Microbial Nutrient Limitation of Different Tea Cultivars: Evidence from Five Representative Cultivars

Soil microbial activity is generally limited by the availability of carbon (C), nitrogen (N), or phosphorus (P) in agricultural ecosystems. Soil ecoenzymatic activity (EEA), ecoenzymatic stoichiometry (EES), and vector characteristics were examined to assess microbial nutrient limitation. Investigating soil microbial nutrient limitation can provide insight into nutrient cycling in tea plantations with different tea cultivars. However, the dynamics of different tea cultivars on soil microbial nutrient limitations and their effect on tea quality remains poor. To address this issue, soil and plant samples were collected from a tea plantation cultivating five representative tea cultivars in Hunan Province, China. Baojing Huangjincha No. 1 (HJC1) and Huangjincha No. 2 (HJC2) were the extra early-sprouting cultivars, Zhuyeqi (ZYQ) and Zijuan (ZJ) were the middle-sprouting cultivars, and Zhenghedabai (ZHDB) was the late-sprouting cultivar, respectively. The results indicated that differences in EEA and EES were significant among five treatments. Notably, ZYQ and ZJ exhibited markedly lower activities of carbon (C), nitrogen (N), and phosphorus (P) acquiring enzymes compared to HJC1 and HJC2, whereas ZHDB showed significantly higher ecoenzymatic activities. Despite a general limitation in C and P for soil microorganisms across all cultivars (VL ranging from 1.42 to 1.59 and VA ranging from 58.70° to 62.66°), the degree of microbial nutrient limitation varied. Specifically, ZYQ experienced a pronounced P limitation (VA = 62.66°, N:P enzyme = 0.52), as evidenced by increased vector angles and decreased N:P enzyme values. Although C limitation was most pronounced in ZYQ (VL = 1.59), it did not significantly differ among the cultivars. These findings suggest that tea cultivars can influence the P limitation of microbial communities. Further analysis revealed that microbial nutrient limitations might adversely affect tea quality via impeding enzyme secretion. This study highlights the critical role of nutrient cycling within the soil-microorganism-plant ecosystem and emphasizes the influence of soil microbial nutrient limitations on tea quality within tea plantations. It is recommended that in the management of tea plantation fertilization, managers need to consider the influence of cultivars and develop specialized cultivar fertilizers.