Ársrit Ræktunarfélags Norðurlands - 02.02.1969, Page 28

SUMMARY
An experiment with triple superphosphate fertilizer was performed
on a newly tilled and drained peat bog at Hvanneyri during the sum-
mers of 1962 through 1966. The new seedbed was sown with Timothy
(Phleum pratense) only.
The major purposes were 1) to compare five levels of phosphorus
(see experimental plan) applied tlie first year (treatment A) to the
effect of adding 26,2 kg P/ha each year thereafter (treatment B) and
2) to compare two methods of phosphorus application, broadcasting
only (method I) vs. broadcasting with subsequent mixing of the soil
surface and fertilizer by a rotatillor (method II).
The major results were as follows: Hay yield increased significantly
with increasing amount of phosphorus applied the first year in all
years for treatment A, but only in 1962 and 1965 for treatment B (see
table I and II). Significantly greater yields were obtained for appli-
cation method I in 1962, 1965 and 1966 for treatment A, but only in
1962 for treatment B (see table III, IV and V).
The phosphorus plant content decreased with years for treatment A.
Phosphorus utilization by the plants was from 21 to 38% for all five
years (see fig. 2 and 3 and table VII). It was concluded that ap-
proximately 30% of the total phosphorus applied at moderate levels
were utilized, assuming a negligible phosphorus absorbtion from soil
reserves.
At the end of the experimental periode the Timothy had been re-
placed by contaminant species, mainly Agrostis, to a much greater
extent for treatment A (53 to 99%) than B (16 to 31%). The Timothy
emerged better and showed more vigor for application method I than
for II.
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