Application Methods of Calcium Supplements Affect Nutrient Levels and Calcium Forms in Mature Tomato Fruits

Abstract

The glasshouse study examined the effects of various application methods of calcium (Ca) on the concentration of Ca, magnesium (Mg), potassium (K), phosphorus (P), boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), and Ca compounds in mature fruits of tomato plants (Lycopersicon esculentum Mill., cv. 21Shijibaofen). Calcium was applied by increasing Ca concentration in nutrient solution (10 mM Ca), spraying the mixture solution of 20 mg/L NAA (methyl α-naphthyl acetate) + 0.5% CaCl2 on the first inflorescence and the two leaves upper and lower the first inflorescence during anthesis, and on the fruits of 1-week- and 3-week-old. The results showed that calcium content in the fruit increased significantly in all Ca treatments except spraying Ca on the 3-week-old fruit. However, Ca application decreased concentrations of K, Mg, P, B, and Mn in the fruit. The fraction of Ca pectate in the fruit significantly increased when increasing Ca concentration in nutrient solution and foliar and 1-week old fruit's application of Ca solution. Meanwhile, Ca application increased vitamin C content and decreased the percentage of titratable acidity in the fruit. It is concluded that spraying Ca solution on the leaves during anthesis and spraying Ca on the young fruits are two effective methods to increase Ca content and improve the fruit quality.