Influence of calcium and magnesium based fertilizers on fungal diseases, plant growth parameters and fruit quality of three varieties of tomato (Solanum lycopersicum)

Notwithstanding the important roles of calcium and magnesium ions in plant growth and development,the use of fertilizers containing them is not yet a common agricultural practice in Cameroon. Such fertilizers were applied on the soil and leaves of three most cultivated varieties of tomato in the Western Highlands of Cameroon. The effects of these treatments on plant health, growth, development, and yield and fruit quality were determined. The combination of soil application of calcium nitrate and foliar sprays of fertilizer containing calcium (T1) led to significant reductions of the severity and incidence of Phytophthora infestans and Septoria lycopersici on leaves of Rio Grande and Rio de Grenier tomato plants seven days after the first foliar application (d.a.f.a) of liquid fertilizers. At the same time significant reductions in the incidence and severity of S. lycopersici were observed on leaves of Roma plants previously treated with a solution of the fertilizer containing magnesium (T2) or simultaneously treated with calcium and magnesium solutions (T3). Twenty-one d.a.f.a there were reductions in the severity of Alternaria solani on leaves of Rio Grande, Rio de Grenier and Roma plants that previously received T3. Applications of T3 also led to the reduction of the incidence and severity of Fulvia fulva on the leaves of both Rio Grande and Rio de Grenier 21 d.a.f.a. T3 was very effective in enhancing the growth in length and yield of Rio Grande and Rio de Grenier plants. The green-life of fruits produced by these two tomato varieties that received T1 was respectively 10 and 6 days longer than that of control fruits. T2 prolonged the shelf-life of fruits from those varieties by 4 and 12 days respectively. On the whole, Rio Grande and Rio de Grenier plant were the tomato varieties whose health, growth, development, yield and fruit quality parameters were the most positively affected by treatments with fertilizers containing calcium oder magnesium. Roma tomato plants were affected to a lesser extent by these treatments. These results could be interpreted in terms of a temporal shift in the resistance of tomato plants to P. infestans and S. lycopersici on the one hand and A. solani and F. fulva on the other hand and also in terms of similarities of responses of closely related tomato varieties to fertilizers.Keywords: Calcium, fungal diseases, green-life, magnesium, shelf-life, Solanum lycopersicu