Influence of Level and Frequency Of Nitrogen Fertilization on Growth, Flowering and Postharvest Quality of Tuberose (Polianthes tuberosa L)

Abstract

This study was conducted to determine the influence of various levels of Nitrogen and frequency of application on growth, flowering and postharvest quality of tuberose. Nitrogen tended to stimulate an increase of leaf length in Kabete but did not influence the number of basal leaves. with the application of 0, 21.25, 42.5 and 85.0 kg N/ha, leaf length increased from 38.2 cm to 39.2, 40.5 and 38.2 cm . However increase this was not significant. Nitrogen application promoted the increase of the spike and rachis length and spike diameter both at Kiambu and Kabete. However, only the spike diameter increased significantly with application of N giving the highest spike diameter at the highest N level. Split N application also positively promoted greater spike and rachis length and spike diameter. The spike growth rate and the number of leaves and florets per spike were not significantly influenced by N level. The distal floret size and colour were not significantly affected by N level. However, the latter decreased while the former tended to increase with N levels. Increased N levels delayed the senescence of flower sepals and the yellowing and senescence of distal florets but it did not prevent their abortion. The application of 0, 21.25, 42.5 and 85.0 kg N/ha significantly delayed senescence of sepals and the unopen distal florets giving the greatest delay at the highest N level. Split application of N did not significantly influence the period to senescence of sepals and the yellowing and senescence of the distal florets. However, the period to the wilting and senescence of the last open floret and the total number of open florets tended to decrease with split N application. Nitrogen application did not significantly influence the period to the wilting and senescence of the last open floret and the number of dry and senesced florets. Both split N application and the levels of N increased the number of spikes produced. However, the increase due to N levels was not statistically significant. The spike yield increased with split N application and rose from 17.5 to 18.0 and 23.8 sterns per plot (m2) at 4 wk, 2 wk and 1 wk application interval, respectively. Nitrogen application increased production and quality of cut tuberose. A level of 42.5 kg N/ha application promoted optimum response for most observed parameters. Split N application was also found to improve yield and quality of cut tuberose with higher frequencies of application giving better results.