Suitability of sul-po-mag as a potassium cum magnesium fertilizer for banana in Kerala

Abstract

The present investigation was carried out in the Department of Soil Science and Agriculture Chemistry, College of Horticulture, Vellanikkara during the period of September 1994 to August 1995. The study was aimed to bring to light the suitability of Sul-Po-Mag as a potassium cum magnesium fertilizer for banana in Kerala. The treatments included Sul-Po-Mag substitutes of potassium to the extend of -25, 50 and 100 per cent in the normal recommended dose of NPK as urea, diammonium phosphate and muriate of potash at the rate of 190 g N, 115 g P205 and 300 g K20 per plant per year. Treatments of muriate of potash supplemented with magnesium and sulphur separately and with magnesium and sulphur together were also included and they were compared with the recommended practice. The experiment was laid out in randomised block design with three replication. During the early stages of growth, the treatments failed to influence the morphological characters such as height, girth and number of leaves of the plant. But at the later stages, the girth and the number of leaves differed significantly and the application of Sul-Po-Mag showed a favourable influence on these characters. No significant difference was observed in characters like total number of suckers, days to flower, days to mature and total duration of the crop among the treatments. Among the bunch characters, numbers of hands, length and girth of fingers and bunch weight were influenced by the difference in treatments while the number of fingers per bunch and weight of fingers remained unaffected. The maximum yield was given by the treatment where potassium was supplied by Sul-Po-Mag and muriate of potash in half doses. Though the treatments differed

significantly in yield from the control, where no fertilizer was applied, the treat- ments of muriate of potash and Sul-Po-Mag are on par indicating that Sul-Po-Mag is as good as MOP for its capacity to meet potassium requirement of the crop. The treatments did not differ significantly in quality parameters such as reducing sugars, total sugars, sugar acid ratio, weight of pulp and peel and pulp peel ratio. But significant difference was observed with total soluble solids, ascorbic acid content, non reducing sugars and acidity. High value of these characters were recorded with Sul-Po-Mag except for the reducing sugars and total sugars. Treat- ments with magnesium and sulphur were found to decrease the sugar content of fruits. High pulp peel ratio of Sul-Po-Mag treatments showed increased storage quality. The nitrogen, phosphorus and sulphur contents of leaves remained unaffected both at vegetative and harvest phases, while potassium, calcium and magnesium differed significantly between the treatments. The contents in leaf of N, P, K, Ca, Mg and S were decisively influenced by the treatments at the time of shooting. Nutrient contents of leaves were found to increase till shooting and a drastic reduction was observed thereafter. Calcium, magnesium and sulphur contents in the fertilizer increased their availability in soil and the plant content. Treatments with Sul-Po-Mag and magnesium showed high content of potassium in leaves. The contents of potassium, calcium, magnesium and sulphur were found to be the highest in the pseudostem followed by leaves. Rhizome and fruit also showed appreciable amount of these nutrients. The total uptake of potassium, calcium, magnesium and sulphur ranged between 365.26-221.06, 73.57-57.97, 4.45-14.5 and 3.71-4.94 g plant-1 respectively. Only the total uptake of magnesium

was decisively influenced by the treatments. The maximum values of uptake of magnesium found in treatment which was supplied with Mg equivalent to that present in half dose of Sul-Po-Mag. Available P, available K and available S contents of the soil were found to be nonsignificant both at vegetative and harvest stages. The sulphate containing treatments were found to decrease the pH of the soil. Maximum electrical conductance was found with Mg supplied treatments. Organic carbon content was found to be significant only at harvest stage. Calcium, magnesium and sulphur contents in the fertilizer were found to increase the soil content of these elements.