Comparative assessment of fertilization of marigold (Tagetes erecta L.) development, yield, quality and residual soil chemical properties

A field trial was conducted on the marigold cultivar LSQUOMoon SapphireRSQUO at the Naresuan University experimental farms in Phitsanulok, Thailand. The aim of this study is to test the hypothesis that mixed compound fertilizer can better improve marigold development, yield and induce an increase in total carotenoid content in the inflorescences. The experiment design is a randomized complete block design (RCBD) with four factors and four replications. The factors were: T1) control (no fertilization); T2) N₂₁P₂₁K₂₁+N₈P₂₄K₂₄ (1:1) = 625 kg ha^‑1; T3) N₂₁P₂₁K₂₁+N₈P₂₄K₂₄ (1:1) + chemical and granular organic fertilizer with hormone mixed formula-HO (312.5 kg ha^‑1) = 625 kg ha^‑1; and T4) HO (625 kg ha^‑1). Plant spacing was 0.5×0.5 m in a plot size of 4.0×2.5 m. The study demonstrated the significant effect fertilization can have on marigold yield, quality and residual soil chemical properties. The number of flowers ha^‑1 (2,254,666.67), flower shelf-life after 72 h (8.35 g plant^‑1) and flower carotenoid (102.68 mg 100 g^‑1 FW) were greater for the HO treatment, but was not significantly different from the treatment N₂₁P₂₁K₂₁+N₈P₂₄K₂₄ (1:1) + HO. Upon completion of the study the soil chemical properties such as N, P, K, Fe, Cu, Zn, Mn, B, pH, CE and organic matter contents were improved by the HO and N₂₁P₂₁K₂₁+N₈P₂₄K₂₄ (1:1) + HO treatments. The results showed the HO fertilizer, and N₂₁P₂₁K₂₁+N₈P₂₄K₂₄ (1:1) + HO treatments produced the highest marigold yield and added significant value to the raw flower by increasing their total carotenoid content.