## 4 Discussion
\begin{tabular}{c} 13.30 \(\pm\) 1.00 \({}^{\text{d}}\) \\ 100 \({}^{\text{d}}\) \\ 19.00 \(\pm\) 1.00 \({}^{\text{b}}\) \\ 19.85 \(\pm\) 5.00 \({}^{\text{c}}\) \\ \end{tabular}  \\ \hline \multirow{4}{*}{16} & \multirow{2}{*}{ \begin{tabular}{c} Tillage \\ No-tillage \\ LPD \\ No-tillage \\ LPD \\ \end{tabular}  } & \begin{tabular}{c} HPD \\ LTD \\ \end{tabular}  & \ \begin{tabular}{c} 245.70 \(\pm\) 4.00 \({}^{\text{c}}\) \\ 301.60 \(\pm\) 7.00 \({}^{\text{e}}\) \\ 206.50 \(\pm\) 4.00 \({}^{\text{a}}\) \\ 67.43 \(\pm\) 4.00 \({}^{\text{f}}\) \\ 231.90 \(\pm\) 7.00 \({}^{\text{b}}\) \\ 63.42 \(\pm\) 5.00 \({}^{\text{e}}\) \\ \end{tabular}  &
\begin{tabular}{c} 0 \({}^{\text{a}}\) \\ 100 \({}^{\text{d}}\)oxidation, thus disrupting the uptake of phosphate [63]. Moreover, some studies have suggested the direct involvement of ROS during allelochemical treatment. For example, polyphenols are responsible for forming superoxide anions [64], hydroxyl radicals formed by donating electrons to molecular oxygen [65], which in turn rapidly change the cellular components, including DNA and proteins, and alter membrane permeability. Some phenolic compounds, such as benzoxazinoids, have been found to have a deleterious effect on nucleic acids and other cellular components such as ribosomes and mitochondrion [66, 67]. Similarly, BOA, an important allelochemical from _S. cereale_ extract, has been reported to have inhibitory effect on plant growth by enhancing peroxidase activity and regeneration of H\({}_{2}\)O\({}_{2}\), and it has also been reported to increase lignin content in the cell by increasing the rigidity of the cell wall [68]. On the other hand, benzoxazolinone is known for its antitoxin activities and effectively blocks lateral root formation in seedlings [67]. The effect of _S. cereale_ biomass on the growth of grass and broadleaf weeds were evaluated in conventional tillage and no-tillage systems. A significant difference was observed in the biomass of weeds when the seeding rate of cover crops increased from 8 to 16 kg ha\({}^{-1}\) in the no-tillage field with the LPD system. The primary reason the increased biomass of cover crop was to enhance the allelopathic effect on weeds. The results of this study support the hypothesis that an increase in the biomass of cover crop enhances the allelopathic effect on grass and broadleaf weeds. In the present study, we observed an increment in the inhibitory effect with the increase in cover crop biomass. Previously, [PERSON] et al. [69] and [PERSON] et al. [70] also described higher inhibition of weeds by increasing the biomass of cover crops. In the present study, complete inhibition of broadleaf weeds in both high plant density (HPD) and low plant density (LPD) of the cultivating crops (_Perilla_) was found when the amount of cover crops was doubled. However, this change was not observed in the case of grass weeds. Higher resistivity of grass weeds on _S. cereale_ biomass has been reported by [PERSON] [71], [PERSON] and [PERSON] [72], and [PERSON] et al. [54]. The results of this study agree with the previous studies, in which the inhibitory effect of _S. cereale_ on grass weeds was weaker than on broadleaf weeds [54]. [PERSON] et al. [54] attributed the wide range of variation in the inhibitory effect of _S. cereale_ extracts with the variability of allelochemical composition in the cover crops. Inhibitory percentages of weeds by the _S. cereale_ cover crops were higher on broadleaf weeds than on grass weeds. Complete inhibition of broadleaf weeds was achieved by increasing the seeding density of cover crop. One of the possible reasons for this could be that broadleaf weeds are highly sensitive to the allelochemicals present in the _S. cereale_ extracts compared to grass weeds. This is in agreement with a previous report by [PERSON] et al. [73]; they found the dry weight of weeds decreased linearly with an increase in seeding rate of cover crops of legumes and oats. However, [PERSON] et al. [74] reported that the cover crop density negatively influenced the weed density.