Sorghum germination inhibition using its water extract cultivated in swampland with different irrigation patterns

One of the allelopathic uses is the application of sorghum water extract for weed control. Drought-shaped abiotic stress plays an important role in the plant contribution of allelopathy. This study aimed to examine the inhibition of sorghum water extracts grown in swampland with different irrigation patterns. The study employed a randomized complete block designed with two factors. The first factor was irrigation patterns, i.e., four weeks of dry and saturated water, alternating weekly saturated and dry water for four weeks, and alternating weekly dry and saturated water for four weeks. The second factor was water extract concentration, consisting of 0%, 2.5%, 5%, 7.5 % and 10%. Dry Ultisol was assigned as a control treatment. The bioassay procedure was set up with 25 sorghum seeds per petri dish. Each petri dish was solved and incubated for four days with a 10 ml sorghum water extract from each of the above treatments. The results showed the highest germination inhibition levels were in the interaction between the dry patterns (dry swampland and dry Ultisol) at 7.5% of water extraction. Sorghum extract, grown in dry swampland, is a potential for good bioherbicide production.


Introduction
Weeds reduce crop yields, utilizing available resources such as water, nutrients, and growing space [1] and synthetic herbicides to manage weeds often done in modern productivity-oriented agriculture. The use of synthetic herbicides that are less profitable can cause environmental and health problems. According to [2], herbicides harm the environment. Thus, an appropriate weed control method in organic farming is needed.
Organic weed management is one way of controlling weeds in crop production systems. Environmentally friendly weed management is needed to overcome the problem of weed resistance to herbicides [3]. Furthermore, [4] the use of organic herbicides in plant derivatives is an alternative inorganic herbicide for weed control. Allelopathy is an environmentally friendly organic herbicide as an implication of weed management that can be as a tool to control weeds. Allelopathy is a way out to overcome weed problems in agricultural cultivation systems [1]. The allelopathic method can be used with allelochemicals to suppress weeds (as natural herbicides) and allelopathic plants as cover crops or mulch [5]. Reducing the dose of synthetic herbicides or replacing them with bioherbicides will lessen the impact on the environment and human health and minimize the expansion of herbicide-tolerant weeds. Using bioherbicides will benefit all stakeholders such as researchers, industry, extension workers, and growers to develop effective and environmentally friendly weed management strategies and lower the dependency on synthetic herbicides [6]. The application of allelopathy as a strategy for controlling weed in sustainable agricultural systems in developing countries is needed. However, to ensure that the allelopathic approach is successful, it must be simple and economically feasible. Weed control strategies that are environmentally friendly can be achieved by utilizing widely distributed and readily available local plants with an allelopathic potential [7]. Sorghum is a plant that produces allelopathy and has wide growing adaptations.
Sweet sorghum is a C4 plant [8]. Sweet sorghum could grow and easily adapted to various environmental conditions with limited inputs [9]. Sorghum plants have the potential as an alternative to replacing plants with low economic value. Sorghum also may be used as environmentally friendly energy sources, and for food needs [10].
Apart from being able to produce and adapt to a wide range of environments, sorghum also has allelopathy. According to [11], sorghum and sunflower are highly allelopathic plants capable of inhibiting other species' plants. Sorghum and sunflower have allelopathic compounds that are environmentally friendly and can suppress weed growth in cotton plants.There is an allelopathic content in various types of plants. Such an experiment [12] revealed different concentrations of aqueous extracts (5, 10, and 15 g /l) of three weeds significantly reduced the percentage of germination, but 15 g / l of M. officinalis extract resulted in Pirsabaq breeding failure. Bioherbicides in the form of sorgaab (sorghum water extract) can reduce weed density, fresh weight, and dry weight by 29%, 31%, and 27% compared to controls on wheat cropping. Spraying extracts derived from sorghum stems and leaves can increase wheat yield by 8% and 19% but causes inhibition of weed species Anagallis arvensis L., Fumaria indica L., and Medicago polymorpha L. [13].
Experiments carried out in the field, proving the role of allelopathy affects the agricultural ecosystem. According to [1], corn planted after sorghum has a significantly lower weed density (23.1%) and biomass (23.6%) than corn produced after fall. The application of environmentally friendly weed control involving two methods is better than a single. According to [1], the application of sorghum-based treatment (mulch and sorghum water extract) is most effective and significantly reduces the weed infestation of corn after the sorghum harvest. Furthermore, [11] reported that powder and water extract of sorghum and sunflower suppressed weed growth better than cotton plants' control treatment. In terms of allelopathic efficiency, sorghum plants are superior when compared to sunflower plants. Shoot and root water extract of Parthenium hysterophorus L at 5% concentration suppress weed growth. The higher the extract concentration, the higher the seed germination inhibition [14].
Allelopathy is environmentally friendly weed control in organic agriculture. One strategy to increase allelopathic traits is through genetic modification. The resulting allelopathy must be safe or non-toxic for both humans and the ecosystem and increase plant productivity at an affordable cost [15]. Some experiments reported that there was a relationship between the growing environment and the plant allelopathy content. Research related to the relationship between allelopathy with biotic and abiotic stress environment has been done; however research on allelopathy in settings stress, especially in the marginal swamplands, has not been carried out. The research will evaluate the water extract of sorghum grows in swamps with different irrigation patterns. This study aims to test the inhibition of sorghum water extract on seed germination under different irrigationpatterns.

