Nitrogen, phosphorus, and potassium fertilization affects the flowering time of rice (Oryza sativa L.)

The transition from the vegetative to the reproductive stage, which is called as flowering, is an important process of plant growth. Many studies had investigated the regulation of flowering in Arabidopsis, but few studies addressed rice and other crops, particularly neglecting the effects of nutrients on rice flowering. This study was conducted to clarify the effects of different nutrients on the characteristic parameters of rice flowering. Five gradients of nitrogen (N), phosphorus (P) and potassium (K) fertilizer were set respectively to study the effects of nutrients on rice flowering time and flowering duration. The results showed that N, P, and K fertilizers affected the growth and the flowering time of rice. The grain numbers per panicle increased by 31.4%, 23.9%, and 48.2%, and the panicle numbers increased by 55.1%, 29.2%, and 6.7% after application of N, P, K fertilizers, respectively. N application delayed the rice flowering time by 1–4 days, and further increasing the N application led to even later flowering. Compared to no nitrogen application (N0), N application treatments prolonged the flowering duration per panicle, per hill, and group by 0.5–1.2 days, 0.7–1.7 days, and 0.7–2.0 days, respectively. After application of P fertilizer, rice flowering was 1 day ahead of schedule, and no significant difference was found between P levels. K application clearly promoted early flowering by 1–3 days, and the higher the application rate of K fertilizer, the earlier the flowering. The application of P and K fertilizers had no significant effects on the duration of rice flowering. The above evidence indicated that fertilization is an important measure to regulate flowering in rice production. This can serve as an optimized protocol for future studies about the physiological and molecular mechanism of flower induction by nutrients.