生草栽培对南丰蜜橘园土壤酶活性及氮循环功能微生物的影响

Effect of grass cultivation on soil enzyme activities and nitrogen cycling function microorganisms in Nanfeng Tangerine Orchard

为有效解决果园长期清耕带来的土壤侵蚀、土壤肥力下降、病虫害加重等负面危害,改善果园生态环境,推广先进的果园生态管理模式,以南丰蜜橘(Citrus reticulita Blanco cv. Kinokuni)为研究对象,设置行间播种白三叶草(Trifolium repens)、黑麦草(Lolium multiflorum)、自然生草和清耕对照4个处理,采用Illumina HiSeq高通量测序技术和荧光定量PCR技术,研究不同生草条件下橘园土壤酶活性及氮循环功能微生物的变化.结果表明,与清耕对照相比,橘园生草显著提高了土壤有机质、全钾、全磷、全氮、碱解氮、速效磷和速效钾含量,改善了土壤肥力;生草显著提高了橘园土壤蔗糖酶、脲酶、过氧化物酶和蛋白酶活性,促进了土壤养分转化,增加土壤氮素供应.不同生草类型对土壤氮循环功能基因丰度产生了明显的影响,黑麦草处理增加了土壤AOA-amoA、AOB-amoA、nosZ和nirK基因丰度(P <0.05),分别比清耕对照提高了398.00%、163.00%、201.62%和100%;对土壤nirS基因丰度影响不显著.白三叶草处理增加了土壤AOA-amoA、AOB-amoA和nosZ基因丰度(P <0.05),分别比清耕对照提高了440%、119.06%和78.25%;对nirK和nirS基因丰度影响不显著.自然生草处理增加了土壤nosZ基因丰度(P <0.05),比清耕对照提高了122.16%;降低了nirK基因丰度(P <0.05),比清耕对照降低了68.18%;对AOA-amoA、AOB-amoA和nirS基因丰度影响不显著.橘园土壤氮循环微生物物种组成较为单一,氨氧化古菌(AOA)优势菌门为泉古菌门,白三叶草处理泉古菌门相对丰度比清耕对照提高了74.66%,而黑麦草和自然生草处理分别下降了33.37%和35.54%;氨氧化细菌(AOB)和nirK、nirS、nosZ型反硝化微生物优势菌种均为变形菌门.冗余分析(RDA)表明,橘园土壤有机质、全氮、全钾、碱解氮、速效磷和速效钾含量是影响土壤酶活性的主要环境因子;土壤有机质、总磷、速效磷、速效钾含量是影响土壤氮循环微生物功能基因丰度的主要环境因子.综上,南丰蜜橘园生草栽培有利于提高土壤肥力,增强土壤酶活性,增加土壤氮循环微生物功能基因丰度,促进土壤氮素转化及南丰蜜橘产业的可持续发展.

To effectively tackle hazards such as soil erosion, fertility decline, aggravation of diseases, and insect pests caused by long-term clearing of orchards, we need to improve the overall ecological environment of orchards, while also promoting advanced ecological management models. The study was conducted in Nanfeng Tangerine Orchard with four treatments: sod culture with white clover(Trifolium repens), sod culture with ryegrass(Lolium multiflorum), sod culture with natural grass, and clear tillage(as a control). Fluorescence quantitative PCR and Illumina HiSeq high-throughput sequencing were applied to examine soil enzyme activities and changes in soil nitrogen cycling function microorganisms in Nanfeng Tangerine Orchard under different treatments. The results showed that grass cultivation significantly increased the content of organic matter, total potassium, total phosphorus, total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in the soil, as well as improving soil fertility. Grass cultivation could improve the activities of invertase,urease, peroxidase, and protease to promote the conversion of soil nutrients and the supply of soil nitrogen.Different types of grass had a significant impact on the abundance of soil nitrogen cycling functional genes. With ryegrass treatment, the levels of AOA-amoA, AOB-amoA, nosZ, and nirK were significantly increased by 398%,163.00%, 201.62%, and 100.00%, respectively, and there were no significant effects on the abundance of nirS(compared with the control). With white clover treatment, the abundances of AOA-amoA, AOB-amoA, and nosZ were significantly increased by 440%, 119.06%, and 78.25%, respectively, and there were no significant effects on the abundances of nirK and nirS compared with the control. With natural grass treatment, the abundance of nosZ was significantly increased by 122.16%, and the abundance of nirK was decreased by 68.18% compared with the control. There were no significant effects on AOA-amoA, AOB-amoA, and nirS. The composition of soil nitrogen cycling microbial species was relatively uniform. The dominant phylum of AOA found was Crenarchaeota. Its relative abundance increased by 74.66% with white clover treatment and decreased by 33.37% and 35.54% with ryegrass and natural grass treatments, respectively, compared with the control. The dominant phylum of AOB, nirK, nirS, and nosZ was Proteobacteria. RDA analysis showed that soil enzyme activity was mainly affected by the content of organic matter, total nitrogen, total potassium, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in the soil. The abundance of functional genes related to soil nitrogen cycling was affected by the content of organic matter, total phosphorus, available phosphorus,and available potassium content in the soil. In conclusion, grass cultivation in the Nanfeng Tangerine Orchard was beneficial for the improvement of soil fertility, enhancement of soil enzyme activities abundance of nitrogen cycling genes, promotion of soil nitrogen conversion, and promotion of the sustainable development of the Nanfeng tangerine industry.