Using .rproj files means that you don't need to set the working directory. And you don't want to set it within a subfolder because that makes it harder to direct where you want the output to go. For example:
#setwd("C:\\Users\\90958427\\OneDrive - Western Sydney University\\PolyTunnelS33_ExperimeNT1_dose\\Modified Data File")
list.files()
Soil_Nutrients<- read.csv("Modified Data File/Soil_Nutrients_Extraction_EXP1.csv")
head(Soil_Nutrients)
Using .rproj files means that you don't need to set the working directory. And you don't want to set it within a subfolder because that makes it harder to direct where you want the output to go. For example: