MATERIALS AND METHODS

Study area: This research was conducted at Kopertis Growth Center Region I Jl. Peratun 1, Percut Sei Tuan, Deli Serdang Regency, North Sumatra Province, Indonesia with an altitude of ± 27 masl, in November, 2018 to January, 2019.

Materials: The materials used were 192 mung bean seeds of the Vima-2 variety, dried decanter solid, arbuscular mycorrhizal fungi, acid soil, water, polybags 30x35 cm, insecticide Prevathon 50 Suspension Concentrate (active ingredient: Chlorantraniliprole), insecticide Decis 25 Emulsion Concentrate (active ingredient Deltamethrin) and other supporting materials.

Study design: This research was conducted using a factorial randomized block design (RBD), with two factors. The first factor is dried decanter solid (DDS) consisting of 4 levels, namely S₀ = 0 g/polybag, S₁ = 150 g/polybag, S₂ = 300 g/polybag and S₃ = 450 g/polybag. The second factor is arbuscular mycorrhizal fungi (AMF) consisting of 4 levels, namely M₀ = 0 g/polybag, M₁ = 6 g/polybag, M₂= 12 g/polybag and M₃= 18 g/polybag.

Application of dried decanter solid: Dried decanter solid (DDS) is obtained from the Palm Oil Mill of Socfin Indonesia Ltd. A dried decanter solid was applied 2 weeks before the seeds were planted. The dried decanter solid was applied by mixing it with polybag soil according to the level of treatment.

Application of arbuscular mycorrhizal fungi: Arbuscular mycorrhizal fungi (AMF) were obtained from the Laboratory of the University of North Sumatra, Medan. The application of arbuscular mycorrhizal fungi is carried out when planting mung bean seeds. Arbuscular mycorrhizal fungi were applied by inserting them into the planting hole with a depth of ±2 cm according to the level of treatment.

Statistical analysis: The research data were analyzed using Analysis of Variance (ANOVA) and continued with Duncan’s Multiple Range Test (DMRT) at 5%.

RESULTS AND DISCUSSION

Plant height: Based on the results of statistical analysis showed that the application of dried decanter solid had a significant effect on plant height. Meanwhile, the application of arbuscular mycorrhizal fungi and the interaction of the two treatments did not significantly affect plant height. The mean of plant height can be seen in Table 1.

The application of dried decanter solid at 2 week after planting (WAP) did not have a significant effect, while at 3, 4 and 5 (WAP) it had a significant effect with the highest mean of plant height in the S₀, namely 14.46, 19.13 and 31.43, respectively, but at 6 WAP did not have a significant effect again. This is presumably because the availability of nutrients in acidic soil is not optimal so it affects plant height growth. Human activities that result in the formation of acid soils such as construction and mining will cause plant death²⁰. Wilting in plants is caused by low soil pH and the dissolution of toxic elements (Al, Fe and Mn) in acidic conditions. The inhibition of root growth is one of the main consequences and the most obvious symptom of Al toxicity²¹. Excess Al will inhibit root cell division-elongation and formation of root hairs and promote the development of swollen root apex. Simultaneously, toxic Al inhibits water and nutrient uptakes¹¹.

Number of branches: Based on the results of statistical analysis showed that the application of solid dried decanter had a significant effect on the number of branches. While the application of arbuscular mycorrhizal fungi and the interaction of the two treatments did not significantly affect the number of branches. The mean number of branches can be seen in Table 2.

Application of dried decanter solid showed the number of branches with the highest means at 2 WAP with S₀ is 1.67, which was significantly different from S₁ (1.19 branches), S₂ (1.11 branches) and S₃ (1.08 branches). At 4 WAP, the highest mean number of branches was found in the S₀ namely 5.61, which was significantly different from the S₁ (4.78 branches), S₂ (4.81 branches) and S₃ (4.69 branches), while in 6 WAP the highest mean was in the S₂, namely 11.75 branches which are significantly different from S₀ (10.28 branches) but not significantly different from the S₁ (11.28 branches) and S₃ (11.25 branches).

The relationship between the number of branches of the mung bean plant at 6 WAP with dried decanter solid application can be seen in Fig. 1.

The application of dried decanter solid with the optimum dose of 300 g/polybag can increase the number of branches by a mean of 11.75 and shows a quadratic relationship with the determination equation ŷ = 10.25+0.009x-0.05x², the value of r² = 0.991 as shown in Fig. 1. It is suspected that the application of dried decanter solid at a dose of 300 g/polybag is appropriate for plant growth so that it affects the growth of the number of plant branches. The type of agricultural management applied influences soil properties, both positively and negatively^22,23. Therefore, proper agricultural practices and soil management can result in soil property improvements such as organic carbon content increases, soil structure recovery and infiltration rate improvement²⁴. In addition, it can also increase bulk density, porosity, soil water content, distribution of nutrients and stability of soil structures.

