A comparative study on the decomposition of edible and non-edible oil cakes in the Gangetic alluvial soil of West Bengal Sudeshna Mondal & Ritwika Das & Amal Chandra Das Received: 16 January 2014 /Accepted: 28 March 2014 /Published online: 16 April 2014 # Springer International Publishing Switzerland 2014 Abstract An experiment has been conducted under laboratory conditions to investigate the effect of decom- position of two edible oil cakes, viz. mustard cake (Brassica juncea L) and groundnut cake (Arachis hypogaea L), and two non-edible oil cakes, viz. mahua cake ( Madhuca indica Gmel) and neem cake (Azadirachta indica Juss), at the rate of 5.0 t ha -1 on the changes of microbial growth and activities in rela- tion to transformations and availability of some plant nutrients in the Gangetic alluvial (Typic Haplustept) soil of West Bengal, India. Incorporation of oil cakes, in general, highly induced the proliferation of total bacte- ria, actinomycetes, and fungi, resulting in greater reten- tion and availability of oxidizable C, N, and P in soil. As compared to untreated control, the highest stimulation of total bacteria and actinomycetes was recorded with mustard cake (111.9 and 84.3 %, respectively) followed by groundnut cake (50.5 and 52.4 %, respectively), while the fungal colonies were highly accentuated due to the incorporation of neem cake (102.8 %) in soil. The retention of oxidizable organic C was highly increased due to decomposition of non-edible oil cakes, more so under mahua cake (14.5 %), whereas edible oil cakes and groundnut cake in particular exerted maximum stimulation (16.7 %) towards the retention of total N in soil. A similar trend was recorded towards the accumu- lation of available mineral N in soil and this was more pronounced with mustard cake (45.6 %) for exchange- able NH 4 + and with groundnut cake (63.9 %) for soluble NO 3 - . The highest retention of total P (46.9 %) was manifested by the soil when it was incorporated with neem cake followed by the edible oil cakes; while the available P was highly induced due to the addition of edible oil cakes, the highest being under groundnut cake (23.5 %) followed by mustard cake (19.6 %). Keywords Edible and non-edible oil cakes . Microbiological decomposition . Microbial proliferation and activities . Plant nutrient status . Soil organic matter . Gangetic alluvial soil Introduction Incorporation of organic residues in soil brings about both direct and indirect effects on plant growth. The direct effect includes the uptake of available nutrients and absorption of humic substances by plants for their metabolism (Mukherjee and Gaur 1980; Vanega et al. 2011), whereas the indirect effect relates to different biochemical processes carried out by different types of autochthonous microorganisms (Saha et al 1992), which make the soil environment more favorable for plant growth (Patra et al. 2011 ; Panda et al. 2012 ). Microorganisms are scavengers in soil. They degrade a great variety of chemical substances including the added organic materials in soil. The incorporated organic sub- stances are broken down by a great variety of chemoheterotrophic microorganisms in soil to derive Environ Monit Assess (2014) 186:5199–5207 DOI 10.1007/s10661-014-3769-7 S. Mondal : R. Das : A. C. Das (*) Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur 741252 West Bengal, India e-mail: acdas2@rediffmail.com