Hindawi Publishing Corporation ISRN Soil Science Volume 2013, Article ID 707569, 7 pages http://dx.doi.org/10.1155/2013/707569 Research Article Effects of Unburned Lime on Soil pH and Base Cations in Acidic Soil Athanase Nduwumuremyi, 1,2 Vicky Ruganzu, 1 Jayne Njeri Mugwe, 2 and Athanase Cyamweshi Rusanganwa 1 1 Department of Natural Resource Management, Rwanda Agriculture Board (RAB), P.O. Box 5016, Kigali, Rwanda 2 Department of Agricultural Resource Management, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya Correspondence should be addressed to Athanase Nduwumuremyi; nduwatha@gmail.com Received 11 August 2013; Accepted 1 October 2013 Academic Editors: R. Ciccoli, W. Ding, W. Robarge, and J. hioulouse Copyright © 2013 Athanase Nduwumuremyi et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Sustainable agriculture is threatened by the widespread soil acidity in many arable lands of Rwanda. he aim of this study was to determine the quality of unburned limes and their efects on soil acidity and base cations in acidic soils of high land of Buberuka. he lime materials used were agricultural burned lime and three unburned lime materials, Karongi, Musanze, and Rusizi. he test crop was Irish Potato. All lime materials were analyzed for Calcium Carbonate Equivalent (CCE) and Fineness. A ield trial in Randomized Complete Block Design was established in 2011 at Rwerere research station. he treatments comprised of the four lime materials applied at four levels: 0, 1.4, 2.8, and 4.3 t ha −1 of CCE. Soil cations (Ca 2+ , Mg 2+ ,K + , and Na + ) were determined by extraction method using atomic absorption spectrophotometer for Ca and Mg and lame photometer for K and Na. he Al 3+ was determined using potassium chloride extraction method. Experimental soil baseline showed that the soil was very strongly acidic (2.8 cmol kg −1 Al 3+ ). he unburned limes were signiicantly ( < 0.001) diferent in terms of CCE and ineness. A higher CCE was recorded in agricultural burned and Rusizi unburned limes (86.36% and 85.46%, resp.). In terms of ineness, agricultural burned and Musanze unburned lime were higher (70.57 and 63.03%, resp.). Soil acidity signiicantly afected from 4.8 to 5.6 pH and exchangeable Al reduced from 2.8 cmol kg −1 to 0.16 cmol kg −1 of Al 3+ . Similarly all cations afected by unburned limes application, signiicantly ( < 0.001) Ca saturation increased from 27.44 to 71.81%, Mg saturation from 11.18 to 36.87% and signiicantly (< 0.001) Al saturation reduced from 58.45 to 3.89%. he increase of Mg saturation was observed only with Karongi unburned lime application. his study recommends therefore, the use of 2.8 t ha −1 of CaCO 3 of Rusizi or Musanze unburned lime as alternative to the agricultural burned lime for improving soil acidity and base cations in acidic soils. 1. Introduction he constraints of sustainable agriculture can be partly attributed to continuous cropping, soil acidity [1], and inadequate soil fertility management [2]. he sustainable agriculture is threatened by widespread acidity in many parts of the tropical region, and applications of lime [3] to these soils have been reported to signiicantly improve soil fertility. Acidity afects the fertility of soils through nutrient deiciencies (P, Ca, and Mg) and the presence of phytotoxic nutrient such as soluble Al [4]. he population pressure in Rwanda triggers subsistence agriculture and is being continuously done on hills and mountains, while soil acidity is covering about one third of arable soils [5]. To feed the growing population, exploitation of all agricultural resources for sustainable agriculture and soil fertility improvement are the most important interven- tions to rely on. he efect of lime is long lasting but not permanent [6]. When values of exchangeable Ca 2+ , Mg 2+ , and pH fall below optimum levels for a given crop species, liming should be repeated. he base enrichment especially of Ca 2+ ions in soil will neutralize exchangeable Al [7] thus enhancing root growth. he base cations include K, Ca, Mg, and Na, and the base saturation is the proportion of the CEC