Íslenskar landbúnaðarrannsóknir - 01.09.1971, Side 74

72 ÍSLENZKAR LANDBÚNAÐARRANNSOKNIR
sláttur um það leyti og síðar getur leitt til
lítillar og ótryggrar eftirtekju seinni slátt-
ar.
ÞAKKARORÐ
Höfundar vilja þakka starfsfólki tilrauna-
stöðvarinnar á Hvanneyri fyrir mikilsverða
aðstoð, sérstaklega þeim Óttari Geirssyni,
Jóni Snæbjörnssyni, Þóru Guðjónsdóttur,
Sigríði Héðinsdóttur og Halldóri Sverris-
syni, svo og Hólmgeiri Björnssyni, Rann-
sóknastofnun landbúnaðarins, sem lagði
tölfræðilegt mat á nokkurn hluta efnisins.
SUMMARY
STUDIES ON PHLEUM PRATENSE (ENGMO)
I. Time of cutting, nitrogen application, association with Festuca rubra (Rubin)
and conservation
Magnús Óskarsson, The Agricultural College, Hvanneyri
Bjarni Guðmundsson, Agricultural Research Institute, Hvanneyri
The effects of time of cutting and nitrogen application on yield and chemical
composition of Phleum pratense (Engmo; N-Norwegian) were investigated in two
experiments during the years 1965—1971. The experiments were located at
Hvanneyri Experimental Station (64° 34 'N, 21° 40 'W), on reclaimed peat soil.
The yield of dry matter from the first cut increased the later in the season it
was taken. The increase in 1). M. yield was closely related to temperature and
global radiation in the main growing season (June). The later the first cut was
taken the lower was the D. M. yiekl from the second cut. Nitrogen applied in
split dressings (80 -J—40 kg N/ha) did not increase the total D. M. yield, compared
with all the nitrogen applied in spring (120 kg N/ha), but it resulted in a
more even distribution of D. M. yield between the first ancl the second cut.
The D. M. yield of Phleum pratense (Engmo; N-Norwegian) was greater than
that of Festuca rubra (Rubin; Danish), expressed as a 6-year average, but it was
noted tliat rnost of the Festuca rubra clisappeared from the sward in the third and
the fourth years. However, in the second year Festuca rubra gave a liigher D. M.
yielcl tlian Phleum pratense.
There was more winterkill of grasses in the treatments where the second cut
was taken late than in those which were cut early. An early first cut appeared to
facilitate the recovery of vegetation in patches wliere winterkilling had taken
place. It seems likely that the incidence of winterkill was greater when the nitro-
gen was applied in split dressings. This was evident in 1968 and 1969.
The crude protein content of Phleurn pratense was decreased by 1,68% for
each week by which the first cut was delayed, but a delay in the second cut only
resulted in a decrease of 0,65% C. P. per week. The highest total yield of C.
P. was obtained when the first cut was taken at a time when Phleum pratense