Durum management for quality targets
Although these new varieties, including Saintly and Hyperno, show the genetic ability to out-yield older varieties, grower uptake has been constrained by concerns over management.
Rob Wheeler, from the South Australian Research and Development Institute, says, “the key challenge with the new varieties is to achieve the required 13 per cent grain protein, without compromising grain size and yield, so appropriate seeding and nitrogen management are essential”.
On behalf of the Southern Australia Durum Growers Association Inc (SADGA), Rob and colleague Kenton Porker have been managing a series of durum agronomy trials. These were supported by the GRDC and the SA Grain Industry Trust (SAGIT), with industry support from sponsors of SADGA.
Initial trials looked at the influence of seeding rate, time of seeding and nitrogen nutrition on durum yield and quality.
The treatments were tested in replicated trials at one or more sites in SA – Hart, Tarlee, Paskeville, Minlaton, Frances and Bordertown – to represent the soil and climatic conditions suited to durum production. New and old varieties were grown under each treatment at each site.
Time of sowing
Trials run for three years (2009–11) identified that varieties with higher yield potential such as Yawa, WID802 and Hyperno were favoured most by early sowing.
At later sowing, yield differences among new varieties were negligible but screenings were more prominent. Screenings were especially a problem with the small-grained cultivars such as Hyperno and Yawa. Larger-seeded varieties such as
Caparoi and Tjilkuri are favoured for later sowing as they are less likely to be downgraded from small grain seed screenings.
Across all trials seeding rate (targeting 150 to 250 plants per square metre) had little impact on the yield or quality of the new varieties. The lack of varietal interactions with seeding rate indicates growers can manage all varieties similarly and should manage new varieties as they would older varieties. Seeding rates can continue to be maintained at 200 seeds/m2 in order to maximise yield and quality in all varieties across the SA durum-growing environments.
Irrespective of background nitrogen levels, in most trials the newer varieties of durum typically fell one to two per cent below the 13 per cent target for DR1-quality grade. In contrast the older varieties – Tamaroi, Kalka and Caparoi – consistently achieved 13 per cent protein.
NVT data suggests that the newer higher-yielding durum lines clearly exhibit an inverse relationship between yield and grain protein: as grain yield increases, protein diminishes.
The trial results suggest that the newer lines do not require extra nitrogen for growth but require more nitrogen to achieve 13 per cent protein. This extra nitrogen should be applied as late as possible to minimise the potential for increased screenings.
Large amounts of early nitrogen should be avoided in varieties with inherent small grain as it increases the risk of downgrading from small grain screenings. While further regional research is required to determine specific nitrogen requirements, the use of split nitrogen applications is important for the new durum cultivars.
The application of nitrogen between flag leaf emergence and grain fill is especially important in the new durum varieties as this nitrogen contributes most to grain protein.
In 2012, with the support of SAGIT, Rob and Kenton commenced an additional trial for the SADGA. This is looking at weed control options as there are limited safe and effective herbicide options for grass weed control in durum.
“The new herbicide Sakura® is not registered for durum and our trials suggest that registration is unlikely due to the level of unrecovered crop damage that occurred in old and new durum varieties,” Rob says.
While the registered herbicide BoxerGold® (2.5 litres per hectare) offered good ryegrass control, improved crop safety was achieved by sowing seed deeper below the herbicide band and using larger seed.
The choice of new, more vigorous varieties such as Saintly and increasing seeding rates from 100 to 300 seeds/m2 resulted in increased yield, improved weed competition and reduced weed seed set.
This work is being continued in 2014 and aims to determine the optimal combination of herbicide, variety and seeding rate for maximum weed control.
“Variety-specific agronomy packages are giving new growers the confidence to add durum to their rotation,” says Mark Hill, chairman of SADGA.
“At our post-harvest meeting, a group of growers from the Victorian Wimmera attended to learn about these trial results and from experienced durum growers.”
The correct durum variety, environment and management are all of equal importance in achieving improved yields and reducing the risk of quality downgrading in durum.
More information:Kenton Porker, SARDI,
0403 617 501,
GRDC Project Code DGA0001