Australian Mungbean Association

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Better mungbean agronomy

Mungbean crops planted on narrower rows (50 cm or less) consistently out-yield crops planted on the traditional summer crop spacing on 1 m and contribute more atmospheric nitrogen to the soil.


21 August, 2015

by Cindy Benjamin


With two seasons of field trial data now analysed, Department of Agriculture and Fisheries (DAF) researcher Kerry McKenzie is able to say with some confidence that planting mungbean crops on narrower row spacing supports higher yields, even if plant population remains the same.

“Our GRDC-funded trials at four sites in Queensland have demonstrated that agronomic decisions at planting do influence crop yield and nitrogen fixation,” he says. “A ten per cent yield increase is worth around $75 per ha based on long term mungbean pricing, which is $3 million more in growers’ pockets if it were achieved across the sown area.”

Although the seasonal conditions will continue to be the main determinant of crop performance with yields twice as high in 2014/15 compared to 2013/14, the right row spacing, plant population and soil nitrogen can all improve the likely outcome regardless of the season.

“There were trials at Dalby and Warra for the last two mungbean seasons and at Billa Billa and Miles for the 2014/15 season only, providing crop data from a wide range of soil types and environmental conditions,” says Mr McKenzie. “There appears to be little difference in variety performance at each row spacing with all varieties performing as well or better at 0.5 m or 0.25 m spacing rather than the traditional summer crop spacing of 1 m.

“Growers are likely to see a benefit if they plant mungbean at 50 cm or less but that doesn’t mean they need to spend more on seed,” he says. “Plant population per metre square did not greatly influence yield so the standard 20–30 plants per m2 remains the recommendation.”

Mr McKenzie says the data indicates that the improved yield from narrower row is most likely due to improved water use efficiency, with the plant roots able to reach the stored moisture between the rows and the larger crop canopy intercepting more light energy.

“Knowing that the population density of 20–30 plants per m2 is adequate for maximum yield, growers will need to consider replanting if less than 10 plants per m2 are established,” he says.

Another benefit of growing robust, high biomass crops is the increase in atmospheric nitrogen fixed. DAF senior soil microbiologist Dr Nikki Seymour, has collected nodulation and N-fixing data at the mungbean trail sites and re-affirms the value of mungbean in low soil nitrogen situations.

“Well inoculated and nodulated mungbean crops can improve the nitrogen efficiency of the rotation provided there is not a high level of nitrogen already in the soil, such as residual fertiliser from a previous crop or mineralisation after a long fallow,” she says. “In high nitrogen situations it is usually better to plant a non-legume crop to make the best use of the available nitrogen.”

All mungbean varieties accumulated more nitrogen when planted in narrower rows except Satin II, which appears to compensate for the wider rows.

In a separate, forward-looking project Dr Seymour is screening the new mungbean germplasm in the plant breeding program to assess their genetic ability to fix nitrogen and their affinity with current rhizobia strains. She says that mungbean generally do not leave behind high levels of nitrogen compared to other legume crops so the screening of germplasm in the breeding program will assist plant breeders when they are selecting for a variety of desirable traits, including increased nitrogen fixation.

The market outlook for Australian mungbean continues to be very positive and interest is growing for spring planting in late September and early October. Damien White, vice president of the Australian Mungbean Association (AMA) says the forecast for a drier than average summer could favour mungbean as a spring or summer crop. “Mungbean is the fastest maturing of the summer crop options, with very high water use efficiency,” he says. “In a dry year this could make mungbean the crop to offer the lowest risk and highest potential return to growers.”

“When conditions could be less than ideal but the potential returns high, it is all the more important to establish the best crop possible at optimal row width and plant density,” he says. “The DAF research has provided compelling evidence to support a change to narrow row spacing wherever it is possible.”

Mr White says the AMA’s crop competition to find the best dryland and irrigated mungbean crops this season will no doubt include nominations from growers who have made the switch to narrower rows. Growers interested in nominating their mungbean crop for the national competition are encouraged to maintain a detailed diary of their management practices throughout the season. The main prize includes an overseas study trip with the Australian Mungbean Association.

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