Effect of long-term use of organic, inorganic and integrated management practices on carbon sequestration and soil carbon pools in different cropping systems in Tarai region of Kumayun hills

A study was undertaken during 2004-05 to 2013-14 to study the influence of different management options includingcropping systems on carbon sequestration and soil carbon pools under Typic haplaquoll soil condition. Complete organicmanagement (as per National Programme for Organic Production standards) with supply of 100% nutrient throughorganic sources, integrated crop management (nutrient and pests) with supply of 50% nitrogen through organic and50% through inorganic and inorganic crop management with 100% nitrogen through inorganic sources while in subplots four cropping systems namely Basmati rice (Oryza sativa L.)-wheat (Triticum aestivum L.)-Sesbania, Basmatirice-lentil (Lens culinaris Medic.)-Sesbania, Basmati rice-vegetable pea (Pisum sativum L.)- Sesbania and Basmatirice-Brassica napus- Sesbania cropping system were tested in strip plot design at G B Pant University of Agricultureand Technology, Pantnagar, Uttarakhand. The three main plot treatments consisted of 100% organic, 50% organic +50% inorganic and 100% inorganic fertilizer. Parameters such as bulk density, soil organic carbon, labile carbon pool,water soluble carbon, dehydrogenase activity were studied in all the treatments besides cropping systems equivalentyield. Bulk density varied from 1.24 to 1.44 Mg/m3 in 0-15 cm soil under different nutrient management practicesand the same increased with the increase in depth. Soil organic carbon (SOC) did not vary significantly amongdifferent cropping systems in 0-15 cm soil. The soil organic carbon content ranged from 10.70 to 11.13 g/kg underdifferent cropping systems. The labile carbon pools and water soluble carbon content decreased with the increase ofsoil depth. The labile carbon pool (2450.21 mg/kg), water soluble carbon (21.39 mg/kg) and dehydrogenase activity(319.44 mg TPF/day/g soil) was higher in 0-15 cm soil depth with organic management of basmati rice-wheat-Sesbania systems compared to other systems and management practices. Among the management practice, basmatirice equivalent yield was higher in organic management (7130 kg/ha) in the year 2014. Among the cropping systems,Basmati rice-lentil- Sesbania (green manuring) (7865 kg/ha) system recorded higher equivalent yield compared toother systems. The carbon sequestration (15.36 Mg/ha) was higher in basmati rice-brassica-Sesbania cropping systemwith organic management practice and the sequestration rate was at par with basmati rice-wheat-Sesbania croppingsystems. Therefore, either basmati rice-wheat-sesbania or basmati rice-Brassica napus-Sesbania cropping systemwith organic or integrated management is better for sequestering higher C in the soil than the present rice-wheatsystem with inorganic management.