I could fertilize you could fertilize he could fertilize we could fertilize you could fertilize they could fertilize
V-ing form
I could be fertilizing you could be fertilizing he could be fertilizing we could be fertilizing you could be fertilizing they could be fertilizing
Perfect
I could have fertilized you could have fertilized he could have fertilized we could have fertilized you could have fertilized they could have fertilized
V-ing perfect
I could have been fertilizing you could have been fertilizing he could have been fertilizing we could have been fertilizing you could have been fertilizing they could have been fertilizing
Negation
Simple form
I could not fertilize you could not fertilize he could not fertilize we could not fertilize you could not fertilize they could not fertilize
V-ing form
I could not be fertilizing you could not be fertilizing he could not be fertilizing we could not be fertilizing you could not be fertilizing they could not be fertilizing
Perfect
I could not have fertilized you could not have fertilized he could not have fertilized we could not have fertilized you could not have fertilized they could not have fertilized
V-ing perfect
I could not have been fertilizing you could not have been fertilizing he could not have been fertilizing we could not have been fertilizing you could not have been fertilizing they could not have been fertilizing
Interrogative form
Simple form
could I fertilize? could you fertilize? could he fertilize? could we fertilize? could you fertilize? could they fertilize?
V-ing form
could I be fertilizing? could you be fertilizing? could he be fertilizing? could we be fertilizing? could you be fertilizing? could they be fertilizing?
Perfect
could I have fertilized? could you have fertilized? could he have fertilized? could we have fertilized? could you have fertilized? could they have fertilized?
V-ing perfect
could I have been fertilizing? could you have been fertilizing? could he have been fertilizing? could we have been fertilizing? could you have been fertilizing? could they have been fertilizing?
Interro-negative form
Simple form
could I not fertilize? could you not fertilize? could he not fertilize? could we not fertilize? could you not fertilize? could they not fertilize?
V-ing form
could I not be fertilizing? could you not be fertilizing? could he not be fertilizing? could we not be fertilizing? could you not be fertilizing? could they not be fertilizing?
Perfect
could I not have fertilized? could you not have fertilized? could he not have fertilized? could we not have fertilized? could you not have fertilized? could they not have fertilized?
V-ing perfect
could I not have been fertilizing? could you not have been fertilizing? could he not have been fertilizing? could we not have been fertilizing? could you not have been fertilizing? could they not have been fertilizing?