Reducing the amount of mineral phosphorus and potassium fertilizers by using its natural sources for Red Globe grapevines

This investigation was conducted during three successive seasons of 2016, 2017 and 2018 in a private vineyard located at Samaloute district, Minia Governorate, Egypt on Red Globe grapevines to study the possibility of reducing the amount of mineral phosphorus and potassium fertilizers by using natural rocks, combined with organic manure (FYM), bio-fertilizers (BF) and elemental sulphur (S). The chosen vines were nine years old, grown in a clay loam soil, spaced at 1.75 x 3 m apart, irrigated under surface irrigation system, and spur-pruned, trellised by Gable supporting system and trained to quadrilateral cordon system. The results revealed the possibility of using 50 % natural rocks of P and K + FYM + BF + S as a partial substitute of mineral phosphorus and potassium fertilizers. Application of 50 % mineral P and K + 50 % natural rocks of P and K + FYM + BF + S exhibited the most suitable management combination for achieving the best yield with its components, physical properties of clusters, improved physical and chemical berry characteristics, vegetative growth, leaf chlorophyll and mineral content of Red Globe grapevines. The treatment also improved the soil properties.