baiyoudo, huyoudo, akadamatuti wo mazete, hiryou wo ireru.

Here are the readings:

• 培養土 = ばいようど
• 腐葉土 = ふようど
• 赤玉土 = あかだまつち
• 混ぜて = まぜて
• 肥料 = ひりょう
• 入れる = いれる

A useful note: 土 is often read ど in compounds, as in 培養土 and 腐葉土, but in 赤玉土 it is read つち.

Because the three nouns are being treated as one list:

• 培養土、腐葉土、赤玉土を混ぜて

This means mix potting soil, leaf mold, and akadama soil. In Japanese, when several nouns are listed together, it is very common to put the particle only once after the whole list.

So this structure is like:

• A、B、C を + verb

rather than repeating:

• Aを、Bを、Cを

Both can exist in some contexts, but using one を for the whole list is very natural here.

混ぜて is the て-form of 混ぜる.

Here, the て-form connects actions:

• 培養土、腐葉土、赤玉土を混ぜて、肥料を入れる。

So the sense is:

• Mix the soils, and then add fertilizer.

In this sentence, て works like and / then to link the first action to the second one.

This is a very common pattern in instructions, recipes, manuals, and gardening directions:

• earlier actions: て-form
• final action: plain dictionary form

So:

• 混ぜて、入れる

means something like:

• mix ..., then add ...

The final dictionary form gives the sentence a neutral instructional style. It is not exactly a direct command like 入れろ, but in context it functions like an instruction.

It is best understood as an instruction rather than a harsh command.

Japanese often uses the plain dictionary form in things like:

• recipes
• manuals
• how-to guides
• gardening instructions

So 肥料を入れる here means something like:

• add fertilizer
• you should add fertilizer
• the next step is to add fertilizer

It sounds matter-of-fact and procedural.

Because Japanese often leaves out the subject when it is obvious from context.

In a sentence like this, the omitted subject is usually understood as:

• you in an instruction manual, or
• one / the person doing the task in a general how-to sense

So Japanese does not need to say:

• あなたは培養土...を混ぜて...

That would usually sound unnecessary.

入れる literally means to put in or to insert, but in many practical contexts it also means to add.

So here:

• 肥料を入れる

means:

• add fertilizer
• literally, put fertilizer in

This is very natural Japanese for adding something to a mixture, container, pot, soil, and so on.

Good question. In 肥料を入れる, 肥料 is the thing being put in, so it takes を as the direct object.

The destination can be marked with に, but it is often omitted if it is obvious.

For example, the fuller version could be something like:

• 混ぜた土に肥料を入れる。
• Add fertilizer to the mixed soil.

But in your sentence, the place it goes is obvious from context, so Japanese leaves it out.

They mainly help separate items in a list and make the sentence easier to read.

Here they show:

1. a list of materials
   
   • 培養土、腐葉土、赤玉土
2. a pause before the next action
   
   • 混ぜて、肥料を入れる

So the commas are doing something similar to commas in English lists and step-by-step instructions.

You are right: normal Japanese usually does not use spaces between words.

So a more standard written version would be:

• 培養土、腐葉土、赤玉土を混ぜて、肥料を入れる。

The spaces in your version are probably there to help learners see the word boundaries more easily.

混ぜる is an ichidan verb.

For ichidan verbs, you usually make the て-form by replacing る with て:

• 混ぜる → 混ぜて
• 入れる → 入れて

So:

• 混ぜる = to mix
• 混ぜて = mix and..., having mixed...

That makes it easy to link actions in sequence.

Not exactly.

• 混ぜる is the plain dictionary form: to mix
• 混ぜて is the て-form, which connects to what comes next

So in this sentence:

• 混ぜて does not just mean mix
• it means mix, and then...

That connection is important because the sentence gives a sequence of actions: first mix the soils, then add fertilizer.