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Background: Weeds reduce water use efficiency in crops due to water used by the weed and to the reduction in crop yield. In addition to the usual presence of weeds in the interrow of different crops, the management of these plants has moved away from the idea of total control. Thus, the amount of water lost through the evapotranspiration of weeds (ETW) must be understood. Objective: Determine the water use and crop coefficient (Kc) of the weed species Commelina diffusa, Cyperus rotundus, and Cynodon dactylon using drainage lysimeters associate with the Normalized Difference Vegetation Index (NDVI). Methods: The experiment was carried out at the Lysimetric Station of the Federal University of Viçosa, in Viçosa-MG, in a randomized block design, with four treatments and four replicates. Reference evapotranspiration (ETo), necessary to calculate Kc, was obtained in situ through lysimeters cultivated with Paspalum notatum. Results: The highest Kc values were found in the final third of the experimental cycle, equal to 1.32, 0.93, and 0.90 for C. diffusa, C. rotundus, and C. dactylon, respectively. The NDVI showed a good correlation with Kc and biomass, with R2 ranging from 30.9 to 54.6% and from 46.1 to 63.1%, respectively. Accumulated ETW values ranged from 336 to 473 mm, with C. diffusa showing the highest water consumption, followed by C. rotundus and C. dactylon. Conclusions: C. diffusa has higher Kc and water consumption than C. rotundus and C. dactylon. NDVI can be used in the estimation of the Kc and biomass of weeds. |
