Lauv som ressurs: Ny bruk av gammel kunnskap

Abstract

There is a long tradition of using foliage as fodder in Norway. From the earliest days of animal husbandry and right up to the mid 1900s, foliage was harvested in large quantities on nearly all farms in Western Norway (Austad & Hauge 2003). Pollarding and coppicing have through ages created a landscape of great historical and aesthetic value. Trees that have been pollarded for many years have a very characteristic growth shape, and they have inspired and facinated many people, from artists and storytellers to scientists. In addition biological diversity is high in and around these old trees. However, pollarding and coppicing are time-consuming and labour-intensive processes, and have therefore been more or less abandoned today.

The aim of this project was to investigate whether the reintroduction of pollarding and coppicing using modem methods and techniques made it possible to maintain the qualities of the cultural landscape, and whether it was possible to use tree-cuttings as fodder and as additives to manure. This is especially important on organic farms where a more extensive management regime is required, and more use must be made of the natural resources on the farm. Given that large areas of the Norwegian cultural landscape are becoming over grown, with the loss of valuable productive areas and areas of historical and biological interest, the result of the project will also be useful in a wider context (Austad et al. 2003ab).

The results confirm that the new method of collecting tree-cuttings is effective (branches from pollarded trees, shrub and undergrowth not exceeding 5-7 cm in diameter were fed into a compost grinder mounted on a tractor). The tree-cuttings (foliage, bark and small pieces of wood) are easy to dry in a barn drier. Ensilage has also been tested with good results for small quanti ties of tree-cuttings (Braanaas 2003).

Chemical analyses of the foliage and tree-cuttings showed that there were differences between the two types of fodder. However, there were also differences between tree-species, and whether it was dried or ensiled. The content of protein was highest in foliage from eim (Ulmus glabra) and rowan (Sorbus aucuparia). The fat content of the samples varied fairly widely, and was highest in ensiled tree-cuttings from alder (Alnus incana) and dried rowan foliage. Tests of in sacco degradability also showed differences between foliage and tree-cuttings. Dry matter and protein in foliage from eim and rowan was broken down much more quickly during incubation than tree-cuttings. The net-energy value of foliage and tree-cuttings was calculated. The quality of eim and rowan foliage correspond to good quality hay and medium-quality silage respectively. Energy values for tree-cuttings were rather lower, but the level was relatively high in eim tree-cuttings. Both foliage and tree-cuttings seem to be very good sources of calcium and magnesium, but have a low content of phosphorus and sodium. The potassium content is probably high enough to meet the needs of sheep. Both foliage and tree-cuttings appear to contain sufficient iron. The content of manganese, zinc, copper, molybdenum, selenium and cobalt varied from one tree spedes to another (Halse et al. 2003, Garmo & Braanaas 2003).

The tree-cuttings were used as fodder for sheep. The sheep on three farms were divided into two groups, one of which was fed as usual, the other with 10-20% tree cuttings. To measure the effects on the sheep, blood samples were taken and analysed and the weight of the sheep was recorded. The results show that the sheep fed on tree-cuttings had a higher content of vitamin B-12 in the blood (which is positive), but their weight was lower, probably because ofthe higher intake of cellulose (Kleppa 2003, Garmo & Braanaas 2003). However, the sheep have a well-developed ability to select elements of their fodder and leave the wood fragments. One interesting observation was that the sheep that were fed partly on foliage and bark in winter also grazed more on scrub and bushes when they were turned out in spring.

The waste product scraps from the tree-cuttings was used experimentally as litter for the sheep to test its absorbency. The used litter was also applied as manure to test its effect on hay production compared with that of straw (wheat), sawdust and pure sheep dung. We were especially interested in whether the carbon-rich cuttings from the deciduous trees improved the C:N balance and reduced the loss of nitrogen from manure. The scraps from tree-cuttings proved to have as good an effect on production as straw (Øpstad et al. 2003).

The three farmers used a total of 233 hours to collect a harvest of tree-cuttings corresponding to 12 516 bunches of twigs. This is equivalent to 537 bunches of twigs/person/day, which is almost five times as effective as the traditional method of harvesting, where a grown man was expected to harvest 120-180 bunches a day (Braanaas 2003). There are also considerable savings in terms of transport, drying and storage compared with the traditional method. These stages of the process were calculated to be about 10 times as effective as the traditional method. A cost-benefit analysis showed that the costs and benefits were approximately equal (Braanaas & Haltvik 2003). The residue, or the wood scraps left after the animals have finished feeding, can also be used as biofuel.

The cultural landscape (including semi-natural vegetation types, biodiversity and buildings and other man-made structures) was also examined. There has been relatively little clearance and cultivation on the farms in recent years, and the study revealed many valuable historical and cultural remains in and near the infields (Bergum & Austad 2003). The farmers who are using the land at present have continued earlier patterns ofland use. The largest concentration of historical and cultural remains was found in marginal areas on steep slopes and in areas where the soil structure is intact and stones have not been cleared away These areas are mainly used for grazing nowadays. At Kvaal, there are large numbers of heaps of stones cleared from fields, while at Kusslid many old footbridges and traces of old roadways have been found. Because of the terrain, terraces are a typical feature of Ytre Åsen and Kusslid. At Kvaal, the old buildings are of particular interest. In addition to man-made structures of these types, biological traces of human activity such as pollarded trees, hay meadows, wooded hay meadows and wooded pastures have been recorded. These include several semi-natural vegetation types that are endangered in Norway today. The magnificent old pollarded eim trees at Kusslid are of special interest.

The topography and other natural conditions have resulted in infields with a mosaic-like structure: the farmland consists of many small production areas and includes a variety of vegetation types and habitats (Røysum et al. 2003). The number of habitat types proved to be about the same on all the farms. The largest number of plant species was registered in the pastures. In all, 232 ± 7 species of vascular plants were recorded on the infields of the three farms, and more than a third of these were common to all three farms. This is probably because the farming methods used and the way people have influenced the vegetation has been similar at all three farms through the centuries. One interesting finding was that the largest number of species was registered on the farm that has been run organically for the longest period of time.

The results of the project show that if new techniques for harvesting, drying and storage are introduced, foliage can be used as a fodder resource in modem sheep farming. Sound resource utilization, including maintenance and use of pasture on the farm is also in accordance with the political objectives of preserving an open landscape and maintaining the qualities of the cultural landscape (Austad et al. 2003d).