Fertilizing Time Effect of Urea in Dual System Azolla‐Rice Paddy to Soil Capital Nitrogen and Rice Yield on Entisol

The purposed of research was to study the effect of urea use in dual system azolla‐rice paddy to soil capital nitrogen and rice yield on Entisol. Research was conducted on rice paddy field at Colomadu, Karanganyar district, Central Java. The experiment arranged in single factor randomized completely block design (RCBD), with eight treatments says D1 (azolla + 100 kg urea /ha at 0 day after planting‐dap), D2 (azolla + 100 kg urea /ha at 30 dap), D3 (azolla + 100 kg urea /ha at 60 dap), D4 (azolla + 50 kg urea /ha at 0 and 30 dap), D5 (azolla + 50 kg urea /ha at 30 and 60 dap), D6 (azolla + 50 kg urea /ha at 0 and 60 dap), D7 (control treatment ‐ without azolla nor NPK fertilizer), and D8 (lokal farmer treatment ‐ 250 kg urea /ha split three times, 50 kg/ha at 0 dap, 100 kg/ha at 30 dap and 100 kg/ha at 60 dap). Azolla inoculums spreaded 7 dap at rates 500 g/m2. Variables observed were soil capital nitrogen, soil total‐N, tissue total‐N, soil organic matter content and rice yield. Data taken was analyzed with anova and followed with Duncan Multiple Range Test (DMRT) at 5 % level of significant. The results show that the use of urea in dual system azolla‐rice paddy increase soil capital nitrogen, soil total‐N, tissue total‐N, soil organic matter content and rice yield at Entisol. The highest soil capital nitrogen (0,953 kg/ha) and rice yield (8 ton/ha) were taken from the treatment of D8 and D3 respectively.