During 2015 and 2016 seasons, Red Roomy grapevines were fertilized with three organic manures (Poultry manure, Plant compost and Farmyard manure) enriched with Spirulina platensis algae as a partial replacement of 25 to 75% inorganic N. The merit was detecting the best source of organic N enriched with Spirulina platensis algae applied with inorganic N that responsible for producing higher yield with better berries quality.
Replacing 50% of inorganic N by 50% organic manures enriched with Spirulina platensis algae at 20 ml/vine was enhancing growth, yield and cluster weight on the other hand replacing 75% of inorganic N by 75% organic manures enriched with Spirulina platensis algae at 40 ml/vine gave favourable effects on vine nutritional status, berries colouration and quality of the grapes. Percentage of shot berries was greatly declined by using N as 25% inorganic N plus 75% organic manures enriched with Spirulina platensis algae at 40 ml/vine. In descending order, the best organic manures in this respect were poultry manure, Plant compost and Farmyard manure.
For enhancing growth and yield of Red Roomy grapevines, it is suggested to supply the vines with N (60g/vine/year) through 50% inorganic N + 50% poultry manure enriched with Spirulina platensis algae at 20 ml/vine/year. Fertilizing the vines with N as 25% inorganic N + 75% poultry manure enriched with 40 ml Spirulina platensis algae gave the best results with regard to berries colouration and quality.