有机肥全量替代化肥对茶园土壤机械稳定团聚体无机氮分布特征的影响

Effect of Total Substitution of Organic Fertilizer for Chemical Fertilizer in Tea Garden on Distribution Characteristics of Inorganic Nitrogen in Soil Mechanically Stable Aggregates

为明确有机肥全量替代化肥对茶园土壤氮素肥力的影响机制。依托5 a茶园有机肥替代化肥试验,选取单施化肥(CF)和全量施用有机肥(OF)为处理,研究了以单施化肥(CF)对照,有机肥全量替代化肥对雨季和旱季茶园土壤理化性质、机械稳定性团聚体组成、团聚体无机氮分布特征的影响,并分析了团聚体无机氮分布的影响因素。结果表明:与CF处理相比,OF处理提高了雨季和旱季表层(0~20 cm)土壤pH值、有机质含量及全氮含量,2个处理雨季土壤pH值差异不显著(P>0.05);在雨季,OF处理下茶园表层土壤阳离子交换量、铵态氮和硝态氮含量低于或显著(P<0.05)低于CF处理,旱季则表现为OF处理显著高于CF处理(P<0.05),分别高27.02%,58.97%,266.84%。不同处理对0.25~2.00 mm和<0.25 mm团聚体质量百分比和GWD有显著影响(P<0.05);与CF处理相比,OF处理提高了0.25~2.00 mm团聚体质量百分比和GWD,降低了<0.25 mm团聚体质量百分比;季节对<0.25 mm团聚体质量百分比有显著影响(P<0.05)。不同处理团聚体铵态氮和硝态氮含量均表现为:<0.25 mm团聚体最高,0.25~2.00 mm团聚体次之,>2.00 mm团聚体最低;雨季OF处理各级团聚体铵态氮和硝态氮含量低于或显著低于(P<0.05)CF处理,而旱季OF处理显著高于CF处理(P<0.05);与雨季相比,旱季显著降低了CF处理下各级团聚体铵态氮和硝态氮含量(P<0.05),增加或显著(P<0.05)增加了OF处理下>2.00 mm团聚体铵态氮含量和各级团聚体硝态氮含量;不同处理下团聚体铵态氮和硝态氮储量占比均表现为0.25~2.00 mm团聚体最高(51.70%,51.14%),>2.00 mm团聚体次之(34.59%,35.51%),<0.25 mm团聚体最低(13.71%,13.34%);与CF处理相比,OF处理显著降低了雨季和旱季<0.25 mm团聚体铵态氮储量占比和旱季<0.25 mm团聚体硝态氮储量占比(P<0.05),显著提高了雨季0.25~2.00 mm团聚体铵态氮储量占比和旱季0.25~2.00 mm团聚体硝态氮储量占比(P<0.05)。相关性分析表明,茶园土壤团聚体铵态氮含量主要受土壤pH值、阳离子交换量和全氮含量的影响,茶园土壤团聚体硝态氮含量主要受土壤pH值、有机质含量和全氮含量的影响;进一步RDA分析表明,土壤pH值和阳离子交换量是土壤机械稳定性团聚体无机氮分布的主要影响因子。综上,茶园有机肥全量替代化肥有利于提高土壤有机质含量,协调雨季和旱季土壤氮素供应,促进大团聚体的形成和土壤无机氮的积累。

In order to clarify the influence mechanism of total replacement of chemical fertilizer with organic fertilizer on the nitrogen fertility of tea garden soil.Based on the 5 a experiment of replacing chemical fertilizer with organic fertilizer in tea garden,single application of chemical fertilizer(CF)and full application of organic fertilizer(OF)were selected as treatments,the effects of total replacement of organic fertilizer with chemical fertilizer on the physical and chemical properties,mechanical stability,aggregate composition,and aggregate inorganic nitrogen distribution characteristics of tea garden soil in rainy and dry seasons were studied,and the influencing factors of aggregate inorganic nitrogen distribution were analyzed.The results showed that:Compared with CF treatment,OF treatment increased the pH value,organic matter content and total nitrogen content of surface soil in rainy and dry seasons.However,there was no significant difference in soil pH between the two treatments in the rainy season(P>0.05);in the rainy season,the cation exchange capacity,ammonium nitrogen content and nitrate nitrogen content in the surface soil of the tea garden under the OF treatment were lower or significantly lower(P<0.05)than those under the CF treatment,while in the dry season,the OF treatment was significantly higher than that under the CF treatment(P<0.05),with an increase of 27.02%,58.97%,and 266.84%,respectively.Different treatments had significant effects on the mass percentage of 0.25-2.00 mm and<0.25 mm aggregates and GWD;compared with CF treatment,OF treatment increased the mass percentage of 0.25-2.00 mm aggregates and GWD,and decreased the mass percentage of<0.25 mm aggregates;seasons had a significant effect on the mass percentage of aggregates<0.25 mm(P<0.05).The contents of ammonium nitrogen and nitrate nitrogen in aggregates of different treatments were as follows:<0.25 mm aggregates were the highest,0.25-2.00 mm aggregates were the second,and>2.00 mm aggregates were the lowest;in rainy season,the content of ammonium nitrogen and nitrate nitrogen in aggregates at all levels of OF treatment was lower or significantly lower(P<0.05)than that of CF treatment,while in dry season,OF treatment was significantly higher than that of CF treatment(P<0.05);compared with the rainy season,the content of ammonium nitrogen and nitrate nitrogen in aggregates at all levels under CF treatment was significantly reduced in dry season(P<0.05),and the content of ammonium nitrogen and nitrate nitrogen in aggregates at all levels under OF treatment was increased or significantly increased in dry season(P<0.05);under different treatments,the proportion of ammonium nitrogen and nitrate nitrogen storage of aggregates showed that 0.25-2.00 mm aggregates were the highest(51.70%and 51.14%),>2.00 mm aggregates were the second(34.59%and 35.51%),and<0.25 mm aggregates were the lowest(13.71%and 13.34%);compared with CF treatment,OF treatment significantly reduced the proportion of<0.25 mm aggregate ammonium nitrogen storage in rainy and dry season and the proportion of<0.25 mm aggregate nitrate nitrogen storage in dry season(P<0.05),and significantly increased the proportion of 0.25-2.00 mm aggregate ammonium nitrogen storage in rainy season and 0.25-2.00 mm aggregate nitrate nitrogen storage in dry season(P<0.05).Correlation analysis showed that the content of ammonium nitrogen in soil aggregates was mainly affected by soil pH,cation exchange capacity and total nitrogen content,while the content of nitrate nitrogen in soil aggregates in tea garden was mainly affected by soil pH,organic matter content and total nitrogen content;further RDA analysis showed that soil pH and cation exchange capacity were the main factors affecting the distribution of inorganic nitrogen in soil mechanically stable aggregates.To sum up,total replacement of chemical fertilizer with organic fertilizer in tea garden is beneficial to improve the content of soil organic matter,coordinate the supply of soil nitrogen in rainy and dry seasons,and promote the formation of large aggregates and the accumulation of soil inorganic nitrogen.