Potassium Research and Agricultural Production - The International ...

e quite justified to use the N/K ratio determined in the given conditions as a sound
basis for yield evaluation.
Apparently the point of inflection of the yield curve corresponds to a value of 2.4 for
N/K.lfthe value were higher or lower, yield in the following season was less. N/K= 2.4
corresponds with a yield of 16 t/ha. On the basis of data not quoted here it seems that
the value of N/K which results in the highest yield generally lies within Levy's optimal
limits (9J. that is between 1.9 and 2.4 or very near to them. The yield corresponding
to the optimum value for N/K varies according to variety.
The following conclusions can be drawn about the correlation we have discussed:
a) A comparison of the mean N/K value for flowering and vintage with that for the
preceding year indicates whether fertility of the site is improving or declining and
whether better or poorer yields are to be expected. Apart from a comparison
between years, a comparison of values for flowering time and vintage is also of
interest. A more favourable ratio at vintage than at flowering indicates the correct
tendency. This indicates that in the relevant year on that area the conditions have
become favourable both for the N/K ratio and for photosynthesis for the formation
of dry matter relative to the increase in potassium supply (frost resistance of .
buds, buds development and metabolic status of the flowers).
b) A value for N/K in the plantation between the optimum (fig. 7) and 5.5 indicated
absolute or relative excess of N in the leaf and a corresponding K deficiency. With
CIIATJGf RAn
lJUD!; rn'
150
/g.1. IOU. 10.0 1010. /gll.
Fig. 8. P content of the vine-leaf and overage yield.
238
1,1