长期不同有机肥替代比例对茶园土壤养分动态的影响

Effects of long-term different substitution rates of organic fertilizers on soil nutrient dynamics in tea plantations

[目的]有机肥部分替代化肥是茶园实现“化肥零增长”的一个重要途径。研究不同有机肥替代比例对土壤养分变化及茶叶产量的影响,为茶园合理高效施用有机肥提供参考。[方法]长期定位试验于2007年在福建省宁德市进行,供试茶树于2006年栽种。试验处理包括不施氮肥对照(CK)、氮磷钾化肥(NPK)处理,以及氮投入总量不变条件下以猪粪替代25%(OM25)、50%(OM50)、75%(OM75)、100%(OM100)化肥氮的有机肥替代处理。氮肥每年分3次追施,磷、钾肥和有机肥一次性基施。于2018-2019年间定期采集表层(0-20 cm)土壤样品,测定土壤养分含量、茶叶产量,同时检测降雨量和地表温度。[结果]施肥显著提高土壤养分含量,但同一养分含量年际间的变异幅度随着有机氮替代比例的上升而增加,除铵态氮含量外,NPK与OM25处理的养分含量及年际间变异系数无显著差异,二者均低于其他有机肥替代比例处理。OM25处理土壤铵态氮平均含量与其他处理相比提升了1.42~3.35倍,显著高于其他处理(P<0.05);硝态氮平均含量的变异系数在有机肥替代处理下超过150%,其含量随有机肥替代比例的升高逐渐提高,但没有表现出显著差异(P>0.05)。CK和NPK处理的土壤钙、镁、锰、铜和锌元素的平均含量显著低于较高的有机肥替代比例处理,OM100处理下土壤有效钙、镁、锰、铜和锌元素的平均含量较最低的CK分别提高了4.12、13.83、2.77、12.32和36.32倍。随着有机肥替代比例的增加,表层土壤pH和速效钾含量随之上升,而铵态氮含量和茶叶的鲜叶产量则呈下降趋势。除铵态氮外,土壤养分含量与取样前7天的降雨量之间存在显著的负相关关系,土壤铵态氮和硝态氮含量与任意阶段的地表温度之间存在显著的负相关关系。[结论]全有机肥模式不利于茶叶增产和土壤养分的供应,且土壤pH的升高对茶树生长有明显的限制作用,降雨过多和地表温度过高也会加剧养分流失风险。低有机质替代比例可以保证氮素的充足和稳定供应,且不会引起pH明显变化,因此是较为适宜的茶园有机肥替代比例。

[Objectives]Substitution of partial chemical fertilizer nitrogen(N)with organic fertilizers is promoted for the sustainable development of tea plantation.We investigated the effects of different organic substitution rates(OSRs)on soil nutrient changes and tea yields for the optimization of fertilization strategy.[Methods]The research based on a positioning tea fertilization experiment,located in Ningde City,Fujian Province,started since 2017,in which the tea trees were planted in 2016.Eleven soil samplings were conducted within one production year(2018-2019)in the treatment plots of no nitrogen fertilizer control(CK),pure chemical fertilizer(NPK),and the plots of substitution of 25%,50%,75%and 100%of chemical fertilizer with pig manure compost(denoted as OM25,OM50,OM75,and OM100).Soil pH,and nutrient contents were measured,and the precipitations,ground surface temperatures,and tea yields were investigated at the same time.[Results]All the fertilization treatments significantly increased soil nutrient contents,however,the coefficient of variation(CV)of soil nutrient contents increased with the enhanced organic substitution rate.Except for NH^(4+)-N,OM25 and NPK treatment were recorded similar soil nutrient contents and CVs,which were lower than in the other treatments.The average NH^(4+)-N content in OM25 treatment was 1.42-3.35 times higher than that in the other treatments(P<0.05).The annual CVs of NO^(3-)-N content exceeded 150%under the OM50-OM100 treatments,and no significant differences existed in the CVs among them.High OSRs increased the average contents of available Ca,Mg,Mn,Cu and Zn.The average available Ca,Mg,Mn,Cu and Zn contents in OM100 were 4.12,13.83,2.77,12.32 and 36.32 times of those in CK and OM25.With the increase of OSRs,surface soil pH and readily available K content increased,while NH^(4+)-N content and fresh tea leaf yield decreased.Except for NH^(4+)-N,soil nutrient contents were negatively correlated with precipitations at 7 days before sampling,and soil mineral N content was negatively correlated with surface temperature at any stage.[Conclusions]Application of 100%organic fertilizer is not conducive to tea yield and soil nutrient supply due to the resulted high soil pH.Excessive rainfall and high surface temperature also exaggerate the unbalanced supply of soil nutrients.Low organic substitution rate could guarantee ampler and stable mineral nitrogen supply,and would not change soil pH in tea plantations,so is suitable for the growth of tea trees.