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Green manures are plants which are grown mainly for the benefit of the soil.
They can be grown as part of a rotation or in an intercropping system to build
soil fertility, or as a cover crop to protect bare soil from erosion. Full details
on the benefits and practice of using green manures can be found in
HDRAs booklet Green manures/Cover crops.
Crotalaria juncea is also known as indian hemp, brown hemp and sannhemp
7 Annual rainfall: Sunhemp can tolerate high rainfall, from 500mm upwards.
7 Altitude: It grows best at altitudes up to 700 metres.
7 Temperature: It grows best between 90C and 280 C. It is not frost tolerant .
7 Soil type: Sunhemp can grown in a soil type from pH 5.0 to 8.4 and does not
tolerate saline soil.
Sunhemp is a legume. This means that it has nodules on its roots which contain
bacteria. These bacteria take nitrogen from the air. This is known as nitrogen
fixation. The plant uses this to grow and when the legume is dug into the soil,
the extra nitrogen is made available to the next crop.
Sow sunhemp at a rate of 12 to 24 kg of seed per hectare. Alternatively
broadcast sow the seeds. Excess moisture is harmful during the first 2 weeks
Sunhemp is a tall shrubby annual, which can reach 1 to 3 meters tall.
Grown as a green manure in rotation with other crops. Sunhemp is particularly
useful for suppressing weeds as it is very fast growing. It also helps increase
soil fertility and control erosion.
Plough under or dig in at any time up to flowering (60 days) as it is able to rot
down at this stage.