* Corresponding author e-mail: prof.lai2014@gmail.com © 2021 NSP Natural Sciences Publishing Cor. J. Rad. Nucl. Appl. 6, No. 2, 109-114 (2021) 109 Journal of Radiation and Nuclear Applications An International Journal http://dx.doi.org/10.18576/jrna/060203 Measurement of Natural Radioactivity in Samples of Fertilized and non-Fertilized Soils in Different Areas of Tikrit, Iraq Khalid Abdullah Muhammad Ali 1 , Laith Ahmed Najam 2* and Farid Majeed Mohammed 1 1 Department of Physics, Faculty of Science, Tikrit University, Iraq. 2 Department of Physics, Faculty of Science, Mosul University, Iraq. Received: 11 Jan.2021, Revised: 4 Feb.2021, Accepted: 23 Mar.2021. Published online: 1 May. 2021. Abstract: The current study aims to measure and calculate the concentrations of natural radioactive elements (226 Ra, 232 Th, 40 K) in samples of fertilized soil and non-fertilized soil in different areas of Tikrit, the administrative center of Salah al-Din Governorate. The measurement was carried out using a gamma-ray spectroscopy system connected with a scintillation detector crystallized by NaI (TI). The results were obtained, and the average concentrations of natural radioactive elements ( 226 Ra, 232 Th, 40 K) were (11.24 ± 0.455 .  −1 ,23.65 ± 1.305 .  −1 , 291.52 ± 9.814 .  −1 ) on the Respectively in fertilized soil samples. The average concentrations of natural radioactive elements in un fertilized soil samples amounted to (5.28 ± 0.216 .  −1 , 11.82 ± 0.617 .  −1 , 154.17 ± 5.253 .Kg -1 ), respectively. Thus, all the results in the samples under study that we obtained are less than the global average recommended by the International Atomic Energy Committees at the United Nations, and accordingly, the areas under study are safe and do not pose a source of danger to the environment. Keywords: fertilized soil, non-fertilized soil, natural radioactive element concentrations. 1 Introduction The radioactivity that emits nuclear radiation from radionuclides has become the important part of life, because it entered the food chain for our food and our health, and it has many agricultural, medical, industry and energy production applications [1]. Previous studies and research indicated that there are three types of emitted radiation, which are gamma rays, alpha and beta particles [2]. According to the sources of radiation, the radioactivity is of two types. As for the natural radioactivity, it occurs to the heavy elements whose atomic number is( Z> 82) ., except for potassium ( 40 K) and carbon ( 14 C), which are among the light elements. Or industrial radioactivity that can be made in laboratories, after bombarding certain nuclei with charged particles or neutrons [3]. The natural radioactivity resulting from the emission of gamma rays depends on the geology of the environment, the quality of the soil, and the geographical conditions of that environment [4]. The radioactivity of the components of the Earth's crust is caused by the presence of natural radioactive chains, such as the uranium ( 238 U) series radioactive thorium ( 232 Th) series, as well as the radioactive uranium ( 235 U) series, in addition to the presence of the radioactive potassium ( 40 K) element, which is present alone [5]. Natural radioactive materials represent one of the most important sources of human exposure to radiation, although these materials contain low levels of the natural background radiation, but the cumulative dose may affect human health [6]. The radioactivity in the soil depends on the radioactivity in the rocks from which the soil was formed (the origin of the soil), and on the total activities that occurred to form the soil. Or inhaling suspended particles from them in the air and transported by winds to different distances and directions, or indirectly through the transmission of radiation through eating food and drinks containing radioactive contaminated materials [7]. The agricultural production process includes a wide range of soil exposed to different radiation sources. In the end, the soil is a vital guide to any radiological risk posed to humans in the near future [8,9]. Adding fertilizers with a wide range, especially phosphate fertilizers, to agricultural soils increases the amount of natural radionuclides present in them [10,11]. Thus, agricultural crops are radioactively contaminated, they may be directly or indirectly with natural and artificial radionuclides. Therefore, all this and consumption of them increases the internal radiation dose and the average annual effective dose [12]. One of the most important factors affecting dose determination of human exposure to radionuclides across the food chain in a contaminated location is the transport factor (T.F) for