Macronutrient application affects morphological, physiological, and seed yield attributes of Calendula officinalis L.

Effects of N, P and K applications alone or in various combinations and ratios were studied on the morphological, physiological, yield attributes and seed production of calendula. Treatment combinations were control (no NPK application), 150 kg ha-1 N, 80 kg ha-1 P, 150 kg ha-1 K, N + P, N + K, P + K and N + P + K, while in a second experiment, different ratios of NPK were compared to determine the best combination and ratio of tested nutrients for optimal growth, quality, yield and seed production. Plants supplied with NPK had vigorous growth, higher leaf total chlorophyll content and flowered earlier with greater flower fresh and dry weight along with improved photosynthetic performance. Plant biomass and seed yield along with leaf N and K was also higher in plants fertilized with NPK. In the second experiment, application of 200:100:100 kg ha-1 NPK resulted in maximum growth, flowering and seed yield along with higher photosynthetic activity. Leaf area and improved leaf nutrients status was observed at 150:150:150 kg ha-1, while 200:200:200 kg ha-1 NPK increased stomatal conductance, photosynthetic rate, leaf P and flower weights. Results demonstrated that higher level of nitrogen along with lower level of P and K are vital for quality calendula flower and seed production.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author