断根追钾条件下减量施氮对烟株后期氮、钾吸收及烟叶产量质量的影响

以烤烟K326品种为材料, 通过田间试验比较了正常施氮但打顶时不断根不追钾(CK)、正常施氮但打顶时断根并追钾(CK+C+K)、减量施氮(为正常施氮量的80%)但打顶时断根并追钾(RN+C+K)对烟株后期氮、钾吸收和干物质累积及烟叶产量、质量的影响, 以期阐明在打顶时断根追钾条件下, 烟株整个生育期的施氮量是否应该减少的问题。结果表明: 断根追钾明显促进烟株后期的生长。RN+C+K虽少施20%的氮肥, 但其与CK+C+K两处理烟株田间中、上部烟叶的开片和SPAD值, 采烤结束时的干物质和氮、钾累积量, 烟叶的产量、产值以及烟碱和钾含量等质量指标皆优于CK。同时, RN+C+K烟株的干物质和氮、钾累积量以及烟叶产量达到了CK+C+K的97.2%、97.8%、98.9%和98.6%, 而产值比后者高2.0%; 其烤后上部叶的烟碱含量比CK和CK+C+K两处理分别降低了6.7%和4.5%, 而钾含量则分别增加了18.9%和5.6%, 且其他化学成分也更为协调。这说明在断根追钾条件下应该减少氮肥施用量, 以更有利于增加烟农收入、降低肥料成本、节省氮肥资源和提高烟叶质量。

Integrated Effects of Reducing N Application and Cutting-Roots with K Top-Dressing on N, K Uptake, and Yield, Quality of Flue-Cured Tobacco

Cutting-roots with K top-dressing at topping of flue-cured tobacco plant, which was supplied with nitrogen fertilizer at the con-ventional rate, had been considered having positive effect on potassium uptake and leaf quality in flue-cured tobacco, due to the improvement of lateral roots’ development and activity. However, it could be inferred that nitrogen uptake of plant be improved simultaneously, which may result in higher concentration of nicotine and undesired quality of leaves. Therefore, we hypothesized that nitrogen fertilization rate during the whole growth period should be reduced in the case that the practice cutting roots with K top-dressing be adopted at the stage of decapitation of flue-cured tobacco, in order to get superior flue-cured leaves. Field experiments were conducted to compare dry matter accumulation (DMA), N and K uptake as well as leaf yield and economic returns for (a) normal fertilization at recommended N rate without cutting-roots and K top-dressing at decapitation (CK), (b) normal fertilization at recommended N rate coupled with cutting-roots and K top-dressing at decapitation (CK+C+K) and (c) reducing nitrogen fertilization rate up to 80% coupled with cutting-roots and K top-dressing at decapitation (RN+C+K). The re-sults showed that the practice cutting roots with K top-dressing enhanced growth in later growth stage of tobacco, with RN+C+K and CK+C+K both showing significant advantages in terms of leaf area and SPAD value on upper and middle position of the stalk, DMA, N and K uptake, leaf yield and economic returns as well as leaf quality compared with CK. In addition, DMA, N and K uptake, leaf yield and economic value in RN+C+K were recorded 97.2%, 97.8%, 98.9%, 98.6%, and 102.0% of those in CK+C+K respectively, while nicotine concentration in upper leaves in RN+C+K were 6.7% and 4.5% less than CK and CK+C+K, and po-tassium concentration in upper leaves in RN+C+K 18.9% and 5.6% higher than CK and CK+C+K respectively. It suggested that nitrogen rate applied to tobacco plant should be reduced in the case of coupling with the practice cutting roots with K top-dressing at stage of decapitation, in order to obtain more desirable leaf quality, higher economic value and higher nitrogen fertilizer utilization efficiency.