Learn Spanish (Latin America): Por más que echan abono, el campo no es fértil. - No matter how much fertilizer they pour, the field is not fertile.

With phrases like por más que or por mucho que, you use the indicative when declaring a known, experienced fact. The speaker knows for a certainty that they are currently applying fertilizer. If this were a hypothetical situation or a future possibility (like 'no matter how much they might pour tomorrow'), you would use the subjunctive echen.

Could I use por mucho que in this sentence instead?

Absolutely. Por mucho que echan abono means exactly the same thing. Both por más que and por mucho que are interchangeable here to mean 'no matter how much' or 'even though', and both follow the exact same rules for choosing between the indicative and subjunctive.

Why use es instead of está for 'is not fertile'?

We use the verb ser (es) because being fertile is treated as an inherent characteristic or permanent quality of the land. Using estar would suggest a temporary state, but the speaker is making a general statement about the fundamental nature of this field.

I usually see echar translated as 'to throw'. Does it always mean 'to pour' with things like fertilizer?