Efecto de la defoliación sobre rendimiento de forraje y grano en Tinopiro

World grain production relies largely on annual crops, which are associated with a high dependence on external inputs and environmental impacts. In this context, perennial crops have emerged as an alternative pathway more sustainable production systems, with intermediate wheatgrass (Thinopyrum intermedium) standing out as a dual-purpose perennial grass with potential for producing grain suitable for human consumption and forage. The decline in grain yield over time represents the main challenge for its adoption, and intra-plant competition has been proposed as one of its main causes. The management of defoliation intensity could modify intra-plant competitive relationships; however, its effect has not yet been studied in this species at the individual plant level and under local conditions. In this context, the objective of this study was to understand how defoliation intensity influences productive responses through modifications in plant structure in intermediate wheatgrass. An experiment was conducted at the “Mario Alcides Cassinoni” Experimental Station (EEMAC), located in Paysandú, Uruguay, from April 2025 to January 2026. The experiment was conducted in outdoor pots under a completely randomized design (CRD), with three defoliation intensity treatments (residual heights of 5, 10, and 15 cm) and twelve replications, with the individual plant within each pot serving as the experimental unit. The different defoliation intensities did not affect the morphogenetic traits evaluated during regrowth (leaf appearance rate and leaf elongation rate), with phyllochron values ranging from 128 to 135 °Cd. During this period, more intense defoliation promoted higher growth rates, whereas the lowest defoliation intensity tended to result in a higher tillering rate. Throughout the reproductive period, differences in tiller dynamics were observed only for reproductive tillers, with the 15 cm treatment showing the highest number. Although these differences were not maintained in absolute terms at harvest, they were maintained proportionally relative to the total. The 10 and 15 cm defoliation treatments resulted in higher grain yield than the 5 cm treatment, although this was not reflected in the harvest index (HI), which averaged 0.13. The 10 cm treatment also showed greater lamina biomass in reproductive tillers. Among the yield components evaluated, individual spike and spikelet yield was greater under the 10 cm treatment, whereas no differences were detected in thousand-grain weight. At the belowground level, the least intense treatment (15 cm) resulted in greater root biomass production. Defoliation intensity applied during the vegetative stage in the first year of plant development modifies plant responses throughout the growth cycle, affecting the rate of biomass production during regrowth, plant structure at harvest, grain yield and its components, as well as root biomass production.