Azolla
Azolla is a floating fern and belongs to the family of Azollaceae, Azolla. The plant hosts a symbiotic blue green alga, Anabaena Azollae, which is responsible for the fixation and assimilation of atmospheric nitrogen. The plant itself in turn, provides the carbon source and favorable environment for the growth and development of the algae. In good conditions, Azolla can readily colonize areas of freshwater, and double its biomass about every three days.

First you need to buy some Azolla plants. This is only needed for the very first time. After this you can breed them by yourself. Buy the specie Azolla pinnata, this specie works best in the Cambodian climate and is used a lot in Vietnam and Thailand.

[pic]
Example of a propagation pond

After you bought some of them, you have to make a propagation pond. Place the Azolla plants on the water surface of your pond. After a while the whole water surface will be covered with the Azolla.
The algae on the Azolla plant, will fix up to about 140 kg nitrogen/hectare. So you don’t longer have to use a commercial nitrogen fertilizer. This leaflet will show the steps for using Azolla to improve the fertility of the soil.

How to use the symbiotic Azolla/Anabaena system?

1. Some days after transplanting your rice seedlings into the paddy, gather the Azolla from the propagation pond and spread it evenly on the area of your paddy. Their must be at least a water level of about 1 cm. Important: Enough Azolla must be left in the pond for future use, so it can multiply itself again. 2. The Azolla plants multiply themselves at great speed, so after some time a big part of your paddy is covered with the Azolla, among your rice plants.

[pic]
River covered with Azolla

The algae on the Azolla fix nitrogen until harvest time of your rice crop. 3. When the rice crop is harvested, the paddy is drained. You must not burn the remaining rice stubbles but have to plough them under together with the remaining Azolla on the bottom of you paddy. The fixed nitrogen by the algae on the Azolla will stay in the soil, so the next year you don’t have to use expensive nitrogen fertilizer because the ground is still very fertile. Important: The first year you use the Azolla, you don’t have benefit from it. You don’t have to use nitrogen fertilizer from the second year.

System of Rice Intensification
The System of Rice Intensification is a methodology for increasing the productivity of irrigated rice by changing the manage- ment of plants, soil, water & nutrients. Several farmers in Cambodia (but also in neighbouring countries like Vietnam) already use the SRI and their rice production has increased and become cheaper. SRI means: Your rice crop will increase by using less water.
This is how the SRI works in steps:

Transplant the seedlings when they are very young (8-15 days, with just two leaves). This maintains greater plant potential for extensive tillering and root growth than older seedlings have. Seedlings are raised in a garden-like nursery rather than in a flooded one.

Seedlings are widely spaced, only one per hill rather than in clumps and in a square pattern at least 25 by 25 cm apart. This gives rice roots more room to grow and the rice plants have more space to develop themselves.

Seedlings are also transplanted very carefully, getting seedlings quickly and gently from the nursery into the paddy and placing the tiny roots in a position so that they can quickly resume their downward growth. Seedling rates are 5-10 kg/ha instead of rates usually 10 times higher.

Water is carefully managed during the vegetative growth stage. The paddy is not kept flooded, as is usual practice. Instead, the soil is kept moist and well-drained, or intermittently flooded and dried if this is appropriate for soil conditions and can save labour.
The goal of water management is not just to furnish water to the plants’ roots but to avoid hypoxic conditions that force the plant to sacrifice a large part of its roots to form air pockets to help keep the root alive. In continuously irrigated soils, most of the irrigated roots die by the start of the reproductive stage. From this stage, for SRI just a thin layer of water is kept standing on the paddy. Only half to one third as much water is used, in comparison with continuous flooding.

[pic]

Weeding by using a push-weeder

Without flooding, weeds can become a real problem. Thus with SRI it is recommended to begin weeding about 10 days after transplanting and to do two of four weedings

at 10-15 days intervals. Using a simple mechanical push-weeder, designed by the IRRI in the 1960s, permits aeration of the soil as well as elimination of weeds.

While SRI was originally developed with chemical fertilizer, this is beyond the reach of most farmers, so application of compost is recommended. Evaluations showed that compost gives higher yields than does fertilizer. Many farmers have modified the method so they apply compost to their inter-season crop rather than to their rice, and get better results from both crops. This practice enhances the size of diversity of microbial populations.

Important: You can’t use Azolla and SRI both! Azolla needs more water to survive, than is used by SRI.

[pic]

[pic]

Azolla/Anabaena & SRI

Cambodia

[pic]
Azollae Pinnata

Local Nabuur Representative Sa Kimsorn Province Battambang District Moung Russey

Dutch Representatives Matthijs Looij Corwin van Strien Ing. K.A. de Vries