氮磷减量施肥对琯溪蜜柚果实产量和品质的影响

摘要

[Objectives] In view of excess fertilization in Guanxi pomelo in Pinghe County,Fujian Province,reduction of nitrogen and phosphorus application was studied for higher yield and better quality fruit.[Methods] The field experiment was conducted with white pulp Guanxi pomelo trees.Based on previous questionnaire,the maximum amount of nitrogen and phosphorus fertilization was set up:N 1.60 kg/(plant·a) (N1),P2O5 1.30 kg/(plant·a) (P 1),with 30％ gradient reducing of nitrogen fertilization and 35％ gradient reducing of phosphate fertilization respectively.Nine treatments were designed as N 1P 1,N 1P2,N 1P3,N2P 1,N2P2,N2P3,N3P1,N3P2,N3P3 and N3P3.The nitrogen,phosphorus and potash fertilizers were orderly applied at flowering (mid-March),steady fruiting (mid-May),filling fruiting (late July or early August) and wintering periods (late November).Calcium and magnesium fertilizers were used in the middle of March,and the furrow was dripped applied along the tree canopy.[Results] Reducing nitrogen and phosphorus fertilization did not significantly decrease,but increased the fruit yields to some extent,and the increment by reducing nitrogen was better than that by reducing phosphorus did.Reducing nitrogen and phosphorus fertilizer improved fruit edible rate,total soluble solids,solid acid ratio and Vitamin C contents,but decreased the fruit aspect ratio,peel thickness and titration acid content.The fruit edible rate,total soluble solids and Vitamin C contents in N2 were significantly higher than in N1,the fruit aspect ratio and Vitamin C content in P2 were significantly lower than in P1,the edible rate in P3 was significantly higher than P1.Among the treatments,N2P2 performed the best.The interaction between reducing nitrogen and phosphorus extremely significantly affected the fruit and soluble solids,and significantly affected the thickness of pericarp,juice yield,edible rate and vitamin C content.The results of principal component analysis and cluster analysis also showed that the fruit quality of N2P2 treatment was the better than the other treatments,with the highest score of 2.20 and higher167.06％ than the second.[Conclusions] Under the current nitrogen and phosphorus fertilizer input levels,reducing nitrogen and phosphorus fertilizer inputs to some extent will not decline but raise the fruit yield and improve the quality of Guanxi pomelo fruit remarkably.For the experimental condition,nitrogen and phosphorus fertilizer could be reduced by 30％ and 35％ respectively from currently quantities,which are 1.12 kg N per plant per year and 0.85 kg P2O5 per plant per year as optimum option.%[目的]针对当前福建省平和县琯溪蜜柚施肥过量问题,研究分析了氮磷减量施肥对琯溪蜜柚果实产量和品质的影响,对提高琯溪蜜柚果实产量和品质,促进当地琯溪蜜柚产业绿色高效发展具有重要意义.[方法]采用田间试验方法,以酸柚砧木白肉琯溪蜜柚为试验材料,以前期问卷调查结果为依据设置氮磷最高施肥量:N 1.60 kg/(plant·a),P2O51.30 kg/(plant·a),结合当地土壤养分状况和琯溪蜜柚需肥特性,以30％梯度递减氮肥用量,分别为高氮(N1)、中氮(N2)和低氮(N3),以35％梯度递减磷肥用量,分别为高磷(P1)、中磷(P2)和低磷(P3),采用双因素交互设计设置N1P1、N1P2、N1P3、N2P1、N2P2、N2P3、N3P1、N3P2、N3P3共9个处理.分别于促花期(3月上中旬)、稳果期(5月中旬)、壮果期(7月下旬或8月上旬)和越冬期(1 1月中下旬)将氮磷钾肥以不同配比施入土壤,于3月上中旬在树冠滴水线范围内撒施钙镁肥.[结果]减少氮磷肥用量不仅没有引起琯溪蜜柚产量的显著降低,反而使其有不同程度的增产,且氮肥减量的增产幅度大于磷肥减量.氮磷减量施肥可以提高果实可食率、可溶性固形物、固酸比和维生素C含量,并降低纵横比、单果重、果皮厚和可滴定酸含量,尤其以中氮中磷(N2P2)处理的果实品质整体较好.随着施氮水平的降低,果皮厚和可滴定酸含量表现出持续减少趋势,中氮水平(N2)的可食率、可溶性固形物和维生素C含量与高氮水平(N1)相比均显著增加;随着施磷水平的降低,中磷水平(P2)的果实纵横比和维生素C含量较高磷水平(P1)显著减少,低磷水平(P3)的可食率较高磷水平(P1)显著增加.氮磷交互作用对单果重、可溶性固形物有极显著影响,对果皮厚、出汁率、可食率和维生素C含量有显著影响.主成分分析和聚类分析结果表明,中氮中磷(N2P2)处理果实主成分综合得分最高,达2.20分,高出第二名中氮低磷(N2P3)处理167.06％,其果实内外品质整体较好.[结论]在当前的氮磷施肥量下,减少氮磷用量不会导致琯溪蜜柚减产,反而具有增产和明显改善果实品质的效果.其中以氮肥减量30％,磷肥减量35％,即施纯N 1.12 kg/(plant·a),P2O50.85 kg/(plant·a)时产量、品质俱佳.