| Sumario: | Greenhouse studies were conducted to evaluate the growth response of itchgrass to water stress. Itchgrass plants produced the greatest aboveground biomass and seeds at 75% of field capacity and these parameters at 50 and 100% of field capacity were similar. With further increase in water stress, seed production was sharply reduced, but itchgrass was still able to produce an average of 63 and 9 seeds plant−1at 25 and 12.5% of field capacity, respectively. Itchgrass plants responded to increasing water stress with increased leaf weight ratio; it was 2.5 times greater at 12.5% of field capacity than at 100% of field capacity. In another study, compared with daily irrigation, intervals of 9 d between irrigations reduced aboveground biomass of itchgrass by 27% and 12-d intervals reduced aboveground biomass by 67%. Compared with the daily irrigation regime, itchgrass seed production was reduced by 61% at intervals of 12 d between irrigations; however, the weed plants produced a considerable number of seeds (153 seeds plant−1) at the 12-d intervals. The ability of itchgrass to produce biomass and seeds under water stressed conditions necessitates strategies that minimize weed survival while maximizing irrigation efficiency for the crop at the same time.
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