Productivity and Soil Carbon Sequestration of Rice-based Cropping Systems in the Brahamaputra Valley Zone, Northeast India

A field experiment was conducted for two consecutive years during 2016–17 and 2017–18 at farmer’s field of Brahamaputra valley zone of Assam to assessed 6 rice-based cropping sequences under rainfed medium land situation for their productivity and soil carbon sequestration potential. The soil of the experimental site was acidic (pH 5.4), sandy loam in texture, medium in organic carbon (0.53%), low in available N (263.40 kg ha-1) and medium in P2O5 (34.60 kg ha-1) and K2O (152.43 kg ha-1). The treatments consisted of 6 rice based cropping sequences replicated four times in randomized block design viz. rice (Oryza sativa L.) - rapeseed (Brassica camprestis L.) - fellow; rice - rapeseed - blackgram (Vigna mungo L.); rice– garden pea (Pisum sativum. L.)-blackgram; rice – lentil (Lens culinaris Medic) - blackgram; rice – garden pea- sesbania (Sesbaniaaculeta) and rice – lentil- sesbania. Performance of different cropping systems and CO2 emission from all cropping sequences were estimated and the highest CO2 – C emission of 2.649 & 2.470 Mg ha-1 in rice-lentil- blackgram sequence during 2016-17& 2017-18 respectively. Among all the sequences, rice-lentil-sesbania sequence was found to be having highest carbon sequestration potential with 2.32 and 1.35 Mg ha-1 in 0-15 cm and 1.97 & 1.88 Mg ha-1 in 15-30 cm depth of soil during 2016-17 and 2017-18, respectively.