Plant material
Water extract of sorghum var. Numbu planted in swampland four-week-olds that have undergone treatment namely wet for four weeks; wet one week and dry one week, repeated once; dry one week wet one week, repeated once; dry for four weeks; and Ultisol dry for four weeks (control). The leaves, stems, and roots were harvested air-dried for seven days, then in a hot air oven at 70oC for 72 hours. The dried plant were chopped 1-2 cm and grounded, and the powder used as an extraction material.

Water extract preparation
Dry powder of sorghum as much as 100 g (or 10% treatment) is immersed in a 1000 mL flask of distilled water and stirred for 24 hours using a shaker at room temperature. The extract then filtered through Whatman No. filter cloth and paper. 1 for removing fiber flakes. The extract was then put into a labeled beaker glass and stored in the refrigerator in dark conditions. Further concentrations (ie, 2.5%, 5% and 7.5%) of this extract were also prepared.

Bioassay with water extract on filter paper
The purpose of the study was to determine sorghum water extract on sorghum seed growth. Petri dishes with a diameter of 9 cm are coated with filter paper as a medium for germination. Sorghum seeds of 25 grains are planted in each petri dish with regular spacing and added with 10 mL extract at different concentrations (2.5%, 5%, 7.5%, and 10%) added per petri dish. Petri dishes then incubated in the growth chamber for four days. Each treatment was repeated 5 times.

Statistic analysis
The research design used in the bioassay test in the laboratory was a complete randomized block design with five replications. Data collected were analyzed statistically with SAS software. ANOVA analysis was continued by the Duncan test if there were significant differences between the means with P <0.05.

