One field experiment was carried out during the two successive winter seasons of
2015/2016 and 2016/2017 at a Private Farm in El-Sowa Village, Abo Hammad District, Sharkia
Governorate, Egypt, to study the effect of cultivars, mineral phosphorus, and mycorrhizae fungi
inoculation on plant dry weight and chemical composition of onion plants under clay soil conditions
and flood irrigation system. The experiment included 18 treatments which were the combinations
among two onion cultivars (Giza 20 and Beheri improved), three levels of mineral phospours fertilizer
(0, 30 and 45 kg P2O5/fad.) and three levels of mycorrhizae (0, 2 and 4 kg/fad.). These treatments were
arranged in a split split plot design system with three replicates. Cultivars were randomly arranged in
the main plots, levels of P2O5 were randomly distributed in the sub plots, while mycorrhizae levels
were randomly arranged in the sub sub plots. The triple interaction treatments among onion Giza 20
cultivar, P2O5 at 45 kg/fad., and inoculation with mycorrhizae at 4 kg/fad., significantly increased dry
weight of roots, bulbs, leaves and total dry weight/plant at 75 days after transplanting, as well as, N, P
and K uptake by roots, bulb and leaves at 105 days after transplanting.