Abstarct: Considering the importance of nanotechnology in various industries, this thesis was conducted in two main parts: one of them in the field of agricultural applications and the other one is in tributary of nanocomposites. For the first part that has conducted in collaboration with the department of Agriculture of University of Shahrood, calcium nitrate fertilizer was milled mechanically. Then the effect of calcium nitrate fertilizer preparation was studied on the amount of calcium absorption in tomatoes and peaches, as two sample plants. The results were very promising and the amount of calcium absorption and the shelf life were increased significantly. The purpose of the second part was synthesis of Al-Al2O3 and Al-SiC nanocomposites with high mechanical strength which were also as light as aluminum. To do this, Al2O3 and SiC industrial powders were milled at different times by making a use of a high-energy planetary ball mill to achieve different distribution in the size of nanoparticles. Then, the milled samples were added to the Aluminum matrix, with the same volume percent of Aluminum and were milled mechanically during equal times. Finally, the Vickers hardness test has investigated the effect of reinforcing phase milling time on the hardness of Aluminum-baxsed nanocomposites. These researches have indicated that the milling of reinforcing phase, has a considerable effect on the hardness of Aluminum-baxsed nanocomposites especially in its early hours.