Joint International Conference on Long-term Experiments ...

Table 2. The effect of soil texture on responses to K application in Hungarian field trials with
winter wheat, set up between 1960 and 2000
Soil
texture
groups
Number
of trials
(n)
K A * AL-K 2 O
mg/kg
(NP)
K 2 O dose
kg/ha**
(K-control)
Grain yield
on NP plots
(NP/NPK)
Relative
yield,%
(NPK-NP)
Surplus,
t/ha
(NPK-NP)
Sands 5 28 75 112 3,08 89 0,41
S. loams 7 35 120 66 4,22 94 0,32
Loams 17 39 160 15 4,15 98 0,06
C. loams 20 46 210 7 3,98 98 0,08
Clay soils 5 56 218 0 4,41 100 0,00
Mean 54 42 171 26 4,02 97 0,13
*Upper limit of plasticity, according to Arany (similar to the US plasticity index).
** K 2 O doses needed for maximum economic yields (~ 95% of maximum yield)
Table 3. The effect of soil texture on responses to K application in Hungarian field trials with
alfalfa, set up between 1960 and 2000
Soil
texture
groups
Number
of trials
(n)
K A * AL-K 2 O
mg/kg
(NP)
K 2 O dose
kg/ha**
(K-control)
Grain yield
on NP plots
(NP/NPK)
Relative
yield,%
(NPK-NP)
Surplus,
t/ha
(NPK-NP)
Sands 2 27 60 120 5.55 78 1.60
S. loams 3 35 163 13 8.42 98 0.26
Loams 2 42 205 46 8.95 90 0.74
C. loams 12 45 172 16 7.74 98 0.18
Clay soils 3 55 150 0 8.50 100 0.00
Mean 22 40 175 20 8,92 96 0,33
*Upper limit of plasticity, according to Arany (similar to the US plasticity index).
** K 2 O doses needed for maximum economic yields (~ 95% of maximum yield)
On the basis of these data sets, new AL-K 2 O supply categories were elaborated for
maize, winter wheat and alfalfa, according to their different responses to K fertilization.
The new AL-K 2 O supply categories for clay loam and clay soils are much lower
than those in former fertilizer advisory systems.
CONCLUSIONS
For evaluating the connection between AL-K2O values and responses to K fertilization
in Hungarian field trials with maize, alfalfa and winter wheat, Bray's relative index
method was a useful tool. The difference between the responses of maize, winter wheat
and alfalfa to K fertilization was also indicated in the different "c" values. AL- K values
indicated the K-supply of the different soils adequately.
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