Soil Fertility as Influenced by K Enriched Azolla

Biological Nitrogen Fixation (BNF) is a major source of fixed N for plant life and to sustain production and productivity of agricultural crops. An incubation experiment was conducted by growing Azollae filiculoides with 2 agriculturally important potassic fertilizers (Potassium Chloride, Potassium shulphate) as main plot in seven concentrations (0, 5, 10, 20, 30, 40 and 50 ppm of K) as sub-plots laid down in split plot design replicated three times. The collected Azolla was incorporated with soil at 10 t/ha and maintained at two moisture condition such as 60 and 100 percent and assessed soil fertility by estimating various available plant nutrients and organic carbon status..The mean organic carbon content of the soil was 0.657 and 0.525% at 60 and 100% moisture contents respectively. The available N content ranged from 216.2 to 327.3 and 191.1 to 285.3 kg/ha from 0 to 40 ppm of K concentration at 60 and 100% moisture respectively because the Azolla had a high N content which released into the soil after decomposition. Azolla also contributed to the supply of phosphorus, potassium, sulfur, zinc, iron and molybdenum in sufficient amounts in addition to other micronutrients besides addition of nitrogen. Among the various concentration, 40 and 50 ppm K were significantly maintained higher and equal soil available P status of 75.17 and 77.33 kg / ha respectively. The fertilizer, K2SO4 with 30, 40 and 50 ppm at 60% moisture content and 40 and 50 ppm of K2SO4 and 40 ppm of KCl produced statistically higher and equal available K at 100% moisture. The soil biological health, mineralization and consequent increase in nutrient status by the application of K enriched Azolla was more under 60% soil moisture content than fully saturated soil.