澳洲坚果低磷适应特征分析

Adaptation Characteristics of Macadamia integrifolia to Low Phosphorus

为探明具有排根的引种作物—澳洲坚果对低磷的适应特征,采用室内控制试验与山地澳洲坚果园调查验证相结合的研究方法,对澳洲坚果幼苗、大树的排根和细根在土壤中的分布特征、根系分泌物“解磷”特性及磷素利用特征进行分析。结果表明:室内控制试验中澳洲坚果61.80%-71.29%的排根及63.81%-82.60%的细根分布在0-40cm的土层,山地果园中澳洲坚果的排根及细根分布在0-40cm土层,80%以上的排根与细根分布于表层0-20cm的土壤,但细根在20-40cm土层中分布比例较排根多;低磷处理或不施化肥(山地果园)能促进排根产生,适度施磷处理(40mg/kg)或不施化肥(山地果园)有助于细根在表层土壤的生长,高磷处理(400mg/kg)或山地果园中长期施含磷(P 2 O 5含量15%)化肥则抑制其排根产生和细根生长;排根及细根均能大量分泌酸性磷酸酶和柠檬酸进行“解磷”,排根分泌量远大于细根,排根越多,酸性磷酸酶和柠檬酸分泌量越大;随着施磷量的升高,澳洲坚果叶片磷含量也升高,但土壤磷含量与叶片磷含量相关性较差,而不施磷处理(0mg/kg)和山地果园不施化肥条件下,澳洲坚果叶片中磷含量均在正常水平(含量为0.068%-0.071%),没有发现缺磷症状,高磷(400mg/kg)处理和长期施用“高磷”的复合化肥澳洲坚果叶片有磷中毒倾向(含量达0.11%);外源含磷复合化肥施入土壤中后,土壤中总磷含量随施入量的增加而升高,尤其山地澳洲坚果园长期施用“高磷”化肥,土壤表层(0-20cm)总磷含量高达3.59g/kg。可见,引种到本地种植的澳洲坚果,仍能适应低磷环境,但为了保障澳洲坚果经济产量,适度的外源磷投入是需要的,生产上采用叶片营养诊断法指导磷肥的施用是必要的。

In order to ascertain the adaptive feature of the crops introduction-Macadamia integrifolia with cluster roots to low phosphorus,the method of combining laboratory tests with mountain orchard was adopted.The distribution characteristics of cluster roots and fine roots of Macadamia integrifolia seedlings and adult tree in soil,the characteristics of“phosphorus-solubilizing”from root exudates and phosphorus utilization were analyzed.The results showed that,in laboratory experiment,61.80%-71.29%of the cluster roots and 63.81%-82.60%of the fine roots were distributed in the soil depth 0-40cm,and the cluster roots and the fine roots were also basically distributed in the soil depth of 0-40cm with mountain orchard.However,the proportion of fine roots in the soil depth of 20-40cm was more than that of cluster roots.Low phosphorus treatment or in mountain orchard without phosphorus fertilizer could promote the production of cluster roots.Appropriate application of phosphorus(40mg/kg)or no application of phosphorus fertilizer under mountain orchard contributed to the growth of fine roots in surface soil(0-20cm),while high phosphorus treatment(400mg/kg)or long-term application of phosphorus fertilizer(P 2 O 5 content15%)in mountain orchard inhibited the formation of cluster roots and fine roots growth.Both the cluster roots and the fine roots could secrete acid phosphatase and citric acid to“phosphorus-solubilizing”.The secretion of acid phosphatase and citric acid from the cluster roots was much larger than that from the fine roots.The more the cluster roots were,the greater the secretion of acid phosphatase and citric acid would be.With the increasing of phosphorus application quantity,the phosphorus content of leaves also increased.There was no much correlation between phosphorus concentration in leaves and soil.The P content in leaves still remained the normal level(0.68%-0.71%)under the treatments of control(0mg/kg)and no P application in the mountain orchard.No symptoms of phosphorus deficiency were found.On the contrary,Macadamia integrifolia leaves tended to be phosphorus poisoning under high P(400mg/kg)treatment and long-term application of“high P”(0.11%).After the application of exogenous phosphorus fertilizer into the soil,the total phosphorus content in the soil would rise with the increase of the application amount.Especially when the“high phosphorus”fertilizer was applied in the mountain orchard for a long time,the total phosphorus content in the surface layer of the soil(0-20cm)reaches 3.59g/kg.In conclusion,Macadamia integrifolia are naturally adapted to low phosphorus.In order to ensure economic yield,appropriate input of exogenous phosphorus was needed.It was necessary to guide the application of phosphorus fertilizer by using the leaf nutrition diagnosis method.