The agronomic pattern of wetland rice with different timings of gibberellic acid (GA3) application treatment

Gibberellic acid (GA3) is an exogenous plant growth hormone that influences plant physiological processes, ultimately affecting plant growth, development, and yield. This study aimed to investigate the agronomic performance of several rice varieties (Oryza sativa L.) cultivated with different timings of GA3 application. The research was conducted in Lengau Seprang Village, Tanjung Morawa Subdistrict, Deli Serdang Regency, at an elevation of 80 meters above sea level from April to September 2021. The study utilized a randomized complete block design with two treatment factors. The first factor was rice varieties, including Inpari 32, Ciherang, and Siporang. The second factor was the timing of gibberellic acid application, which included 0, 1, 2, and 3 applications (at 20, 45, and 60 days after transplanting). The research results indicated that the different timings of GA3 application did not significantly affect all observed parameters. Siporang exhibited the highest average values for plant height, panicle length, and flag leaf area. However, it produced the lowest grain weight per hill compared to the other two varieties. The highest grain weight was obtained from the Inpari 32 variety.


Introduction
Rice stands as essential agricultural products that form the foundation of a population's diet that fulfills dietary needs of the Indonesian population.Therefore, its availability and sufficiency are of utmost priority.As of now, the majority of rice production comes from paddy fields, making the increase in rice production in these lands crucial for national rice self-sufficiency [1].
In 2020-2022, Indonesia experiences La Nina which is very favorable for increasing rice production due to rain throughout the year.Unfortunately, production was only able to increase slightly in 2020 by 0.09%, then decreased by 0.42% in 2021 and increased slightly by 0.61% in 2022.Even though throughout 2020 -2022, when the climate was very favorable, production barely increased.Therefore, we need to know how to increase maximum production [2].
National rice production increase can be achieved through various strategies and actions, both through intensification and extensification efforts.One alternative for improving rice yield through intensification is the selection of superior varieties and the use of growth regulators.Superior rice varieties are those that exhibit higher yields, resistance to diseases, and adaptability to their growing environments.The use of superior rice varieties is a strategy for increasing rice production [3,4,5].The use of local superior varieties can also be considered to boost rice production because these varieties adapt well to specific regions and offer unique advantages tailored to local environmental conditions, climate, and local needs.Siporang is one such local variety from South Tapanuli.Siporang's advantages include its excellent adaptation to the North Sumatra region, a delightful taste, and the potential to yield up to 6 tons per hectare.
The use of growth regulators in rice is believed to enhance grain yield.Several research findings indicate that the application of GA3 can increase rice yields [6,7].Additionally, this hormone has the ability reduce negative effects of abiotic stress [8].
The objective of these research was to study the changes in agronomic patterns and yields of two superior rice varieties and one local variety with different timing of GA3 application.

Materials and methods
This research was conduct on irrigated field in Lengau Serpong, Tanjung Morawa, Deli Serdang regency at an altitude of 80 MASL from April to Juni 2021.The first factor was the rice paddy varieties, namely Inpari 32, Ciherang, and Siporang.The second factor was the timing of gibberellic acid (GA3) application, which included 0, 1, and 2 applications (at ages 20, 45, and 60 days after transplanting), by spraying it on the plants at the recommended dosage of 40 grams per hectare in accordance with the Gibron product recommendation, which contains 10% GA3.The method of applying GA3 involves dissolving the GA3 powder in water at a rate of 1 gram per 15 liters of water (1 Knapsack).The plot applications utilized a sprayer to facilitate spraying, using the following calculation formula: (Ga3x dosis) x (15 x 1000 ml)/ha.For a plot size of 1 m 2 , the successive amounts of GA3 given for one, two, and three applications were 240, 120, and 80 ml respectively.

Results and discussion
Table 1 showed the characteristic age of plant, morphology, production of three varieties Siporang is a local rice variety from South Tapanuli, while Ciherang and Inpari 32 are national superior varieties.Morphologically, Siporang plants are relatively taller compared to Ciherang and Inpari 32.This variety also has a longer growth duration (Table 1).

Plant height
Vertical measurement of plant is the characteristics used to measure the productivity and quality of rice plants.It is influenced by various factors, including the variety, growing environment, and farming practices.This morphological criterion is often associated with lodging resistance.Plants that are excessively tall are generally more prone to lodging, which can affect harvest yields and post-harvest handling.
The statistical analysis results indicated that the timing of GA3 application did not have a significant effect on plant height, but each variety has different heights (Table 2).The lack of a significant effect from the timing of GA3 application is suspected to be due to the endogenous GA3 levels being sufficient for the plant's needs.Additionally, different plant types may respond differently to GA3, and in this case, the three varieties tested did not show a significant response to GA3 application.
Siporang is the variety with the highest average plant height, while Inpari 32 and Ciherang have the The plant height characteristic can be a determinant of plant yield as it is closely related to the photosynthesis process.Rice plants with shorter stems tend to utilize photosynthesis more efficiently than those with longer stems [10].According to [11], an ideal plant height with the potential for high yield is around 100 cm.Giving gibberellin had no significant effect on plant height, but some varieties, thought to be due to plant genetic factors which to research results (12), the genetic character of each variety means that the ability to respond to each variety is different to the application of gibberellin.The difference in height is only caused due to the variety variance, these results indicate that the genetic determine their ability to environment adaptation.

