Study On K Absorption Dynamic Of Flue-cured Tobacco

As the important economic crop, the economic benefit of flue-cured tobacco is determined by tobacco leaf yield, quality and production input. The quality elements of tobacco is K, not only combustibility is good, the other quality indicators are more appropriate when the K content is high in tobacco leaf. But K content in tobacco leaf is generally low in China. Therefore, in order to improve K content and quality of tobacco leaf in our country, the characteristics of K transformation in soil, the lows of K uptake and distribution in tobacco were studied. According to the largest flue-cured tobacco area Liangshan prefecture in Sichuan, the main flue-cured tobacco cultivars yunyan85 and yunyan87 were used in the soil culture and field experiment. The characteristics of K absorption, K accumulation, K distribution in tobacco and the characteristics of K transformation in tobacco soil were studied to proposes a relatively optimal K application rate, time and ratio of basal and topdressing. Provide a theoretical basis for rational fertilization. The main results are as follows:(1)The content and proportion in total K content of available and slowly available K in tobacco soil were increasedas the K. application rate increased. K supplying enhanced when increased K application rate, but the excessive application of K goes against the increase of K using efficiency. When the K application rate was exceed 180 kg ha-1, available and slowly available K content in the soil after planting were higher than preplant soil. Especially the soil planted yunyan85. In the pot culture experiment with the K application 270 mg kg-1, available and slowly available K content in the soil after planting were 52.4% and 81.3% higher than preplant soil, and the K using efficiency in the three maturities were decreased 3.1,8.0 and 4.9 percent point when compared with the K application 180 mg kg-1. In the field experiment, available and slowly available K content in the soil after planting were 77.2% and 78.9% higher than preplant surface soil under the K application 360 kg ha-1.(2) The yield, K content, K accumulation and K distribution rate of flue-cured tobacco were all increased at the first, and then decreased with the increase of K application rate. The yield (2238.2 kg ha-1) and K accumulation rate (52.16 kg ha-1) were equivalent to the highest yield (2239.1 kg ha-1) and K accumulation (53.47 kg ha-1) of tobacco leaf when the K application rate was 158 kg ha-1 (About 75% of the conventional K rate). When the available K content of soil is rich (=200 mg kg-1) or above level, decrease the appropriate K application rate can improve the economic benefits of plant yunyan 85.(3) The peaks of K accumulation for yunyan85 were appeared when the flower budded (65 days after transplanting) and middle leaf matured (95 days after transplanting). The change of K accumulation rateshowed a double-peak curve with the extension of days after transplanting, peak periods were in the later vigorous growth stage (85-95 days after transplanting) and middle leaf maturity (85-95 days after transplanting). Adjust the period of K topdressing to the peak of K accumulation rate can increase the K content of tobacco leaf.(4) When the total K application was 158 kg ha-1, the method of K topdressing stage was before the later vigorous growth stage (85-95 days after transplanting) and middle leaf maturity (85-95 days after transplanting), each stage used 15%-20% K fertilizer of total K application rate, the reduced proportion of K accumulation in tobacco leaf were 37.2-42.0 and 15.4-60.3 percent point within 5 days and 10 days after topping when compared with conventional fertilization. K content of middle and upper leaf has reached 3.21% and 3.37%. K using efficiency has increased 12-18 percent point. It shows that applied K fertilizer before the peak of K accumulation rate for flue-cured tobacco could shut down the spillover rate, increase K content of tobacco leaf and K using efficiency.