Evaluation growth and yield of wheat in competition with different densities of three species of Phalaris spp.

Because of morphology similarity and the same growth needs of Phalaris with wheat, this weed imposes the highest yield loss in wheat production to farmer. Phalaris is one of the important weeds in autumn wheat cultivation in Khuzestan, Fars, Golestan and Mazandaran provinces, especially. The results of the research indicate that exhibit different behavior by different species of the same genus of plant in the same conditions, irrespective of crop or weed. Therefore, this present study was carried out to appraise yield losses in wheat caused by the interference of three space of the phalaris in different weed density.

An experiment was conducted in a completely randomized block design with split plot arrangement of treatments with three replications at Golestan east during 2019-2020 and 2020-2021 growing season. The treatments were three Phalaris spp. (P. brachystachys, P. minor and P. paradoxa) (as main plot) and five weed densities (0 (control), 10, 30, 50 and 100 plant. m-2) (as subplot).

Based on the results, in the first and second growing season, the lowest dry weight of wheat in competition with density of 100 plants per m2 of the P.‬brachystachys was estimated at 589.61 and 758.77 g/m2, respectively. Also, in the growing seasons, the minimum leaf area index was estimated in competition with P. brachystachis, by 2.87 and 2.77, respectively. The maximum wheat yield was estimated at 4679 and 5102 kg ha-1, respectively, under weed-free condition, in the first and second growing season. On the other hand, in both experimental years, the estimated grain yield loss due to the presence of the first weed, was not significant difference in competition with different Phalaris species. Therefore, according to the results wheat grain production in competition with Phalaris has an inverse relationship with increase in weed density. Also, maximum yield loss due to the presence of Phalaris, regardless of the type of space, will occur at a density of more than 100 plants per m2. Too, there was no significant difference between harvest index (37-40%) in experimental plots.

Generally, more affected the growth and yield of wheat compared to Phalaris by the competition intensity and weed density. Thus, increasing weed densities and subsequently increasing the competitiveness of the studied Phalaris species, was imposes significant changes on growth characteristics, some yield components and wheat yield. According to regression analysis, there was a significant decrease in wheat yield with increasing the weed density. Estimation showed that maximum crop yield loss will occur in competition with densities above 100 plants per m2 of Phalaris.