Rit Landbúnaðardeildar : B-flokkur - 01.10.1954, Side 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