[A. no nitrogen (Control), B. urea (60 kg nitrogen ha−1), C. Azolla incorporated (30 kg nitrogen h −1)+urea (30 kg nitrogen ha−1), D. Azolla dual cropping (30 kg nitrogen ha−1)+urea (30 kg Nha−1), E. Azolla incorporated (30 kg nitrogen ha−1)+dual cropping (30 kg nitrogen ha−1)].