Smith's poor performance allegedly included racing his quad bike towards cows so that the frightened animals jumped through a fence, Mickleson claimed.
He was also regularly late to work, didn't get his own working dogs, which were vital to the job, and allowed two puppies to die, Mickleson claimed.
Smith denied the charges.
He claimed he had been driving a quad bike on the farm in May last year and came around a corner to see the cows up ahead.
He slowed from about 20km/h to 6km/h and yet one of the cows about 20m ahead still jumped into the fence, Smith told the ERA hearing.
Smith claimed Mickleson came up to him afterward angry and swearing.
He said he tried to explain he hadn't been speeding but Mickleson told him it was "my way or the highway".
Smith said he was upset with how the matter had been handled but put it behind him as he had not been given a formal warning.
But Mickleson claimed he had given a formal warning. He said he saw Smith speeding down a laneway and a cow jumping into the fence. He claimed it was the second time Smith had done it.
In an incident shortly after, Mickleson claimed Smith had cruelly allowed two puppies to die.
But Smith denied it. He said Mickleson had asked him to feed and keep an eye on two puppies that had recently been born.
He said Mickleson was going away to the South Island and told him to put horse blankets over the pen containing the puppies and their mother.
Smith said he did as told but when he came back the first evening to feed the pups, one had died.
When he then went back next morning to check and feed again, the other pup had died.
Mickleson had claimed he told Smith his main task was to look after the pups.
But Smith denied that, saying it was one of many tasks left to him and he had done what was asked and the pups' death wasn't his responsibility.
When Mickleson returned a week later, however, he was "very upset" by the deaths, he told the ERA.
He claimed he and his daughter had successfully cared for the newborn pups the weekend prior and that while he was away the mother dog had dug a hole about a foot and a half deep to try and warm the pups.
"He felt this was a clear case of neglect and cruelty towards farm animals," the ERA ruling stated.
Mickleson claimed he took a few days to cool off and then called a meeting with Smith.
He claimed he hadn't intended to fire Smith but when Smith didn't show contrition or acceptance of what had happened, Mickleson fired him, giving him two weeks' notice.
However, Smith's contract required Mickleson to give 48 hours' prior warning if he had serious concerns about the job being done.
Then Smith should be entitled to a support person of his choosing at the meeting after which Smith should be given time to respond to the allegations.
Depending on the outcome of the discussion and severity of the concerns, Mickleson would only then be able to give a final warning notice.
However, Mickleson and Smith both said these processes were not followed.
The ERA ruling said it was important such processes were followed to ensure workplace grievances were investigated properly.
Also following proper procedure and keeping a record of it ensured employers could prove why they sacked employees and protected workers from unreasonable bosses.
The ruling stated that because Mickleson didn't follow these procedures the dismissal was unjustified.
Smith told of the hurt he suffered from the dismissal and that it took him more than two months to find another job.
He was consequently awarded $18,000 in damages for hurt and humiliation along with more than $7000 in lost wages and unpaid holiday pay.
