Conventional tillage and cereal-cereal cropping systems cause degradation of soil health and quality by depleting soil organic carbon as well as other nutrients. Therefore we studied the “Effect of long term zero tillage and different moisture regimes on soil organic carbon and its fractions in legume based cropping systems of north-western Indo-Gangetic Plains”. Field experiment was conducted during2017-18 and 2018-19 on an on-going long term experiment on ‘Effect of varying moisture regimes in zero-till wheat succeeding mungbean and sorghum’ since 2006 at Soil Research Farm, Department of Soil Science, CCS HAU, Hisar. The experiments consisted of two cropping systems (mungbean-wheat, MW and sorghum-wheat, SW), three tillage practices viz. CT-CT (conventional tillage in both kharif & rabi seasons), CT-ZT (conventional tillage in kharif & zero tillage in rabi seasons) and ZT-ZT (zero tillage in both kharif & rabi seasons); and three moisture regimes {IW/CPE = 0.60(M_0.60), 0.75 (M_0.75) and 0.90 (M_0.90)}.The zero tillage ZT-ZT increased the soil organic (SOC) by 24.75, 23.16 % and 10.61, 9.98 % in surface and subsurface depth as compared to conventional tillage CT-CT in MW and SW, respectively, over all the moisture regimes. The soil organic carbon was found 11.1 and13.1 % higher in M_0.90 as compared to M_0.60 in MW and 9.6 and 10.0 % higher in M_0.90 than M_0.60 in SW over all the tillage practices in surface and subsurface soil respectively. The highest value of soil organic carbon (0.87 and 0.52 %) in surface and sub-surface soil was observed in ZT-ZT under MW cropping system in M_0.90. At surface and sub-surface depths, the dissolved organic carbon (DOC) was significantly higher (15.24 and 17.26 %) in mungbean-wheat cropping system as compared to sorghum-wheat cropping system. The DOC was also significantly higher in ZT-ZT (23.33 and 16.54; and 22.09 and 14.43 %) and CT-ZT (9.33 and 9.02; and 10.17 and 8.87 %) as compared to CT-CT over all the moisture regimes in mungbean-wheat and sorghum-wheat cropping systems at surface and sub-surface depths, respectively. The  DOC was substantially higher at M_0.90 (20.39 and 18.80; and 21.79 and 21.04 %) and M_0.75 (7.89 and 6.34; and 8.08 and 7.15 %)  as compared to M_0.60  over all the tillage practices in mungbean-wheat and sorghum-wheat cropping systems at surface and sub-surface depths, respectively. At surface depths, the light fraction (LF) carbon was significantly higher (6.51 %) in mungbean-wheat cropping system as compared to sorghum-wheat cropping system and sub-surface depth. It was 7.39 % higher in MW as compared to SW cropping system. The LF carbon was significantly higher in ZT-ZT (35.09 and 32.87; and 21.00 and 20.67 %) and CT-ZT (23.68 and 22.69; and 24.20 and 17.79 %) as compared to CT-CT over all the moisture regimes in mungbean-wheat and sorghum-wheat cropping systems at surface and sub-surface depths, respectively. At M_0.90 (25.93 and 16.17; and 23.01 and 20.75 %) and M_0.75 (12.35 and 10.64; and 11.50 and 11.32 %) light fraction carbon was substantially higher as compared to M_0.60 over all the tillage practices in mungbean-wheat and sorghum-wheat cropping systems at surface and sub-surface depths, respectively. The heavy fraction (HF) carbon was also significantly highest in ZT-ZT over all the moistute regimes under MW as compared to SW cropping system. The HF was higher in magnitude as compared to LF carbon in surface as well as in sub-surface soils. Therefore Long term zero tillage with inclusion of legumes can be a promising alternative to sustainably increase organic carbon  in soilfor cereal-cereal cropping systems which ultimately plays a pivotal role to sustain the crop productivity and optimum ecosystem functioning with improving soil health.

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