Learn Turkish: Gübre vermedikçe ekinler kuruyor. - Unless you give fertilizer, the crops dry up.

It uses the converb suffix -dikçe (meaning 'as long as') combined with the negative suffix -me. Literally, vermedikçe means 'as long as giving does not happen.' In English, this naturally translates to 'unless... give.'

The English translation says 'unless you give', but where is the 'you' in vermedikçe?

Words with the -dikçe suffix do not take personal endings. The person doing the action has to be understood from the context of the sentence. Here it is a general statement, so the 'you' in the translation is the general 'you' (meaning 'anyone'). It could also be translated passively: 'Unless fertilizer is given.'

Why isn't gübre marked with the accusative case (gübreyi)?

We only use the accusative case for specific direct objects. Because the sentence refers to giving fertilizer in general, rather than a specific batch of fertilizer we have already talked about, gübre stays in its bare, dictionary form.

Since this is a general fact about crops, why does the sentence use the present continuous kuruyor instead of the aorist (simple present) kurur?

While the aorist (kurur) is the standard tense for general facts and would work perfectly here, Turkish speakers often use the present continuous (-yor) to describe ongoing natural processes or general situations that are currently true. Both sound natural in this context.