3264 Life Sci. Int. J., Vol: 9, (Issue, 1, 2, 3, & 4) Jan., April, July & Oct. 2015 Page: 3264-3269 EFFECT OF HUMIC ACID ON SOIL MICRONUTRIENTS UNDER DIFFERENT WET AND DRY CYCLES USING TWO SOIL SERIES Muhammad Iqbal Jakhro 1 , Gul Mohammad Panezai 2 , Sajida Parveen 2 , Mohammad Hashim Tareen 2 , Mohammad Saleem 2 and Sanaullah 2 1 Sindh Agriculture University Tandojam, Sindh, Pakistan 2 Agriculture Research Institute Quetta, Balochistan, Pakistan Email of Corresponding Author: iqbal.jakhro@gmail.com ABSTRACT The unavailability of micronutrients in calcareous soil is one of the major causes of low crop production. Humic acid extracted from low grade coal have exhibited potential for enhancing the availability of soil micronutrients. For this purpose a pot experiment was conducted at the department of Soil Science Sindh Agriculture University Tandojam during 2013 to study the effect of different levels of coal derived humic acid on soil micronutrients. The experiment was laid out in randomized complete design (factorial) with treatments of three factors (A, B and C) which were replicated thrice. Factor A was four humic acid levels (0, 5, 10 and 15 mg kg -1 ), factor B was two wet and dry cycles (first cycle-3 months and second cycle-6 months) and factor C was two soil series (Guliana and Missa). The results revealed that humic acids levels, wetting and drying cycles, soil type and their interaction were statistically highly significant. Amon the micronutrients, the greater Cu and Zn concentration (0.63 an 0.60 mg kg -1 ) were recorded at medium HA (10 mg kg -1 ) while, maximum Fe and Mn concentration (4.10 and 6.19 mg kg -1 ) were observed at HA (15 mg kg -1 ). While, Guliana soil series exhibited combatively higher concentration of micronutrients except Fe which was greater in Missa soil series. The first wetting and drying cycle showed higher concentration of micronutrients except Cu which was maximum at second wetting and drying cycles. So, it is suggested that coal derived humic acid can be used as potential source of soil amendment for enhancing soil fertility and productivity. KEYWORDS: humic acid, low grade coal, soil type, wetting and drying cycles, micronutrients INTRODUCTION One of the important components of high quality soil is organic matter which directly affects soil physical, chemical and biological properties and its presence in sufficient quantity is indispensible for sustainable crop production and friendly environment (Bloem et al., 2005). In tropical and sub-tropical areas of the world where high temperature results in high decomposition rate of soil organic matter affecting soil fertility and productivity with low crop growth and yield (Giardina et al., 2000; Steiner et al.,2007). In developing countries like Pakistan where inputs are in short supply and removal of crop residues for fuel and feed purpose further enhance the loss of organic matter in soil resulting in low yield. However, the enriched deposits of low rank coal containing humic acid are found in large quantities in Pakistan which can be used as a source of organic matter by extracting its humic acid contents (Hai and Mir, 1998) because it contain phenolic, acidic, amino and quinione groups which helps in the availability of nutrients in calcareous alkaline soil poor in organic matter. This has aromatic structure and is soluble in alkali because it is surrogated by carboxyl, phenolic, hydroxyl, and alkyl groups which are connected together through either linkage (Gaines et al., 1983). The application of coal-derived sodium humate under calcareous soil increased growth, yield and nutrient uptake of various crops (Van de Venter et al., 1991; Sharif et al., 2002 a,b; Sarir and Durrani, 2006; El-Nemr, 2012 and Daur and Bakhashwain, 2013). MATERIALS AND METHODS A pot experiment was conducted at the department of Soil Science Sindh Agriculture University Tandojam during 2013 to study the effect of different levels of coal derived humic acid on soil micronutrients. The study was aimed to evaluate the role of humic acid in releasing plant nutrient. The experiment was based on randomized complete design (factorial) with treatments of three factors (A, B and C) which were replicated thrice. The detail of the treatments is as under: