[en] A field experiment was carried out at the Plant Nutrition and Fertilization Unit, Soils and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Inshas, Egypt on wheat and chickpea inter cropping. The Objective of this current work is to study Organic matter decomposition under clean agriculture system in sandy soil using nuclear technique. The lowest portion of nitrogen derived from fertilizer was resulted from application of compost and chickpea straw treatments. It is worthy to mention that full recommend dos of fertilizer (20 kg N fed-1) was efficiently used by shoots of chickpea plants. Portion of nitrogen derived from fertilizer by seeds of chickpea was lower than those recorded with shoots. Generally, there was no big significant difference between nitrogen gained by shoots and seeds from the organic materials. This holds true with all treatments. More declines in nitrogen derived from soil percentages were resulted from application of cow manure and compost treatments under different rate of mineral fertilizer, the application 100% MF treatment induced higher nitrogen derived from soil pool as compared to the other treatments. The best value of nitrogen derived from air was detected followed by compost, while the lowest value was recorded with wheat straw. In general, nitrogen derived from air by shoots lower than those up taken by seeds of chickpea plant. Application of wheat straw and compost treatments were enhanced the nitrogen derived from fertilizer by straw of wheat plant as compared to caw manure, maize stalk, chickpea straw, but Ndff% in grains of wheat , cow manure and maize stalk increased as compared to the other treatment. Application of organic materials, chickpea straw and cow manure achieved the highest value of Ndfo% by straw of wheat plant as compared to maize stalk, compost and wheat straw. But values of nitrogen derived from organic in grains of wheat plants, the application of chickpea straw and wheat straw increased as compared to other treatments. The highs percentages of nitrogen derived from soil in wheat were recorded when the maize stalk was added , compared to the other treatment reached to 3.3 % in wheat straw corresponding to 1.9 % in grain with application of cow manure treatment . This hold true with both straw and grains. The portion derived to straw was much more than that derived to grains