Challenging good plant management for harvest success
The trial based in Keith SA, funded by AgriFutures Pasture Seeds Program, shows moisture stressing of lucerne plants provides a significant boost to seed yields by up to 52% when irrigation is delayed.
The 2020 trial managed by Lucerne Australia trial committee follows on from 2019 protocols established to compare standard irrigation schedules with delayed watering.
Under high stress conditions clean lucerne seed yields improved by 14% through to 52% across 29 varieties. With industry benchmark varieties, Aurora and Siriver produced an increase of 16% and 36% in seed yield respectively under high stress watering compared to standard watering management indicating a positive yield response can be achieved for any variety.
“We can stress lucerne a lot more than we have been, and far from being detrimental to seed production, it can actually improve it,” says lucerne seed grower Simon Allen, ‘Warrawee Park’ Keith SA, member of the Lucerne Australia executive and trial committee.
“The trial results have been pretty exciting. It appears data to date challenges ideas around how hard you can stress lucerne plants to maintain forage production and improve seed yield.”
Trialling standard and stressful irrigation management on lucerne
The trial, established June 2018, set out 29 lucerne varieties into three management plots experiencing either a standard irrigation practice, moderate or high moisture stress schedule.
“Standard irrigation practice mirrors industry management for lucerne, including four waterings over summer before signs of water stress were exhibited in the plant”, said Scott Hutchings, Lucerne Australia deputy chair and Cox Rural agronomist, Keith SA.
He added: “The moderately stressed and highly stressed plots were limited to only three waterings, delayed on the third timing depending on the plant’s moisture stress symptoms of leaf wilt or leaf drop.”
“All trial plots had the same management for pests, fertiliser, forage management and harvest over the two years.”
As trial coordinator, Mr Hutchings noted “having more trial data and results will help provide confidence to growers in allowing lucerne plants to stress that little bit longer, knowing it will still improve seed yields plus save irrigation costs.”
Economic analysis from the trial estimates a $723/ha improvement using high stress irrigation strategy by reducing water costs and increasing seed yield.
Adapting findings for lucerne seed producers
“The next step is to replicate treatments on the plants for a third season, monitoring physical changes in the plant with time-lapse photography. Photos showing the degree of water stress applied to plants depicting leaf wilt and drop will be published with the final results for growers to compare to their own lucerne crop situation” said Mr Hutchings.
From a grower perspective, Mr Allen states “there is still work to be done in adapting watering management at a commercial scale to suit individual farms.”
“We haven’t consciously changed too much in terms of watering management on farm yet because we would like to have a little more data to adopt into a large-scale commercial operation.”
“Some seed producers use flood irrigation while others use centre pivots, so refining trial results to change standard water management to high stress watering still requires work. There are no half amounts when using flood irrigation so changing watering schedules will be the starting point.”
“Every season’s different. To be able to follow up the last two years of trial work with a cool wet summer if La Nina eventuates will provide a good comparison for the trial results dataset.” said Mr Allen.
Long term trial site hits strategic targets
Mr Allen leased the trial site to Lucerne Australia for the three-year project, which has now been extended by AgriFutures Pasture Seeds Program for an additional two years (five years in total) providing a longer term research site to examine the limits of moisture stress in mature stands of lucerne. The extension will also facilitate the development of resources and tools, such as a Ute Guide, to help growers and advisors adopt modified water management strategies to optimise seed production.
“Being a perennial plant, it takes a number of years to establish with performance responding to the size and depth of the root system. It has been good to have a long-term trial site to examine results over time,” said Mr Allen.
“The continuance of the Lucerne Variety Trial for five years supports growers to adjust their irrigation management with confidence improving seed yield and gross margins,” said Mr Hutchings.
The Lucerne Variety trial site will host a field day on Wednesday, 3 March 2021 (7.30am – 10.30am) for growers to inspect varieties prior to the third harvest. Register now via Lucerne Australia.
Soil moisture levels at the trial site across the three plots recording available moisture to plants from irrigation and rainfall events can be found here.
|Sowing Date:||22 June 2018|
|Seeding Rate:||3 kg/ha|
|Seeder Setup:||Knifepoints, presswheels on trial seeder|
|Fertiliser:||100 kg/ha Granulock Z banded|
|Location:||Warrawee Park, Keith, SA|
|Annual Rainfall:||460 mm|
|Soil Type:||Sandy loam over clay/limestone base|
|Irrigation Type:||Flood Irrigation|