ORIGINAL ARTICLE Soil enzyme activities with biomass ashes and phosphorus fertilization to rice–wheat cropping system in the Indo- Gangetic plains of India Sandeep Sharma • H. S. Thind • Yadvinder Singh • Varinderpal Singh • Bijay Singh Received: 20 October 2014 / Accepted: 13 February 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract Bagasse ash (BA) and rice husk ash (RHA) contain significant quantities of P and many other nutrients. Application of biomass ashes has been shown to improve crop yields and soil properties. The present experiment was conducted to determine the effect of BA and RHA application in combination with different doses of P fertilizer on soil enzyme activities in rice–wheat rotation in the Indo-Gangetic plains of India. Both BA and RHA significantly increased the dehydrogenase, alkaline phosphatase and phytase activities as compared to no ash application in the 0–0.15 m soil layer. Activities of these enzymes also increased with P fertilization. Biomass ashes and P fertilizers showed little effect on enzymatic activities in the 0.15–0.30 m soil layer. Application of biomass ashes and P fertilization significantly increased Olsen- P and organic carbon content in soil over control. Enzyme activities were significantly and positively correlated with Olsen-P, organic carbon content and wheat grain yield. This study suggests that soil quality can be improved by applying biomass ashes and P fertilization on a loamy sand soil under rice–wheat system. Keywords Biomass ashes Á Dehydrogenase Á Alkaline phosphatase Á Phytase Á Rice–wheat Introduction Due to the dramatic rise in prices for commercial fertilizers, search for alternative sources of plant nutrients has become increasingly important, par- ticularly for resource poor farmers of South Asia (Lopez et al. 2009). Regular additions of organic materials such as, municipal biosolids, animal ma- nures, crop residues and agro-industrial wastes are of utmost importance in maintaining the fertility and productivity of agricultural soils (Solaimalai et al. 2001). Ashes from combustion of biomass are the oldest mineral fertilizers in the world (Schiemenz and Eichle-Loebermann 2010). Biomass ashes are nearly free of N but contain significant quantities of P, K, Ca, Mg and micronutrients essential for plant nutrition (Vance and Mitchell 2000; Bhattacharya and Chat- topadhyay 2002; Patterson et al. 2004). The recycling of biomass ashes in agriculture may solve the problem of their disposal as well as reduce the doses of commercial fertilizer application (Sander and Andren 1997; Perucci et al. 2006; Bougnom and Insam 2009). Bagasse and rice husk are the two important agro- industrial by-products that are generally used as fuel in sugar and rice mill industry, respectively. In India about 7.63 million tonnes of bagasse ash (BA) and 6.37 million tonnes of rice husk ash (RHA) are produced S. Sharma (&) Á H. S. Thind Á Y. Singh Á V. Singh Á B. Singh Department of Soil Science, Punjab Agricultural University, Ludhiana 141 004, Punjab, India e-mail: sandyagro@rediffmail.com 123 Nutr Cycl Agroecosyst DOI 10.1007/s10705-015-9684-7