IDENTIFYING opportunities to integrate a spring-sown summer crop, specifically soybean, into a winter wheat-based cropping system in Western Australia is the aim of a new project from CSIRO.
Break crops add diversity and sustainability to cereal-based cropping systems and soybean could serve as a potential break crop for winter cereals in WA.
The difference between spring-sown summer soybean and current break crop options is that current break crops - canola, pulses and pastures - are autumn-sown and grow during winter, meaning they are winter crop types.
Whereas the summer soybean in the CSIRO trial, which received $149,405 in funding from the Council of Grain Grower Organisations (COGGO), will be sown in spring (August-September) and grow during the summer (October- February) using soil water stored during winter fallow and summer rainfall.
The WA Wheatbelt has experienced climate change, characterised by decreased winter rainfall and increased summer rainfall in many areas, while cropping systems are also facing soil degradation.
Problems with weeds and diseases are prevalent, which can pose a serious risk for growers.
CSIRO research scientist Chao Chen said the current break crops which were winter type crops were not able to use the increased summer rainfall and to relieve the time pressure to manage winter weeds efficiently.
"Summer soybean offers a number of unique opportunities to serve as a break crop for winter cereals to adapt to climate change," Dr Chen said.
"Soybean is a legume that has a unique role in sustainable agriculture, due to its ability to fix atmospheric nitrogen.
"Its integration into the WA cropping systems has the potential to address the challenge of the continued decline in soil fertility and it can also help to improve yield and maintain protein of following wheat crops."
A crop rotation with distinctly different growth patterns of crops allows opportunities to manage weeds, insects and diseases pressures.
Rotating winter wheat and summer soybean would increase the ability to kill or suppress weeds and reduce disease infestation.
Soybean is also economically the most important legume crop in the world and integrating it into the cropping system in WA would boost value for money.
Dr Chen said the project addressed an urgent need of novel break crop options to tackle the challenges facing cropping systems in WA and is hoping to achieve two main outcomes.
"The first is that growers produce a cash crop by introducing a new legume break crop and reducing the cost of fertiliser which will provide a substantial economic benefit for growers," she said.
"The second is that growers produce improved sustainability of cropping systems as soybean in the rotation may contribute to enhancement of soil organic matter to improve long-term soil health.
"Thus this project will also provide long-term environmental benefits to WA growers.
On top of that, recommendations on the suitable growing area, sowing time, variety choice, management practises and rotation pattern will assist growers to achieve optimum yield and crop rotation.
Furthermore, the outcomes could also serve as a guideline for soybean breeders to improve the production and adaptability by selecting high-yielding cultivars to suit variable environments.
Dr Chen said the project was public good research that would directly benefit WA growers.
"The identified cultivar characteristics, sowing times and production of soybean and its sequence pattern with wheat from this project would be publicly available for growers," she said.
"This research has the potential to provide WA growers both a new cash crop with increased diversity of cropping options, as well as a sustainable cropping system and a reduction in the cost of fertiliser.
"Furthermore, soybean could be grown as a forage which makes it a very flexible crop in cropping systems for WA growers."
The project will combine field experimentation with crop modelling to assess biomass and yield of soybean and its effects on the yield of subsequent wheat.
The main advantage of the approach is that it is time and labour efficient to achieve desirable outcomes.
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