PCA of soil and plant variables measured in six processing tomato fields. Soil physicochemical parameters and plant variables separated primarily by site along PC1, which explained 42% of variation. Samples separated secondarily by management within site, and a significant site  management interaction was observed.

source: Schmidt, J. E., Vannette, R. L., Igwe, A., Blundell, R., Casteel, C. L., & Gaudin, A. C. (2019). Effects of agricultural management on rhizosphere microbial structure and function in processing tomato plants. Applied and environmental microbiology, 85(16), e01064-19.