The aim of this research was to study the possibility of biofertilizers using and organic
manuring (biogas fertilizer) instead of chemical fertilizers for potato growth and production.
Two field experiments were carried out at the Vegetables Experimental Farm of Fac.Agric
Moshtohor, Zagazig Univ. during two successive spring seasons of 2001 and 2002 Azotobacler chrococcum and Azospirillurm lipoferum were used as nitrogen fixing bacteria.
While, B. megateriumt var. phosphaticum was used as phosphate solubilizing bacteria. Biogas
manure and ammonium sulphate were used as organic and inorganic fertilizers, respectively.
Biogas manure was added at a rate of 6 ton/fed.(90 kgN/fed.)as well as using ammonium
sulphate at the same level of nitrogen.
Obtained results indicated that the highest records of evoluated CO2 were observed in biogas manure treatments. Whereas, the highest records of N2-ase activity were observed in
rhizosphere of potato plants inoculated with asymbiotic N2- fixers. Inoculation of potato tubers
with phosphate solubilizing bacteria combined with various treatments under investigation
increased CO2 evolution and N2-ase activity.
Inoculation of potato tubers with Azotobacter & Azospirillum and a half dose of ammonium sulphate receiving gave higher records of NH4-N and NO3-N in rhizosphere soil than the application of full dose from ammonium sulphate. Biogas manure amendment showed the highest records of N and P in rhizosphere soil.
Growth characteristics of potato plants were significantly increased with biogas manure
application in combination with potato tuber inoculation with phosphate solubilizing bacteria.
Potato tuber inoculated with Azotobacter & Azospirillum combined with B.megaterium var.
phosphaticurn showed the highest records of carbohydrate content in tubers. Insignificant
difference in tuber yield/ fed. was observed between asymbiotic N2 - fixing bacteria and biogas
manuring treatments.Generally, tuber yield/fed. was higher with Azotobacter & Azospirillum
and biogas manuring treatments than ammonium sulphate application. Therefore, the use of
biofertilizers or organic manuring may be recommended as a substitute for chemical fertilizers
in potato crop production especially for exportation.
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