Cultivation of Azolla filiculoides for the reclamation and utilization of heavy saline soil

• Main Authors: Shang Deng hui, Wu Ho, Chen Xi pan, Gu Rong sain
• Format: Conference Proceeding
• Language: English
• Published: 1987
• Subjects: azolla; china; chine; cultivation; cultivo; lolium; pratique culturale; reclamation; recuperation des sols; rehabilitacion; saline soils; sesbania; sol salin; suelo salino

Experiments have shown that the salt-resisting limit of Azolla filiculoides is 0.7% (salt water) and its alkali-resisting limit is 0.3% (Na2CO3 + NaHCO3). Therefore, it can be cultured as a pioneer plant for reclaiming coastal heavy saline soil. Cultivated on soil containing 0.35% salt for 110 d and irrigated with water containing 0.2% salt, azolla produces 90-105 t fresh wt/ha, or an average daily yield of 818-955 kg/ha. During the same period, Sesbania produces only 21.2 t/ha. When A. filiculoides is cultured with seawater containing 0.1-0.5% salt, it has a nitrogenase activity of 0.5-0.25 with seawater containing 0.3% salt shows no nitrogenase activity. By cultivating azolla in spring and autumn for two successive years, the salt content of saline soil may be decreased from 0.35 to 0.1%. The desalination rate is 71.4%, 1.8 times higher than that of water leaching or 2.1 times that of Sesbania. The humification coefficient of azolla is 0.42, higher than that of Spartina anglica (0.19-0.25), Sesbania (0.32), or ryegrass (0.22). Thus, after 2 yr, the organic matter in the 0-10 cm soil layer increases from 0.58 to 1.10%. The rate of increases is higher than that achieved by planting S. anglica or Sesbania during the same period. Soil fertility is improved to the level of a soil that can yield 2.3-3.0 t seed-cotton/ha. Reclamation for two successive years by cultivating azolla, Sesbania, and ryegrass gives a higher net income from cotton than other reclamation methods.