Australian Mungbean Association
Australian-grown mungbeans have quality written all over them!
Mungbean planting depth
10 January 2017
by Paul McIntosh, Pulse Australia
Although mungbeans and chickpeas are both legumes, these two species use different mechanisms to germinate and emerge from the soil.
Many growers have adopted deep planting practice for chickpeas, which has produced many successful crops, due to the hypogeal emergence of chickpea seedlings. While it might take three weeks for the seedlings to emerge from a depth of six inches or more. Hypogeal emergence in where the cotyledons remain below ground level as storage organs and as a regrowth insurance policy in case the emerging tops get knocked off by birds, insects or even a hail storm.
In contrast, mungbeans use the epigeal emergence mechanism where the initial cotyledon leaves poke through the soil surface and then open up to catch the sunlight. If these cotyledon ’leaves’ are broken off or damaged it is highly unlikely the plant will recover and may well die. The upshot of this is that mungbeans are not going to emerge from soil depths like chickpea seedlings can.
The usual recommendation for planting mungbean in Australia is a planting depth of 30 to 50 mm. I am not sure where these figures originated from and maybe they are simply a best estimate from past fellows.
Growers and researchers have used this recommendation successfully in a variety of soil types so until other information is provided this continues to be the industry recommendation.
To my mind though, 50 mm deep is pretty shallow in our hot summer environment to plant a legume like mungbeans that has sensitive rhizobium bacteria all over the seed. Keeping in mind that the average length of a mungbean seedling shoot is about 50 mm, care would be needed if planting too much deeper than 50 mm. Even large mungbean seed with good germination % and vigour will not emerge effectively if you plant them at 150 mm in rubbly soil.
The real test for effective planting is whether you are achieving very good seed to moist soil contact without hard packing the soil surface with your press wheels. A rubber tyred roller may be a better option in some areas.
Experience with your soil types using your own machinery will provide the best information. It is worth hopping on and off the air-conditioned tractor quite a lot to check the seeding depth and as the hot and windy day wears on, you may need to even consider the option of pulling up for the day and planting more hectares very early in the morning of the next day. A patchy strike in a mungbean crop is a nightmare for future agronomic decisions.