author(s)
Sampa Baidya and Arun Bhai Patel

abstract
Aquatic and free-floating water meal (Wolffia arrhiza L.) known for its fast reproduction rate was grown in differing restricted zones of supplementary feed based intensified carp polyculture in cement tanks (5m x 4m x 1m) with soil beds. While wolffia could not spread beyond the restricted zone, fishes could consume wolffia as per their desire by entering in the wolffia-zone from below. The main objective of the study was to evaluate the effects of area of wolffia-growing zone as % of total water surface area of the culture system on the overall soil quality of the culture system .Three levels of wolffia-zones viz. 10% (T₁), 20% (T₂), 30% (T₃) of the total surface area were evaluated against control without any wolffia (C). The culture period was 75 days and stocking density was 2 fish m^-2. The seeding rate of wolffia (0.5kg m^-2), feeding regime (constant feeding rate @2% d^-1 offered once a day) and fertilization rate involving cow dung, urea and single super phosphate were the same in all treatments throughout the study period. While no marked differences in the soil quality parameters between treatments with wolffia-zone and control (without wolffia zone) were noticed. The present investigation suggested that last stage of culture period unused feed, fertilization, excretory product used to sedimented and increase different nutrient level i.e. Total Nitrogen, Total Phosphorous, organic carbon, and iron but due to co-cultivation of wolffia difference between final stage to nutrient load is not significant difference than the intial stage of nutrient level. However, in the later stage of experiment, the improved soil quality parameter was noticed than the initial stage of experiment. Therefore, it appears to be advantageous to grow Wolffia arrhiza in part of the aquaculture production in supplementary feed based intensified carp culture systems in integrated manner.