|Authors: ||M. Pešaković, R. Miletić, Z. Karaklajić-Stajić, M. Lukić, D. Đukić, L. Mandić|
|Keywords: ||Azotobacter, oligonitrophyles, mineral fertilizers, plum planting, soil|
The paper shows the effect of increasing NPK fertilizer rates on the developement of the Azotobacter and oligonitrophyles over the three-year period (2003-2005). The investigation was carried out in the plum planting established by Fruit Research Institute Čačak (Serbia) according to the randomised block design with three replications.
The soil was treated with 8:16:24 + 3% of MgO mineral fertilizer as follows: treatment N1 – 400 kg ha-1; treatment N2 – 600 kg ha-1; treatment N3 – 800 kg ha-1 and treatment N4 –1000 kg ha-1. Unfertilized soil was used as the control.
The effect of the studied mineral fertilizer rates was determined three times over the growing season.
It was checked by identification of the number of Azotobacter (by the fertile drop method on Fyodorov’s medium) and oligonitrophyles (by indirect rarefaction method on Fyodorov’s medium). The data obtained showed that the use of high mineral fertiliser rates (N3 and N4) induced a decrease in the number of Azotobacter and oligonitrophyles.
On the other hand, the use of lower fertilizer rates (N1 and N2) enhanced the number of the studied group of microorganisms.
The most pronounced fertiliser effect was recorded in the second sampling period and in the first year of the experiment.
Considering the soil biological properties, the N2 treatment (600 kg ha-1) can be recommended as the most favourable one for ‘Cacanska Rodna’ growing in the stated agro ecological conditions.
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