Hi,

In the interest of possible future moon colonies, space agencies have searched for new ways to grow plants in places they normally would not grow. This has led to the creation of a kind of synthetic soil. It is made with a common mineral called zeolite, which can store nutrients and release them over time. The artificial soil is already being used by some farmers and may be developed as a new kind of a fertilizer. Because of its ability to release nutrients gradually, such a fertilizer would cause less pollution when washed away into surrounding streams and rivers.

I have a few questions about the above passage.

Q1) Does 'would' in the underlined sentence have a hypothetical meaning?

Q2) I'm not familiar with a case in which 'would' is paired with a 'when' clause. Could you explain constructions of this kind? Can you use 'if' in place of 'when'?

Q3) What would be a subject and a verb that are missing in the 'when' clause?

Thank you.
1 = didn't grow, weren't growing

2 = if

3 the fertilizer was washed
Thank you for the reply. So you are saying that the 'when' clause has hypothetical meaning, right? It is a little surprising to learn that's the case here because 'when', as far as I know, is normally used to refer to something the speaker knows will happen at some point in time.
Teachers: We supply a list of EFL job vacancies
1. Yes. would is hypothetical. The soil under consideration may be developed as fertilizer. It appears that this fertilizer has not yet been developed.

2. I don't think it's accurate to say that the would is paired with the when-clause. A when-clause can occur independently of any modal verb used in an accompanying clause. I'm inclined to say that this would is paired with an implicit if-clause, which is not uncommon:

Because of its ability to release nutrients gradually, such a fertilizer would cause less pollution when washed away into surrounding streams and rivers if it were [available for use / used].

Of course, it hasn't been developed as a fertilizer yet, so it isn't available, and it can't be used. It is this very impossibility that makes the would hypothetical.

3. ... when such a fertilizer [might be / was] washed away into ...

CJ
Thank you very much for your answers, CJ. Now I can see the 'when' clause was used independently.

Could I ask you another question?

The verb omitted in the 'when' clause is in the past tense form. Could you explain why that is so? Is it because the event expressed in the 'when' clause is hypothetical? Would the present tense form work here as well?
jooneyThe verb omitted in the 'when' clause is in the past tense form. Could you explain why that is so? Is it because the event expressed in the 'when' clause is hypothetical? Would the present tense form work here as well?
Tenses are usually used together in particular groupings. A sentence normally has only tenses in the present-point-of-view grouping or in the past-point-of-view grouping - unless there is an overriding reason to mix the two.

Present POV: present, present perfect, imperatives, will, can, may, must, should, shall

Past POV: past, past perfect, used to, would, could, might

The present doesn't work in that when-clause very well, but frankly the past doesn't either - precisely because of the hypothetical nature of the statement. I think this is the exact reason why the writer made a when-clause without a verb. Emotion: smile

CJ
Site Hint: Check out our list of pronunciation videos.
I learned something new today. Thank you so much.Emotion: smile