Abstract: The present study aims to improve the efficiency of nitrogen fertilizer applied to soil by reuse of date palm by-products after grinding and mixing with sandy loam soil. The date palm by-products collected from different areas, then air dried and grinded. Two fractions selected (i.e., less than 0.5 and 1-2 mm size). The powder mixed with sandy loam soil at the rates of 0.0, 1.0, 2.5, 5.0, 7.5 and 10.0% (w/w). The treated soil incubated at field capacity in plastic container for 30 days. After the incubation period, the soil was air dried and passed through a 2.0 mm sieve. The physical and chemical analyses of sandy loam and treated soils performed. The PVC transparent columns with of 6.0 cm diameter and 30.0 cm length packed with sandy soil at 1.6 g cm-3 soil bulk density to 20 cm depth and then a 5 cm surface layer of treated soil applied. The soil columns arranged as follows: 1) size fraction of date palm by-product, 2) the rate of date palm by-products applications and 3) rate of water applied (5 and 10 pore volumes). The fertilizer applied at the required rate (250 mg L-1) to soil surface and then the water applied at required rates (0.2 and 0.4 cm min-1). The leachate out of soil columns received. Volume of leachate and concentration of NO3 was determined. At the end of experiment, the soil was cut to 2.5 cm slices for determining the soluble NO3. Total NO3 in soil and percolate were calculated and then the loss of fertilizers and fertilizer use efficiency calculated under the experimental conditions. The results showed that increasing the rate of date palm by-products reduced the NO3 in leachate and increased NO3 in soil columns. In addition, increasing water application rate increased fertilizers loss in the leachate. The fine fraction of date palm by-products reduced the NO3 leaching out of soil by about 14.86 and 5.90% for low and high water application rate, respectively in case of fine fraction, reduced nitrate losses. The corresponding values for coarse fraction were 9.73 and 4.35%, respectively. According to the present results, it is possible to reuse the date palm by-products for increasing the fertilizers use efficiency and reduces the problems of groundwater pollution and accumulation of these by-products in farm.