EFFECT OF PGPR (Plant Growth Promoting Rhizobacteria) CONCENTRATION ON THE GROWTH AND YIELD OF SEVERAL VARIETIES OF SORGHUM PLANTS IN DRY LAND

¹Uun Ilwati, ²Lestari Ujianto,3 Suwardji

¹Master of Dryland Agriculture Study Program, Postgraduate, University of Mataram

^2.3Master of Dryland Agriculture Study Program, Postgraduate, University of Mataram

Jl. Majapahit No. 62 Mataram, Nusa Tenggara Barat, Indonesia

Email: uun.yunanda@gmail.com

ABSTRAK

This study aims to determine the effect of PGPR concentration onsorghum varieties on the growth and yield of sorghum plants. The experimental design used in this study was a group random design with factorial experiments. This experimental design consists of two factors, namely PGPR concentration (K0 without PGPR, K1 with PGPR 20ml/l per plant, K2 with PGPR 40ml/l per plant and K3 with PGPR 60ml/l per plant) and Sorghum varieties (V1 is the Soper 9 variety, V2 is the SR2401 variety and V3 is the SR2404 variety). Based on the analysis of the results of the study, it was found that the concentration of PGPR and sorghum varieties had a real effect on several sorghum growth parameters, including the number of leaves, leaf area and stem diamater but there was no significant difference in plant height. On the yield parameters of sorghum concentration and varieties have a real effect on the weight of 1000 seeds, root length, panicle length, number of seeds per panicle, wet pruning and brix level.The interaction between PGPR concentration and sorghum varieties has a significant effect on the number of seeds per panicle. The concentration of PGPR at 60 ml/l gives higher yields compared to other concentrations and the SR2404 variety is a variety that has a significant effect on every parameter observed.It is hoped that this research can be one of the references and guidelines for farmers and the community in general in determining the varieties and concentrations of PGPR used in sorghum cultivation in dry land.

Keywords: Sorghum (Sorghum bicolor L), PGPR (Plant Growth Promoting Rhizobacteria), Sorghum varieties.

ABSTRACT

This study aims to determine the effect of PGPR concentration and sorghum variety on the growth and yield of sorghum plants. The experimental design used in this study was a randomised block design with a factorial experiment. This experimental design consisted of two factors, namely PGPR concentration (K0 without PGPR, K1 with 20 ml/l PGPR per plant, K2 with 40 ml/l PGPR per plant, and K3 with 60 ml/l PGPR per plant) and sorghum variety (V1 is the Soper 9 variety, V2 is the SR2401 variety, and V3 is the SR2404 variety). Based on the analysis of the research results, it was found that PGPR concentration and sorghum variety significantly influenced several sorghum growth parameters, including the number of leaves, leaf area, and stem diameter, but did not significantly differ in plant height. For sorghum yield parameters, concentration and variety significantly influenced 1000-seed weight, root length, panicle length, seeds per panicle, wet weight, and Brix content. The interaction between PGPR concentration and sorghum variety significantly influenced seeds per panicle. A PGPR concentration of 60 ml/l yielded higher results compared to other concentrations, and the SR2404 variety had a significant effect on all observed parameters. It is hoped that this study can serve as a reference and guideline for farmers and the general public in determining the variety and PGPR concentration to be used in sorghum cultivation on dry land.

Keywords: Sorghum (Sorghum bicolor L), PGPR (Plant Growth-Promoting Rhizobacteria), Sorghum varieties.

PENDAHULUAN

Sorghum (Sorghum bicolor L.) has great potential to be developed in Indonesia because it is adaptive to dry land, high productivity, and resistant to pests. This plant is easy to cultivate with multipurpose, including food, feed, and industrial materials.(Andriani & Isnaini, 2013; Azrani et al., 2016).

The development of sorghum cultivation in West Nusa Tenggara (NTB) has high prospects given the availability of large dry land, especially in North Lombok Regency (KLU) covering an area of 38,000 ha (Hermanto et al., 2013). The main obstacle is low rainfall (<3 month/year) which limits agricultural productivity (BPS KLU, 2017). Sorghum cultivation is a strategic solution to increase agricultural yields on marginal land, supported by a number of studies that have been conducted in the region.

