Environmental requirements for successful azolla growth
1987
Lumpkin, T.A. (Wahington State Univ., Pullman, Washington (USA). Dept. of Agronomy and Soils)
Azolla is traditionally grown under cool, wet conditions. The plant prefers a placid water surface, temperatures between 20 and 35 deg C., water pH of 4-7 and rich in all essential plant nutrients except N, solution salt content 0.3%, exposure to 25% full sunlight, long daylength, and freedom from competitors, insects, and diseases. Efforts to expand its use in the humid tropics have met with limited success and a host of environmental problems. High temperatures and humidity stimulate insects and diseases that attack azolla. Algal blooms compete for nutrients and cause a change in pH and poor water circulation. Areas dependent on monsoon rains rarely have water for multiplying azolla before the rice growing season and usually suffer from intermittent droughts, which desiccate intercropped azolla. Excessive rainfall and typhoons can cause flooding which can wash away the entire azolla crop. Water is usually deficient in P and the applications of phosphate fertilizer and possibly other nutrients such as Fe, Mo, and K are required for the azolla crop.
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