Learn Spanish (Latin America): Esta tierra no tiene la cantidad necesaria de nutrientes. - This soil does not have the necessary amount of nutrients.

Tierra is a versatile word. When capitalized (la Tierra), it means the planet Earth. When lowercase, it usually means "land," "dirt," or "soil." Another common word you might see for soil or ground is el suelo.

Why does necesaria come after cantidad?

In Spanish, descriptive adjectives usually come after the noun they describe to distinguish or specify exactly which one we mean. Here, necesaria tells us exactly what kind of amount (cantidad) we are talking about.

How could I apply this lesson's grammar to say "The fewer nutrients this soil has, the worse it is"?

You would use the proportional structure mientras menos... peor: Mientras menos nutrientes tiene esta tierra, peor es. Notice that we use the indicative verbs (tiene, es) because we are stating a general, factual correlation.

Do I always need de when saying "amount of" something?

Yes! Just like in English, when you connect a noun of measurement or quantity (cantidad) with the thing being measured (nutrientes), you need the preposition de (of).