Foliar Calcium and Magnesium Application Effect on Potato Crop Grown in Clay Loam Soils

Calcium (Ca) and magnesium (Mg) are of the secondary nutrients that required by plants for healthy growth. So, two field experiments were conducted at Kafr Bosat Village, Talkha District, Dakahlia Governorate, Egypt (Latitude 30° 43' 22.01" N, Longitude 30° 16' 44.50" E) during the winter growing seasons of 2014/2015 and 2015/2016 to investigate the effect of foliar Ca and Mg application and their interactions on the growth, yield, quality, nutrient concentration and uptake of potato crop (Solanum tuberosum, L. - c.v. salany) that grown in clay loam soil. The experiment was designed as a spilt plot design with three replicates; the main plots were assigned for three levels of foliar application of Mg; Mg0, Mg1 and Mg2 (control, 0.2 and 0.4 % Mg as magnesium sulfate), and the sub plots were devoted to three levels of foliar Ca; Ca0, Ca1 and Ca2 (control, 0.6 and 0.8 % Ca as calcium nitrate). Results showed the importance of Ca and Mg supplies, where they illustrated that foliar application of Ca and Mg levels significantly increased plant growth parameters at 90 days as plant fresh weight, leaf area and chlorophyll a, b and total concentrations; tubers yield and its quality as % of dry matter, starch and protein contents, and uptake of N, P, K, Ca and Mg (kg fed-1) in shoots and tubers at harvest. Plant tuber yield and average tuber weight increased with increasing foliar application of Ca, whereas number of tubers plant-1 was decreased.  Also, results at 90 days, demonstrated that foliar application of Ca and Mg levels significantly increased N, Ca and Mg concentrations in leaves, but K concentration was decreased. At harvest, tubers content of N, P, K, Ca and Mg increased significantly with foliar application of Ca up to Ca2 (0.8 % Ca) and spraying with Mg up to level Mg1 (0.2 % Mg). Interaction between foliar application of Ca and Mg levels had a significant effects on plant growth parameters, tubers yield and its quality and nutrients uptake in dry shoots and tubers yield. The highest values of tubers yield (17.251 ton fed-1), dry matter % of tuber (24.78 %), starch % (18.24 %) and contents of N, P, K, Ca and Mg in shoots and tubers were recorded by the interaction of Ca2×Mg1. It could be concluded that foliar applications of Ca and Mg at 0.8 % Ca as calcium nitrate and 0.2 % Mg as magnesium sulphate were more important to improve plants growth and increase tubers yield and their quality under this conditions.