest tillage is undesirable due to the need for retaining nutrients in the cropping system. The soil is mostly cropped in that period, limiting post-harvest tillage. Two control strategies against E. repens are presented that merge the objectives of achieving a significant reduction of E. repens while having the soil covered with plants during the post-harvest period. Strategy I is an integration of rhizome fragmentation by soil cultivation within two days after harvest in early August with subsequent sowing of a catch crop to suppress shoot growth from the rhizome fragments. Strategy II also includes growing a catch crop but is preceded by a mid-summer fallow period lasting 4-6 weeks where repeated soil cultivations are conducted to fragment, weaken and desiccate the rhizomes. Strategy II controlled 91-90% of the E. repens population while strategy I only controlled up to 40%, mainly because of the weakening and desiccation of rhizomes caused by repeated cultivations. However, the fallow period may lead to undesirable nutrient leaching from sandy soils and the grower will have to desist from growing a profitable maturing crop, aspects that should be counterbalanced against the urgency for E. repens control and other possible control options. Strategy I appears to be more relevant for low infestation levels of E. repens while strategy II would be more appropriate where infestations have become large

Learning from a long-term crop rotation experiment

A crop rotation experiment was established in 1996/97 at three locations representing differ-ent soil types and climates. Three factors were tested: i) crop rotation with different propor-tions of N2-fixing crops, ii) with and without a catch crop, and iii) with and without animal manure. A green manure crop increased yields in the following cereal crops, but at the rota-tional level, total yields were larger in crop rotations without a green manure crop. There were positive effects of animal manure and catch crops on yield. However, except for the coarse sandy soil, the yield effects of catch crops and animal manure decreased over time when a grass-clover green manure was included in the rotation. The problems with perennial weeds increased over time depending on crop rotation and use of catch crops. This stresses the im-portance of considering long-term effects in the evaluation of crop management measures

Nitrogen use efficiency of cereals in arable organic farming

The effect of nitrogen (N) supply and weeds on grain yield of spring barley, winter wheat and winter rye was investigated from 1997 to 2004 in an organic farming crop rotation experiment in Denmark on three soil types varying from coarse sand to sandy loam. Two experimental factors were included in the experiment in a factorial design: 1) catch crop (with and without), and 2) manure (with and without). The apparent recovery efficiency of N in grains (nitrogen use efficiency, NUE) from NH4-N in applied manure varied from 29 to 38% in spring barley and from 23 to 44% in winter cereals. The NUE of above-ground N in catch crops sampled in November prior to the spring barley varied from 16 to 52% with the largest value on the coarse sandy soil and the smallest value on the sandy loam soil. The NUE of N accumulated in grass-clover cuttings varied from 14 to 39% with the lowest value on the coarse sandy soil, most likely due to high rates of N leaching. The NUE declined with increasing amounts of N accumulated in the grass-clover cuttings. This indicates that grain yields can be improved by removing the grass-clover cuttings and applying the N contained in the cuttings in spring to the cereal crops, possibly after fermentation in a biogas reactor

Special issue of Organic Agriculture — Organic 3.0

It is an honor to be able to present this special issue of Organic Agriculture: Organic 3.0 for the Organic World Congress in India 2017. In this issue, we have collected a number of papers relevant for the theme Organic 3.0. This special issue of Organic Agriculture about Organic 3.0 is published in connection to the science track “Innovative research for Organic 3.0” at the Organic World Congress in Delhi, India, November 2017. In the foreword to the proceedings (Rahmann et al. 2017), the challenges listed correspond well to those described and discussed in these five papers. The fact that the paper by Rahmann et al. (2016) that has been online in Organic Agriculture since December 2016, already after 6 months has been downloaded more than 3,000 times shows the great interest in this subject. Together, these papers give a valuable basis for the further discussion of Organic 3.0 and the future development for the organic sector and beyond. Organic agriculture—whether 2.0 or 3.0—can be one option to solve future problems, and the ideas behind organic agriculture should be integrated as much as possible in many types of agriculture: agroecological, small-holder, conventional, conservation tillage, etc. But organic agriculture should also learn from conventional and other types of agriculture and if necessary take a critical view on, e.g., minimum requirements that result in negative effects on public goods. Governments, NGO’s, farmers, researchers, and other stakeholders should all contribute to developing organic as well as other forms of agriculture. It is our hope that this special issue will be one step in bringing organic and truly sustainable agriculture forward

Effect of Elymus repens on yield of winter wheat, spring barley and faba bean in an organic crop rotation experiment

The impact of crop rotation, nutrient levels and use of catch crops on effect of E. repens on a sandy soil at Jyndevad on yield of winter wheat (2006), spring barley (2007-2008) and faba bean (2006-2008) was studied in an existing organic crop rotation experiment (Olesen et al., 2000; Rasmussen et al., 2006). Some of the objectives were to determine the yield loss at different levels of infestation of the weed, and to determine whether this relationship was influenced by the treatments. For all crops, the treatments had a high impact on the yield. The two treatments that had no manure applied for up to 12 years consistently had the lowest yields. In spring barley, the two treatments with manure and with catch crops consistently had the highest yields. In faba bean, the treatment with manure and without catch crops had the highest yields. As for the effect of E. repens shoots on yield, in spring barley, there was a larger decrease in the system without grass clover. The same tendency was seen for winter wheat. For spring barley and faba bean, within each system (with or without grass clover), the yield in treatments without manure was less influenced by E. repens than in treatments with manure

Tolerance of four spring barley (Hordeum vulgare L.) varieties to weed harrowing

We investigated the tolerance to weed harrowing of four spring barley varieties and examined the possible interactions between varietal weed suppressive ability and two nutrient levels. Tolerance was defined as the combined effect of crop resistance (ability to resist soil covering) and crop recovery (the ability to recover in terms of yield). The weed harrowing strategy was a combination of one pre- and one post-emergence weed harrowing. In terms of yield, the four varieties responded significantly differently to weed harrowing and the response depended on nutrient level. At the lower nutrient level, weed harrowing caused an increase in yield of 4.4 hkg ha-1 for a strong competitor (cv. Otira), while there was no effect on yield at the higher nutrient level. For a weaker competitor (cv. Brazil), weed harrowing caused no change in yield at the lower nutrient level, whereas yield decreased by 6.0 hkg ha-1 at the higher nutrient level. There were marked differences between the weed suppressive ability of the four varieties when not harrowed, with less pronounced but significant differences when harrowed. Weed harrowing did not change the weed suppressive ability of a variety. Varieties that are tall at post-emergence harrowing and have increased density after pre-emergence harrowing, are the ones that benefit most from weed harrowing

Conditioning of Leverage Scores and Computation by QR Decomposition

The leverage scores of a full-column rank matrix A are the squared row norms of any orthonormal basis for range(A). We show that corresponding leverage scores of two matrices A and A + \Delta A are close in the relative sense, if they have large magnitude and if all principal angles between the column spaces of A and A + \Delta A are small. We also show three classes of bounds that are based on perturbation results of QR decompositions. They demonstrate that relative differences between individual leverage scores strongly depend on the particular type of perturbation \Delta A. The bounds imply that the relative accuracy of an individual leverage score depends on: its magnitude and the two-norm condition of A, if \Delta A is a general perturbation; the two-norm condition number of A, if \Delta A is a perturbation with the same norm-wise row-scaling as A; (to first order) neither condition number nor leverage score magnitude, if \Delta A is a component-wise row-scaled perturbation. Numerical experiments confirm the qualitative and quantitative accuracy of our bounds.Comment: This version has been accepted to SIMAX but has not yet gone through copy editin