生物质炭改善果园土壤理化性状并促进苹果植株氮素吸收

Applying biochar to improve soil physical and chemical properties and nitrogen utilization by apple trees

【目的】探究生物质炭对苹果植株生长、土壤理化特性和氮素利用的影响,为生产上苹果园合理应用生物质炭提供依据。【方法】以两年生红富士/平邑甜茶为试材,以400℃亚高温热解木材产生的生物质炭为供试肥料,采用^(15)N同位素示踪技术进行了盆栽试验。设底施生物质炭0、15、30、45和60 g/kg,分别以CK、T1、T2、T3和T4表示。调查了苹果植株生长发育、土壤理化性质、根际微生物数量及氮素的吸收、利用和损失。【结果】添加生物质炭的所有处理植株株高、茎粗和总干重均显著高于CK;T2、T3和T4处理的根系活力均显著高于T1和CK处理,但三个处理间差异不显著;随着生物质炭用量的增加,土壤容重逐渐降低,T3和T4处理的土壤容重分别为1.22和1.20 g/cm3,两者间差异不显著,但均显著高于CK、T1和T2处理;T3和T4处理的土壤有机质、碱解氮、有效磷、速效钾和根际土细菌、放线菌、真菌数量均显著高于其他处理,两者间差异不显著;与CK相比,添加生物质炭显著增加了植株对肥料^(15)N的吸收,T4和T3处理植株^(15)N利用率分别为15.18%和15.63%,均显著高于其他处理;土壤^(15)N残留率以T4处理最高,为38.16%,T3次之,T1最低,为30.02%;氮素损失以T1处理最高,为58.54%,T4处理最低,为45.66%,且T4与T3处理间差异不显著。通过对植株生物量和氮素利用效率与生物质炭施用量进行拟合分析,两者出现最大值时的生物质炭施用量分别为64 g/kg和55 g/kg。【结论】施用生物质炭降低了土壤容重,提高了土壤碱解氮、有效磷和速效钾含量及根际土壤细菌、放线菌和真菌数量,促进了苹果植株根系和地上部的生长及对肥料氮的吸收,增加了土壤对氮的固定,减少了氮的损失,提高了氮肥利用率,本试验条件下适宜的生物质炭施用量为55~64 g/kg土。

[Objectives] The paper investigated the effects of different amounts of biochar on apple growth, soil physical and chemical properties and nitrogen utilization, which would provide a basis for rational application of biomass carbon in apple orchards.[Methods] Two-year-old apple trees （Malus×domestica Borkh. ‘Red Fuji’）/Malushupehensis were used as tested materials and biomass carbon produced by pyrolysis of wood under 400℃ was used as fertilizers in a pot experiment. Biochar was applied at rates of 0, 15, 30, 45 and 60 g/kg, which represented as CK, T1, T2, T3, and T4 in turn. Plant and soil samples were collected to investigate apple growth and development, the physical and chemical properties of soil, the population of rhizosphere microorganisms and their effects on nitrogen uptake, utilization and loss using the 15N trace technique.[Results] The plant height, stem diameter and total dry weight of all the treatments which were added biochar were significantly higher than those of CK. The root activities of T2, T3 and T4 were significantly higher than those of T1 and CK, but there were no significant differences between the three treatments. With the increased addition of biomass carbon, soil bulk density was decreased gradually, the soil bulk density of T3 and T4 were 1.22 and 1.20 g/cm3, respectively, and the difference between the two treatments was not significant, but the density was significantly higher than that of CK, T1 and T2. Soil organic matter, alkali hydrolyzable nitrogen, readily available phosphorus, readily available potassium and rhizosphere soil bacteria, actinomycetes and fungi were highest in the T4 treatment, followed by the T3 treatment, the difference was not significant, but were significantly higher than other treatments. Compared with CK, the addition of biochar significantly increased the uptake of fertilizer 15N, and the 15N utilization rates of the T4 and T3 treatments were 15.18% and 15.63%, respectively, which were significantly higher than those of other treatments. The residual rate of soil 15N was highest in T4 （38.2%）, followed by T3, and the lowest was T1 （30.0%）. The highest nitrogen loss was T1 （58.5%）, the lowest was T4 treatment, and the difference between T4 and T3 was not significant. Through the analysis of plant biomass and nitrogen use efficiency and biomass carbon dosage, the maximum amount of biomass carbon was in range of 64-55 g/kg.[Conclusions] Biochar application decreased soil bulk density, improved the soil nutrient contents and rhizosphere soil bacteria, actinomycetes and fungi, apple plant root and shoot growth and absorption of nitrogen fertilizer, increased the soil nitrogen fixation, reduced nitrogen loss, and improved the utilization rate of nitrogen fertilizer. Under the condition of this experiment, the suitable biomass carbon amount was 55-64 g/kg.