Íslenskar landbúnaðarrannsóknir - 01.09.1970, Qupperneq 20

18 ÍSLENZKAR LANDBÚNAÐARRANNSOKNIR
increments at both sites but potash only little at Korpúlfsstaðir and none in
Þykkvibær. There was also a strong positive interaction between nitrogen and
phosphorus on total yield and quantity of saleable potatoes at the two sites
beyond the lowest fertilizer rates. Potash and the highest rate of nitrogen
seemed to lower dry matter a little.
To produce good yields 200—250 kg N per hectare are necessary in the sandy
soil at Þykkvibær ancl 100—200 kg N per lrectare at Korpúlfsstaðir. At both
sites 300—350 kg P203 per hectare seem necessary. Although there was only
small influence of potash the recommendation is to use potash in about equal
quantity with phosphorus to reduce the risk of aftercooking blackening. The
influence of potash remains, however, to be investigated further.
HEIMILDARRIT
REFERENCES
Birch, J. A., Devine, J. R., Holmes, M. R. J-,
WlTHEAR, J. D., 1967: Field experiments
on the fertilizer requirements of maincrop
potatoes. /. agric. Sci. Camb. 69, 13—24.
Boyd, D. A., 1961: Current fertilizer practice
in relation to manurial requirements. Proc.
Fertil. Soc. No. 65.
Boyd, D. A., Dermott, W„ 1967: Fertilizer
requirements of potatoes in relation to
kind of soil and soil analysis. J. Sci. Fd.
Agric. 18, 85-89.
Cooke, G. W„ 1967: The Control of Soil Fer-
tility. Crosby Lockwood and Son, London,
bls. 322.
COOKE, G. W„ WlDDOWSON, F. V„ VlLCOX, J-
C„ 1957: The value of midseason top dress-
ings of nitrogen fertilizer for main-crop
potaoes. /. Agric. Soc. 49, 81—87.
Dickins, J. C„ Harrap, F. E„ Holmes, M.
R. J„ 1962: Field experiments comparing
the effects of muriate and sulphate of pot-
ash on potato yield and quality. /. Agric.
Sci. Camb. 59, 319—326.
Herlihy, M„ Carroll, P. J„ 1969: Effects of
N, P and K and their interactions on
yield, tuber blight and quality of potatoes.
/. Sci. Fd. Agric. 20, 513-517.
IviNS, J. D„ 1963: Agronomic management of
the potato. í bókinni: The Growth of the
Potato. Butterworths, London, bls. 306.
JOHANSSON, O., 1967: Potato fertility. Váxt.
Ndr-nytt, 23, 22—26 (sjá: Soils and Fer-
tilizers 1967, 30, 3849).
KÚRTEN, P. W„ Burghardt, H„ 1959: The
importance of phosphorus and potassium
for the efficiency of nitrogen fertilizing in
potato cultivation (á þýzku). Phosphor-
saure, 19, 1—15.
Ontario Department of Agriculture, 1966: Po-
tato production in Ontario. Publ. No. 534,
bls. 47.