Effect of irrigation water salinity and cutting age on the components of biomass of Echinochloa pyramidalis

The objective was to evaluate the effect of salinity of irrigation water and different cutting ages on the biomass components of Echinochloa pyramidalis. Seedlings were planted in plastic pots (volume of 8 L) with sandy-textured Quartzarenic Neosol, under greenhouse conditions. The design was completely randomized in split plots with salinity levels (0.75, 2.0, 4.0, 6.0 and 8.0 dS m-1) in the main plot, and cutting ages (21, 28, 35, 42 and 49 days) in the subplots, with five replicates. After the standardization cut, the dry masses of total forage, dead forage, live forage, green leaf blade, green stem and ratios of live material/dead material and leaf/stem were determined. There was no interaction between the factors studied. Salinity decreased the dry masses of total forage, green leaf blade and green stem. Salinity had no effect on the dry masses of dead forage or ratios of live material/dead material and leaf/stem. Salinity changed the partitioning of dry matter, reducing the percentage of stems, and increasing the percentage of leaves in the dry mass of total forage. The advance in the cutting age caused increases in the dry masses of total forage, dead forage, live forage, green stem and green leaf blade. From the cutting age of 28 days, dead forage dry mass had a very sharp increase. The increase in stem dry mass rose from the 35th day. The extension of the cutting age promoted a decline in the live material/dead material and leaf/stem ratios. The cut of Echinochloa pyramidalis at 21 days, when it presents the best leaf/stem ratio is recommended.