Spatial variability of soil microelements in a small scale tea garden and the influencing factors

Objectives Studying the spatial variation of microelements and the influencing factors could improve nutrient management for high tea yield and quality.

Methods There were 94 soil samples (0–30 cm) collected randomly in an ecological tea garden within 2 km² at Zhongfeng Town, Mingshan District, Ya’an in 2020. The soil pH, organic matter (SOM) and available iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) contents were analyzed. Data obtained were screened by the threshold value method (mean ± three times of standard deviation) before using geostatistics and the GIS spatial analysis method for the spatial variation modelling. Additionally, the correlation of the nutrient contents was regressed with the influencing factors of soil microelements.

Results The average contents of available Fe, Mn, Cu, and Zn in the tea garden soil were 56.0 mg/kg, 28.0 mg/kg, 1.2 mg/kg, and 1.8 mg/kg, with the coefficients of variation of 52.59%, 89.95%, 38.81%, and 32.90%, respectively. These results showed a moderate variation. Available Cu showed a pure nugget effect, and the global Moran’s I index was negative. The optimal interpolation models of available Fe and Mn were exponential, while available Zn were spherical. The nugget effect ranged from 36.57% to 61.85%, showing moderate spatial correlation. The global Moran’s I index of available Fe, Mn, and Zn was positive. Available Fe showed a high (P<0.05) spatial autocorrelation. The spatial distribution of available Fe was higher in the south and lower in the northern region of the research area. In contrast, available Mn exhibited a decrease with the increasing slope. Available Cu and Zn were distributed in patches, with high concentrations along the perimeter and low in the middle of the region. Available Fe was (P<0.05) affected by organic matter and pH. Available Mn was (P<0.05) related to slope only, available Cu content showed no correlation with the influencing factors, and available Zn content was (P<0.05) positively related to organic matter.

Conclusions The soil available Fe, Mn, Cu, and Zn contents in the study area are relatively abundant with a moderate variation. The available Cu shows spatial isolation, while Fe, Mn, and Zn show spatial aggregation. The available Fe and Zn are affected by organic matter, and available Mn is merely related to the slope. No obvious relationship is found between the soil available Cu and the various factors, implying that it can be adopted to reveal the drivers of its spatial distribution from the perspective of farm management.