The crop of Kerrin wheat weighed 17.398 tonnes a hectare, beating the record he set in 2017 of 16.791t/ha by 0.607t/ha.
The variety was developed by European seed company KWS and is used for stock feed.
The crop was sown on April 19 last year on the same 8.6ha paddock on his farm near Ashburton that set the old record.
It was sown at 70kg/ha aiming for 120-130 plants a square metre and resulting in 126 plants/square metre.
The crop was given a post drill pre-emergence weed spray and various insecticides and fungicides throughout the season.
He also monitored the crop for trace element deficiencies.
“The crop had 304kg of nitrogen per hectare, which works out at 22kg per tonne of grain yield, which I believe is the lowest rate for any world record.
“It’s very sustainable production,” he said.
Watson believes the decision to change to liquid nitrogen helped boost the crop to the record-breaking yield.
“My reasoning for that is that we have seen a lot of stripping (poor fertiliser spreading) over the years. We were trying to spread urea to 32 metres and sometimes the quality wasn’t good enough and it wouldn’t spread. We were getting stripping.
“It can only amount to 5-6% but it is significant over the crop growth period because we are not over-applying nitrogen because it always shows up.”
He bought a 48m spray boom, giving him an even spread of liquid fertiliser.
He also extensively monitored the crop with moisture probes to help tell the right times to irrigate and was aided by good weather.
“It was also a very good growing season in Canterbury, probably one of the best growing seasons we have had.”
It was never too hot and the crop received timely rainfall, he said.
In the lead-up to harvest on February 17 he was quietly confident it had broken the record because it had a good grain weight thanks to good weather.
Watson said he unofficially knew once the crop was weighed at harvest but received official confirmation from Guinness on July Wednesday.
“We knew pretty much straight away.”
He credited Bayer Crop Science, which did much of the background coordination to make the record attempt possible including funding and organising the necessary people to witness it.
Watson said he has not ruling out trying to break his record again.
“There’s always better, higher-yielding varieties coming through and there’s always room for improvement. You might tweak something differently the next year, try something new and that’s what we are always trying to do.”