In order to study the effect of calcium-potassium Equilibrium in hydroponics culture nutrient solution on growth, nutritional status and productivity of tomato plants (cv. Red spring) an experiment was conducted at a private hydroponic farm in Qena Governorate through the Soils and Water department, faculty of Agriculture, South Valley University, Egypt. The site is at (latitude 26° 11' 22.2'' N to Longitude 32° 44' 25.5'' E), and 81 m above sea level.
Tomato plants were grown hydroponically using six types of nutrient solution: 1) standard solution adapted with nutritive needs of tomato plants (balanced in Ca and K), 2) Ca deficient solution, 3) Ca excess solution, 4) K deficient solution, 5) K excess solution and 6) Ca and K excess solution.
The obtained results showed that, Compared to balanced Ca-K solution or those deficient in Ca or K content, “Red Spring" tomato plants grown in nutrient solution rich Ca or in K or rich in both Ca and K present higher and significant growth parameters, cluster number/plant and fruit numbers/cluster. Significant differences were obtained in leaves mineral contents (N, P, K, Ca, Fe and Zn) as a result of varying Ca-K equilibrium of nutrient solution. However, the antagonism between Ca, K and Mg Clearly observed. Fruit physical and chemical characteristics significantly affected by varying the Ca-K equilibrium in the nutrient solution.