土壤微生物碳(C),氮(N),磷(P)养分需求和代谢限制与环境养分的可用性密切相关。然而,目前尚不清楚有机肥和化学肥料如何根据苹果园的土壤酶化学计量改变微生物的养分限制。因此,本研究在2008年建立的苹果园长期试验的基础上,运用土壤酶化学计量学的理论和方法,系统地研究了肥料和化肥配施对土壤碳的影响,N,和P周转相关酶活性(β-1,4-葡萄糖苷酶,BG;亮氨酸氨基肽酶,NAG;β-1,4-N-乙酰氨基葡萄糖苷酶,LAP;和酸性或碱性磷酸酶,PHOS)及其化学计量特征,并分析了它们与环境因素和微生物碳利用效率的关系。实验设计了四种处理方法,例如,无施肥输入作为对照(CK),单施化肥(NPK),肥料和化肥联合施用(MNPK),和一次性施用粪肥(M)。结果表明:①在果树的不同生长阶段,粪肥处理(MNPK和M)的土壤微生物生物量C(microC)含量显着高于无粪肥处理(CK和NPK)。NPK中微生物生物量N(microN)的含量,MNPK,M治疗增加了89%,269%,和213%,分别,与CK相比(P<0.05)。②与施肥处理相比,CK在发芽阶段具有较高的叶片N和P含量(29.8g·kg-1和2.17g·kg-1),单独发芽阶段的叶片P含量与土壤速效磷(AP)含量呈极显著负相关。③土壤酶化学计量分析表明,本研究所有数据点都在1:1线以上,表明微生物群落具有很强的磷限制。矢量长度和角度范围为0.56-0.79和59.3°-67.7°,分别,在果树的生长期,在这项研究中,矢量角度>45°,这也反映了微生物对磷的强烈限制。④RDA和随机森林模型分析表明,有机碳和速效氮(AN)是影响载体长度的主要理化因子;AP,AN,土壤含水量是影响矢量角的主要理化因子。结合SEM分析,AN和溶解的有机碳(DOC)直接影响microC和microN,AP直接影响microP和microN,DOC和AP直接影响向量长度,AP和microN直接影响矢量角度。此外,微生物碳利用与矢量长度呈正相关,与矢量角度呈负相关。总之,肥料和化肥的配施通过影响果树不同生长阶段土壤碳磷含量来调节微生物碳磷代谢,从而影响微生物的碳利用。该研究为肥料和化肥改善土壤质量和保持土壤健康提供了科学依据。
Soil microbial carbon (C), nitrogen (N), and phosphorus (P) nutrient requirements and metabolic limitations are closely related to the availability of environmental nutrients. However, it is unclear how manure and chemical fertilization shift nutrient limitations for microbes in terms of the soil enzymatic stoichiometry in an apple orchard. Therefore, based on the long-term experiment located in an apple orchard established in 2008, this study applied the theory and method of soil enzyme stoichiometry to systematically investigate the effects of the combined application of manure and chemical fertilizers on soil C, N, and P turnover-related enzyme activities (β-1,4-glucosidase, BG; leucine aminopeptidase, NAG; β-1,4-N-acetylglucosaminidase, LAP; and acid or alkaline phosphatase, PHOS) and their stoichiometric characteristics and analyzed their relationships with environmental factors and microbial carbon use efficiency. The experiment was designed with four treatments, such as, no fertilization input as the control (CK), single application of chemical fertilizer (NPK), combined application of manure and chemical fertilizer (MNPK), and single application of manure (M). The results revealed that:① at different growth stages of fruit trees, the soil microbial biomass C (microC) content of manure fertilizer treatments (MNPK and M) was significantly higher than that of no manure fertilizer treatments (CK and NPK). The content of microbial biomass N (microN) in the NPK, MNPK, and M treatments increased by 89%, 269%, and 213%, respectively, compared with that in CK (P<0.05). ② Compared with those in the fertilization treatments, CK had higher leaf N and P contents (29.8 g·kg-1 and 2.17 g·kg-1) at the germination stage, and the leaf P content at the germination stage alone was significantly negatively correlated with soil available phosphorus (AP) content. ③ Soil enzyme stoichiometry analysis demonstrated that all data points in this study were above the 1:1 line, indicating that microbial communities had a strong phosphorus limitation. The range of vector length and angle was 0.56-0.79 and 59.3°-67.7°, respectively, in the growth period of fruit trees, and the vector angle was >45° in this study, which also reflected the strong phosphorus limitation of microorganisms. ④ RDA and random forest model analysis showed that organic carbon and available nitrogen (AN) were the main physical and chemical factors affecting vector length; AP, AN, and soil water content were the main physical and chemical factors affecting vector angle. Combined with SEM analysis, AN and dissolved organic carbon (DOC) directly affected microC and microN, AP directly affected microP and microN, DOC and AP directly affected vector length, and AP and microN directly affected vector angle. In addition, microbial carbon utilization was positively correlated with vector length and negatively correlated with vector angle. In summary, the combined application of manure and chemical fertilizers regulated microbial carbon and phosphorus metabolism by affecting soil carbon and phosphorus content at different growth stages of fruit trees, thereby affecting microbial carbon utilization. This study provides a scientific basis for manure and chemical fertilizers to improve soil quality and maintain soil health.