In this article, we report on the biodegradation of soy-protein-grafted polyethylene, which was successfully synthesized by a graft copolymerization method with benzoyl peroxide as the radical initiator. The biodegradation behavior of the grafted Polyethylene was ascertained by a soil burial test. The weight-loss percentage was measured as a function of the number of days, and it was observed that the percentage weight loss increased with increasing number of days. To further substantiate the degradation, microanalysis of the soil containing the samples was carried. out. An increase in microorganism colonies was observed with increasing number of days. The hydrolysis of the samples taken from the soil after a specified number of days also corroborated the findings and revealed a continuous loss of weight. The effect of the degradation of the grafted samples on the growth of plants (wheat and soybean) was studied, and we observed that the products of degradation were not harmful to the growth of the plants. (c) 2008 Wiley Periodicals, Inc. J Appi Polym Sci 111: 2460-2467, 2009