Abstract:

In order to improve fertilizer utilization rate, reduce nicotine content in upper tobacco leaves, improve tobacco quality, increase flue-cured tobacco yield and promote farmers' income, this experiment studied the effects of fertilizer synergist γ-polyglutamic acid (γ-PGA) on the growth and yield of flue-cured tobacco in Changsha tobacco-growing area, and explored the suitable application period of fertilizer synergist for Changsha high-quality flue-cured tobacco production. Through the field experiment, a random block design was adopted, and a total of 4 treatments were set up (CK, local conventional fertilization; T1, increased application of synergistic agents in the rosette stage; T2, increased application of synergistic agent in the early stage of vigorous growth; T3, increased application of synergists during both the rosette stage and the early stage of vigorous growth, and each treatment was repeated 3 times). The results showed that compared with CK, adding fertilizer enhancer was beneficial to increase fertilizer utilization rate and improve agronomic traits of tobacco plants. In particular, T3 treatment significantly increased plant height, the area of the uppermost leaf and the third leaf from the top by 7.75%, 29.45% and 15.63% compared with control, respectively. The SPAD value of the third leaf from the top was increased to improve the economic characteristics of tobacco leaves, increase the yield and output value, and improve the grade structure of tobacco leaves. Among them, the yield, output value and proportion of high-grade tobacco under T3 treatment were the highest, which were significantly increased by 32.05%, 34.35% and 5.70 percentage points compared with the control, respectively. There was no obvious difference in the appearance quality of the upper tobacco leaves after all treatments. However, the chemical content of tobacco leaves was suitable, and T3 treatment reduced the nicotine content of upper tobacco leaves to 3.07%, and the coordination was good. T3 treatment improved the sensory quality of upper tobacco leaves, and its total score was 63.50 points, 2.00 points higher than that of control. In summary, T3 treatment with fertilizer synergist γ-polyglutamic acid applied at the rosette stage and the early stage of vigorous growth was conducive to improving fertilizer utilization rate, improving agronomic traits of tobacco plants, increasing SPAD value of upper tobacco leaves, improving economic properties of flue-cured tobacco leaves, improving grade structure of tobacco leaves, reducing nicotine content of upper tobacco leaves, basically coordinating chemical composition, and improving sensory quality of upper tobacco leaves.

Key words: fertilizer synergist, upper tobacco leaf, fertilizer utilization rate, yield and production quality, flue-cured tobacco