MSc

In Kerala, a major portion (80 %) of cultivated soils is deficient in available magnesium and in many cases, crop growth is found to be limited by magnesium deficiency. Tomato (Solanum lycopersicum L.) which belongs to the family solanaceae is an important vegetable crop of Kerala susceptible to magnesium deficiency. Hence the particular study will be helpful in deciding the rate of magnesium to be applied along with major nutrients for yield maximization of tomato in magnesium deficient Ultisols.

Field experiment entitled “Soil test based fertilizer prescriptions for tomato (Solanum lycopersicum L.) in magnesium deficient Ultisols of Kerala” was conducted at College of Horticulture, Vellanikkara during rabi 2016, to test verify the formulated fertilizer prescription equations for tomato (var. Anagha) and to identify optimum rate of magnesium to be applied, along with recommended fertilizer package, for maximizing the yield. Experiment consisted of 12 treatments viz., absolute control (T1), soil test based package of practices recommendations of KAU (T2), Soil test crop response correlation studies (STCR) + Integrated plant nutrient
system (IPNS) for target 25t ha-1 (T3), STCR + IPNS for target 30 t ha-1 (T4), T3 +
MgSO4 at 40 kg ha-1 (T5), T3 + MgSO4 at 60 kg ha-1 (T6), T3 + MgSO4 at 80 kg ha-1 (T7), T3 + MgSO4 at 120 kg ha-1 (T8), T4 + MgSO4 at 40 kg ha-1 (T9), T4 + MgSO4 at
60 kg ha-1 (T10), T4 + MgSO4 at 80 kg ha-1 (T11) and T4 + MgSO4 at 120 kg ha-1 (T12).

Among the different treatments, T8 (STCR + IPNS for target 25 t ha-1 + MgSO4 at 120 kg ha-1) gave the maximum yield (37.75 t ha-1), number of fruits (79.66) and benefit- cost ratio (3.09). With regard to the quality of fruits, the highest titratable acidity (1.31 %), total soluble solids (TSS, 5.93 oB) and ascorbic acid content (18.34 mg 100 g-1) were observed in treatments T10, T12 and T8 respectively. Chlorophyll content of the leaves was higher in magnesium applied plots compared to
absolute control.




Results of the linear correlation studies revealed that fruit yield and chlorophyll content were positively correlated with the uptake of nitrogen and magnesium. Quality parameters were also positively and significantly correlated with the nutrients applied. Among the nutrients, phosphorus and magnesium were positively correlated with titratable acidity. Ascorbic acid content of fruit was found to be positively and significantly correlated with all macro and micro nutrients. Total soluble solids were significantly and positively correlated with phosphorus uptake.

Response curve was fitted to determine the optimum level of magnesium to realize maximum yield response. The results revealed that the optimum dose of magnesium sulphate required is 105.10 kg ha-1, in order to get maximum yield of tomato.

From the study, it can be concluded that the fertilizers applied as per STCR + IPNS target yield equations along with required magnesium application contribute much towards the crop requirements for better yield. Future works have to be done in varying soil conditions with different sources of magnesium for different crops.