Studies on Arbuscular Mycorrhiza and its Relations with Plant Nutrition and Improving Soil Fertility using Tracer Technique

The present study was carried out to study the occurrence of arbuscular mycorrhizae fungi (AMF) on root colonization and spore density of rhizosphere of some medicinal plants. Isolation and identification of some AMF strains and study their effects on growth of black cumin and anise plants in greenhouse experiment fertilized with different labeled nitrogen (¹⁵N) doses under sandy loam soil conditions were also investigated. The occurrences of AMF diversity and mycorrhizal colonization have been studied in rhizosphere soils of 22 medicinal plants in Sekem Company Farm at Sharkia Governorate-Egypt. AMF was observed in almost all plants. The highest root colonization was observed in black cumin plants, being 77% and the lowest was in parsley plants, being 18.17%. The highest spore population (368/100 g rhizosphere soil) was recorded in anise plants and the lowest was observed in lemon grass plants (103/100 g rhizosphere soil). The effect of AMF inoculation on black cumin and anise plants fertilized with different labeled nitrogen doses have been studied. The maximum AMF root colonization in black cumin plants was 83.67% after 120 days in the treatment composite of AMF, Az.chroococcum and B.megatherium in the presence of half nitrogen (M₆N₁) fertilizer rate. While the maximum colonization in anise plants reached 76.67% after 120 days in the same treatment and the same nitrogen dose (M₆N₁). The highest spore density in black cumin plants was 377/100 g soil with the composite treatment (M₆N₁), while in anise plants was 385/100 g soil in the dual inoculation of AMF and Bacillus megatherium using half nitrogen dose (M₅N₁). All growth parameters of black cumin and anise plants were enhanced with AMF inoculation as compared to the un inoculated plants. Application of ¹⁵N technique has a good and unique performance in distinguish of N-sources uptake by plants (nitrogen derived from fertilizer (Ndff) and consequently the nitrogen use efficiency (%NUE)).Therefore, it could be possible to partially replace AMF as bio fertilizer instead of some chemical fertilizers to reduce the costs and avoid the hazard of environmental pollution