Answer: Experimental
Step-by-step explanation:
Experimental study is the study in which researcher has some control over the variables where he can experiment and test over the groups. Observational study provides no control to researcher .He can only observe the process.
According to the question, study conducted by farmer is experimental as farmer has the control over quantity variable of land , grouping choice of crop etc.He is dividing the land equally in four parts,sowing same crops into 4 groups in each piece depicts that he is testing or experimenting everything equally.