In North Lombok Regency, the productivity of sorghum plants on dry land is still limited, which is in the range of 1.5–3 tons per hectare, so various research efforts have not provided optimal achievements.(Apliza et al., 2020), far below the international average of 6–9 tons per hectare (McGuire, 2015).The main factor that hinders dryland optimization is the low physical, chemical, and biological properties of the soil (Ngawit et al., 2020).

The strategy of increasing dryland productivity can be carried out through the application of NPK fertilizers combined with biological fertilizers, such as PGPR (Plant Growth Promoting Rhizobacteria). These rhizosphere bacteria double as biostimulants that increase the efficiency of nutrient absorption and phytohormone production, as well as as bioprotectants that increase plant resistance to abiotic stresses (drought, salinity, temperature fluctuations) due to climate change.(Asri Ningrum et al., 2017; Hasan et al., 2024).

The selection of sorghum varieties is a critical aspect in cultivation given its wide diversity of characteristics, including: productivity, harvest life, and seed quality. The selection of varieties must take into account the intended use: (1) quality seed varieties for human consumption, (2) high-pruned varieties for animal feed, (3) high-productivity superior varieties with optimal inputs, or (4) sweet stem varieties for bioethanol production.(Tabri & Zubachtirodin, 2014).

Therefore, this study aims tofind out the influence of PGPR on the growth of several sorghum plant varieties in dry land, as well as provide recommendations for farmers in sustainable dryland management.

METODE PENELITIAN

 This research was carried out in Akar-Akar Village, Bayan District, North Lombok Regency, in the period from January to April 2025. The method used is a factorial Group Random Design (RAK), which consists of two main factors: (1) PGPR concentration (K0: no PGPR; K1: 20 ml/l per plant; K2: 40 ml/l per plant; K3: 60 ml/l per plant) and (2) sorghum varieties (V1: Soper 9; V2: SR2401; V3: SR2404).

The two factors combined resulted in 12 different treatment combinations. Each combination was repeated three times for a total of 36 test units. The research materials include PGPR, sorghum seeds from three varieties (SR2401, SR2404, and Soper 9), and NPK Pelangi fertilizer. The equipment used includes hoes, scythes, handsprayers, cups, plastics, rulers, digital scales, meters, buckets, brix measuring instruments, copers, and various stationery.

Pelaksanaan percobaan meliputi: (1) persiapan petakan percobaan, (2) penanaman dan pemupukan, (3) penetapan sampel tanaman, serta (4) pemeliharaan hingga panen. Pengamatan meliputi parameter pertumbuhan (tinggi tanaman, diameter batang, jumlah dan luas daun, panjang akar, bobot brangkasan basah-kering, kadar klorofil) dan hasil panen (panjang malai, jumlah dan bobot biji per malai, bobot 1000 biji). Analisis data menggunakan ANOVA 5% dilanjutkan dengan uji DMRT apabila menunjukkan perbedaan nyata..

RESULTS AND DISCUSSION

Based on the results of the variance analysis (Table 1), PGPR concentration did not show a real influence on the parameters of plant height, stem diameter, and dry pruning weight. However, the PGPR concentration factor exerts a noticeably different influence on growth parameters and other outcomes. On the other hand, varieties have a significant effect on all observed parameters, including plant height, stem diameter, leaf characteristics (number and area of leaves), root length, weight of wet cuttings, as well as crop components (panicle length, weight of 1000 seeds, seed weight per panicle, number of seeds per panicle) and brix content. The interaction between PGPR concentration and variety only showed a noticeably different effect on the parameters of the number of seeds per panicle.

