施氮过量对椪柑园土壤和树体矿质养分及果实品质的影响

[目的]探明过量施用氮肥对椪柑园土壤和树体矿质养分及果实品质的影响,为柑橘生产上科学施用氮肥提供参考依据.[方法]以8年生太田椪柑为试验材料,进行连续施氮致树体氮含量过量处理,以正常施肥管理为对照(CK),监测土壤和树体矿质养分、叶片叶绿素含量及果实品质的变化情况.[结果]施氮过量的椪柑果园土壤pH明显低于适宜值(5.50~6.50),并使其他矿质养分含量受到不同程度影响;施氮过量的椪柑果实成熟期(盛花后195 d)土壤有机质含量为15.42 g/kg,显著高于CK(9.50 g/kg)(P<0.05,下同),碱解氮含量为323.92 mg/kg,高于适宜值(100.00~200.00 mg/kg),且显著高于CK(91.75 mg/kg).施氮过量后椪柑果实成熟期叶片氮含量为3.12%,显著高于CK (2.62%),也致使其他养分含量发生不同程度变化;叶片叶绿素总量显著升高,盛花后165 d较CK增加73.3%;果实中氮含量显著升高,果实发育后期出现粗皮大果症状,并伴随着蔗糖含量小幅升高.相关性分析结果表明,土壤和叶片中的氮含量与果皮厚度呈显著正相关,果实氮含量与柠檬酸含量呈显著正相关.[结论]氮肥施用过量会打破椪柑园土壤、树体和果实中其他矿质养分的平衡,树体叶绿素含量升高,光合产物进一步积累,导致果实粗皮大果,因此生产上应依据果园营养状况合理施用氮肥.

Effects of excessive nitrogen application on orchard soil and tree mineral nutrients and fruit quality of ponkan

[Objective]To supply reference for applying nitrogen fertilizer scientifically in citrus production,this study revealed the effects of excessive nitrogen application on soil of ponkan orchards,mineral nutrients in ponkan tree and fruit quality.[Method]Using eight-year-old Ota ponkan(Citrus reticulata Blanco cv.Ponkan)trees as materials,they were treated by excessive nitrogen application continuously.The pokan seedlings treated by ordinary fertilization were as control(CK).Variation of mineral nutrients in soil and pokan seedlings,chlorophyll contents in leaf and fruit quality were monitored.[Result]The result showed that soil pH in orchard with excessive nitrogen application was greatly lower than that optimum value(5.50-6.50),and other mineral nutrients were also affected at different extents.At fruit mature stage (195 d after flowering),the organic matter content in soil with excessive nitrogen application was 15.42 g/kg,significant-ly higher than that in CK soil 9.50 g/kg(P<0.05,the same below).Available nitrogen in treatment soil was 323.92 mg/Kg, higher than optimum value(100.00-200.00 mg/kg)and significantly higher than CK(91.75 mg/kg).With excessive nitro-gen application treatment,leaf nitrogen content was 3.12% at fruit mature stage,significantly higher than 2.62% in CK;other mineral nutrients in ponkan leaves were also changed at various levels. Meanwhile,total chlorophyll in leaf in-creased significantly,and it rose by 73.3% compared to CK 165 d after full bloom.Nitrogen in fruit was also increased, the pokan had rough peel and large-size fruits after the fruit grew,and sucrose content in fruit also increased slightly. Cor-relation analysis suggested that there were significant positive correlations between soil and leaf nitrogen contents and fruit peel thickness,as well as between fruit nitrogen content and citrate content.[Conclusion]Excessive nitrogen application breaks the balance of other nutrients in soil,trees and fruits in ponkan orchard.It also leads to chlorophylls content in-crease,photosynthate accumulation and ponkan fruit with rough peel and larget-size fruit.Therefore,nitrogen fertilizer should be used properly and scientifically in ponkan production.