Añadí el fertilizante al sustrato después de revisar el drenaje.

Añadí is the first-person singular preterite of añadir.

So it means I added as a completed action in the past.

In this sentence, the speaker is describing a finished sequence:

• first, they checked the drainage
• then, they added the fertilizer

In Spain, this tense is very common for narrating completed past actions.

The accent mark in añadí is part of the normal preterite ending for many -ir verbs in the yo form.

Compare:

• añado = I add, I am adding
• añadí = I added

The accent shows the stress falls on the last syllable:

• a-ña-DÍ

Without the accent, it would not be the correct written form.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

Here, añadí clearly means I added, so yo is not necessary.

You could say:

• Yo añadí el fertilizante...

But that usually adds emphasis, contrast, or clarification, such as:

• Yo añadí el fertilizante, pero tú revisaste el drenaje

In a neutral sentence, leaving out yo sounds natural.

Al is the contraction of a + el.

So:

• a el → al

In this sentence:

• al sustrato = to the substrate / growing medium

This is required because the verb añadir normally uses the pattern:

• añadir algo a algo
  to add something to something

So:

• Añadí el fertilizante al sustrato
  = I added the fertilizer to the substrate

Because with añadir, Spanish normally uses a to express what something is added to.

The usual structure is:

• añadir algo a algo

So:

• añadir fertilizante al sustrato = to add fertilizer to the substrate

If you used en, it would sound more like talking about location, not the normal verb pattern. In other words:

• a focuses on the target of the addition
• en would focus more on where something is physically located

Spanish uses definite articles more often than English.

Here, the speaker is probably referring to specific things already understood in context:

• el fertilizante = the fertilizer
• el sustrato = the substrate
• el drenaje = the drainage

Even when English might sometimes say fertilizer, substrate, or drainage without the, Spanish often prefers the article.

This is especially common when talking about materials, processes, or parts of a known setup.

Because después is followed by de before a noun or an infinitive.

So the correct pattern is:

• después de + noun
• después de + infinitive

Examples:

• después de la lluvia = after the rain
• después de revisar el drenaje = after checking the drainage

So después revisar is not correct.

After después de, Spanish commonly uses the infinitive when the subject is the same as in the main clause.

Here, the same person did both actions:

• I checked the drainage
• I added the fertilizer

So Spanish uses:

• después de revisar el drenaje

This is very natural and compact.

A more explicit version is also possible:

• después de que revisé el drenaje

But the infinitive version is usually simpler and more common when the subject is the same.

Yes, you could.

Both are correct:

• después de revisar el drenaje
• después de que revisé el drenaje

The difference is mainly style:

• después de revisar el drenaje is shorter and more streamlined
• después de que revisé el drenaje is more explicit because it includes a fully conjugated clause

When the subject is the same, Spanish often prefers the infinitive version.

Yes. A very natural alternative is:

• Después de revisar el drenaje, añadí el fertilizante al sustrato.

This means the same thing.

The difference is emphasis:

• Añadí el fertilizante... después de revisar... starts with the main action
• Después de revisar..., añadí... starts with the earlier step in the sequence

Both are correct and natural.

The ñ is pronounced like the ny sound in English canyon, but usually more smoothly and as a single sound.

So añadí sounds roughly like:

• ah-nya-DEE

Not exactly English ny, but that approximation helps.

This sound also appears in words like:

• España
• niño
• mañana

In gardening or horticulture, sustrato usually means the growing medium where plants grow.

It is often more specific than tierra.

• tierra often means soil, earth, or dirt
• sustrato can refer to potting mix, planting medium, or another material used to support plant growth

So in this sentence, sustrato is a more precise word for the material the fertilizer was added to.

Yes.

The sentence presents a clear sequence:

1. revisar el drenaje
2. añadir el fertilizante al sustrato

The phrase después de makes that order explicit.

So the speaker is saying the fertilizer was added only after checking the drainage first.