Microbial Biomass Turnover in Indian Subtropical Soils under Different Sugarcane Intercropping Systems

Changes in soil organic C (C org ), total N (N t ), available nutrients, soil microbial biomass C (C mic ) and N (N mic ), and mineralizable C and N in the sugarcane ( Saccharum officinarum L.) rhizosphere were evaluated under intensive sugarcane cropping systems with intercrops including wheat ( Triticum aestivum L.), maize ( Zea mays L.), rajmash ( Phaseolus vulgaris L.), green gram [ Vigna radiata (L.) R. Wilczek var. radiata ], cowpea [ Vign aunguiculata (L.) Walp.], lentil ( Lens culinaris Medik.), mustard ( Brassica rapa L.), potato ( Solanum tuberosum L.), and sesbania ( Sesbania rostrata Bremek. & Oberm.) in subtropical soils of India. Organic C increased significantly when maize (25%), wheat (24%), mustard (19%), potato (17%), and rajmash (13%) were intercropped with sugarcane, while legume intercrops substantially increased N t and available N. Increase in microbial respiration was greater where maize (42%), wheat (37%), or mustard (31%) were intercropped compared with pulse crops. Soil microbial biomass C accounted for 2.7 to 3.3% of C org content and N mic accounted for 2.6 to 3.7% of N t under different intercropping conditions. A higher CO 2 evolution rate and wider C mic /N mic ratios were recorded with cereal and mustard intercrops, whereas higher N mineralization was recorded with pulse intercrops. Results indicate that intercropping with pulse crops and incorporation of their labile C substrate improved N mineralization. The build up of the C pool and C mic in the case of cereals, mustard, and potato intercropping should promote long‐term stability.