Contents lists available at ScienceDirect Soil & Tillage Research journal homepage: www.elsevier.com/locate/still Crop rotation and residue management effects on soil enzyme activities, glomalin and aggregate stability under zero tillage in the Indo-Gangetic Plains Geeta Singh a , Ranjan Bhattacharyya a, ⁎ , T.K. Das a , A.R. Sharma a , Avijit Ghosh a , Shrila Das a , Pramod Jha b a Indian Agricultural Research Institute, New Delhi, 110 012, India b Indian Institute of Soil Science, Bhopal, India ARTICLE INFO Keywords: Legume based cropping systems Soil aggregation and organic carbon content Soil microbial biomass carbon ABSTRACT This 3-year study investigated the effects of crop rotation and residue management (surface retention of residues under zero tillage) on soil carbon pools, selected soil physical properties (soil aggregation, mean weight dia- meter) and biological properties (glomalin and ergosterol contents, soil respiration and enzyme activities) and their inter-relationships in a semi-arid soil of India under rainfed condition. The field study consisted of three different cropping systems (pearl millet-wheat, pearl millet-chickpea and pearl millet-mustard) in the main plots and three residue management practices (no residue, crop residue and Leucaena mulch cover) in the sub-plots, with three replications. All crops were cultivated adopting zero tillage (ZT). Surface (0–15 cm) samples were taken from fields after 3-years. Results revealed that crop rotation had no impacts on total soil organic C (SOC), Walkley-Black C (WBC) and soil aggregation, but significantly affected labile C. However, residue retention or addition significantly affected total SOC, labile C and soil aggregation. Plots under crop residue and Leucaena mulching had ∼30 and 26% higher large macroaggregates (> 2 mm diameter) than no residue treated plots. A similar trend was observed for the proportion of macroaggregates, resulting in about 20 and 17% increase in mean weight diameter (MWD), respectively, in the crop residue and Leucaena added plots compared to the residue removal plots (∼0.91 mm). The residue retained plots had ∼40 and 13% higher soil glomalin content compared with residue removal (∼290 μgg -1 soil) and Leucaena added plots, respectively. Both soil glomalin and ergosterol contents were significantly (P < 0.05) related with large macroaggregates and there were sig- nificant relationships between glomalin and WBC concentration and glomalin and MWD in the surface soil. Glomalin, microbial biomass C, dehydrogenase, fluorescein diacetate (FDA), glucosidase and alkaline phos- phatase activities were significantly increased by both crop rotation and residue management. Thus, the legume based cropping system (pearl millet-chickpea system) with ZT and residue retention under rainfed conditions had significant impact on soil aggregation and biological health, even after a short-term adoption. 1. Introduction Crop residue is either serving as a feedstock for cattle or more often is burned in the fields in the western Indo-Gangetic Plains (IGP). The latter causes environmental concerns. Recent efforts to sustain crop production and enhance environmental quality are optimum utilization of crop residues and adoption of zero tillage (ZT) practices. Adding surface mulch impacts plant establishment and improves crop growth after establishment. In addition, crop residues provide a number of environmental services when left in the field, including contributing to the formation of soil organic C (SOC), improving soil structure, preventing erosion, reducing evaporation from the soil surface, sup- porting living organisms, contributing nutrients to the soil, and pro- viding water filtration and retention capacity (Lal, 2010; Nicholson et al., 2014). Double cropping with conventional management practices is not feasible under rainfed condition. Adding surface mulch impacts plant establishment and improves crop growth after establishment in semi- arid regions due to more moisture conservation. Conservation agri- culture (CA), which involves ZT with crop residue management, ef- fectively improves soil organic matter (SOM) and maintains crop yields in many situations in India (Bhattacharyya et al., 2012a, b; Das et al., https://doi.org/10.1016/j.still.2018.08.006 Received 12 December 2017; Received in revised form 27 July 2018; Accepted 12 August 2018 ⁎ Corresponding author. E-mail address: ranjan_vpkas@yahoo.com (R. Bhattacharyya). Soil & Tillage Research 184 (2018) 291–300 0167-1987/ © 2018 Published by Elsevier B.V. T