Table 1. Summary of the results of the variety analysis (Anova) on all sorghum observation parameters

Plant Growth Parameters

Based on the results of variety analysis (Table 2), it shows that the plant height parameters, stem diameter and leaf area of variety 1 produce a significantly different effect from variety 3 but not significantly different from variety 2. In the parameters of the number of leaves and root length, variety 1 is significantly different from variety 2 and variety 3, but variety 2 and variety 3 are not significantly different. In the chlorophyll b parameters, variety 2 is significantly different from variety 3 but not significantly different from variety 1. In all observation parameters, the response of varieties 3 was higher than those of varieties 1 and 2, it can be seen from the average results that were the highest compared to the others. PGPR has an optimal influence on 3 varieties so that plant growth becomes better than other varieties.

Table 2. Average plant height, stem diameter, number of leaves, leaf area and sorghum root length due to the influence of sorghum varrietas at the age of 56 HST

Remarks: the number of numbers followed by the same letter in the same column shows that the treatment is not significantly different according to the DMRT 5% follow-up test

Based on the DMRT test, the highest PGPR concentration (60 ml/l) had a significant effect on the increase in leaf area compared to other concentrations, but it did not differ significantly from the 20 ml/l and 40 ml/l treatments on the parameters of leaf count and root length. At chlorophyll a content, a dose of 60 ml/l showed a noticeable difference with controls (0 ml/l) and 20 ml/l, but no significant difference with 40 ml/l. Overall, the 60 ml/l treatment produced the highest average value on all growth parameters compared to controls, suggesting that the increased PGPR dose was directly proportional to the increase in plant growth. This is due to the ability of microorganisms in PGPR to provide nutrients optimally, where the higher the concentration given, the better the availability of nutrients for plants so as to encourage more optimal growth (Rohmaniati & Sarjan, 2023). In line with the statement of Wulandari et al., (2021) A positive relationship was observed between increasing the dose of PGPR and accelerating plant growth. The mechanism of action of PGPR includes the production of phytohormones, vitamin compounds, and organic acids that act as growth stimulants, as well as increasing the efficiency of nutrient absorption by plants (Rahni, 2012). Rhizobacteria in PGPR function as plant growth promoters (Husein et al., 2022).

Table 3. Average number of leaves at age 56 HST, Leaf area, root length and

Chlorophyll a due to the influence of PGPR concentration

Remarks: the number of numbers followed by the same letter in the same column shows that the treatment is not significantly different according to the DMRT 5% follow-up test

Sorghum yield parameters

The analysis of Table 3 shows that sorghum varieties have a significant effect on wet sage weight, panicle length, seed weight per panicle, weight of 1000 seeds, and number of seeds per panicle. In brix levels, varieties 1 and 2 are not significantly different, but they are significantly different from variety 3.

Table 4. Average Weight of Wet Pruning, Dry Pruning, Panicle Length, Weight of Permlai Seeds, Weight of 1000 Seeds, Weight of Panicle Seeds Due to the Influence of Sorghum Varieties

Remarks: the number of numbers followed by the same letter in the same column shows that the treatment is not significantly different according to the DMRT 5% follow-up test

The test results showed that sorghum varieties had a noticeable effect on all observation parameters. The SR2404 variety (variety 3) produces the highest average value in each parameter. In addition, the weight of 1000 seeds is not only used to estimate the need for seeds per hectare, but also an indicator of the quality of seed production of a genotype (Andayani, 2021). The results of the analysis showed a noticeable difference in the observation of the weight of 1000 seeds. The variety that is able to provide more seeds is Variety 3 which is SR2404. While the variety that has the least ability to provide seeds is the Soper 9 Variety.

The analysis showed a marked difference in panicle length between sorghum varieties even though they were grown under the same soil conditions. The SR2404 variety (Variety 3) shows the highest panicle length, while Soper 9 reaches only 14.84 cm - lower than the description of the variety (18.61 cm). This disparity is thought to be caused by: (1) soil nutrient deficiencies, and (2) ineffectiveness of PGPR application in influencing panicle growth.

Analysis showed a noticeable influence of the variety on seed weight per panicle, with SR2404 yielding the highest weight. This variation is caused by genetic differences in the allocation of dry matter to plant organs (stems, leaves, seeds) which are more dominant than environmental influences. (Andayani, 2021).

