钾肥基施利于甘薯块根产量的形成

Basal application of potassium benefits the yield formation of sweet potato

【目的】研究不同施钾方法对甘薯块根产量形成的影响,可为甘薯高产稳产寻找合理的钾肥施用方法,并阐明其增产机理。【方法】选取典型的食用型甘薯品种红香蕉和北京553为试材,于2013~2014年两个生长季在山东农业大学农学试验站进行田间试验。设4个施钾处理:不施钾肥(CK)、全部钾肥基施(JS)、全部钾肥封垄期追施(FS)、基施钾肥和封垄期追施钾肥各占50%(^(1/2)JS+^(1/2)FS)。在主茎第4、5片展开叶上标记~13)CO_2,24、48和96 h后取样,用质谱仪(Isoprime 100)测定不同部位的^(13)C含量。从甘薯栽秧后50 d开始,每隔20 d取样直到收获。按根、茎、叶、柄四部分分别称重,将主茎自功能叶所在位置至基部等分为三段,取上、下两端用于测定蔗糖含量。收获期测定生物产量和块根产量,计算经济系数。【结果】甘薯施用钾肥能显著提高生物产量、经济系数和块根产量,增产21.33%~34.38%。各施钾处理之间比较,生物产量差异不显著,经济系数和块根产量差异显著,其中基施钾肥处理的经济系数和块根产量最高。栽秧后50 d,基施钾肥处理植株干物质积累量和功能叶光合产物在块根中的分配率都显著高于其他施钾处理。栽秧后50 d和110 d,基施钾肥处理光合产物源端装载和库端卸载的效率显著高于其他处理,栽秧后150 d,所有施钾肥处理趋于一致。栽秧后50 d,基施钾肥处理光合产物转运效率显著高于其他施钾处理,栽秧后100 d和150 d,施钾肥处理间效果趋于一致。在栽秧后50~130 d,基施钾肥处理的块根膨大速率一直高于其他施钾处理。【结论】在相同供试土壤和气候条件下,钾肥施用时间越早,越有利于甘薯早发、快长,促进块根早形成、快膨大;光合产物由叶片向块根运转效率的高值持续期越长,越有利于提高光合产物在块根中的分配。因此,全部钾肥基施甘薯经济系数和块根产量最高,是最经济有效的施肥方法。

【Objectives】In order to search the reasonable potassium application method for high and stable root tuber yield of sweet potato and clarify the yield-increasing mechanism, the effect of potassium application methods on yield formation of sweet potato was studied through field experiment and lab analysis. 【Methods】A filed experiment was conducted with two typical edible sweet potato cultivars of Beijing 553 and Hongxiangjiao in 2013 and 2014. The potash application treatments included no K（CK）, all applied as basal fertilizer（JS）, all applied when the field was completely covered by crop（FS）, and half potassium applied as basal fertilizer and half potassium applied when the field was completely covered by crop（^（1/2）JS ＋ ^（1/2）FS）. ^（13）CO_2 was labeled when the fourth or fifth leaves fully unfolded. Samples for ^（13）C detection using Isoprime 100 were collected in 24 h, 48 h and 96 h after labeling. Since the 50 days after transplanting, samples were collected until harvest in interval of 20 days. The samples were divided into four parts： root, stem, leaf and petiole, and weighed separately. The main stems were parted up, mid and bottom from the functional leaf to the bottom, and the sucrose content was determined. The biomass and yield were investigated and the economic index was calculated at harvest.【Results】All the K application treatments increased the biomass, economic coefficiency and root tuber yields significantly, and the root tuber yields were increased from 21.33% to 34.38%. The biomass of sweet potato were similar in all the K application treatments, but the economic coefficiencies and root tuber yields were significantly different, with the highest in treatment of all potash basal applied（JS）. The dry matter accumulation and photosynthate distribution rate in root tuber were significantly higher in JS than in the other treatments at 50 d since planting. Compared with treatment of FS and ^（1/2）JS ＋ ^（1/2）FS, the photosynthate loading and unloading rate was significantly accelerated in JS at the 50 d and 110 d after planting, and became similar at 150 d after planting;the photosynthate distribution rate to root tubers was significantly higher in JS at 50 d after planting and became similar at 110 d and 150 d after planting; the bulking rate of root tubers in JS was much higher from 50 d to 130 d since planting. 【Conclusions】Earlier application of potassium is in favor of transportation of photosynthate from functional leaves to root tubers, and the rapid transformation could last longer, which will stimulate the expansion of tuber and formation of tuber yield. Therefore, all the potash fertilizer should be basal applied under the tested soil and climate conditions.