The type of seed chosen for planting is based on the length of the growing season where it will be sown. The average for the Wanganui area has the numbers 100-102, but at Mr Redmayne's property trials have shown the CRM (comparative relative maturity) figure can be pushed up to 105-107.
The aim is to have maize flowering at Christmas, around the longest day of the year, when it will get maximum sunshine hours.
Harvesting of maize for grain begins in April, when it has made use of all that autumn sunshine and when the grain has a moisture content of 25 per cent. The grain is then dried to 14 per cent moisture, for storage.
A yield of 12.5 tonnes of grain/hectare is average. Mr Redmayne's top yield was 19.7 tonnes/ha - but he said the lower Turakina Valley was known to be especially productive.
A top yield for maize grown for silage would be 30 tonnes/ha and an average one 20 tonnes/ha. When maize is made into silage, the entire plant is harvested.
The Kairanga silt loam on Mr Redmayne's property is fertile and there are tile drains below the surface.
The maize roots quickly work their way down through the friable soil to the water table below and they never need irrigation. A drought is an ideal season for growing maize on his property.
Trials to get better maize varieties are going on all the time - in New Zealand mainly by Pioneer, the company with 90 per cent of the seed market. Mr Carter said the trials were worthwhile.
"The yields have got better, so the breeding programme is obviously working."
Maize seed is planted with a little bit of general purpose fertiliser - especially nitrogen and potash. Modern cultivation machinery uses GPS and rows are accurate to 2cm. Mr Carter said the latest machines were expensive but "quite fun" to drive.
One of the pitfalls of cultivation is reduced growth at the edges of fields, where the machines turn and soil gets extra compacted. Mr Redmayne avoids this by having the middle of his fields sown first and giving the outside edges an extra deep ripping.
The plants get a side dressing of fertiliser when they are about knee or "redband height". It's drilled into the soil to prevent losses to the atmosphere. "It gives the crop a boost at exactly the time it needs those nutrients," he said.
He grows maize for grain rather than silage and ploughs the rest of the plant back into the ground. Putting that organic matter back into the soil reduces the amount of fertiliser he needs to apply.
Cattle graze the crop stubble during winter, unless it's so wet that they would compact the ground.
Mr Carter also grazes cattle on empty maize fields. He said they ate some stubble, fallen leaves, weeds and spilt grain. It looked unpalatable, but they preferred it to their usual pasture.
The only insect pest for maize is a cutworm that can eat young plants to the ground. It's not common and can be controlled by sprays.
Mr Carter and Mr Redmayne sell their grain to agricultural services provider PGG Wrightsons.
Much of it goes to feed chickens, or is ground up and added to dairy feed.