They want to grow the mythical 20t/ha crop.
Hamish Brown from Plant & Food Research and Rob Craigie from FAR have been leading trial work pushing sowing dates back in an effort to lift crop yields as part of the “20t/ha before 2020” programme.
This is a key research goal for FAR and Plant & Food as part of a research initiative covering cropping systems.
At the recent Foundation for Arable Research Crop Expo, Brown outlined how crop scientists have been experimenting with just how early they can get wheat crops into the ground without risking frost damage during the critical flowering stage.
For three years scientists have been drilling wheat in March and April and while in the first year there was no yield advantage to these early sown crops due to harsh climatic conditions, this changed in the second year.
By moving the sowing date back to the last week in March, growers on irrigation land saw a .4t/ha yield advantage in feed wheat crops. On dryland this yield advantage was stretched to an average of 1.5t/ha.
“This was the average; in the later maturing varieties the differences were even more marked, indicating the potential for big yield advantages to early sowing.”
Last year (2012) they had the first trial wheat crops in the ground on February 27 with subsequent drilling in the third week of March and mid-April.
Craigie says that while the February-sown crop was looking good in December, they did have some issues with weed control in these earlier sown crops.
Aphids and associated barley yellow dwarf disease (BYDD) are also a potentially bigger issue with those earlier crops, but diseases had not been an issue in the trial crops. There was also a potentially higher risk of lodging.
The greatest risk with early sowing is frost damage around flowering so only varieties with a strong vernilisation requirement and late flowering should be considered for early sowings. Wheat will delay its flowering if sown early, but every four days earlier sowing equals one day earlier flowering.
“Frost sensitivity changes and increases as the plant goes reproductive.”
Brown says what they want is for the flowering period to occur when there was no risk of frost. At Lincoln they don’t want crops flowering before November 15 because they run the risk of frost damage. Conversely Gore has a warmer temperature profile and a lower frost risk at that time of year.
The Fairlie Basin has a higher frost risk because it is so far inland.
Brown says growers around Lincoln who plant before March 1 are running into considerable frost risk and growers further inland run an even greater risk.
The extent of frost damage depends on how far the temperature falls below the frost sensitivity threshold for any given growth stage and how long the temperature stays below that threshold. Damage increases with colder frosts because the sensitivity threshold is exceeded by more and for longer.
Brown suggests growers looking to get their wheat crops in the ground early select varieties that have a later flowering date such as Wakanui and Richmond.
This trial work is on-going as scientists assess the harvest results from the crops sown in February and look at crop management issues for those early sown crops.
Plant scientists have been experimenting with just how early they can get wheat crops in the ground as they aim to grow a 20t/ha crop by 2020.