Can I Remove 'Yield' from This Sentence for Better Clarity?

Yes, based on the context provided, you can remove 'yield' from the sentence 'Therefore, the lowest average yield in 2013, the medium average yield in 2018, and the highest average yield in 2021 were selected for analysis.' The sentence would then read: 'Therefore, the lowest average in 2013, the medium average in 2018, and the highest average in 2021 were selected for analysis.' This makes the sentence more concise and easier to understand without losing any meaning.