Based on the results of the research on the average brix content of SR2404 of 19.75 things, it shows that this variety can be used as a raw material for bioethanol. Sarath et al. (2008) explained that sweet orgum is a potential raw material for bioethanol production because it has a fermented carbohydrate (FC) content in the stem of 15–25%. In addition, sorghum also produces large amounts of biomass and has multi-functions, making it a prime candidate as a biofuel-producing crop.(Stamenković et al., 2020).

Table 5Average Weight of Wet Pruning, Dry Pruning, Panicle Length, Weight of Strawberry Seeds, Weight of 1000 Seeds, Weight of Strawberry Seeds due to the Influence of PGPR Concentration

Remarks: the number of numbers followed by the same letter in the same column shows that the treatment is not significantly different according to the DMRT 5% follow-up test

The weight of seeds per panicle produced in the soper 9 variety in this study was 72.63g per panicle when converted to hectares to 3.87 tons/ha. This result is still not optimal when viewed from the description of the potential yield of 10.17 tons/ha. Many factors cause this, including soil quality (lack of nutrients, inappropriate pH), insufficient fertilizer dosage and poor plant management.

The effect of PGPR concentration on the average result can be seen in table 3. In the parameters of wet pruning and the number of seeds per panicle, the K0 treatment (concentration 0ml/l) was significantly different from the treatment of K1 (concentration of 20ml/l), K2 (concentration of 40 ml/l) and K3 (concentration of 60 ml/l) but K1 was not significantly different from K2. At a concentration of 60 ml/l of wet pruning and the number of seeds per panicle produce the highest results, at this concentration PGPR has the maximum effect. The bacterial content in PGPR plays an optimal role in seed formation and wet space.

In panicle length, K0 is significantly different from K2 and K3 but not significantly different from K1. This means that at concentrations of 0ml/l and 20ml/l it exerts the same effect. The concentration of 60 ml/l described the effect of the highest panicle length, which was 19.96 cm. This shows that the Rizobacteria contained in PGPR provide an optimal effect according to research conducted by Hidalgo (2024) Bacillus megaterium and Pseudomonas japonica bacteria treated in sorghum varieties, with a conscious concentration of bacteria of around 10⁷ CFU/g soil, significantly increasing panicle length along with other variables such as plant height and plant diameter. In line with research conducted by Shivashakarappa et al., (2022) PGPR inoculation on similar cereals (foxtail millet) improves growth and yields, including panicle length, through increased nutrient uptake and growth hormone activity.

The analysis showed that the seed weight per panicle at K0 (0 ml/L) was not significantly different from K1 (20 ml/L), but significantly different from K2 (40 ml/L) and K3 (60 ml/L). The conversion results showed an increase in productivity in line with the concentration of PGPR: 3.56 tons/ha (K0), 3.72 tons/ha (K1), 4.6 tons/ha (K2), and 5.35 tons/ha (K3). The optimal concentration of 60 ml/L is thought to have a positive effect through the mechanism: (1) the provision of element P for the generative phase by rhizobacteria, (2) the production of phytohormones (IAA and gibberellins) by Pseudomonas sp., and (3) the increased efficiency of nutrient absorption by Rhizobium which accelerates flowering (Sitawati et al., 2022). Similar results were also reported in maize crops, where the use of Bacillus spp. and Pseudomonas spp. had a positive effect: increasing the growth and production of forage and seeds (Khuzzaimatul et al., 2023). According to Setiawati, et al. (2014) Several types of rhizosphere bacteria have the ability to increase the availability of nutrients for plants. The genus Bacillus and Pseudomonas are known to have phosphate dissolving activity, while Serratia spp. has multifunctions as a phosphate solvent, nitrogen fixator, and growth hormone synthesis IAA (indol acetic acid). Phosphate as an essential element for plant growth is generally bound in soil compounds that are difficult to obtain. The role of phosphate-dissolving bacteria in the root zone is crucial in converting the bound phosphate into a form available for plant absorption. (Siregar et al., 2016). As a decomposer, phosphate-soluble bacteria increase soil fertility through the secretion of low-molecular organic acids that dissolve phosphate. Its metabolic activity is supported by the availability of simple carbon compounds from root exudate and plant residues.(Susilo et al., 2021).

