Epsilon Archive for Student Projects

Abstract

Abstract
A prerequisite to be able to use semi-natural pastures in an optimal way is knowledge about their conditions and properties. One thing to consider is the amount of herbage mass that can be produced during one season on different types of semi-natural pastures. That knowledge makes it easier to choose which type of animals and how many you are able to have in each paddock to maintain a high biodiversity and achieve the desired production of the animals at the same time.

This study was performed in nine different semi-natural pastures around Uppsala. The paddocks were already mapped with regard to different vegetation types. Exclosure cages were placed on previously fertilized, mesic, dry, shaded and wet vegetation. Primarily, small exclosure cages made of metal wires with the size of 0.5*0.5 m were used, three per vegetation type and paddock. In one paddock, traditional larger exclosure cages of 2*1 m placed in the vicinity of the small cages were also used on mesic, dry and wet vegetation to perform a methodology study, to investigate if small exclosure cages would give approximately the same results as the traditional larger ones. A total of 117 small and 9 large cages were used in the study giving 126 exclosure cages altogether. The grass in all cages was cut with a scissor at a stubble height of 1-2 cm six times during the grazing season between May and September. The samples were dried and the annual yield as well as differences between vegetation types were analyzed statistically using the mixed procedure. A separate analysis was also performed to statistically analyze if there was a difference in the estimation of herbage production between the small and large exclosure cages.

This study showed that previously fertilized and wet vegetation produced most, with an annual yield of approximately 5000 kg DM per ha. Mesic vegetation had an annual production of just over 3000 kg DM per ha while the dry and shaded vegetation produced least, yielding hardly 2000 and 1000 kg DM per ha and year, respectively. The production obtained in the present study was higher than values reported earlier (Pelve, 2010), especially the yield on dry pastures was considerable higher in this study. It is possible that part of the difference between the two studies are due to favourable weather conditions during the season of 2010 compared with the prevailing weather conditions in the earlier study.

Small exclosures gave less accurate results with a bigger variation, especially on wet land which is more uneven and hummocky which complicates the placing of this type of exclosure cages. The lower accuracy is to some extent compensated by the possibility to use much more sample units when using small cages compared to when one works with the larger, traditional cages.