## 4 Discussion
pintoi_[51; 52; 53] that concurrently reduced weed growth in some tropical upland crops as well as improving soil fertility and erosion [53]. Moreover, plant-derived allelochemicals and their interactions of plants-weeds-soils-microorganisms may actively regulate and contribute to promoting crop yields [11; 54]. Thus, it is suggested that the allelochemicals and nutritional effects of _A. pintoi_ may help elevate rice yield in the current study. On the other hand, when competitive weeds are inhibited by this candidate material, rice plants will have more opportunities to absorb multi-nutrients, thereby providing an advantage for their own growth. However, the allelochemical decomposition and nutrient contents of _A. pintoi_ in paddy soils and their effects on rice production should be comprehensively investigated in future studies. In this study, we found that the field trials applying _A. pintoi_ materials did not provide the same level of dry weight inhibition as a synthetic herbicide and hand-weeding treatments, but rice yield was significantly promoted (Table 4). Therefore, it may be advantageous, because the remaining weeds can be managed by lower doses of herbicides [7]. Moreover, this legume grows abundantly in the tropic and subtropics, and farmers can easily collect a large amount; however, a dose of 200 g/m\({}^{2}\), which is equivalent to the amount of 2 tons/ha of dried plant materials, would require much time and fieldwork from farmers. There is a conspicuous question about whether adding doses of 100-200 g/m\({}^{2}\) of dried allebotatic plant materials into paddy fields may affect the growth of crops and weeds. In fact, our research team has conducted numerous field experiments using different dried plant materials at similar doses, but few plant species exhibited weed inhibition ability. Although the decomposition of plant materials can enrich soil fertility and promote crop yields, some potent allebotatic plant species with limited biomass resources are not feasible given the current trend of the declining labor force in agricultural production in many rice-producing countries [7; 11; 17]. Our findings suggest that _A. pintoi_ is a promising candidate plant that may contribute to developing effective bioherbicides for weed management in rice fields. Basically, the allebotatic responses depend on their released allelochemicals into the environment, which can be extracted by using suitable solvents to obtain high yields of potent phytotoxic substances (allelochemicals) [10; 34]. In this study, we used different solvents to obtain MeOH, hexane, and EtOAc extracts to determine phytotoxic activity and detect major allelochemicals of _A. pintoi_. Among them, phenolics are the largest class, with a vast number of reported phenolic allelochemicals. MeOH and EtOAc extracts revealed the highest TPC, but their inhibitory effects on the germination rate, root length, and shoot height of _E. crus-galli_ and _L. sativa_ were lower than those of the hexane extract. In contrast, hexane extract had the lowest TPC, but showed the most potent suppressing effects against the growths of tested plants (Table 5 and Figure 2). These results imply that phenolic compounds might not be the major allelochemicals in _A. pintoi_. However, nonpolar, volatile, and low molecular weight compounds in hexane extract might be the main factors corresponding to the phytotoxic responses of _A. pintoi_. These compounds are appropriately identified by GC-MS. Accordingly, methyl palmit is the most dominant compound detected in the hexane extract, which has been previously reported as an alleochemical with suppression against chlorophyll and antioxidant enzymes (superoxide and dismutase peroxidase) of weeds [55]. In addition, palmitic acid, the second most abundant compound detected in hexane extract, is a well-known weed inhibitor, which exhibited prevention on superoxide dismutase and chlorophylls a and b of weeds [56; 57; 58].