Soil Science Society of America Journal Soil Sci. Soc. Am. J. 77:558–567 doi:10.2136/sssaj2012.0365 Received 31 Oct. 2012. *Corresponding author (kaleemabbasi@yahoo.com). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Effect of Wood Ash and Compost Application on Nitrogen Transformations and Availability in Soil-Plant Systems Soil Fertility & Plant Nutrition S oil quality deterioration and soil fertility depletion are the two major ecolog- ical problems throughout the world (Harden, 2001; Lal, 2001), but they are especially serious in the heavily populated, underdeveloped, and ecologically M. Kaleem Abbasi* Nadia Afsar Nasir Rahim Department of Soil and Environmental Sciences Faculty of Agriculture The University of Poonch Rawalakot Azad Jammu and Kashmir Pakistan Application of organic–inorganic by-products, that is, wood ash (WA), compost, and organic manures is a valuable restoration strategy that can alleviate the physical conditions and improve the nutrient status of degraded soils. To get the maximum benefts, proper management and N turnover of these resources need to be examined. The aim of this study was to investigate the effects of WA and compost applied alone or with N fertilizer on different fractions of mineral N, that is, mineralization, nitrifcation, and recovery of N in soil-pant systems. Laboratory and greenhouse experiments were conducted at the University of Poonch, Rawalakot Azad Jammu and Kashmir, Pakistan. In the incubation experiment, soil (Humic Lithic Eutrudepts, Inceptosols) from an arable feld was collected (0–15 cm) and amended with WA, compost, and N fertilizer diammonium phosphate (DAP) [(NH 4 ) 2 HPO 4 ]. In addition, a pot experiment was conducted in the greenhouse to examine the response of sorghum [Sorghum bicolor (L.) Moench] to these amendments. Results indicated that WA and compost signifcantly increased N mineralization by releasing a maximum of 48.5 and 76.1 mg N kg –1 , respectively compared to 21.9 mg N kg –1 in the control. Combined application of 1/2DAP with WA and compost resulted in a signifcant reduction in the extent of total mineral nitrogen (TMN) disappearance observed in N fertilizer (DAP, full) treatment. Both WA and compost signifcantly increased nitrifcation potential and accumulation of NO 3 – –N at the end was 36.4 and 70.5 mg kg –1 , respectively compared to 10.3 mg kg –1 in the control. Wood ash applied alone or in mixtures signifcantly increased soil pH by 0.99 to 1.45 units. Results obtained from the greenhouse experiment indicated that WA alone did not affect most of the growth characteristics, however, N contents and N uptake by sorghum were signifcantly increased by WA and compost. Plant N uptake in the combined treatments (1/2DAP+compost, 1/2DAP+WA+compost) was 44 and 57 mg plant –1 , respectively, signifcantly higher than the 31 mg N plant –1 in the full DAP treatment. The increase in N uptake and plant dry matter yield was associated with N released from added amendments and a signifcant correlation existed between TMN and plant N uptake (R 2 = 0.56) and TMN and plant dry matter yield (R 2 = 0.61). The present study demonstrates the existence of substantial amount of N reserve present in these amendments. After proper combinations and management, N from these resources can be taken into account as potential source for the management of nutrient poor soils and plant growth. Abbreviations: DAP, diammonium phosphate; HKH, Hindu Kush Himalaya; TMN, total mineral nitrogen; WA, wood ash; WFPS, water-flled pore space. Published online February 1, 2013