Effect of nitrogen and phosphorus nutrition on growth, flowering, flower yield and chlorophyll content of different varieties of African marigold (Tagetes erecta L.)

Abstract: A field experiment was conducted to study the effect of N and P2O5 nutrition on growth, flowering, yield and chlorophyll content of different varieties of African marigold on the medium black calcareous soil during two consecutive years. The treatments consisted of all combination of three levels of nitrogen (100, 150 and 200 kg N ha^-1) and three levels of phosphorus (50, 100 and 150 kg P2O5 ha^-1) with three varieties of African marigold viz., Local Orange (V1), Pusa Basanti (V2) and Pusa Narangi (V3). The growth parameters like plant height, number of primary and secondary branches as well as leaf area exhibited increasing trend with increase in nitrogen level which were highest at N3 (200 kg N ha^-1). The phosphorus application failed to influence the growth of plant except plant spread. The maximum total chlorophyll content, 1.452 and 1.431 mg g^-1, respectively was found due to addition of nitrogen and phosphorus. The higher number of flowers, diameter of flower, number of ray florets per flower and flower yield was recorded at higher level of each nutrient i.e. N3 (200 kg N ha^-1), and P3 (150 kg P2O5 ha^-1). Number of days to first flower was advanced with increasing levels of N. Variety Pusa Narangi produced the biggest flower diameter (6.20 cm), highest number of flowers per plant (56.34), flower yield (183.0 quintal ha^-1), leaf area (13.89 cm²) and total chlorophyll content (1.432 mg g^-1) in leaves. The interaction effect of N and P was found significant for plant spread at 60 DAT and at the end of harvest season. The combination N3P3 (200 kg N ha^-1 and 150 kg P2O5 ha^-1) recorded maximum plant spread (42.87 and 56.65 cm) at 60 DAT and at the end of harvest season, respectively. Treatment combination N2P3 (150 kg N ha^-1 and 150 kg P2O5 ha^-1) recorded significantly larger flower diameter (7.79 cm).