AimWe aim to find a simple agricultural waste processing method to improve soil water retention and soil enzymes vitality, control soil-borne pathogens, and enhance plant resistance against biotic stress.MethodsWe extracted polysaccharides from different agricultural wastes. We tested the antimicrobial activity of the extracted polysaccharides on different soil-borne pathogens and the effect of the addition of these polysaccharides on the soil water status and soil enzymes. Besides this, we investigated the efficiency of the peanut shells polysaccharides in improving tomato growth and defense under Fusarium solani and Ralstonia solanacearum infection in a greenhouse study.ResultsResults showed the efficiency of all extracted polysaccharides as antimicrobial agents against different soil-borne pathogens. In addition, all polysaccharides increased the soil water holding capacity by about 116% more than that in the non-treated soil and increased the water retention to reach about 30% after eight days, besides their positive role in improving the soil enzymes, which improves the soil health. The peanut shells polysaccharides, which are the best ones as antimicrobials and soil amendments, showed interesting improvements in tomato growth under normal and pathogen infection conditions. The polysaccharide treatment decreased the bacterial and fusarium wilt in tomato plants, and induced resistance mechanism through up-regulating secondary metabolism defense compounds defense enzymes such as phenylalanine ammonia-lyase, and antioxidant enzymes detoxify the oxidative stress markers.ConclusionPolysaccharides from agricultural wastes can be a promising soil amendment to improve the soil properties and so improve plant growth and defense mechanism against pathogen infection.