The analysis showed a positive correlation between the increase in PGPR concentration and the yield, where the concentration of 60 ml/L resulted in the highest weight of 1000 seeds. This mechanism is thought to be through: (1) increased phosphorus (P) availability through microbial dissolution, and (2) stimulation of growth hormone production by PGPR bacteria.(Marom et al., 2017). In PGPR research on peanuts, the greater the concentration of PGPR, the greater the yield of wet pods because PGPR helps the absorption of nutrients (Marom et al., 2017). According to Anesta et al. (2016), the application of PGPR significantly increases the weight of 1000 grains of rice grain when compared to crops without PGPR treatment.

The results showed that root length at a concentration of 60 ml/l resulted in the longest root length of 35.82cm compared to others. The concentration of 60 ml.l is not significantly different from the concentration of 20 ml/l and 40 ml/l but is significantly different from without PGPR. Researchconducted by Sitawati and Hendiriau, (2018) showed that theincrease in results due to PGPR administration was mainly due to bacterial activity in producing phytohormones, especially IAA (indol acetic acid). This hormone stimulates the growth of root hairs, thereby increasing the absorption capacity of water and dissolved nutrients from the soil..

A PGPR concentration of 60 ml/L results in the highest brix levels (19.11°Wx), indicating an optimal effect on sugar accumulation. This increase in brix value is influenced by the application of NPK (Potassium) and Agrocyl (Silicate) fertilizers through the mechanism: (1) inhibition of enzymes (invertase, peroxidase, polyphenol oxidase, phosphatase, and ATPase), and (2) increased energy supply for sugar synthesis through reduction of phosphatase activity.(Hawari et al., 2021).This is in line with the results of a study by Apliza et al., (2020) which concluded that the addition of Si fertilizer can significantly increase yield and sorghum brix content.

Table 6. Jasmine seeds due to the interaction of PGPR concentration and sorghum varieties

Remarks: the number of numbers followed by the same letter in the same column shows that the treatment is not significantly different according to the DMRT 5% follow-up test

Analysis of 5% DMRT (Table 4) revealed a significant interaction between PGPR and variety concentrations on the number of seeds per panicle, with the optimal combination of SR2404 and PGPR 60 ml/L yielding 4530.5 seeds/panicles. Allegedly, PGPR increases nutrient availability, while SR2404's genetic superiority contributes more than other varieties. According to Ikhwan et al. (2016), the effectiveness of rhizosphere bacteria depends on their adaptation in the host rhizosphere environment. The N-anchoring bacteria and P solvents in PGPR are thought to increase the availability of essential nutrients for grain filling, resulting in higher seed weights than controls. According to Safrida et al., (2019) Plant height growth is determined by external factors (such as temperature, light, air, and nutrient availability) as well as internal factors (including genetics, morphology, food reserve storage capacity, and resistance to stress).

The results of this study show that the application of PGPR increases nutrient availability, while the genetic advantage of the SR2404 variety contributes more dominantly. According to Ikhwan et al. (2016), the effectiveness of rhizosphere bacteria depends on their ability to adapt to the host rhizosphere's environment. The N-anchoring bacteria and P solvents in PGPR are thought to increase the availability of essential nutrients for seed filling.

CUTPULAN

Based on the results and discussion above, it can be concluded that the highest PGPR concentration (60 ml/l) has a real influence on the parameters of wet swab weight, panicle length, seed weight per panicle, weight of 1000 seeds, number of panicle seeds and brix content. The SR2404 variety is the variety that produces the highest average yield in each parameter. The interaction between concentration and variety is found in the number of seeds per panicle.

The implications of this study can be suggested to farmers or the general public if sorghum is cultivated on dry land, then PGPR with a concentration of 60 ml/l is added during cultivation. And use the SR2404 variety to get the highest yield.

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