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close this bookLow-external Input Rice Production (LIRP): Technology Information Kit (IIRR, 292 p.)
close this folderIntegrated nutrient cycling
View the document(introduction...)
View the documentIntegrated nutrient cycling in lowland rice production: an ecosystem approach
View the documentNutrient cycling on a basic irrigated or rainfed rice farm
View the documentUsing soil test values to determine fertilizer needs for rice
View the documentFertilizer placement in wetland rice
View the documentUsing limited nitrogen fertilizer with HYVs
View the documentTreatment for zinc deficiency in lowland rice
View the documentFertilizer from livestock and farm wastes
View the documentChicken manure for lowland rice
View the documentFood, fodder, fertilizer and fuel from paddy dikes
View the documentUsing rice straw for lowland rice farming
View the documentAzolla: green manure profile
View the documentUsing azolla as fertilizer for lowland rice
View the documentMultiplying the azolla
View the documentTroubleshooting common problems in azolla production
View the documentGreen leaf manuring in lowland rice
View the documentGreen manure utilization in lowland rice
View the documentSesbania aculeata: a bio-fertilizer source for lowland rice
View the documentIndigofera: green manure profile
View the documentCrotalaria: green manure profile
View the documentLablab bean: cover crop/green manure profile
View the documentRice bean: green manure profile
View the documentSesbania spp.: green manure profile
View the documentAnimal and green manure practices among the Mangyans (Alangan tribe in Mindoro)
View the documentWaste management practices (Tuwal and Ayangan tribes in Ifugao)

Using azolla as fertilizer for lowland rice

The agronomic importance of azolla arises from its capability to fix nitrogen through its symbiotic relationship with the blue-green algae, Anabaena azollae. The azolla-anabaena association can fix nitrogen proportional to the biomass produced. Chemical analysis showed that azolla contains 4-5% N. 1-1.5% and 2-3% K on a dry weight basis.

When azolla is grown in paddies and then incorporated into the soil as green manure, its nitrogen content is released upon decomposition and can be used by the crop. Azolla can replace at least 50% of the inorganic nitrogen requirement of rice.

There are three methods of producing and utilizing azolla on a one hectare lowland rice farm: the tatluhan, dalawahan and isahan methods. The choice of which method to use depends on the water supply, drainability of paddies, doubling time of azolla and cultural practices on the farm.

TATLUHAN METHOD:

If the ricefield has a steady supply of water, good drainage, enough phosphorous and the farmer adapts the transplanted, straight-row method, the best way of producing and utilizing azolla is the tatluhan method. The azolla is grown with the rice crop and incorporated into the soil three times -- during the first and second weedings and during land preparation for the next crop.

1. Make sure that the paddies are flooded and then plowed and harrowed once every 3 weeks before transplanting.


Tatluhan

2. Twenty days before transplanting of rice seedlings, gather the azolla from the inoculum pond and broadcast it evenly on the one hectare area. Leave at least 10 kg in the pond for future use.


Gather the azolla

3. One day before transplanting (DBT), drain most of the water from the paddies and apply basal fertilizer. (Note: Half of the nitrogen requirement of the crop will be supplied from urea or other inorganic nitrogen fertilizer.)


Drain most of the water

4. Make sure the paddies are flooded about 1 cm deep to float some of the azolla and prevent all of them from being turned under during harrowing. The azolla will have increased to about 1,600 kg.


Make sure the paddies are flooded about 1 cm deep

5. Transplant the seedlings in straight rows.


Transplant the seedlings

6. Let the azolla grow. Twenty days after transplanting, incorporate the azolla in the soil with a rosary weeder. The incorporation should coincide with the first weeding. Allow the remaining azolla plants to grow and if necessary, re-seed the field with azolla from the inoculum pond.


Let the azolla grow

7. Forty days after transplanting, drain the paddies and incorporate the azolla in the soil with a rotary weeder during the second weeding. Let the surviving azolla plants multiply further until harvest time. Turn them under during land preparation for the next cropping.


Forty days after transplanting


DALAWAHAN METHOD:

The dalawahan method is best used when only one weeding of the field is needed and/or when the growth of azolla is below normal because of insufficient phosphorous. The azolla is grown with rice and incorporated during weeding 20 days after transplanting and then again during land preparation for the next crop.

1. Follow steps 1-5 in the tatluhan method.

2. Allow the remaining azolla to multiply further and re-seed the field with azolla from the inoculum pond to increase biomass production.


Allow the remaining azolla to multiply

3. Incorporate azolla into the soil during the land preparation for the next cropping.


Incorporate azolla into the soil

ISAHAN METHOD:

In the isahan method, the azolla is grown with the rice crop but it is not incorporated during cropping. It is best used where doubling time of azolla is slow, where paddies cannot be drained, where water supply is inadequate or where direct seeding is practiced. The biomass is incorporated only once -- during land preparation for the following crop. It is this next crop that will directly benefit from the azolla.

1. Prepare the land, apply basal fertilizer end transplant the seedlings.

2. Seven days after transplanting, gather azolla from the inoculum pond and broadcast it uniformly over the one hectare area. Leave at least 10 kg in the pond to multiply for future use.


Seven days after transplanting

3. If the doubling time of azolla is 7 days, after 56 days the 50 kg azolla will have increased to about 13 tons. Maintain the rice crop and control the weeds with rotary weeder or handweeding. Do not drain to prevent dehydration and death of azolla.

4. Allow the azolla to proliferate until harvest time or as long as there is moisture. Incorporate it during land preparation for the next cropping.


Allow the azolla to proliferate

Isahan Method for direct seeded rice

1. Prepare the land according to the approved cultural practices in lowland rice culture.
2. Drain most of the water, leaving at least 1 cm deep to facilitate levelling of the soil.
3. Apply basal fertilizer and broadcast the rice seeds uniformly.
4. Two weeks after germination, broadcast azolla evenly into the field. Leave at least 10 kg in the pond for future use.
5. Allow azolla to proliferate until harvest time and incorporate it during the land preparation for the next cropping.

Table 1. Environmental Factors Affecting Growth of Azolla (Summary).

FACTORS

RANGE

Temperature

20°C - 25°C

Light

50% full sunlight

Relative Humidity

85 - 90%

Water

5 - 12 cm

pH

4-7

Salinity

90 -1 50 mg/li

Table 2. Guide in Using the Isahan, Dalawahan or Tatluhan Methods.

CONDITION IN FIELD

METHOD

Water Supply

Drainage

Azolla DT

1st Choice

2nd Choice

3rd Choice

Good

Good

Fast1

Tatluhan

Dalawahan

Isahan

Good

Good

Moderate2

Dalawahan

Isahan

-



to Slow3




Good

Poor

Fast to Slow

Isahan

-

-

Poor

Good or

Fast to Slow

Isahan

-

-


Poor





1 Fast -- 4 to 6 days
2 Moderate -- 7 to 9 days
3 Slow -- more than 9 days

SOURCE: National Azolla Action Program, UPLB, Los Ba Laguna, Philippines.