Effects of Nitrogen and Phosphorus on Growth of Hymenachne Acutigluma and Uptake of Nitrogen and Phosphorus Containing Wastewater from Catfish (Pangasianodon Hypophthalmus) Pond

Abstract

This research was studied on effects of nitrogen (N), phosphorus (P) and the ratios of N:P on growth and uptake of Hymenachne acutigluma on three levels of nitrogen (N) (30, 60 and 120 mg/L; N1, N2, N3) combined with three levels of phosphorus (P) (5, 10 and 20 mg/L; P1, P2, P3). Every treatment was repeated four times at controlled condition for the period of six weeks. Water was replaced and water quality was assessed once a week. Growth of H. acutigluma and uptake of N and P by the plants were monitored at the start and the end of the experiment. The results showed that N, P and N/P ratios influenced the growth and N and P uptake of tested plants. However, the shoots were less affected by interaction influence of both N and P. The growth and accumulation of N and P of the plants in N3P1 conditions was better than other conditions. The mole ratio of N:P was lower than 13.3 could limit growth of H. acutigluma and uptake of N and P of this plant species, especially in low and medium N conditions. The treatment efficiency of NH₄⁺ -N, NO₃ˉ -N, TN, PO₄³ˉ-P and TP were 85.7- 95.1%, 70.1-81.6%, 64.8-74.3%, 48.8- 80.3% and 35.9-76.9% respectively. At 120 mgN/L and 5 mgP/L conditions, H. acutigluma reduced N and P by 6.4% and 29.5%, respectively.