Band-steaming for intra-row weed control

Steaming the soil prior to crop sowing has the potential of eliminating weed seedling emergence completely. Thus, steaming might be a perspective technique for intra-row weed control in non-herbicidal row crops of high value, where manual weeding can be very laborious. This paper presents some preliminary results with the effects of steaming on weed seedling emergence. The work is part of a joint project involving both biological and technical aspects of steaming. The overall objective is to develop an applicable technique for applying steam in bands corresponding to the intra-row area of a row crop. Band-steaming is expected to use much less energy as compared to current steaming techniques for arable usage

Prospects and limitations for agricultural engineering in the development of sustainable weed control methods – examples from European research

This paper gives a brief review of the major achievements in European research on physical weed control methods for agricultural and horticultural crops. Most of the work has emerged from an increasing awareness and concern about pesticide consumption in many Western European countries. Also an increasing interest in organic farming has further pushed the development of more sustainable weed control methods. Generally, the research has been joint projects between engineers and agronomists and the results have so far revealed some prospects as well as limitations for non-chemical methods to become useful solutions, not only for the organic growers but also for the conventional ones. A number of investigations have focussed on rather simple low-tech mechanical weeding principles, such as harrowing, brush weeding, hoeing, torsion weeding, and finger weeding, aiming at describing the weeding mechanisms for a better optimisation of the usage. In some crops, such as transplanted vegetables, potatoes, maize, winter oil seed rape, and partly small grain cereals, mechanical weed control has been quite effective and may become a relevant alternative to chemical weed control. However, current mechanical methods generally work with low selectivity, as they do not distinguish between weed and crop plants when applied into the crop row. Attempts to change the constructions and materials of the weeding tools have not decisively improved the selectivity and more intelligent methods capable of controlling only the weeds are therefore needed. The first step in that direction was the introduction of electronic steering systems for automatic guidance of inter-row hoes. They are based on image analysis of the crop row, and the technology is considered to be a kind of platform for the development of more advanced systems for robotic weeding in the rows of row crops, such as sugar beets, maize, and most vegetables. However, recent studies have shown that such an ambition may be difficult to fulfil because weed plants growing right beside the crop plants are the most harmful ones in terms of suppressing the crop plants. Whether any computer-based system would be able to guide a cutting device with sufficient accuracy and speed to remove those weeds in a practical situation in row crops seems questionable. Hence, other projects have been started with a view to avoid this challenge, trying to look for less complicated methods with more short-termed prospects of being applicable in practice. Steaming the soil prior to crop establishment and in bands corresponding to crop rows appears to have some potential in that context since an almost complete intra-row weed control can be achieved without affecting the crop. However, as with most other thermal methods, high energy consumption is a key-issue that needs to be solved

Vasily Grossman and Ilya Ehrenburg: Soviet Jews on the Nazis and Soviets

Vasily Grossman and Ilya Ehrenburg were both significantly influential writers in the Soviet Union during and after World War II. Grossman and Ehrenburg were both Jewish war correspondents and witnessed Nazi war crimes. Prosecutors at the Nuremberg Trial used The Hell of Treblinka, written by Grossman, as evidence. Following the war, Joseph Stalin and the Soviet Union began to implement increasingly anti-Semitic policies. Jewish citizens faced discrimination, the Soviet state opposed “dividing the dead” of World War II, and it culminated in the Jewish Doctors Plot in 1953. Both writers covered extensively the Holocaust and how to treat Germany after the war. Grossman was a lot less aggressive compared to Ehrenburg’s fierce hostility. Ehrenburg did not take a strong explicit stance on Soviet discrimination, at times defending Stalin. Grossman, instead, wrote extremely critical comparisons between Soviets and Nazi policies

Aspects of steaming the soil to reduce weed seedling emergence

Aspects of using steam for intra-row weed control in organic row crops are presented

Evidence of mixed scaling for mean profile similarity in the stable atmospheric surface layer

A new mixed scaling parameter $Z=z/\sqrt{Lh}$ is proposed for similarity in the stable atmospheric surface layer, where $z$ is the height, $L$ is the Obukhov length, and $h$ is the boundary layer depth. Compared to the parameter $\zeta = z/L$ from Monin-Obukhov similarity theory (MOST), the new parameter $Z$ leads to improved mean profile similarity for wind speed and air temperature in large-eddy simulations. It also yields the same linear similarity relation for CASES-99 field measurements, including in the strongly stable (but still turbulent) regime where large deviations from MOST are observed. Results further suggest that similarity for turbulent energy dissipation rate depends on both $Z$ and $\zeta$. The proposed mixed scaling of $Z$ and relevance of $h$ can be explained by physical arguments related to the limit of z-less stratification that is reached asymptotically above the surface layer. While the presented evidence and fitted similarity relations are promising, the results and arguments are limited to a small sample of idealized stationary stable boundary layers. Corroboration is needed from independent datasets and analyses, including for complex and transient conditions not tested here.Comment: Submitted to Journal of the Atmospheric Sciences for peer review. Version 2 corrects typos in the references and online abstract. Version 3 includes peer review change