Effect of brown manuring practices on yield, nutrient dynamics and soil micro-flora in wet seeded rice in the coastal deltaic ecosystem

A field experiment was conducted at Pandit Jawaharlal Nehru College of Agriculture and Research Institute, Karaikal during October 2020 - January 2021 to investigate the effects of brown manuring on yield, yield attributes, nutrient availability, nutrient uptake and soil micro-flora in wet seeded rice. The experiment was carried out with ten treatments (T1 - rice with dhaincha 15 kg ha-1 + 2,4-D 0.5 kg ha-1, T2-rice with dhaincha 20 kg ha-1 + 2,4-D 0.5 kg ha-1, T3 - rice with dhaincha 25 kg ha-1 + 2,4 - D 0.5 kg ha-1, T4 - rice with dhaincha 15 kg ha-1 + bispyribac sodium 25 g ha-1, T5-rice with dhaincha 20 kg ha-1 + bispyribac sodium 25 g ha-1, T6-rice with dhaincha 25 kg ha-1 + bispyribac sodium 25 g ha-1,T7 - rice alone + 2,4 - D 0.5 kg ha-1, T8 - rice alone + bispyribac sodium 25 g ha-1, T9 - rice alone with hand weeding twice at 20 and 40 DAS, T10- unweeded control) replicated thrice in a randomized block design. The result from the study showed that the yield (4.82 t ha-1) and yield attributes of rice were significantly enhanced when co-cultured with dhaincha 25 kg ha-1 + 2,4-D or bispyribac sodium 25 g ha-1application was comparable with other brown manured treatments but superior than rice alone. Co-culturing with dhaincha 25 kg ha-1 with rice resulted in higher nutrient availability (208.9, 32.8, 231.6 kg N, P, K per hectare respectively), nutrient uptake (65.6, 16.4, 69.7 kg N, P, K per hectare respectively) by rice and soil microbial population at harvest (brown manuring either with 2,4-D or bispyribac sodium). Therefore, co-culture of brown manure involving a post-emergence herbicide was more competitive against weeds and the dead residue proved to be simulative to wet sown rice crop for boosting growth and yield.