Rit Landbúnaðardeildar : B-flokkur - 01.10.1954, Page 73

Rit Landbúnaðardeildar : B-flokkur - 01.10.1954, Page 73
71 þeim tíma, er sáð var í þær. Er það gert með því að bera saman hlut- föll grastegundanna í sáðblöndunni við það, sem finnst í sléttunni við talningu. Hefur sýnt sig, að axhnoðapuntur, rýgresi, fóðurfax og jafn- vel hávingull hafa dáið út víðast hvar á fyrstu árum, en háliðagras helzt lifað af sáðgresinu. Auk þess hafa innlendu grösin fljótt komið inn í slétturnar. Gerður var samanburður á gróðurfari í mismunandi jarðvegi sunn- anlands og norðan. Kom þá í ljós, að flokka mátti sléttur niður í ólík gróðursvæði. Með hliðsjón af tegundahlutfalli þessara gróðursvæða voru síðan gerðar tillögur um notkun fleiri en einnar sáðblöndu og harðgerðari grasstofna. English Summary. In the summers of 1951 and 1952 the author studied the winterkilling of grasses in 288 hayfields of long lay on 130 farms in South- and North-Iceland. The aim of this survey was to studj7 the factors possibly affecting the severe damage of hay- fiekls occuring in later years and to seek the proper remedies. In this report the subject is dealt with in tow parts. I. The winterkilling and II. The change in the Flora of the ficlds. The first part starts with a description of the phenomena with biological and physical explanations. Then follows a review of winterkilling in the Icelandic literature from the time of the writing of the Sagas to present time. This shows that the phenomena is not new in Icelandic agriculture and that it has often been the cause of grassfailures in earlier days. It is pointed out bjr a studj' of the meteorological data of 4 to 5 previous years that low temperature in earlj' spring is the main cause and snow is not a protection if it remains long on an unfrozen ground. Winter- killing being caused by severe weather can never be completely avoided but the survey of fields with diff. properties and management and corresponding variation in the damage shows that some means of protection against it are possible. The factors affecting winterkilling are shown in the diagrams as % of damaged fields over the expected 50%, as one unaffected and one damaged field was studied at random on each farm. The winterkilling is most severe in South-West- and North-East- Iceland. The farms on the middlelowland are most affected as this is the zone of weather changes. Fields with N- and E-slopes are more affected than any others except level fields. Fields on the peatsoils are more damaged than any others especially if poorly drained or if the surfacewater does not have free access to the ditches but freezes and thaws alternatively in the field. Seeded fields are worse off than selfseeded, and newly seeded more damaged than older fields which could prove that the imported grasses are less winterhardy than the native ones and that last years seedmixtures are poorer, lacking meadow foxtail, bentgrasses and red fescue. Based on these facts some means of protection against winterkilling are recommended such as selection of proper soils and layouts for new fields, proper draining, and run off for surfacewater, and also how the winterkilled spots can be improved by leveling with a roller early in spring, mowing regularly or reseeding as the last alternative. In the final part are described the botanical compositions of the hayfields and how they have changed during the years, every species being given a brief discussion with a diagram showing its % in the winterkilled and undamaged fields

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Rit Landbúnaðardeildar : B-flokkur

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