Joint International Conference on Long-term Experiments ...

Table 4: Results of regression analysis
Treatments Regression equation R value
Control y = 11,83Ln(x) + 105,02 0.7652
N1 y = 14,097Ln(x) + 93,719 0.7971
N2 y = 12,989Ln(x) + 89,133 0.8198
N3 y = 11,83Ln(x) + 105,02 0.7652
NPK group y = 13,019Ln(x) + 88,636 0.8043
Limed group y = 15,419Ln(x) + 111,97 0.8153
In the 1970s Stanford and co-workers (Stanford and Smith (1972), Stanford (1973),
Stanford et al. (1974)) advanced the concept of potentially mineralizable N (Npot) and a
related mineralization rate constant (k) for use in characterizing soil-available N. Since
then this concept has been used, modified, and discussed in great detail by numerous
scientist, but they theory has been accepted generally.
This theory assumed that organic nitrogen mineralization at optimum temperature and
moisture followed first-order kinetics. Accept the above mentioned theory our results
have made possibility to estimate the potentially mineralizable N of the soil and its rate
constant. Our results have confirmed that the correlation between 1/Nt and 1/t is linear.
The potentially mineralizable N-contents (Npot) and the constant of the mineralization
(k) were calculated according to Filep and Tóthné (1980) (Table 5.).
It can be established that the applied treatments has not remarkably effect on the values
of Npot, but higher constant rate of mineralization was achieved in the limed treatments
than the treatments without lime. The lowest mineralization rate constant was
established in the control.
Table 5: Calculated Npot and k values
Treatments Npot (mg/kg) k (35ºC)
Control 277.799 0.056
N1 233.247 0.057
N2 233.451 0.058
N3 234.028 0.058
NPK group 233.551 0.058
Limed group 249.885 0.064
3. Interpretation of results of chemical and biological analysis to yield
Obtained results of biological analysis can be compared to the yield (Figure 2.).
The constant of the mineralization was the lowest in the control. Increasing dose of onesided
N slightly increased the k value and decreased the yield, especially N2 and N3.
This effect can be explained by the increasing acidization of soil and the increasing
content of easily soluble N fractions in these treatments. The higher k was obtained in
the case of the limed group. It can be explained the above mentioned more favourable
soil conditions. The result of NPK treatment-group was better than the results of N
treatments and control but worse compared to the limed group.
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