Fig. 1:

Graph of the number of branches at 6 WAP to the application of dried decanter solid

Furthermore, cropping patterns and soil management can change the soil properties, nutrient levels, organic carbon content and soil organisms living conditions, so affecting the biological processes majority^24-28.

Flowering age: Based on the results of statistical analysis, shows that the application of solid dried decanter has a significant effect on flowering age. While the application of arbuscular mycorrhizal fungi and the interaction of the two treatments had no significant effect on flowering age. The mean flowering age can be seen in Table 3.

Based on Table 3, it can be seen that the highest mean age of flowering with dried decanter solid application was found in S₁, S₂ and S₃, namely 34.50, which was significantly different from the S₀, namely 33.67, while the highest mean with the arbuscular mycorrhizal fungi application was in M₃, namely 34 .50 and the lowest mean in M₂, namely 34.00.

The relationship between the flowering age of mung bean plants and dried decanter solid application can be seen in Fig. 2.

Figure 2 showed the relationship between the application of solid dried decanter to the flowering age, which is positive linear with the regression equation ŷ = 33.91+0.001x, the value of r² = 0.6.

Fig. 2:

Graph of flowering age with dried decanter solid applications

Based on the graph, it can be seen that without the administration of dried decanter solid, it shows an earlier flowering age compared to the application of dried decanter solid. It is suspected that the weathering process of the dried decanter solid is imperfect so the availability of nutrients from the solid cannot be absorbed by plants. The decomposition of organic matter is largely a biological process that occurs naturally. Its speed is determined by three major factors: soil organisms, the physical environment and the quality of the organic matter. In the decomposition process, different products are released: Carbon dioxide (CO₂), energy, water, plant nutrients and resynthesized organic carbon compounds²⁹.

Total chlorophyll: Based on the results of statistical analysis, showed that the application of dried decanter solid had a significant effect on total chlorophyll. While the application of arbuscular mycorrhizal fungi and the interaction of the two treatments did not significantly affect total chlorophyll. The mean of total chlorophyll can be seen in Table 4.

Based on Table 4, it can be seen that the amount of chlorophyll with the highest mean application of dried decanter solid was found in S₀, namely 52.45 mL g^–1, significantly different from S₁ (47.45 mL g^–1), S₂ (47.39 mL g^–1) and S₃ (47.67 mL g^–1). While the highest mean of arbuscular mycorrhizal fungi applications was found in M3 namely 49.50 mL g^–1 and the lowest mean in M2 namely 47.91 mL g^–1.

The relationship between the chlorophyll total in mung bean leaves and the dried decanter solid application can be seen in Fig. 3.

Figure 3 showed the relationship between the application of dried decanter solid to the chlorophyll total of the leaf that is quadratic with the determination equation ŷ = 52.22-0.036x+0.000005x², the value of r² = 0.942. Based on the graph, it can be seen that the highest amount of chlorophyll was in the S₀, namely 52.45 mL g^–1. This is presumably without the addition of solid dried decanter which has sufficient nitrogen content to make the plant leaves greener. This is in accordance with Fathi³⁰ who states that nitrogen functions to accelerate plant growth, make plant leaves greener and fresher and contain lots of green leaf grains that play an important role in the process of photosynthesis.

Fig. 3:

Graph of chlorophyll total with dried decanter solid applications

In addition, nitrogen has the function to increase the protein content in plants.

Seed weight per plant, seed weight per plot and weight of 100 seeds: Based on the results of statistical analysis, it was shown that the application of dried decanter solid had a significant effect on seed weight per plant, seed weight per plot and weight of 100 seeds. While the application of arbuscular mycorrhizal fungi and the interaction of the two treatments had no significant effect on seed weight per plant, seed weight per plot and weight of 100 seeds (Table 5).

Based on Table 5, it can be seen that the application of dried decanter solid had a significant effect on seed weight per plant sampled at 55, 62 and 77 DAP. Application of dried decanter solid, the highest seed weight per plant at 55 DAP was found in S₀ namely 9.44 g which was significantly different from S₁ (6.62 g), S₂ (6.90 g) and S₃ (6.83 g), while the highest mean at 62 DAP was in S₂, namely 9.91 g, which was significantly different from the S₀, namely 6.19 g, but not significantly different from the S₁ (9.36 g) and S₃ (8.52 g), while the highest mean was at 77 DAP was found in S₀ namely 9.58 g which was significantly different from the S₁ (7.74 g) and S₂ (5.62 g) but not significantly different from the S₃ namely 7.67 g.

