Hävd av strandängar
Svensson, Andreas; Bengtson, Johan; Andersson, Lars; Widmark, Louise; Lassbo, Mikael; Bengtsson, Roger; Nordström, Thomas
To promote the birdlife in grazelands and increase the multiplicity of plants and animals in flooded meadows (used for harvesting fodder) there is call for a continued cultivation of these areas. For many years these areas were harvested manually, or grazed by cattle from farms located nearby. Due to the rationalization in farming has the cultivation of flooded meadows diminished in extent. These meadows are unique with their plants and animal life and characterized by the annual flooding with nutritious water from local lakes and water-courses. To maintain the cultivation by the use of grazing animals would the livestock of the local region have to be increased a lot. Since this option isn't feasible today, there's an enhanced need for mechanization of cultivation practices at flooded meadows. As the cultivation of flooded meadows has been discontinued will the shores be choked with tall-growing species which means that the amount of biomass increases. This results in a soil with a reduced oxygen content which leads to a slower decomposition of plant remnants. The process elevates the ground and causes overgrowing into much the same as mainland vegetation. Birds of flooded meadows needs low vegetation and distances of at least 100 meters to the nearest bushes or trees. Plant remnants needs to be taken away otherwise it will become a disturbing element for these birds. These meadows will thereby turn into a beneficial environment for nesting and feedseeking birds. The experiences from cultivation of flooded meadows in our country are of various kinds. From conventional ley harvest methods practised in the south to the management of wetland cultivation up north. New methods have been tried out here and there, using for example special constructed machinery or applied military training with crawler type vehicles. These measures can be used for the actual work of putting flooded meadows in order. An essential problem is the carrying capacity for this kind of soil. Therefore considerable requirements are made upon the bearing parts of the used vehicles. To reduce the pressure from beneath the wheels needs the load either be decreased or the carrying surface be increased. The bearing wheels sinks until the surface of support becomes as large, as the pressure on its surface becomes equal with the carrying capacity. Resistance to taxiing comes of tracking and calls for extra energy. To avoid this effect it is better to increase the diameter of the wheels than of the width of the tyres. When the carrying capacity is crucial it is no more than the connected surface layer that gives it any support. At passage across the field becomes the surface of the soil exposed to shearing. The shearing can be decreased through an additional number of wheels or having the machines equipped with crawlers. On soils like these it is the axial weight that influences the carrying capacity. Alternative methods to put fields like these in order is to mill off soil, burn off vegetation or to use a pasture trimmer. Special purpose machines are nowadays under testing. These machines are manufactured by the companies LVR AB and NOVASS AB. Another of these machines is being developed and tested privately by Jossi Kyllenen. There are different kinds of mowers and one of these is the knife mower which is low in weight, power efficient and shears the grass but sensitive towards strange objects lying in the way of its course. Another is the rotary mower that is more dependable in service and works through a combination of shearing and striking. The latter one has a higher capacity but requires an increased engine effect and weight of the tractor. There is also the flail forage harvester that strikes off the grass with flails and transports the material directly to a carriage. The machine can on the other hand pick up pieces of soil and gravel together with the harvested material. Dry soils can be cultivated with conventional ley machines while wet soils sometimes just allow one or two passages across at maximum. The later condition requires direct loading into a collector trailer, alternatively with the mower aggregate mounted in the front of the tractor. When harvesting hey it's often necessary to turnover the material at least once. For the purpose of harvest are various balers and self-loading trailers obtainable. Balers are usually heavy while self-loading trailers can be found in many sizes and often equipped with bogie. They are also flexible as they can carry small loads on quite wet soils. Transport of the harvested material can be done through two different systems. Either directly to final disposal or through transhipment at the roadside of fields. When distances of transport are less than 30 to 40 kilometers transport by tractor can be considered as less expensive than transport by truck. Round bales and rectangular big bales are easy to load and transport on open-sided trailers. The trailers can take a full load with a relatively good utilization of the loading capacity of the carriage. Because of their weight these bales must be loaded on carriages by machine. Using small bales is another beneficial alternative, but these bales need to be heaped up during long-distance transport which requires extra labour to a certain extent. Harvested material that is not baled can either be transported with a self-loading trailer or a truck carrying containers. The self-loading trailer is good at shorter distances of transport but less suitable for transhipment. The removed material can be deposited in the following ways: • Forage to livestock. The forage can be of special value if classified as KRAV-approved feed. It can also become horse-feed to a certain extent. • Green manuring of arable land. The material needs in this case to be chopped. Material with nitrogen deficiency can tie itself to the nitrogen of the soil in connection with the decomposition. The nitrogen dissolves itself when the process of decomposition is concluded. • Soil at vegetable production. The material should be chopped and the method can result in positive effects upon noxious insects, weed, soil moisture and soil structure. • Composting. Fresh material should be mixed with other substances. Two alternatives are: 1. Windrow composting has many disadvantages and is not recommended. 2. Compost blended with parkwastes has more advantages than drawbacks. • Retting. In the process of retting biogas is produced. Research is in progress and several interesting byproducts can be extracted, as for example forage. The condition is an existing and suitable plant for biogas production located nearby. • Incineration. It requires particular furnaces with certain properties of combustion. • Landfill. The material is not suitable for established municipal set-ups and the initial cost for new set-ups can be extensive. Not recommended. Other important issues to take into consideration: • How is the nutrient and energy content of the green forage utilized? • Is there any economic value in the green forage? • How can transportation work be minimized? • Which resources and possibilities are available? Finally, from a general point of view it is nearly impossible to decide which machinery that is most suitable for a particular type of soil or the cost of cultivation of flooded meadows. The conditions varies a lot between the regions, which means that many aspects needs to be taken into account for in each case.
Rapport - Sveriges lantbruksuniversitet, Institutionen för lantbruksteknik
Publisher: Institutionen för lantbruksteknik, Sveriges lantbruksuniversitet
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