Abstract

                                A field experiment was conducted during Rabi 2013, at wetland of Tamil Nadu Agricultural University, Coimbatore to study the nitrogen fixing potential of the selected diazotrophs on rice (ADT 43) under three different rice production systems viz., lowland, System of Rice Intensification (SRI) and aerobic methods of cultivation. The pH of the soil was found to be alkaline 7.5. The texure of the soil was clay loam. The available nitrogen and phosphorous was low with 192.8 and 19.8kg ha-1 respectively. The available potassium was found to be medium with 425.3 kg ha-1. Among the three different rice growing systems, grain and straw yield were found to be maximum with application of 75% recommended dose of N with the combined inoculation of diazotrophic isolates viz., Azospirillum lipoferum (AsLC1I), Azotobacter chroococcum (AbSKN) , Beijerinckia indica (BeSC2S2), Derxia gummosa (DeLTP2 ) and Pseudomonas fluorescens (PsAKK3) in comparison with the standard strain A.lipoferum (Az - 204) in SRI (7.1 t/ha and 8.78 t/ha), followed by lowland (6.1t/ha and 6.8 t/ha) and aerobic rice (4.23 t / ha and 5.5 t/ ha). The nitrogen uptake was found to be maximum in the above treatment at all three rice growing systems. Among the three systems, SRI (110 kg / ha) recorded maximum nitrogen uptake followed by lowland (81.6 kg / ha) and aerobic rice (70 kg/ ha).

Key words : Rice, Diazotrophs, Lowland, SRI, Aerobic, Grain and Straw yield, N uptake