指数施肥对紫椴实生苗生长和根系形态的影响

【目的】指数施肥是根据苗木的相对生长速率添加与幼苗对应养分需求剂量的养分加载方式之一。研究不同施肥方式及不同施氮(N)量对紫椴(Tilia amurensis Rupr.)幼苗生长、养分含量、根系形态的影响,旨在揭示紫椴对N素的需求利用规律,为苗圃培育优质合格紫椴苗木提供参考。【方法】以1年生紫椴播种(实生)苗为供试材料,在大田培育环境下,设定常规施肥(200 mg/株,CK)、1倍指数施肥(207.46 mg/株,编号E100)和2倍指数施肥(414.92 mg/株,编号E200)3种施肥处理。每次施肥间隔时间为7 d,共施氮肥10次至整个生长季结束,每周进行紫椴幼苗苗高、地径的测定,用于绘制生长曲线。最终苗木收获时,先分离出根系进行形态指标的扫描,获得总根长、总根表面积、总根体积。最后全株烘干用于测定各器官的生物量、N积累量及N浓度。【结果】指数施肥比常规施肥显著促进紫椴幼苗的苗高、地径的增长。不同指数施肥处理下,单株生物量以E100、E200处理分别比CK高出1.63与1.66倍(P<0.05),不同处理下根茎比大小表现为CK>E100>E200。3种处理下苗木的根、茎、叶含N量大小顺序均为E200>E100>CK,全株含N量分别达到349.24、338.21、94.48 mg/株。不同处理下根、茎、叶中N浓度大小顺序均为E100>E200>CK。不同处理下幼苗的根长、根表面积、根体积、比根长、比根表面积、根系组织密度具有相同的趋势均为E100 >E200 >CK。不同施肥处理苗木N素收获指数大小表现为E100>E200>CK,E100是CK的3.45倍。E100处理下的苗木质量指数比CK提高了0.89倍。【结论】指数施肥与常规施肥相比显著提高了苗木的生长、养分积累利用、根系形态特征和N肥收获指数,依据以上评价指标,可得指数施肥E100(207.46 mg/株)处理下的紫椴播种苗生长表现为最好。

Effects of exponential fertilization on growth and root morphology of Tilia amurensis seedlings

【Objective】Exponential fertilization is one of the nutrient loading methods,which adds the required nutrients into soil,according to the relative growth rate of seedlings.The effects of different fertilization methods and different nitrogen content on the growth,nutrient content and root morphology of seedlings were investigated in this study to reveal the regularity of the nitrogen absorption and the utilization of Tilia amurensis seedlings and provide scientific reference for cultivation of high quality seedlings.【Method】Under field conditions,nitrogen fertilization experiment was conducted with one-year-old seedlings of Tilia amurensis.Further,three treatments were applied:conventional fertilization(200 mg per seedling,CK),1 time exponential fertilization(207.46 mg per seedling,No.E100),and 2 times exponential fertilization(414.92 mg per seedling,No.E200).The fertilization interval time was seven days,and nitrogen fertilizer was applied for 10 weeks until the end of the growing season.During the experimental period,the height and base diameter of seedlings were measured weekly after fertilization,and the data were used to plot the growth curve.When these seedlings were harvested,roots were separated from the plants for scanning and calculating their morphological indexes(root length,root surface area,root volume).After drying,the biomass,nitrogen content and nitrogen concentration of each plant organs were determined.【Result】Exponential fertilization significantly improved the height and base diameter growth of T.amurensis seedlings compared with those by conventional fertilization.The seedling mean biomass of E100 and E200 treatments were 1.63 and 1.66 times higher than that of CK(P<0.05),respectively.The of shoot to root ratio was CK>E100>E200 with increasing amount of nitrogen.The tendency of N content in roots,stems and leaves of seedlings was E200>E100>CK.The nitrogen content of the whole plant in E200 was 349.24 mg per seedling,whereas nitrogen contents of the whole plant in E100 and CK were 338.21 and 94.48 mg per seedling,respectively.The order of N concentration in roots,stems and leaves was E100>E200>CK.The root length,root surface area root volume,specific root length,specific root surface area,and root tissue density of the seedlings had the same trend which was expressed as E100>E200>CK.The nitrogen harvest index of seedlings showed E100>E200>CK(the index of E100 was 3.45 times of CK).The seedling quality index of E100 was 0.89 times higher than that of CK.【Conclusion】Seedlings with nitrogen exponential fertilization have a better performance in growth,nutrient accumulation and root morphological characteristics than that of conventional fertilization,and the seedlings of Tilia amurensis treated with exponential fertilization at E100(207.46 mg per seedling)grew best based on earlier measured indexes.