The relationship between seed weight per plant of mung bean at 77 DAP with the application of dried decanter solid can be seen in Fig. 4.

Figure 4 showed the relationship of dried decanter solid application to seed weight per plant, namely quadratic with the determination equation ŷ = 9.798-0.024x+0.0005x² value of r² = 0.873. Based on the graph, it can be seen that the highest number of seed weights per sample plant was found in S₀, namely 9.58 g. This is presumably without dried decanter solid having sufficient phosphorus content so that it affects seed weight per sample plant, on the other hand, phosphorus also affects plant root growth so that it has a positive correlation with the growth of all plants. This was in accordance with the opinion of Samosir and Lahay³¹ which stated that phosphorus (P) is important for accelerating root growth, accelerating plant maturity, accelerating fruit and seed formation and increasing production.

Fig. 4:

Graph of seed weight per plant with dried decanter solid applications

Sources of phosphate in the soil as mineral phosphate, namely phosphate limestone, plant residues and other organic matter and artificial fertilizers (double phosphate, super phosphate and others). The absorption and conversion of organic phosphorus into inorganic phosphorus are carried out by microorganisms.

Table 5 also showed that the application of solid dried decanter had a significant effect on seed weight per plot at 55, 62 and 77 DAP. In the application of dried decanter solid, it can be seen that the highest mean of seed weight per plot at 55 DAP was found in S₀, namely 37.34 g, which was significantly different from the S₁ (26.40 g), S₂ (27.35 g) and S₃ (25.84 g), while the highest mean at 62 DAP was found in S₂, which was 41.24 g, which was significantly different from the S₀ namely 25.55 g, but not significantly different from the S₁ (36.44 g) and S₃ (33.45 g). while the highest mean at 77 DAP was found in S₀ namely 37.23 g which was significantly different from S₁ (28.16 g), S₂ (21.34 g) and S₃ (27.07 g).

The relationship between seed weight per plot of mung bean at 77 DAP and the application of dried decanter solid can be seen in Fig. 5.

Figure 5 showed the relationship of the application of dried decanter solid to seed weight per plot, namely quadratic with the determination equation ŷ = 37.74-0.098x+0.000x², the value of r² = 0.959. Based on the graph, it can be seen that the highest number of seed weights per plot in S₀, namely 37.23 g. It is suspected that the availability of nutrients without the provision of the solid dried decanter is available compared to the provision of the solid-dried decanter, in general, organic matter undergoes a decomposition process so that it can be utilized by plants. One of the obstacles to the decomposition process of organic matter is c-organic. According to Li et al.³², the relationship between c-organic and total nitrogen in the soil is very important. The availability of c-organic as an energy source, if its availability is excessive, it will inhibit the development of microorganisms, due to the excessive increase in c-organic compared to the total nitrogen content in the soil.

Fig. 5:

Graph of seed weight per plot with dried decanter solid applications

As a result, an increase in c-organic will inhibit the formation of proteins, which will inhibit the activities of microorganisms. Therefore, the c-organic and total N-content in the soil is used to determine the level of weathering and the rate of decomposition of organic matter and the availability of nutrients in the soil.

The application of dried decanter solid had a significant effect on the weight of 100 seeds at 62 DAP. The dried decanter solid application showed that the highest mean weight of 100 seeds at 55 DAP was found in S₀ and S₁, namely 7.75 g and the lowest in S₂, namely 7.63 g, while the highest mean was at 62 DAP, in S₀, namely 8.27 g which was significantly different from S₁ namely 7.63 g and S₂ namely 7.30 g but not significantly different from the S₃ which was 7.76 g, while the highest mean at 77 DAP was found in S₁ namely 8.11 g and the smallest in S₂ namely 7.43 g. This was presumably due to the minimum availability of nitrogen elements when filling the seeds which has an impact on the leaves turning yellow it affects the results of the seed-filling process. According to Sehgal et al.³³, an increase in N translocation to seeds during seed filling causes an acceleration of leaf aging so that the seed filling period becomes shorter and consequently the yield will decrease. To slow down leaf senescence, it is necessary to add N when the plants start to flower, which also increases the supply of N when filling the seeds.

Figure 6 showed an increase in production from the first harvest at 55 DAP to the second harvest at 62 DAP, namely 1403.08 to 1640.16 g, but there was a decrease in yield in the third harvest at 77 DAP, namely 1365.53. A decrease in crop yields can occur due to physiological changes in plants such as yellowing leaves that interfere with leaf function which is bad for plants. Yellowing of leaves is a genetically regulated form of leaf senescence³⁴. Several factors cause yellowing of leaves including age, pathogens, harvesting, mechanical damage and environmental stresses³⁵.

