## 4 Discussion
In the present study, we found that, in the _Perilla_ cultivating field, the HPD system reduced the weeds (grass and broadleaf) by 40% compared to the LPD. However, the result indicated that the grass weed density remained higher in both HPD and LPD systems. The present study indicated that _S. cereale_ contains allelochemicals that can inhibit the growth of weeds selectively, and this varies widely in tillage and no-tillage systems. Therefore, the higher inhibitory properties of _S. cereale_ on both grass and broadleaf weeds can be used for mitigating the weed problems in _Perilla_ fields as well as for sustainable weed management in organic farms by reducing the use of herbicides. Different tillage or no-tillage systems affect the soil structure, nutrients, water retention potential, pH, and temperature [75], and it causes significant variations in the germination, growth density, and composition of weeds [76, 77]. The result of this study indicated that an increase in the _S. cereale_ biomass significantly increased the weed suppression rate in the no-tillage system. It has been reported that the no-tillage system has a better water and soil conservation system and produces more cover crop biomass, which directly influences the weed suppression rate [78]. According to [PERSON] et al. [79], cover crops in combination with no-tillage further improves the soil structure, and the soil integrity and number of biological pores increased, which ultimately upgrades the soil's hydraulic behavior [80]. [PERSON] et al. [81] observed a faster infiltration of applied water in the no-tillage and cover crops system compared to the tillage and cover crops system. [PERSON] et al. [PERSON] et al. (2013) studied the increased infiltration of water via macropores created by earthworms, which could maintain the continuity of soil pores in the different horizons in the no-tillage and cover crops system [PERSON] et al. (2014). Contrarily, a lower infiltration of water in the tillage system is often caused by the disruption of pore continuity and destruction of the large soil aggregates, which results in particle slaking and pore clogging [PERSON] et al. (2015). An increase in the concentration of phenolic compounds in mulches of cover crops was correlated to a strong inhibitory effect on weeds [PERSON] et al. (2015). Moreover, high levels of phenolic compounds such as \(p\)-coumaric acid, ferulic acid, vanillic acid, salicylic acid, and \(p\)-hydrobenzoic acid were reported in the decomposed residue of \(S\). _cereale_, indicating that the presence of a higher biomass in the fields would increase the allelochemical concentration and suppress weed growth [PERSON] et al. (2015); [PERSON] et al. (2015). However, the presence of these allelochemicals in the soil alone is not sufficient to explain the inhibitory effect of \(S\). _cereale_ extracts on weeds tested in the field. Microbial metabolism is an important factor for the degradation or accumulation of allelochemicals in the soil, which influences the allelochemical's effect on the weeds [PERSON] et al. (2015); [PERSON] et al. (2015). The results indicate that the synergetic effects of these compounds in the presence of other competitive variables are an important factor for weed control. Further research is required to support the evidence of the synergetic effects of the phenolic compounds and the role of microbial metabolism under field conditions. [PERSON] contributed by carrying out the experiments and writing the manuscript. [PERSON] supervised the experiment. [PERSON], [PERSON] and [PERSON] contributed by analyzing phenolic compounds and editing of the manuscript. This research received no external funding. This work was supported by funding from the KU research professor program. The authors declare that they have no conflict of interest.