في التربة مغذيات.

Because Arabic often makes sentences without a written verb in the present tense.

This is a nominal sentence. Arabic can express there is / there are just by putting a location first and the thing that exists after it:

في التربة مغذيات
literally: In the soil [are] nutrients

So this is a very natural way to say an existential idea like There are nutrients in the soil.

You could also say توجد مغذيات في التربة, but the original sentence is simpler and very common.

Starting with في التربة puts the location first. In Arabic, this often gives the meaning of there are ... in ....

So:

في التربة مغذيات
= There are nutrients in the soil

If you said:

مغذيات في التربة

that would feel less like a normal full sentence on its own, unless the context supports it. And if you said:

المغذيات في التربة

that would more likely mean The nutrients are in the soil or The nutrients in the soil, depending on context.

So the original order is especially good for introducing the existence of something.

This is very common in Arabic existential sentences.

• التربة has الـ, so it is definite: the soil
• مغذيات has no الـ, so it is indefinite: nutrients / some nutrients

In sentences like this, the thing being introduced often appears as an indefinite noun. That is part of what helps create the meaning there are ...

So:

في التربة مغذيات
naturally means There are nutrients in the soil

If you made مغذيات definite:

في التربة المغذيات

that would no longer be the normal existential pattern, and it would suggest specific nutrients already known from context.

Because ت is a sun letter.

In Arabic, when الـ comes before a sun letter, the ل sound is not pronounced, and the next consonant is doubled.

So:

• written: التربة
• pronounced: at-turbah or, in full case-ending pronunciation, at-turbati

After في, you would hear something like:

fī t-turbati

The spelling stays التربة, but the pronunciation changes because of the sun-letter rule.

Because it comes after the preposition في.

Prepositions in Arabic make the following noun genitive, so:

• في = in
• التربةِ = the soil, in the genitive case

So the full vocalization is:

فِي التُّرْبَةِ مُغَذِّياتٌ

The ـِ on التربةِ is there because في requires it.

It is in the nominative case.

In this sentence, في التربة is the predicate-like part at the beginning, and مغذيات is the postponed subject.

So the structure is often explained as:

• في التربة = fronted prepositional phrase / predicate
• مغذياتٌ = delayed subject

That is why مغذيات is nominative:

مُغَذِّياتٌ

In normal unvoweled writing, you do not see the final case ending, but grammatically it is there.

مغذيات is a plural noun meaning nutrients.

It has the ending ـات, which is the common ending of the sound feminine plural. In Arabic, this ending is not used only for biologically female things. It is also used for many non-human nouns, especially in formal, scientific, or abstract vocabulary.

So even though nutrients are not feminine in the real-world sense, مغذيات is grammatically a feminine-plural form.

Yes, it can.

With non-human plurals in Modern Standard Arabic, agreement is often treated as feminine singular rather than full plural agreement.

For example, you may see:

المغذيات مهمة
= The nutrients are important

Notice that مهمة is feminine singular in form.

In your sentence, there is no adjective or verb that shows this agreement, so you do not see the effect directly. But it is useful to know for later.

Yes. That is correct and natural.

It means nearly the same thing:

• في التربة مغذيات = There are nutrients in the soil
• توجد مغذيات في التربة = There are / exist nutrients in the soil

The version without a verb is often more compact and very typical Arabic style. The version with توجد is a little more explicit.

A fully vocalized version is:

فِي التُّرْبَةِ مُغَذِّياتٌ

This shows:

• فِي = preposition in
• التُّرْبَةِ = the soil, genitive after في
• مُغَذِّياتٌ = nutrients, nominative as the delayed subject

Hearing or reading the vowels can make the grammar much clearer, especially in short sentences like this.