不同氮形态对连作平邑甜茶幼苗生长及土壤尖孢镰孢菌数量的影响

摘要

[目的]研究盆栽条件下不同形态氮对苹果砧木—平邑甜茶幼苗生长以及对连作土壤微生物的影响,为连作建园时科学施肥、减轻苹果连作障碍提供依据. [方法]试验于2015年露地进行,以平邑甜茶幼苗为试材,以连作土为对照1 (CK1)和溴甲烷熏蒸为对照2(CK2),设置施入铵态氮(T1)、硝态氮(T2)和酰胺态氮(T3)3个不同形态氮处理(N 180 mg/L),于2015年8月测定平邑甜茶生物量、光合参数和土壤微生物等相关指标.[结果]铵态氮(T1)和酰胺态氮(T3)处理均能明显提高连作条件下‘平邑甜茶’苹果幼苗的生物量,其中T1处理的株高、地径、鲜重、干重与CK1相比分别提高了35.3％、24.4％、42.0％、57.7％.添加3种形态氮素均可不同程度地提高平邑甜茶幼苗叶片的净光合速率(Pn)、气孔导度(Gs)和根系呼吸速率,其中T1处理的Pn、Gs和根系呼吸速率分别比CK1提高了27.6％、35.6％、43.3％,却并未达到CK2的效果.实时荧光定量PCR结果表明,CK2尖孢镰孢菌的基因拷贝数降低最为明显,比CK1降低了52.6％,T1也有效地降低了尖孢镰孢菌的基因拷贝数,而T2和T3处理尖孢镰孢菌的基因拷贝数与CK1没有显著性差异.T-RFLP结果表明,T1和T3处理的真菌群落结构与CK1有明显差异,T1处理与CK2的真菌群落结构较为相似,T2处理的真菌群落结构与CK1较为相似. [结论]铵态氮处理可更好地提高连作平邑甜茶幼苗的生物量、净光合速率以及根系呼吸速率,降低土壤尖孢镰孢菌的基因拷贝数,明显改变连作土壤的真菌群落结构,可作为减轻苹果连作障碍的措施.%[Objectives] To provide a theoretical basis for reasonably applying fertilizers and alleviating the growth obstacles of replanted apple,a pot experiment was conducted to study effects of different nitrogen forms on growth of apple rootstock (Malus hupehensis Rehd.) seedlings and the replanted soil microorganisms.[Methods] The experiment was carried out in 2015.M.hupehensis Rehd.Seedling was used in this study,and the biomass,photosynthetic parameters and soil microorganisms were determined in August 2015.Three N fertilizer treatments were designed as follows:ammonium nitrogen (T 1),nitrate nitrogen (T2) and amide nitrogen (T3) (N 180 mg/L),and took the apple replanted orchard soil (CK1) and methyl bromide fumigation (CK2) as the control.M.hupehensis Rehd.seedlings were planted in pots with different treatments.[Results] Compared with the replanted soil control (CK1),the biomass amounts ofM.hupehensis Rehd.seedlings were significantly improved with the ammonium nitrogen (T1) and amide nitrogen (T3).The plant height,ground diameter,fresh weight and dry weight of the ammonium nitrogen (T1) were increased by 35.3％,24.4％,42.0％,57.7％.Different nitrogen forms could increase the net photosynthesis stomatal conductance and root respiration rate.The net photosynthetic rate,stomatal conductance in leaves of the seedlings and root respiration rate of ammonium nitrogen of T1 were increased by 27.6％,35.6％ and 43.3％ compared with CK1,respectively,but they did not reach the highest effect of the methyl bromide fumigation (CK2).Real-time quantitative PCR results showed that the ammonium nitrogen (T1) effectively reduced the gene copy number ofFusarium oxysporum,which was decreased by 41.3％ compared with the replanted soil control (CK1).The copy numbers of the nitrate nitrogen (T2) and amide nitrogen (T3) had no significant differences with the soil control (CK1).T-RFLP results showed that soil fungal community structure was changed by the ammonium nitrogen (T1) and amide nitrogen (T3) greatly,the fungal community structure in the ammonium nitrogen (T1) was similar to that in the methyl bromide fumigation (CK2),and the structure of the nitrate nitrogen (T2) was similar to that in the soil control (CK1),while an independent fungal community was formed in the amide nitrogen (T3).[Conclusions] Ammonium nitrogen greatly improved the biomass ofM.hupehensis Rehd.seedlings,net photosynthetic rate and root respiration rate,reduced the gene copy number of Fusarium oxysporum,and changed the community structure of soil fungi.Therefore,the appropriate dosages of ammonium nitrogen could be used as a measure to reduce the apple replanted disease.