To study the effect of biofertilizers on physiological parameters and yield of three varieties of Oat (Avena sativa L.), field experiments were conducted during winter seasons 2016-2017 and 2017-2018 at Al- Zubair district (20 km. West of Basrah province) in sandy loam soils. A split plot arrangement, using RCBD with three replicates, the main plots contained varieties: V1 (Genzania), V2 (Shaffaa), V3 (Carloup), Biofertilizer, treatments were at the sub plots: B0 (control), B1 (NPK mineral

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... lizer as recommended), B2 (biofertilizers NPK), B3 (mineral fertilizer PK+ biofertilizers N), B4 (mineral fertilizer K+ biofertilizers NP), B5 (mineral fertilizer P + biofertilizers NK), B6 (mineral fertilizer N + biofertilizers PK). Data were collected on Flag leaf area FLA, Leaf area duration LAD, Leaf area index LAI, Crop growth rate CGR, Relative growth rate RGR, Net assimilation rate NAR, Plant high Tillers number m2 and grain yield t ha-1. The results showed that the adding of biofertilizers NPK (B2) led to a significant increase in the studied traits (FLA, LAD, LAI, CGR, RGR, NAR, and grain yield). The grain yield were increased about 189.96 and 197.3% as compared with control in each seasons respectively. Cultivar Genzania resulted in highest grain yield among studied varieties in the first season (5.774 t ha-1), while cultivar Shaffa gave the highest grain yield in the second season (8.691 t ha-1). The interaction between Ganzania and B2 treatment recorded the highest seed yield (8.429 tan ha-1) in the first season. While, in the second season all varieties that interacted with B2 treatment produced the highest seed yield.