Íslenskar landbúnaðarrannsóknir - 01.03.1979, Síða 80

78 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
ÞAKKARORÐ
Höfundar þakka starfsfólki til-
raunastöðvarinnar á Hvanneyri árin 1964
— 1975 fyrir vel unnin störf við til-
raunirnar. Einkum vilja þeir þakka Jóni
Snæbjörnssyni fyrir hans þátt í starfinu.
Þá vilja þeir þakka forstöðumönnum
Bændaskólans á Hvanneyri og Búnaðar-
félags Islands fyrir veitta aðstöðu til
SUMMARY
Effects of tractor traffic on soil and vegetation
Óttar Geirsson
Agricultural Society of Iceland,
Bmdahöllinni, Reykjavik,
and
Magnús Óskarsson
Agricultural College,
Hvanneyri, via Borgarnes.
The effects of tractor traffic on yield and
soil ofgrassland were investigated in three
experiments on reclaimed peat soil at
Hvanneyri Experimental Station during
the years 1964 — 1975.
The yield (hkg hay/ha at 85% D.M.)
was found to be lower on experimental
plots subjected to tractor traffic than on
plots free of such traffic. This diíference in
yield was smallest in the early years of the
experiments but it gradually increased,
reaching a maximum of 30 - 40% in some
subsequent years. The average reduction
in yield due to tractor traffic (compaction)
for all experiments and years was 16%.
The reduction in yield was relatively
greater on plots which did not receive any
nitrogen application than on those re-
ceiving 120 kg N/ha.
Differences appeared in botanical com-
starfa. Búnaðarmálastjóri heimilaði Ótt-
ari Geirssyni að ljúka verkinu, eftir að
hann var kominn til starfa hjá Búnaðar-
félagi Islands frá Bændaskólanum á
Hvanneyri, og er ljúft að þakka það.
öllum öðrum, sem veittu aðstoð við
verkið á einn eða annan hátt, er þakkaður
þeirra hlutur.
position between traffic treatments. While
the participation of Poa pratensis in the
sward declined equally with or without
tractor traffic, Festuca rubra disappeared
much more rapidly from traffic plots
whereas Phleum pratense became more
prominent in plots subjected to tractor
traffic. Bog plant species or species which
thrive well on poorly drained or moist
soils, such as Cares species,Eriophorum sp.,
Poa annua, Agrostis stolinifera, Stellaria media
and Equisetum sp., were by far most do-
minant in the traffic plots. Similarly, a
higher percentage of mosses was found
there.
A relationship was found to exist
between the reduction in yield and soil
moisture content at the time of traffic tre-
atments in spring. The wetter the soil
when compacted by tractor traffic in
spring, the greater was the reduction in
yield that summer.
Soil moisture measurements showed
that samples from tractor traffic plots had
a higher wáter content than samples from
plots free of such traffic.
Chemical analysis indicated that the
percentages of most plant nutrients '.vere
similar in the yield irrespective of traffic