Cultivation of calcareous soils faces many difficulties due to its properties, as it lacks organic matter, as well as low availability of nutrients, especially phosphorous. This study, using two cereal crops (wheat and barley) to study the effect of compost as a source of organic matter and nano-hydroxyapatite as a source of phosphorus onsome properties of calcareous soil and P content in plants. The main plots were compost (C) with three doses C0 (without C), C1 (12 ton/ha) and C2 (24 ton/ha),

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... the sub plots were different sources of phosphorous [the traditional P CaH6O8P2 (S0) and nano-hydroxyapatite (nHAP) with two rates of S1 (1.5 g/L) and S2 (3 g/L)]. The nano-hydroxyapatite is characterized by X-ray powder diffraction (X-ray), scanning electron microscopy (SEM). Obtained results stated that the biological yield, grain and straw of both wheat and barley were significantly increased with treatments as compared to C0 and S0, especially with C2 and S2. In addition, there is a positive trend between treatments rate and P contentin straw and grain of both crops, the maximum increase was observed with C2 and S2.Also, the application of compost led to a change in soil chemical properties, pH wasdecreased at treatments applied and such decreases were proportional to treatments concentration increase. An opposite trend was observed with organic matter (OM) and available phosphorus. In addition, there is a positive and highly significant correlation between grain yield with P content in plants.