Leaf area
Surface area is a plant characteristic that can be used to assess the potential for assimilate formation.Larger leaves have the advantage of capturing more light for the photosynthesis process.The research findings indicate that the widest average leaf area is found in Siporang, while Ciherang and Inpari 32 have nearly the same leaf area (Table 3).Siporang's taller stature compared to Ciherang and Inpari 32 (Table 2) and its larger leaf area (Table 3) indicate a higher photosynthetic capacity to support seed production.The leaf part serves as the site for light capture for photosynthesis, thus, broader leaves have a higher photosynthetic capacity, leading to higher potential yields [13,14].Maximum Leaf Area Index (LAI) before flowering is crucial for rice plants, because this phase is a critical stage in seed filling.High yields are obtained from canopies that can capture more energy during this period [15].
Treatment of time application GA3 did not have positive response in terms of leaf quantity, but each rice variety will give a different growth response.According to (16), the genetic characteristics of each plant variety influence growth and production.

Panicle length
The average measurements for panicle length statistically show that the panicle length, from highest to lowest, is in the order of Siporang, Ciherang, and Inpari 32 (Table 4).Siporang has a higher yield potential compared to the other varieties.The panicles longger have the potential to produce more grains.Some studies have reported a significant positive correlation between plant height and panicle length [17,18].
The findings from this research suggest that Siporang exhibits greater yield potential than the other two varieties.Increased panicle length in plants holds the promise of higher grain production.Several studies have highlighted a strong positive link between the height of the plant and the length of its panicles.[17,18].[19] reported that Oryza sativa japonica cv.Kita-ake, which has tall plant stature, produced lush panicles despite late flowering.
Regarding 6 the number of panicles and the weight of filled grains per hill, the variance analysis results show that 4 the weight of filled grains per hill is only influenced by the variety factor, while the timing of GA3 application has no significant effect.As for the parameter of the number of panicles, neither the variety nor the timing of GA3 application had a significant impact (Table 5).
Application of gibberellin to several varieties had no significant effect on panicle length.It is suspected that genetic factors are more influential than the provision of the growth regulator gibberellin. 6 This observation was consistent across the count of panicles and the weight of mature grains per hill.Number of panicles and the weight of filled grains per hill.

Number of panicles and the weight of filled grains per hill
Regarding the number of panicles and the weight of filled grains per hill, the variance analysis results show that the weight of filled grains per hill is only influenced by the variety factor, while the timing of GA3 application has no significant effect.As for the parameter of the number of panicles, neither the variety nor the timing of GA3 application had a significant impact (Table 5).The results of this study indicate that despite Siporang having taller plant height, a larger leaf area, and longer panicles, it produces the same number of panicles as the other varieties.However, it record the lowest weight of filled grains.Inpari 32, on the other hand, produces the highest filled grain weight.Although statistically, panicles number produced by each variety is not significantly different, Siporang has the highest number of panicles.However, it records the lowest weight of filled grains per hil.Even though Siporang yields a higher quantity of panicles, its grains are comparatively smaller than those of the other two varieties.
The application of gibberellin to several varieties had no significant effect on panicles number.This is because genetic and environmental factors exert a greater influence than the mere application of GA3.According to (20) genetic factors will play a good role if environmental condition is optimal.Conversely, when the environment is at its best, plant growth and yield become predominantly determined by genetic factors.

Conclusion
GA3 applied to the plant does not affect plant height, leaf area, the length of panicle, or hill in a crop field.Despite showcasing taller plant height, a larger leaf area, and longer panicles, Siporang still ends up producing the lowest weight of filled grains per hill.Inpari 32 is variety that produces the highest average 4 weight of filled grains per hill compared to Ciherang or Siporang.

Table 1 .
The morphological characteristics of the three varieties used in the study Note: days after planting (DAP)[9]

Table 2 .
Plant height of three lowland rice varieties with different application times for gibberelin acid at 4 -7 weeks after transplanting (WAT) Note: W0 = control; W1 = 60 days after transplanting; W2 = 45 and 60 days after transplanting; W3 = 20, 45 and 60 days after transplanting.The Duncan's multiple range test (p=0.05) is not significantly by the numbers in columns and rows that are preceded by the same letter.

Table 3 .
Leaf area of three lowland rice varieties with different application times for gibberelin acid

Table 4 .
Panicle length of three lowland rice varieties with different application times for gibberelin acid

Table 5 .
Number of panicles and weight of filled grains per hill of three lowland rice with different application times for gibberelin acid Note: Numbers followed by different letters indicate presence significant difference based on the Duncan test at the 5% level (P≤0.05)