Effect of mineral and biological nitrogen fertilization on Thompson seedless grape transplants [electronic resource]: III. effect on microbial activity in me soil rbizosphere.

Includes references.

A pot experiment was carried out in 200 1 and 2002 seasons on Thompson Seedless grape transplants to study the effect of two sources of nitrogen fertilizers (mineral and biological) on microbial activity in the rhizosphere of transplants. The experiment included three levels of mineral nitrogen (M)=zero, M2=5 and M3=10g N I plant I year) and four levels of biological nitrogen (B)=zero, B2=50, B3=100 and B4=200ml) of liquid culture of free living nitrogen fixation bacteria "Azotobacter chroococcum". Thus, the study is a factorial experiment in a randomized complete block design. The activity of Azotobacter expressed as counts of bacteria and C02 evolution in the rhizosphere were determined after 45, 90, I3S and 180 after inoculation time. Results proved that the levels of mineral nitrogen showed more or less similar values. On the contrary, the levels of biological nitrogen increased Azotobacter activity and the highest values were obtained by levels (B3) &(B4). Regarding the interaction between mineral and biological nitrogen, fertilizing with mineral nitrogen alone had no promising effect on both the count and C02 evolution. This is excepted because the soil of these treatments was 80t inoculated with Azotobacter. On the contrary, fertilizing with biological nitrogen alone increased counts of bacteria and C02 evolution compared with those of unfertilized plants. The promising biological nitrogen treatment was (M) x B4) in the two seasons. However, other combinations [treatments (M2 x B3), (M2 x B4) and (M3 x B4)] gave the highest values of bacteria counts and C02 evolution In other words, combining mineral with biological nitrogen showed more increase in the activity of the bacteria in the rhizosphere of transplants than adding any form alone and the recommended treatment was (M2 x B3)

Summary in Arabic.

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