Agrochimica, Vol. LVII - N. 1 January-March 2013 Received 4 January 2013 – Received in revised form 23 February 2013 – Accepted 26 March 2013 *  Corresponding author: basak.soil@gmail.com 2 Present address: Directorate of Medicinal and Aromatic Plant Research, Boriavi, Anand, Gujrat 387 310, India 3 Present address: Central Soil and Water Conservation Research and Training Institute, Research Centre, Madhya Marg, Chandigarh 160 019, India Soil biochemical properties and grain quality as affected by organic manures and mineral fertilizers in soil under maize-wheat rotation B.B. BASAK 1,2,* , D.R. BISWAS 1 , S. PAL 1,3 1 Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi 110 012, India Keywords: dehydrogenase, grain yield, manure, microbial biomass carbon, rotation, urease Abbreviations: CRI, crown root initiation; FYM, farm yard manure; RDF, rec- ommended dose of fertilizers; TPF, triphenylformazan. Introduction. – The green revolution of the 1960s and 1970s which resulted in dramatic yield increases in the developing Asian countries is now showing signs of fatigue in productivity gains. Intensive agriculture practice without adherence to the scientific principles and ecological aspects has led to loss of soil health as well as depletion of freshwater resources and agrobiodiversity (Kesavan and Swaminathan, 2008). In order to improve the health of soil ecosystem to sustain or increase agri- cultural production, it is essential to improve soil biological quality in addition to physical and chemical properties. Soil microbial communities perform necessary ecosystem services, including nutrient cycling, patho- gen suppression, stabilization of soil aggregates and degradation of xeno- biotics. Measurements of biologically active fractions of organic matter, such as microbial biomass carbon and nitrogen, better reflect changes in soil quality and productivity that alter nutrient dynamics. Soil enzyme activity is not only considered as an important indi- cator of soil health and quality, but it reflects the real picture of soil microbial activity. Soil enzymes are believed to be able to discrimi- nate between soil management practices probably because they are related to microbial biomass, which is sensitive to different treatments (Nannipieri et al., 1990). Soil enzyme activities are important for