Influence of different NPK fertilization levels and humic acid rates on growth, yield and chemical constituents of roselle (Hibiscus sabdariffa L.)

Abstract

In order to study the influence of NPK fertilization levels (0.0, 50, 75 and 100 of recommended dose), humic acid rates (0.0, 2.0 and 4.0 l/fed.-1 as foliar spray) and their combinations on growth and productivity of roselle, two field experiments were conducted for two summer seasons of 2017 and 2018 at the Experimental Farm of Faculty of Agriculture (Ghazala Farm), Zagazig University, Egypt. The recommended dose (RD) of NPK were (N fertilizer at 68 + P2O5 fertilizer at 32 + K2O fertilizer at 24 kg/fed.-1). The experimental design was split-plot which arranged in three replicates. Furthermore, the obtained results referred that the highest values of plant height, number of branches/plant and total dry weight/plant were achieved with 100% of RD compared to the other levels. Also, the same trend were obtained toward the yield components (fruit number/ plant, sepals and seed yield per plant and per fed.-1) and chemical constituents (N, P and K percentages as well as total soluble solids). In addition, the highest values of abovementioned parameters were recorded by 4 l Fed.-1 humic acid which followed by 2 l Fed.-1 humic acid with significant difference between them and control (untreated plants). Generally, it could conclude that humic at 4 l/fed.-1 combined with 100% RD, showed a uniform influence in enhancing of roselle growth and its productivity under Sharkia Governorate conditions.

Effect of NPK combinations on some growth and yield indicators of two varieties of roselle plant (Hibiscus sabdariffa L.)

“…The results of the same table showed that the fertilizer combinations caused a significant effect on the plant height, as the C6 combination gave the highest average plant height 195.05 cm, and it did not differ significantly from the average of the C5 combination, which amounted to 189.05 cm, compared to the C0 treatment (no addition), which gave an average 138.45 cm, with an increase of 40%, while combinations C1, C2, C3 and C4 gave averages of 148.45, 153.65, 165.2 and 175.75 cm, respectively. This superiority may be attributed to the role of KPN fertilizer combinations in stimulating cell division and elongation, which provided a suitable environment for plant growth and thus increased the efficiency of the photosynthesis process and increased the representation of dry matter in the plant, which was reflected in the length of one internode and also the number of internode, and thus was reflected positively in the height plant, especially when the soil suffers from A decrease in the level of NPK [10].…”

“…Potassium is essential for many important physiological activities and processes, such as the process of carbon analysis and the transfer of nutrients resulting from the process of carbon metabolism to the lower organs of the plant [9] in addition to activating enzymes and reducing the absorption of harmful ions such as sodium. (Na +2 ) and iron ions in silty and saline soils [10]. Studying the process of balance between these three elements, which are called the main elements, is of great importance, as the presence of an element in the soil solution in a quantity that exceeds the other elements has a negative effect on the absorption of the other elements.…”