Is there any zakaah due from one who cut corn before it ripened to provide food for his animals?

Firstly: 

In the answer to question no.
99843 we explained that zakaah
is due on grains of types that are measurable and storable, if what the land
produces reaches five wasqs, i.e., three hundred saa‘s.  This is equivalent
to 612 kg of good-quality wheat; some scholars give the amount as 653 kg.
One-tenth is to be given if the crop was irrigated by rainwater, rivers or
springs, and half of one tenth is to be given if it was irrigated by costly
(artificial) means. 

Based on that, if the corn is of a type that is measurable
and storable, if the amount produced exceeds three hundred saa‘s, because
the cultivated land covers a large area, then for the corn that is produced
zakaah must be given at the rate of half of one tenth, because water was
brought from the well to irrigate the crop, which can only be done by costly
means such as machines, fuel and so on. 

Secondly: 

What we have mentioned above about the minimum threshold
(nisaab) for zakaah on grains is the first condition for zakaah being
obligatory. The second condition is that this minimum amount should have
been in his possession at the time that zakaah became due. 

The time when zakaah becomes due on grains is when they
become hard, and on other crops it is when they become visibly ripe. This is
the view of the majority of fuqaha’, apart from Abu Haneefah, who said that
zakaah becomes due when the crops begin to appear; it is also different from
the view of those, among the Hanbalis and others, who say that the time when
it becomes due is when it is harvested. 

In al-Mawsoo‘ah al-Fiqhiyyah (15/12 it says: 

The majority of fuqaha’ are of the view that zakaah becomes
due on crops when they have visibly ripened, because in that case the crop
is fully developed.

End quote. 

Al-Maawardi (may Allah have mercy on him) said: 

With regard to the zakaah on grains, it becomes obligatory
when they become dry, hard, strong and been harvested. The zakaah should be
paid after they have been threshed and sifted, when only the grain is left.

Al-Haawi al-Kabeer, 3/243 

Ibn Qudaamah (may Allah have mercy on him) said: 

The time when zakaah becomes due on grains is when they
become hard, and in the case of crops is when they have visibly ripened.

Ibn Abi Moosa said: Zakaah becomes due on grains on the day
of harvest, because Allah says (interpretation of the meaning): “but pay
the due thereof (its Zakat) on the day of its harvest” [al-An ‘am 6:141]. 

To sum up: if he disposed of the crop or grains before zakaah
became due, then he does not have to do anything, because he disposed of it
before it became due. This is similar to the case if he had eaten or sold
his livestock before zakaah became due on it. But if he disposed of it after
zakaah became due on it, then zakaah is not waived, as would also be the
case if he had done that with the livestock. According to both scholarly
views, zakaah does not definitely become obligatory until the crops are in
the basket and the grains are on the threshing floor. If they are destroyed
before that, not by his actions or due to any negligence on his part, then
he does not have to give zakaah. 

Al-Mughni, 2/300 

Based on that, if a person cuts a crop on which zakaah is
ordinarily due in order to use it as animal feed, for example, he does not
have to give zakaah on what he cut, because what he cut was not the grain or
crop on which zakaah is due. What is left of hard (i.e., fully developed)
grains should be examined, and if it reaches the minimum threshold (nisaab)
then zakaah is due on it, otherwise it is not. 

It is not permissible for the one who has grains to
deliberately cut them before they are fully developed with the aim of
evading zakaah, otherwise he is sinning, and some scholars regard it as
obligatory for him to pay zakaah in this case.

Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have
mercy on him) said: 

In our opinion there are two conditions: 

1.That the minimum threshold
(nisaab) be reached

2.That this amount should be in
his possession at the time when zakaah becomes due

The words “when the grain becomes hard (i.e., fully
developed) and the crop becomes visibly ripe, zakaah becomes due” – he
previously stipulated that the minimum amount should be in his possession at
the time when zakaah becomes due. 

The time when it becomes due is when the grain becomes hard,
i.e., when it becomes strong and fully formed, and does not yield if pressed
(i.e. it is not soft). 

The crop becoming visibly ripe, with regard to the fruit of a
date palm, is when it turns red or yellow; with regard to grapes, it is when
they soften up and become sweet. In other words, instead of being hard they
become soft, and instead of being sour they become sweet. 

When the grain is hard and the crop is visibly ripe, zakaah
becomes due; before that it is not due. 

In addition to that we could also say: if it is destroyed –
even by his own actions – such as if the grain is harvested before it
becomes hard (fully developed), or the crop was cut before it ripened, then
no zakaah is due on them, because that happened before zakaah became due.
But they said that if he did that in order to evade zakaah, it is still
obligatory for him, as a punishment that fits his crime and because everyone
who uses tricks to evade some duty, that duty becomes binding on him.

Ash-Sharh al-Mumti‘ ‘ala Zaad
al-Mustaqni‘, 6/75-80 

To sum up: 

If this farmer cut the grain before it became hard (i.e.,
fully-formed), then he does not have to pay any zakaah. He does have to pay
zakaah if the grain was hard and fully-formed, if what was harvested reached
the minimum threshold (nisaab). 

And Allah knows best.