Chickpea growers actively monitoring the progress of their crops this winter may be interested in new research showing cereal stubble load can impact the incidence and impact of frost events.
Temperature is one of the most important factors in producing a high yielding chickpea crop, and how stubble management practices influence the thermal profile of the crop canopy is the focus of a research investment by the Grains Research and Development Corporation (GRDC).
Dr Andrew Verrell, senior research agronomist with the New South Wales Department of Primary Industries (DPI), is leading the team monitoring the impact of stubble residue management practices on pulse crop growth and yield as part of a whole farm system approach.
“Chickpeas require an average air temperature of 15°C for flowering, pod development and retention,” said Dr Verrell.
“Improving the harvest index of the chickpea crop is linked to the accumulated heat units during the growing season, and this research is showing stubble management practices may influence growing season temperatures.”
Stubble may have a significant effect on the growth and development of the chickpea crop as stubble is known to reflect radiation and to act as an insulating layer over the soil surface, influencing the thermal profile of the crop canopy.
Dr Verrell said trial results indicated stubble cover may lead to a higher incidence of frost events than bare soil, as the air above the bare soil surface is warmer at night due to heat loss from the soil.
Initial trials demonstrated that flattened heavy stubble loads of 10-12 tonne a hectare were on average 1-2°C cooler on top of the stubble, relative to the warmer bare soil surface.
“Flat heavy, stubble loads can result in up to a week’s delay in floral initiation compared with crops sown into bare soil, due to the impact on the thermal profile of the crop canopy,” Dr Verrell said.
Flattened high stubble loads also recorded substantially more frost events compared with bare soil and standing stubble in the initial trials.
“Sowing into flattened stubble leads to a delay in heat unit accumulation in the crop,” he said.
“In addition, frost risk is reduced by sowing chickpeas between standing wheat rows as this is comparable to sowing into bare soil.”
However, he urged growers to take a whole cropping system perspective when determining how to manage stubble.
“If you spread stubble residues there may be a delay in flowering and pod development, but spreading stubble may have other benefits in the farming system such as soil moisture retention,” said Dr Verrell.
GRDC Senior Regional Manager North Jan Edwards agrees it is important growers take a whole farm approach when weighing up the benefits of different stubble management treatments.
Ms Edwards said the research provided valuable insights for growers and their advisors into the different impacts of stubble treatments on chickpea crop development and yield potential.
“Across the northern grains region soil moisture is an important yield constraint for dryland growers and moisture can be retained and improved through effective stubble management,” she said.
“So this research provides important information to assist growers with decision making in terms of weighing up soil moisture gains with chickpea grain yield across a whole farming system.”
She said growers with chickpea in the paddock this season may also find it useful in terms of assessing the various impacts stubble treatments are having on crop development.
For more information about Dr Verrell’s research click here.