Lesson 6.33.0 TROPICAL VEGETABLES

 

FOOD FOREST COURSE 

AGRO-ECONOMY Lesson 6.33.0 TROPICAL VEGETABLES

In a subtropical or tropical Permaculture system, where crops are grown in continuous succession, it is important to constantly add fertility to the soil.  The soil’s fertility is increased by the addition of nitrogen and added organic matter and intercropping with tropical legumes is the perfect solution.

Tropical legumes can be easily grown between the main crops and can add to the total food production.  Most legumes of tropical and temperate origin are introduced species into Australian soils and often the right bacteria aren’t present.  This means that the roots on the legume plants don’t develop the root nodules that harbour the bacteria to fix nitrogen from the air into the soil.  This can be remedied by adding the right strains of bacteria to the legume and this is done by inoculating the bacteria into the soil.  These bacteria can be bought at the local produce/nursery stores.  Just let them know which particular legume you are wishing to purchase the bacteria strain for, and they will work out the correct strain for you.  These bacteria are kept in peatmoss in the fridge and once the packet is opened it deteriorates quickly.  The cost of the bacteria is minimal, and it certainly makes a difference to the end result.

When the seeds are ready to be broadcast onto the soil, simply add the inoculant to the seed with some milk, or flour and water, to enable adhesion to the seed.  Alternatively, the bacteria can be watered into the soil if the plants are already established.  It is best to water it in on an overcast and humid day so that the bacteria won’t be killed off by the hot, drying sun.

How can you tell if the right bacteria are already present in the soil?  When pulling up an entire plant you should be able to observe small nodes on the roots.  Even a seedling will show you whether the right bacteria are present or not and you will see the nodules with the naked eye.  When these are present you will know that the right bacteria are already there to enable the plants to fix nitrogen from the air into the soil.  It was interesting when someone once pointed out to me that when you see the Desmodium vine (Glycine javonica) growing then the right bacteria are present for the pigeon pea (Cajanus cajan) to fix nitrogen from the air into the soil.  This proved to be correct, as when we pulled up a young pigeon pea there were many nodules present on the root system.

A green manure crop that is systematically chopped and dropped will have the same effect as applying compost without the same amount of handling!  A green manure crop will also put back much more nitrogen whereas compost will use up much more of its own nitrogen supply in the conversion process.

 

 Additional benefits of inter-planting with legumes is forage for livestock, mulch and fuel.  Also, in the case of pigeon pea, the peas can be harvested and used to make a delicious dahl.  Text from the roots, Elisabeth Ferkonia (Aus.) PDC studied with Bill Mollison.