Íslenskar landbúnaðarrannsóknir - 01.09.1977, Page 22

20 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
EFTIRMÁLI.
Tilraunir þær sem hér um ræðir, voru gerðar
í tilraunastöðvum Rannsóknastofnunar land-
búnaðarins og í bændaskólunum á Hvann-
eyri og Hólum. Höfðu tilraunastjórarnir þar
SUMMARY.
The effect of sulphur fertUzation on hay yield
and its influence on sulphur content of grass.
ÁSLAUG HELGADÓTTIR,
Friðrik Pálmason
and
Hólmgeir Björnsson.
Agricultural Research Institute,
Keldnaholt, Reykjavík.
The influence of sulphur fertilizer on hay
yield and sulphur content in grass was in-
vestigated.
Significant increases in sulphur content
were obtained by the use of sulphur fertiliz-
ers. In eight of the experiments investigated
(see Tables 8 and 9) yield increased signi-
ficantly by the sulphur application. These
experiments were located at Grænavatn,
Arnarvatn Skjaldfönn, Nedri-Tunga, Fell,
Miklahólt, Stóra-Mástunga and Geitasandur.
They were all but one on light mineral soils.
yfirumsjón með framkvæmd þeirra. Ingi-
björg Einarsdóttir vann að efnagreiningu og
Lilja Ólafsdóttir teiknaði myndir. Vélritun
handrits annaðist Klara Sigurðardóttir.
In three of these experiments, where different
levels of S-application were tried, yield did
not increase beyond the lowest ievel, 5,8
kg/ha of S. In nearly all experiments small
amounts of sulphur were supplied with the
phosphorus fertilizer.
The critical level of sulphur in grasses was
estimated to be 0,095%, which corresponds
to the maximum yield of 63 hkg/ha. Most
of the total N/total S ratio, (N/S)t> values
lie between 10—20, and (N/S)t = 16 was
estimated at the limits of the maximum
yield. This value agrees well with values
cited in the literature for grasses with ade-
quate sulphur supply.
The critical sulphur value found here is
considerably lower than those found in the
literature, probably because of the late
sampling dates in our case, which means a
late developmental stage at the sampling
time. This explanation of the discrepancy is
based on the good agreement of the (N/S)t
values found and those cited in the literature.