Ρίχνω λίγο νερό στο χώμα πριν βάλω τον σπόρο.

Because Greek usually drops the subject pronoun when the verb ending already shows who is doing the action.

Here, ρίχνω means I pour / I throw / I put, so εγώ is not necessary.
You could say Εγώ ρίχνω..., but that would add emphasis, like I pour..., not someone else.

Yes, ρίχνω literally often means throw, but in everyday Greek it is also used much more broadly for things like:

• pour
• put
• add
• drop

So in this sentence, ρίχνω λίγο νερό is a natural way to say I pour / add a little water. It does not sound like you are violently throwing water.

Because λίγο agrees with νερό, and νερό is neuter singular.

Greek adjectives and quantity words usually agree with the noun in gender, number, and case:

• λίγος = masculine
• λίγη = feminine
• λίγο = neuter

So:

• λίγο νερό = a little water
• λίγος χρόνος = a little time
• λίγη ζάχαρη = a little sugar

Because λίγο νερό is an indefinite quantity: a little water / some water.

Greek does not always need an article in that kind of phrase, especially with mass nouns like water, milk, sugar, etc.

Compare:

• λίγο νερό = a little water / some water
• το νερό = the water

So here the sentence is talking about some water, not a specific previously mentioned water.

στο is the contraction of:

• σε = in, at, to, on
• το = the

So:

• σε το → στο

This is extremely common in Greek:

• στο = to the / in the / on the
• στη = σε + τη
• στον = σε + τον

So στο χώμα means something like in the soil / on the soil / into the soil, depending on context.

In Modern Greek, σε is a very broad preposition. It can correspond to several English prepositions, including:

• to
• in
• at
• on
• sometimes into / onto

So στο χώμα can mean in the soil, on the soil, or into the soil, depending on the situation.

Greek often uses one preposition where English uses several different ones.

Because after πριν (before), Greek normally uses the form that refers to a single, complete action, not the ongoing/habitual present form.

• βάζω = I put / I am putting, imperfective
• βάλω = perfective form used here after πριν

So πριν βάλω τον σπόρο means before I put the seed as one completed action.

Using βάζω here would sound wrong in standard Greek.

Because βάζω has an irregular perfective stem.

This is very common in Greek verbs: the form you learn in the dictionary is often the imperfective / present stem, but other tenses or moods use a different stem.

Here:

• dictionary form: βάζω
• perfective form: βάλω

You can think of βάλω as the form used for one-time, complete putting.
That is why it appears after πριν in this sentence.

Because τον σπόρο is the direct object of the verb βάλω.

In Greek, direct objects usually go in the accusative case.

So:

• ο σπόρος = the seed (nominative, subject form)
• τον σπόρο = the seed (accusative, object form)

Also notice that masculine nouns in -ος usually lose the final -ς in the accusative singular:

• ο σπόρος
• τον σπόρο

Yes, Greek could say έναν σπόρο if the speaker means a seed in an indefinite sense.

But τον σπόρο is also very natural, because Greek often uses the definite article in places where English might choose either the or a, depending on context.

Here τον σπόρο suggests a specific seed the speaker is about to plant.

So both are possible in the right context, but they are not exactly the same nuance:

• τον σπόρο = the seed, a specific one
• έναν σπόρο = a seed, one seed

No, Greek word order is fairly flexible.

The given order is natural and neutral:

Ρίχνω λίγο νερό στο χώμα πριν βάλω τον σπόρο.

But you could also say:

Πριν βάλω τον σπόρο, ρίχνω λίγο νερό στο χώμα.

That changes the focus a little, but the meaning stays basically the same. Greek can do this because verb endings, articles, and case forms help show what each word is doing.