Three weedy grasses, Echinochloa crus-galli (L.) P. Beauv. Echinochloa colona (L.) Link. and Echinochloa stagnina (Retz.) P. Beauv. were grown for four months in the greenhouse of Botany Department , Faculty of Science at New Damietta to examine the effect of age on plant biomass, ash, proteins, total carbohydrates, lipids and fiber content. Plants were collected from the field and replanted in greenhouse, with the same age and size. Biomass and ash content increased by increasing the age in E. colona and E. stagnina but increased in E. crus-galli till the fourth harvest then decreased. Protein, crude lipid and crude fiber content were decreased gradually by the increase of the age, in the three species throughout the progressive harvests. By the increase of the age total carbohydrates increased in E. crus-galli and E. colona but remained largely unchanged in E. stagnina. The crude fiber was a relatively high in E. crus-galli and E. colona but this was not good for forage use of the grass. The amount of PEPC and Rubisco protein was higher in E. stagnina than in E. crus-galli and E. colona and this lead to increase in plant biomass of E. stagnina than E. crus-galli and E. colona. It is recommended using E. stagnina as fodder additives due to its high content of protein and biomass and low fiber content.
The obtained results will be useful for the optimum managing strategy of these three grasses as invasive weeds in field crop as well as use them as a source of natural forage in particular in summer.