Trees in Your Garden Give you Fertilizer

Backgrounder

Do you have a vegetable garden but not enough fertilizer? Today we are going to talk about an idea especially for gardeners or farmers who do not have livestock to supply manure as fertilizer for their garden. At the International Institute of Rural Reconstruction (IIRR) in the Philippines they plant leguminous trees between garden plots. Leaves from the trees are added to the soil as fertilizer. So the trees are a built-in source of fertilizer right there in the garden.

What does this garden look like?  Here is the plan.

• Dig two garden plots side by side. Use the double digging method to prepare the beds. Double digging is done by turning over the top soil and mixing it loosely with compost or mulch, and by loosening the subsoil at the same time.
• Plant two rows of leguminous trees beside these plots. Some recommended tree species for this garden are Gliricidia sepium, Leucaena leucocephala, Calliandra calothyrsus, and Flemengia macrophylla. These trees have been tested at IIRR and give good results. Plant the rows of trees about one metre away from the garden plots. They should not shade the garden.
• On the other side of the trees, dig 2 more garden plots.
• Then plant two more rows of trees, and so on. Two rows of trees for every two garden plots of one to two square metres will provide enough green leaves to fertilize both plots.

You will have to wait one year after planting the trees before you can cut and use the tree leaves to fertilize the soil. But you can have a garden the first year if you want. In other words, the first year you dig the plots and plant the trees, you can plant your vegetables, but you will not be able to use the leaves as fertilizer. You can start using the leaves when the trees are one year old or when they are 3 metres high or have a stem diameter of more than one centimetre.

When the trees are the right age or size, and about two weeks before planting the garden, cut the trees back to about one metre above the ground. Place the cut branches, with their leaves on them, over the garden plots. Leave them for two days so that the leaves will dry out a bit and be easy to remove from the branches. Then shake the branches or pick off the rest of the leaves by hand. Spread the leaves over the garden plot. (The bare branches can be used as fuel for cooking.) There should be at least 8 centimetres of leaves covering the entire bed. Dig the leaves into the soil, mixing them with the soil to a depth of 15 centimetres. Let them decompose for 10-14 days. Then plant the vegetables.

Later on, you can trim the trees whenever you need leaves, or when the trees begin to shade the garden plots. When you trim the trees, always leave one branch on each tree a bit longer than the rest. This will help make sure the tree survives in case of dry weather.

For the most productive garden possible the International Institute of Rural Reconstruction suggests that you use bio-intensive gardening for this garden plan.

Bio-intensive gardening includes the following techniques:

1. double digging to prepare the garden plots;
2. adding organic materials (compost, manure) to the soil to improve soil structure and provide nutrients for the plants;
3. planting lots of different types of vegetables, especially local varieties;
4. using non-chemical pest control.

For more information about bio-intensive gardening, and about gardening with trees, write to the International Institute of Rural Reconstruction, Silang, Cavite, Philippines 4118.