Results and discussions
The results of an analysis of variance, the growth of sorghum sprouts are in Table 1. The results of the study show that the treatment of irrigation patterns and the treatment of sorghum water extract concentration significantly affected all observational variables. There was an interaction between the irrigation pattern and the water extract concentration except for the dry weight of sprouts + cotyledons. The control treatment (extract concentration 0%), both in swampland and ultisols, produced higher regular sprouts than other interaction treatments ( Table 2). This result indicated that without the addition of sorghum extract, there was no seed germination inhibition.
In general, the higher the extract concentration, resulted in the lower the normal sprouts. At 2.5%, seed germination was inhibited, but normal germination was higher than 50%. In the 5% extract concentration treatment, seed germination was increasingly inhibited. At this concentration, the normal sprouts produced are below 50%. The aqueous extract at a concentration of 10% from all irrigation patterns inhibited sorghum seed germination. All sprouts produced were abnormal. Irrigation patterns in swampland land, mainly dry and dry Ultisol, have the highest seed inhibition than other irrigation patterns. These results indicate that to produce extracts with high inhibition, sorghum should be planted in swampland or in Ultisols with a dry irrigation pattern. These results indicate that sorghum planted in swampland or in Ultisols with a dry irrigation pattern produced high allelopathic content. However, the biomass produced from swampland with dry irrigation patterns was lower than other treatments.
The metabolic activities are not normal resulted in the lower regular sprout. High number of regular sprouts, on the other hand, indicate that seeds can carry out normal germination processes. Sorghum aqueous extract allelopathy plays an essential role in seed germination. According to [5], allelopathic compounds are released by plants into the environment through decomposition, washing, volatilization, and root exudates. The interaction of irrigation patterns and sorghum water extract concentration significantly affected the abnormal sprout variables ( Table 2). Interaction of dry irrigation patterns in the swamp and dry soil in Ultisol with 7.5% water extract concentration produced the highest abnormal sprout of 73% and 74%. The interaction of irrigation patterns with 0% extract concentration (control) resulted in lower abnormal sprouts than other treatments ( Table 2). These results indicate that the presence of allelopathy negatively affects seed germination. In general, the higher the concentration of water extract, the higher the normal germination rate. A water extract concentration of 7.5% with a dry irrigation pattern in swampland and dry Ultisol soil resulted in the highest abnormal sprouts. These results indicate that the irrigationpattern affects the efficacy of allelopathy. Allelopathy at a concentration of 7.5% had the most effect on sorghum seed germination. Sorghum water extract contains allelochemical compounds that affect the root growth of the target plant. According to [16], allelopathy is a secondary metabolite derived in the form of allelochemicals in donor plants and will affect root growth and development of recipient plants.
The interaction of irrigation patterns and concentration of water extracts showed a significant effect on plumula's length ( Table 2). The highest plumule length obtained from control plants (0% extract concentration) in all irrigation pattern treatments. These results indicate that the allelopathic compounds affect seed germination. The interaction of dry irrigation patterns in swampland land and concentrations of water extracts of 7.5% and 10% produced the lowest length of the plumula, which were 0.938 cm and 0.038 cm. These results indicate that sorghum grown in drought stress conditions in swamps and Ultisols produced biomass with the highest seed inhibition, namely at a water extract concentration of 7.5% and 10%.  The interaction between irrigation patterns and water extract concentration significantly affected the radicle length (Table 2). At concentrations extract of 0% (control), all irrigation patterns produced the highest radicler length. This result showed that the interaction of all irrigation patterns with 0% extract concentration (control) has no inhibitory effect on recipient plants. Interaction of dry irrigation patterns in swamp and Ultisol with a concentration of 7.5% water extract produced the lowest radicler lengths of 0.095 cm and 0.040 cm. Thus, sorghum planted in drought stress in both swampland and Ultisols with a water extract concentration of 7.5% produced the highest seed inhibition. The higher the water extract, the shorter the length of the radicles. The dry irrigation pattern in swampland soil and Ultisol resulted in the shortest radicle length. Data analysis results showed that the reduction in radicle length was higher than the reduction in plumule length at all extract concentrations tested.
Thus, the radicle is more responsive and sensitive to aqueous extract of sorghum than the plumule. In general, the highest concentration of sorgoleone compounds is in the sorghum root component. According to [5], a high concentration of sorgoleone and some phenolic acids in the root exudate of sorghum var Enkath was higher than that of var. Rabeh. Thus, it is necessary to get the right sorghum cultivars for controlling environmentally friendly weeds.
