Stubble affects frosts

August 09, 2017

New research shows cereal stubble load can impact the incidence and impact of frost events.

Chickpea growers actively monitoring the progress of their crops this winter may be interested in new research showing cereal stubble load can affect 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.

NSW DPI senior research agronomist Andrew Verrell 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,’’ Dr Verrell said.

‘‘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 to 12tonne/ha were on average 1 to 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.

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.’’

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