Dw. James et al., NITROGEN AND POTASSIUM FERTILIZATION OF POTATOES - EVALUATING NUTRIENT ELEMENT INTERACTIONS IN PETIOLES WITH RESPONSE SURFACES, American potato journal, 71(4), 1994, pp. 249-265
We studied the effects of fertilizer N and K rates on the nutrient con
centrations in petioles of Russet Burbank potato grown on a low-K, low
-Cl, highly calcareous Millville silt loam soil. Phosphate and CaSO4 w
ere applied uniformly so that P and S did not limit plant growth. An i
ncomplete factorial experimental design, utilizing 14 combinations of
fertilizer N and K, including two forms of Y, was used to develop a mu
lti-dimensional regression model. This model was then used to produce
response surfaces as an aid to analysis of the results and to illustra
te the fertilizer treatment effects and their interactions on petiole
chemistries. Nitrogen, K and Cl fertilizers had complex effects on pet
iole concentrations of NO3-N, SO4-S, Cl, K, Ca and Mg. Nitrate-N and C
l were mutually antagonistic. Soil N had a large positive effect on pe
tiole K and Mg levels and, to a lesser extent, petiole Ca levels. Ther
e was competition between K and Mg in petiole concentration. The sum o
f K, Ca and Mg was essentially constant across fertilizer treatments a
nd sampling times. The sum of NO3-N, SO4-S and Cl was highly variable.
The ratio of cations to anions ranged between three and five across f
ertilizer treatments and sampling times. The data indicate that calibr
ation of the major nutrient element concentrations in potato petioles,
as a guide to fertilization, requires knowledge of background soil fe
rtility conditions with respect to N, K, Cl, Ca and Mg, and an underst
anding of the antagonisms and synergisms among these elements.