This paper presents results from fiber hemp experiments in southern Sweden carried out during 2004-2006. Field trials were performed, testing two monoecious varieties (Beniko and Futura 75) at a seed ...rate of 30 kg/ha. The trials were harvested at one to three stages in the autumn each year. Mean fiber strength varied between 304 and 353 MPa for Beniko and between 257 and 496 MPa for Futura 75, based on results from 2004 to 2006. Mean fiber thickness varied between 111 and 133 μm for Beniko and between 109 and 134 μm for Futura 75, based on results from 2005 to 2006.
The quality of fibres obtained from flax, hemp and reed canary grass is dependent on the moisture characteristics of the crops. In this study, the adsorption equilibrium moisture contents of ...un-retted and dew-retted flax straw, un-retted and frost-retted hemp stalks and spring-harvested reed canary grass were determined using the dynamic gravimetric method at different temperatures (5, 15, 25
°C) for relative humidities in the range 35–95%. Non-linear regression was used to fit five commonly used three-parameter isotherm models the modified Henderson model, the modified Chung–Pfost model, the modified Halsey model, the modified Oswin model and the modified Guggenheim–Anderson–de Boer (GAB) model to the data obtained. The goodness-of-fit of the models was compared using the mean relative percentage deviation, the standard error of estimate and residual plots. The modified Halsey model was considered the best for predicting the equilibrium moisture content of un-retted flax and spring-harvested reed canary grass, and the modified Oswin model for predicting the equilibrium moisture content of dew-retted flax and un-retted hemp, while the Chung-Pfost model was the best for predicting the equilibrium moisture content of frost-retted hemp. For flax and hemp, there were statistically significant differences between un-retted and retted plant materials, whereas the differences between varieties were small.
Results from hemp experiments in European countries indicate that long day conditions may be beneficial for the fibre content and quality of hemp. The long day conditions during summer in Sweden are ...therefore of interest. This paper presents results from the first fibre hemp experiments carried out in Sweden since the 1960s. Field trials were performed in southern Sweden, during the years 1999-2001, testing three monoecious varieties (Felina, Fedora and Futura) at seed rates of 30 and 60 kg/ha. Total biomass yield in autumn varied from 7.8 to 14.5 ton DM/ha and fibre yield from 1.9 to 3.3 ton DM/ha. The highest fibre yields per hectare were produced by the variety Futura, the lowest by Fedora. The seed rates 30 and 60 kg/ha gave similar biomass and fibre yields, but the plant density was lower and the stem diameter was larger at 30 kg/ha. Results of chemical analyses of stem and leaves are presented.
Metals in agricultural structures are often subjected to adverse environmental conditions resulting in high corrosion rates (up to 200 μm/yr). The different factors enhancing metal corrosion in farm ...buildings include high humidity and temperature, high concentrations of aggressive gases, acids, and salts (from silage and feed residues, cleaning agents, manure, fertilizers, preservatives), mechanical destruction and bacteria causing microbially induced corrosion. The importance of microbially induced corrosion is not yet clarified and a reduction in corrosion by biofilms on metals has also been reported. Corrosion products found in animal houses are similar to those resulting from classic corrosion mechanisms, which may lead to the conclusion that the fundamental mechanisms of metal corrosion in animal buildings are similar to the classic ones. Different methods to detect, measure and predict corrosion are described. The economic losses by corrosion in agriculture are evaluated. By corrosion prevention, a reasonable amount of expense can be saved. Prevention includes: (1) the choice of corrosion resistant materials such as stainless steel or non-metallic materials; (2) designing against corrosion; (3) control of the aggressive environment; and (4) application of coatings. When protective coatings are used, such as zinc layers and painting systems, surface preparation of the metal is of the utmost importance. Zinc layers should be thick enough (>50 μm), and zinc-coated steel should be protected in areas of extreme aggressiveness, such as fittings at floor level. Reports about the durability of different painting systems in agricultural structures are reviewed. The development of new environmentally friendly products is discussed. Guidelines for maintenance of previously painted steelwork are formulated.
This final part of the literature review gives an overview of the knowledge on durability of concrete structures, concrete being undeniably one of the most frequently used building materials for ...solid and slatted floors in animal houses and for manure and silage storage structures. Resistance against corrosion caused by lactic and acetic acids is of major importance both for floors and silos. Concrete manure tanks, walls of manure pits in animal houses and the underside of concrete slats and slabs are exposed to biogenic sulphuric acid corrosion. Different demands for producing a high-quality and durable concrete structure are discussed. This includes correct specification of the concrete mix (water/cement ratio, cement content), compaction and curing. The influence of the cement type, pozzolanic additions, aggregate type, polymer additions, application of cement-bound surface layers, impregnation with water repellents or pore blockers and application of coatings, on the corrosion resistance is reviewed.
Agricultural environments can be very aggressive to building materials and components due to the specific physical and chemical agents present. It is therefore evident from several viewpoints that ...the consideration of the durability of building materials and components is an important aspect of design. Economic considerations, animal welfare, pollution control and environmental aesthetics are all linked with durable design. In this review, an overview of the existing knowledge on durability of different building materials and components subject to this specific environment is given.
The first part of the review focuses on the characteristics of the agricultural environment and the durability of timber structures. Different farm buildings are examined, including animal houses for cattle, pigs and poultry; slurry pits; horticultural buildings; farm roads; and silos and other storage systems for agricultural products. The susceptibility to degradation of these buildings or their components is highlighted. The use of wood in agricultural structures, its deterioration and methods for protection are dealt with. The review reveals that little has been published about timber degradation in specific agricultural environments. Laboratory tests and field trials are mostly developed to simulate decay in timber either in contact with the ground or in above-ground structures. Recent research focuses on fungal decay and attack by insects and (seldom) bacteria on different types of wood under a variety of environmental conditions (temperature, humidity, etc.). Methods to distinguish between fungi are proposed. Different measures to quantify the degree of decay are investigated. New diagnostic methods for detecting incipient wood decayin vitro and in situ are developed. New wood preservatives are being proposed continuously, including different methods to retard the leaching of boron from treated timber and the use of monomers that are polymerized in situ. Continuously, more attention is paid to the design of environmentally benign methods for preserving wood in service.
Drainage properties of and ammonia emissions from slatted floors and drainage channels were investigated using a laboratory arrangement development for the purpose. The arrangement consists of a ...steel-framed box with two levels in order to simulate different slatted floor systems. The slatted floor under test is laid on the top level and manure is dropped on to it from various heights. The lower level consists of a drainage channel, the top of which is covered by a lid perforated with holes of different shapes.
Drainage experiments on slatted floors for cows with slits from 30 to 45 mm wide showed an average total drainage value for faeces and urine of 72% and an average urine drainage value of 82%. Drainage experiments on slatted floors for pigs showed results varying between 38 and 46% for total drainage depending on different drainage arrangements. The best drainage capacity was obtained when the drainage channel cover had holes giving a large drainage area.
The ammonia experiments on slatted floors for cows with 2 and 30 mm spacing showed an accummulated ammonia emission of about 8 and 3 g respectively, during the 20 h testing period. On slatted floors for fattening pigs, the accumulated ammonia emission was calculated to be about 2 g during the 20 h testing period. These ammonia emission results are related to the mass quantities and the nitrogen contents of faeces and urine, which normally are dropped to slatted floor surfaces in animal buildings.
Concrete in agriculture Svennerstedt, B
Rapport - Sveriges Lantbruksuniversitet, Institutionen foer Lantbrukets Byggnadsteknik (Sweden),
1991
73
Journal Article