The interaction between irrigation patterns and concentration of water extracts showed a significant effect on the dry weight of sprouts with no cotyledons ( Table 2). The dry irrigation pattern in wetlands and dry land in Ultisol with 0% extract concentration (control), resulting in the lowest sprout dry weight without cotyledons. Interaction dry irrigation pattern of swamp and dry soil in Ultisol with 7.5% water extract concentration produced the lowest dry weight of sprout without cotyledon, 0.0013 g, and 0.0014 g. The results showed that sorghum planted in dried swam soils and ultisols was toxic to germination of seeds at a concentration of 7.5 percent. Furthermore, the higher the extract concentration applied, the smaller the dry weight of sprouts without cotyledons was produced. This result means that the higher the concentration of water extracts, the seeds tend to experience disruption of germination metabolism because of higher allelopathic potential in water extracts. The dry irrigation pattern on swamp and ultisol soil produced the lowest seed (with no cotyledon) dry weight. Therefore, cultivating sorghum on marginal swampland lands and Ultisols with drought stress produced biomass with high allelochemical content and high efficacy on seed germination. Table 2 shows the highest average sprouts dry weight with cotyledons resulted from the treatment of dry irrigation patterns on swampland and dry-wet on swampland. This result showed that the pattern of dry irrigation in swampland, as well as dry-wet in swampland, produced sorghum biomass with the highest seed inhibition. The sorghum extract concentration treatment showed that the highest extract concentration resulted in the highest dry weight of sprouts with cotyledons. The germination seed metabolism process could not be effective and led an increased dry weight of the sprout. The result of this study showed, the higher the water extract applied, the higher the cotyledon weight. The higher the water extract concentration, the greater the inhibition of seed germination (Table 2). According to [5], allelopathic plants either have positive or negative effects on the surrounding plants. In this study, water extracts tended to produce inhibition of recipients.
There was an interaction between the irrigation pattern and the water extract concentration on the fresh weight of plumules ( Table 3). The dry irrigation pattern in the swampland with an extract concentration of 10%, resulting in the lowest plumula fresh weight, 0,0006 g, however it was not significantly different from other interactions, especially at 10% concentration. This studied showed that the interaction of dry irrigation patterns in swampland with an extract concentration of 10% produces the highest drought and allelopathic stress and has a role in the inhibition of the plumula's fresh weight.
The interaction between irrigation patterns and water extract concentration significantly affected the fresh weight of radicles (Table 3). Dry irrigation patterns in swampland with a water extract concentration of 7.5% yielded the lowest fresh weight of radicles, although not significantly different from other interactions, especially at a concentration of 7.5%. This result shows that the interaction of dry irrigation patterns in swampland with an extract concentration of 7.5% resulted in the highest drought stress, therefore inhibiting radicle fresh weight. According to [5], the allelopathic effect of plants depends on biotic and abiotic factors. The allelopathic approach will reduce dependence on chemical pesticides, which are proven to be environmental contaminants. The higher the concentration of aqueous extract, the lower the radicles' fresh weight. When compared between the plumula's fresh weight, the IOP Conf. Series: Earth and Environmental Science 694 (2021) 012027 IOP Publishing doi:10.1088/1755-1315/694/1/012027 7 radicle's fresh weight was more affected by an extract. This was due to the radicles were in direct contact with the water extract in the growing media.
The interaction between irrigation patterns and water extract concentration significantly affected the fresh weight of cotyledons (Table 3). The dry irrigation pattern in the swamp and dry land in Ultisol with 10% extract concentration yielded the highest fresh cotyledon fresh weight of 0.0421 g, 0, 0416 g, and significantly different from other interactions, especially the concentration of 10%. This result shows that the interaction of dry irrigation patterns in the swamp and dry soil in Ultisol with an extract concentration of 10% produces the highest stress. Allelopathic water extracts affect the metabolic activities of seed germination.
The interaction between the irrigation pattern and the water extract concentration showed a significant effect on the plumula's dry weight ( Table 3). The pattern of dry irrigation in swampland with an extract concentration of 10%, resulting in the lowest plumula's dry weight, 0,0001g. This result shows that the interaction of dry irrigation patterns in swampland with an extract concentration of 10% produces drought stress with the highest allelopathic activity.
The concentration of extract significantly affected the dry weight of radicles (Table 3). This experiment showed that the dry irrigation patterns in swampland and Ultisols soil at 7.5% extract concentration treatment, resulting in the lowest radicle dry weight, 0, 00001 g. This result shows the irrigation pattern's interaction with the extract concentration of 7.5% produces drought stress with the highest allelopathic activity and suppressing the radicle dry weight. The higher the concentration of sorghum extract, the smaller the dry weight of the radicles. Radicler dry weight is more sensitive compared to the dry weight of the plumula. This result was due to the radicle was in direct contact with the bioassay media. According to [14], roots are more sensitive to allelopathic than the shoots.
The interaction between irrigation patterns and water extract concentrations significantly affected the dry weight of cotyledons ( Table 3). The higher dry weight of cotyledons resulted from all irrigation patterns in swampland (with 10% extract concentration) and dry irrigation patterns in swamps, and dry irrigation patterns in Ultisols (with extract concentration 7.5%). Therefore, the interaction between the irrigation pattern and the extract concentrations of 10% and 7.5% reduced dry weight of cotyledons higher than the other treatment combinations. The higher the concentration of the extract, the greater the dry weight of the cotyledons. The results of the experiments show that water extract of sorghum can inhibit seed germination. According to [5], sorghum and sunflower have allelopathic compounds that inhibit plant growth. Root growth disrupted due to decreased activity of the root meristem. Allelopathic can, moreover, also reduce the cell length of the root [16].

Conclusions
Sorghum at a water extract concentration of 7.5% in a dry irrigation pattern on swampland and dry on Ultisol soil inhibit seed germination better than the other treatments. Sorghum cultivated in swampland or Ultisols with a dry irrigation pattern produced high allelopathic content.