Effects of nitrogen, phosphorus and potassium on the growth and flowering of some bedding plants

Abstract

This study was carried out to determine the effects of N, P and K on the growth and flowering of salvia, French marigold, celosia, China aster, coleus, zinnia, petunia and pansy cultivars grown for bedding.The experimental plots consisted of: (1) Plots lacking either one or all of the 3 nutrient elements, (2) standard amounts of all the 3 nutrient elements, (3) double amounts of either one or all of the 3 nutrient elements, (4) four-fold amounts of standard level, and (5) half-amounts of standard level. The plants were grown in clay pots filled with clayish soil. The results obtained in this study are as follows:1. In salvia, total fresh weight of leaf-stem and bud-flower parts was increased by increasing P application and the effect of N and K on the growth and flowering was not conspicuous in this nutritional treatment levels.2. French marigold was responsive to increasing N and P levels in respect to the total fresh weight. However, the effect of K was not conspicuous.3. Celosia was more responsive to K than N and P. The flower head (crest) size was the smallest in K-lacking plot.4. In China aster, as N and P levels were increased, increase in the total fresh weight of leaf-stem and bud-flower parts was observed. However, the plant response to K was not conspicuous.5. Growth and flowering of zinnia and coleus were apparently affected by N and P fertilization. The leaves of coleus receiving higher amount of N showed bright colour, but the leaf colour of plants in the plot which was supplied an excess of K (2K) were dull coloured.6. Although the response of petunia to P and K was not conspicuous, the vegetative growth became vigorous and number of flowers increased by increasing N level.7. Effects of N and P on the growth and flowering of pansy was apparent in this study, but there was no response to K.From the above results, the patterns of growth and flowering response to N, P and K in the bedding plants may be classified into 4 groups as follows: N-, P-, K-, and N-P-types.N-type is a group of plants responsive to N, i. e. petunia.P-type is a group sensitive to the P, i. e. salvia, China aster. Plants belonging to K-type are more affected by K fertilization than N and P, i. e. celosia. French marigold, coleus, zinnia and pansy belong to N-P-type, which are responsive to both N and P.