Root length: Based on the results of statistical analysis, shows that the application of dried decanter solid has a significant effect on root length. While the application of arbuscular mycorrhizal fungi and the interaction of the two treatments did not significantly affect root length. The mean of root length can be seen in Table 6.

Based on Table 6 it can be seen that the highest mean of root length with the dried decanter solid application was found in S3, namely 45.50 cm which was significantly different from S₀ (32.58 cm) but not significantly different from S₁ (42.08 cm) and S₂ (44.00 cm), while the highest mean in the application of arbuscular mycorrhizal fungi was in M3 namely 45.42 cm and the lowest mean in M1, namely 37.08 cm.

The relationship between the root length of the mung bean plant and the application of dried decanter solid can be seen in Fig. 7.

Fig. 6:

Histogram of total harvest with the application of solid dried decanter and arbuscular mycorrhizal fungi

Fig. 7:

Graph of root length with dried decanter solid applications

Figure 7 showed the relationship between the application of dried decanter solid on root length, which is positive linear with the regression equation ŷ = 34.94+0.027x, the value of r² = 0.816. Based on the graph, it can be seen that the longest root length is in the S3, which was 45.50 cm. It was suspected that the application of dried decanter solid is able to improve soil porosity so that the loose soil structure can facilitate the development of roots in the soil, on the other hand, dried decanter solid is also able to store water so that the availability of water is always sufficient for plant growth. Plant root systems greatly impact the soil and there is a functional link between root density, soil depth and soil properties. Plant root systems may intensify the hydrological and ecological function of rainfall regulation, storage and infiltration by increasing soil porosity, non-capillary porosity and field capacity³⁶. In addition, factors influencing soil's total and non-capillary porosity are organic matter, structure and soil arrangement, cultivation, fertilization and rainfall³⁷. Furthermore, the external impact has a significant effect on the root system. The distribution of soil moisture is one of the key factors to guide the root system³⁸. According to Jin et al.³⁹, the root system will grow optimally in soil conditions that are both physical and chemical. The root system has a positive correlation with the resulting growth. Long plant roots will increase the ability to absorb water and nutrients so as to produce optimal growth in plant height, number of leaves and number of stalks.

In principle, plants are the same as humans who need nutrients for their growth and development. Plant food substances are in the form of simple elements called nutrients, namely chemical elements needed by plants to carry out physiological processes so that plant life takes place properly, both under optimum conditions and under stress. The application of dried decanter solid (DDS) is useful in adding soil nutrients because it contains nutrients such as N, P, K and Mg which are needed for plant growth and development processes. In addition, the rate of uptake of nutrients by the plant root system depends on the speed at which plant roots reach nutrients, where the movement of nutrients in the soil is influenced by many factors. These factors include soil factors (moisture, buffering capacity, temperature) and plant factors (root length, root density and root infection) by arbuscular mycorrhizal fungi. Mycorrhiza is a symbiotic association between fungi and plants that colonizes the root cortex tissue of plants, occurring during the active growth period of the plant. Plant growth is increased in the presence of mycorrhiza due to increased nutrient uptake, resistance to drought, production of growth hormones and growth regulators, protection from root pathogens and toxic elements.

The results of this study indicated that the application of dry decanter solid (DDS) and arbuscular mycorrhizal fungi (FMA) is proven to increase the growth and production of mung bean in acid soils, but has not yet reached the optimal stage, so in the future, a deeper study is needed to analyze other factors that affect the interaction between plants and arbuscular mycorrhizae.

CONCLUSION

The application of dried decanter solid 300 g/polybag significantly increased plant height, the number of branches and seed weight per plot, besides the application of dried decanter solid 450 g/polybag significantly increased root length. Meanwhile, without the application of dried decanter solid, a faster flowering period, more chlorophyll and higher seed weight per plant were obtained compared to the application. The application of arbuscular mycorrhizal fungi and the interaction of the two treatments did not give optimal results on all parameters of the growth and production of mung beans. It remains to be further investigation is needed by increasing the dose of arbuscular mycorrhizal fungi application to obtain optimal results.

SIGNIFICANCE STATEMENT

The application of dry decanter solids aims to increase the availability of nutrients in the soil needed to optimize the growth and production of mung beans in acid soils, then the available nutrients can be properly absorbed by plant roots through symbiosis with arbuscular mycorrhizae which play an active role in colonizing plant root cortex tissue. The results showed that there was an increase in plant growth and production with the application of dry decanter solids and arbuscular mycorrhizae compared to without application. Based on this, a more in-depth study is needed regarding the mechanism of interaction between plants and arbuscular mycorrhizae to determine the effectiveness of use.