Ini D. Edem et al./ Elixir Agriculture 52 (2012) 11555-11564 11555 Introduction Slash and burn method of land clearing is an integral part of the traditional farming system (bush fallow rotation) widely used as a means of land clearing to pave way to tillage in southern Nigeria. Depending on management practices being used, human activities like bush burning, fossil fuel and deforestation have alter the atmosphere’s composition and earth balance. The invention of deliberate fire ignition and its control by man started the anthropogenic modification of biosphere 14 . Fire has long been recognized as a disturbance that maintains grasslands and savannas and prevents invasion of woody species 1,2, 23 . Therefore, prescribed fire is often employed as a land management tool to suppress the encroachment of woody plants into grass-dominated ecosystems. In humid tropics, the balance between trees and grasses, stand structure and dynamics, and shrub cover and abundance is determined to a large extent by fire frequencies and interactions between fire and other disturbance factor 5, 13, 19, 20 . Above and below ground productivity often increase following fire as a result of microclimatic modification due to removal of litter and standing crop, and changes in nutrient availability and distributions 3, 7, 12, 15, 16 ,. Most land that is left unused in a cropping year is often set on fire by farmers. This is common with the livestock farmers, for the animals to browse on young plants that grow after burning. Before the plants come up to cover the ground surface, the soil is exposed to climatic element of rainfall. Subsequently, soil aggregates are dispersed; pores are clogged with particles and further result in much higher rates of surface runoff 11 . The level of alteration may even be enormous if quantity of trash is large and the residence time of burning is long, or a thin, dry litter is completely incinerated 21 . More severe burns may alter such fundamental characteristics as texture, mineralogy and cation-exchange capacity 8 . Atmospheric concentration of several green house gases (GHGs) has changed drastically since the industrial revolution because of biomass burning and other factors like bush burning and fossil fuel combustion. The concentration of CO 2 responsible for 62% of the total radiative forcing by earth has increased by 35% from 280% around 1750 to 377% in 2006 24 . The concentration of methane (CH 4 ), responsible for 20% of the radiative forcing of the earth, has also increased by 155% from about 700 ppb around 1750 to 1785 ppb in 2004. the atmospheric concentration of nitrous oxide (N 2 O), responsible for about 6% of the radiative forcing of the earth has increased by 18% from about 270 ppb around 1750 to 318.6 ppb in 2004 23 . According to Ruddiman 20,21 , soil cultivation is not as obvious a source of atmospheric CO 2 as are fossil fuel combustion, deforestation, and biomass burning. Yet world soils have been a dominant source of CO 2 ever since the dawn of settled agriculture 7 . Despite these challenges, a number of countries have successfully implemented soil emission inventories and several others including Nigeria are in the process of joining the crusade Tele: E-mail addresses: inidennis117@yahoo.com © 2012 Elixir All rights reserved Effects of biomass burning on soil properties and air quality under slash-and- burn agriculture Ini D. Edem 1,* Oliver A. Opara-Nadi 2 and Christiana J. Ijah 3 1 Department of Soil Science, University o f Uyo, P.M. B.1017, Uyo, Akwa Ibom State, Nigeria. 2 Department of Soil Science, Abia State University P.M.B. 2000 Uturu. 3 Department of Soil and Environmental Sciences Akwa Ibom State University, Obio Akpa. ABSTRACT Changes in soil properties, soil organic C (SOC) and total nitrogen (TN) stocks associated with different heating temperatures from 50, 100, and 150 kg/m 2 dry biomass that provided for different heat intensities were compared with natural soil temperature of arable land adjacent to the burnt plots. Soil samples were collected in three replicates from control and burnt plots and soil temperatures were measured with soil thermometer placed at surface and sub-surface layers, while gas emissions were measured with sensitive gas dictators. The induced temperatures were highly variable at the soil surface whereas below 15cm depth, the temperature rise was not more than 37 0 C. Modifications of various soil physico-chemical parameters caused by fire were related to increasing temperatures. The passage of fire promoted SOC and TN stocks, mean weight diameter, the aggregation of 2 mm stable structures which become even more resistant to disrupting action of water. The pH decreased to 5.4 at higher temperatures following burning before ashes mineralized. However, both organic matter and ECEC increased at increasing soil temperature. Potassium content remained surprisingly constant as the soil temperature increased. Air quality measurement revealed that NO 2 , SO 2 H 2 S and CO 2 were above the limits indicating air pollution through these activities. Despite the merits of quick release of occluded nutrients, heating temperatures of slash-and-burn method of land clearing altered soil and air quality. © 2012 Elixir All rights reserved. ARTICLE INFO Article history: Received: 19 September 2012; Received in revised form: 11 November 2012; Accepted: 16 November 2012; Keywords Slash-and- burn, Traditional farming, Soil quality, Modification, Gas emission. Elixir Agriculture 52 (2012) 11555-11564 Agriculture Available online at www.elixirpublishers.com (Elixir International Journal)