P. Csatho, CORRELATIONS BETWEEN 2 SOIL EXTRACTANTS AND CORN LEAF POTASSIUM CONTENTS FROM HUNGARIAN FIELD TRIALS, Communications in soil science and plant analysis, 29(11-14), 1998, pp. 2149-2160
Corn (Zea mays L.) leaf weight, leaf potassium (K) content at the flow
ering stage, and ammonium lactate (AL)- and neutral normal ammonium ac
etate (NH4Ac)-extractable K were determined in a network of 27-year-ol
d long-term Hungarian field trials (''OMTK trials'') with different K
fertilization rates on nine locations representing various agro-ecolog
ical and soil conditions of the country. Corn leaf weights at the flow
ering stage were affected less by soil-extractable K than by the diffe
rent agro-ecological conditions. Corn K contents, however, were much m
ore affected by K rates than leaf weights. The additional effect of th
e higher K rate, however, was not significant. Leaf K contents were af
fected by site also. There was no significant correlation between corn
leaf K content and leaf weight. Above 1.5% K leaf content, however, l
eaf weights did not increase. Corn leaf weight increased together with
soil test values up to 150-160 mg kg(-1) soil-extractable K. There wa
s a poor linear correlation between soil-extractable K and leaf weight
(r = 0.40*). There was a significant quadratic polynomial correlatio
n between soil-extractable K and leaf K content (R = 0.60**). The low
er limit of good K supply, indicated by leaf K content at flowering (1
.5% K), was usually reached when the soil-extractable K level reached
150 mg kg(-1). The most significant linear correlation was found betwe
en NH4Ac- and AL-extractable K (r = 0.91**). Both the AL and NH4Ac me
thods identied the different soil K levels similarly. As a first attem
pt, new NH4Ac-extractable K supply categories were established for Hun
garian conditions. Soil and plant K analysis data proved to be useful
tools in adapting the results from long-term field trials for improved
fertilizer recommendations.