Influence of Various Densities of Wild Oat and Holy Thistle on the Productivity of Wheat (Triticum aestivum)

Weed competition is one of the major biotic constraints to wheat crop productivity. Avena fatua L. and Silybum marianum (L.) Gaertn. are among the worst weeds of wheat crop throughout the world, greatly deteriorating the quality of wheat and subsequently reducing its market value. In this context, experiments were conducted in two years, 2018 and 2019. Different seeding rates of wheat (80, 100, 120, and 140 kg ha⁻¹) and different sown weed ratios (A. fatua: S. marianum; 1:8, 2:7, 3:6, 4:5, 5:4, 6:3, 7:2, 8:1, and 0:0) were investigated. The weed ratio and wheat densities were indirectly proportional. However, wheat seed at the rate of 140 kg ha⁻¹ had minimal weed interference. Yield losses were 17.5% at weed density 1:8 and 7.2% at 8:1. However, in terms of wheat density, the highest percent losses were computed at 80 kg ha⁻¹, while the lowest were recorded at 140 kg ha⁻¹. Due to the large leaf canopy of S. marianum, it is not possible for other species to sustain. Hence, it has been concluded that S. marianum is the main factor causing reduction of yield-related parameters, followed by A. fatua and the other weeds. Due to the morphological mimicry of wheat crop by A. fatua during the vegetative growth stage, it cannot be easily distinguished from wheat. Therefore, managing A. fatua and S. marianum before seed setting is recommended for reducing the future weed problem. Based on current studies, it is suggested that sowing wheat seed at the rate 140 kg ha⁻¹ is recommendable to better compete with all the field weeds.