Íslenskar landbúnaðarrannsóknir - 01.09.1970, Qupperneq 34

32 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
S U M M A R Y
WATERSOLUBLE CARBOHYDRATES IN GRASS
Eriðrik Pálmason,
Agricultural Research Institute, Reykjavík, Iceland
Watersoluble carbohydrates (WSC) were determined with the anthrone method
in grass samples from field experiments and in some hay samples from farms
in Iceland. In the field experiments N P, K and lime was tested on a mixed
sward. In the P-K experiment the predominant species was Phleum pratense.
Other samples were from a cutting-time trial and a trial comparing Phleum
pratense and Festuca rubra. The hay samples were from a collection of 450
samples taken in the year 1968 from farms in all district of the country.
Concentration of WSC in dry matter is generally higher in second cut than
in first cut. In June and July the WSC-concentration was falling in 1. cut
from 30—15% in DM. In 2. cut the concentration of WSC was falling in August,
but an increase was notecl in September. Phosphorus and potassium had an
WSC accumulating effect, but the concentration of WSC tended to íall again
near maximum dry matter yield. A nitrogen shortage resulted in WSC accu-
mulation but overoptimal nitrogen dressing had depressing effect on WSC-
concentration in 2. cut but not in 1. cut as compared to optimal dressings.
In liming experiments on a peat soil at Reykhólar in the northwestern region
of Iceland the concentration of WSC in dry matter was generally not affected
by liming. Though tlie heaviest lime dressings of 8 ancl 12 tons/ha did cause
an accumulation of WSC per hectare.
Calciumnitrate (15.5% N) and ammoniumnitrate (33.5% N) with lime proved
to increase DM-yield and to have a decreasing effect on WSC-concentration in
DM as compared to the effect of ammoniumnitrate alone in experiments on
a peat soil in Hvanneyri in the middelwest-region of Iceland.
Chlorophyll, WSC and crude protein was measured in 33 hay samples from
farms. The samples were taken at random out of 450 samples after protein
analysis had been carried out, except that a wide variation in proteincontent
was secured. Tliree cjuality groups according to appearance ancl cure were
representated: 1 excellent hay, 2 good hay, 3 badly cured hay. The results
indicate that these quality groups might be detected through chlorophyll and
WSC analysis together.