Elegimos la enmienda orgánica a falta de compost.

No. In this sentence, enmienda is being used in an agricultural/gardening sense.

Enmienda orgánica means a soil amendment or organic amendment: a material added to soil to improve its structure or quality.

So although enmienda can mean amendment in other contexts, here it does not mean a legal or political amendment.

Because enmienda is a feminine singular noun in Spanish.

So:

• la enmienda
• orgánica agrees with it in gender and number

That is why both words are feminine singular:

• la = feminine singular article
• orgánica = feminine singular adjective

In Spanish, adjectives often come after the noun, especially when they are classifying or describing the type of thing.

So:

• enmienda orgánica = organic amendment

This is more natural in Spanish than putting the adjective first. In this case, the adjective is simply identifying what kind of amendment it is.

A falta de is a fixed expression meaning something like:

• for lack of
• in the absence of
• since there wasn’t any
• because we didn’t have

So a falta de compost means:

• for lack of compost
• since there was no compost available

It introduces the idea that one option was chosen because another one was unavailable.

Because compost is being used here as a general material noun, not as a specific, identified item.

So Spanish commonly says:

• a falta de compost

rather than:

• a falta del compost

Use del compost only if you mean a specific compost already known in the conversation, such as the compost we were expecting.

Compare:

• a falta de compost = in the absence of compost in general
• a falta del compost = in the absence of the specific compost

Yes, compost is used in Spain, especially in gardening, agriculture, and environmental contexts.

It is usually treated as a masculine noun when an article is used:

• el compost

But in your sentence there is no article because of the structure a falta de + noun.

Depending on context, you may also hear related words such as:

• compostaje = composting
• abono = fertilizer/manure, sometimes more general than compost

Elegimos can be two different tenses:

1. Present indicative
   elegimos = we choose

2. Preterite (simple past)
   elegimos = we chose

These two forms are identical for nosotros with elegir.

So, without more context, the sentence could mean either:

• We choose the organic amendment for lack of compost
• We chose the organic amendment for lack of compost

Only the surrounding context tells you which one is intended.

Yes, both elegir and escoger can mean to choose.

In many contexts they are interchangeable:

• elegimos
• escogimos

However, elegir is extremely common and often feels slightly more standard or neutral. In a sentence like this, elegimos sounds perfectly natural.

So this is not really a grammar issue, but a vocabulary choice:

• elegir = to choose / select
• escoger = to choose / pick

Both would work.

Yes, you probably could, but the nuance is slightly different.

• a falta de compost = in the absence of compost / for lack of compost
• por falta de compost = because of a lack of compost

In many practical contexts, both are understandable. But a falta de is a very common set phrase when one thing is used because another is unavailable.

So in this sentence, a falta de compost sounds especially natural.

Not exactly.

They are related, but not always identical:

• abono usually refers to fertilizer or something added mainly to provide nutrients
• enmienda usually refers to something added to improve the soil’s condition, structure, or properties

An enmienda orgánica may improve the soil and can also contribute nutrients, but the term is a bit more technical and specific than abono.

So if this sentence comes from gardening or agriculture, enmienda orgánica is probably deliberate vocabulary rather than just a synonym for fertilizer.

Because the direct object is not a person.

The personal a is used before specific human direct objects, for example:

• Vemos a María

But here the object is a thing:

• la enmienda orgánica

So no personal a is needed:

• Elegimos la enmienda orgánica

The a in a falta de compost is part of the expression a falta de and has nothing to do with the personal a.

Yes. It is a productive expression and can be used with many nouns.

Examples:

• A falta de pan, comimos arroz.
• A falta de tiempo, lo haremos mañana.
• A falta de pruebas, no pudieron condenarlo.

It usually means:

• since there wasn’t any...
• in the absence of...
• for lack of...

So your sentence follows a very common Spanish pattern.