Growth and yield of soybean varieties with biochar application

. Climate change cause a temperature increase, decreasing soil fertility and causing a reduced microbial and nutrient availability, and increased salinization, so it cannot support the growth of soybean plants. Soybeans are vulnerable to climate change, which can lead to lower yields. Biochar is an organic material that can improve soil's physical, chemical, and biological fertility. This study aims to obtain soybean varieties and biochar types that increase growth and yield in low soil fertility cultivation. This research was conducted in August 2022 – June 2023 at the Agricultural Faculty Experimental Field of Universitas Sebelas Maret. The research was designed in randomized complete block design factorial with three replications. The first factor was soybean varieties, and the second factor was types of biochar. Data analyzed using analysis of variance (ANOVA), followed by DMRT 5% if there was a significant difference. The results showed that Demas 1 variety significantly affects growth and yield with biochar addition compared to Dena 1 and Gepak Kuning. The addition of rice husk biochar can increase the growth and yield of 3 soybean varieties, compared to the addition of sugar palm fiber biochar and without the addition of biochar.


Introduction
Climate change can have a negative impact on soil properties and processes, which could threaten global food security since global demands for food and fiber for an increasing population are met by the soil.Climate change has potential negative impacts on soil health such as soil's organic matter, texture, hydrology, salinity, and fertility [1].Soybean plants belong to the category of crops that are susceptible to the effects of climate change, as they experience reduced yields under its influence [2].Low soil fertility resulted from climate change that caused by reduced microbial activity, reduced nutrient availability, and increased salinization inside the soil could also negatively affect soybean growth and yield, especially in alfisol soils that are already poor in nutrients and organic matter [3].Alfisol soil also has a clay-like texture that has a low porosity and slow drainage, making it prone to expansion and shrinking that could happen from temperature changes.This condition will be exacerbated due to the impact of climate change.
The challenges posed by climate change-induced soil fertility issues in alfisol soils can be addressed by incorporating soil-amending substances to enhance their quality.One of the soil-amending substance that can be used is biochar [4].Biochar is an organic material synthesized through a pyrolysis process that comes from agricultural waste that could be easily obtained.The utilization of biochar as agricultural waste is a significant endeavor in promoting sustainable agriculture [5].Biochar significantly affects soil fertility in degraded soil by fixing the chemical, biological, physical characteristics of the soil, and bind plant macronutrients [6].The results showed that biochar increased soybean yields by increasing soil nutrient levels and soybean nutrient uptake.Applying biochar to plantings can provide a positive response to the stability of soil aggregates, soil CEC, soil organic C content, water and nutrient retention due to an increase in soil carbon [7].Applying biochar such as rice husk improves soil penetration resistance because the formation of stable soil aggregates causes an increase in soil porosity and reduces soil density [8].
The use of biochar in crop cultivation is not to replace the role of fertilizer, but as a complement to fertilizer.Applying biochar can provide nutrients for plants, thereby increasing plant growth and yields.The information presented highlights the need for research on diverse biochar variations.This study aims to obtain soybean varieties and biochar types that increase growth and yield in low soil fertility cultivation

Materials and method
This research was conducted in August 2022 -June 2023 at the Agricultural Faculty Experimental Field of Universitas Sebelas Maret, Jumantono, Karanganyar.The study used a randomized complete block design with three replications.The treatment factors were soybean varieties, namely Dena 1, Demas 1, Gepak Kuning and biochar types, namely control (0 tons/ha), rice husk (15 tons/ha), and sugar palm fiber (15 tons/ha).Data analyzed using analysis of variance (ANOVA), followed by a DMRT level of 5% if the data was significant.Variables observed were plant height, number of leaves, stem diameter, flowering age, dry weight of stover, number of pods per plant, number of seeds per pod, weight of 100 seeds, number of root nodules, and harvest index.

Soybean growth components
Plant growth which includes the vegetative and generative phases plays an important role in the life cycle of plant.Vegetative growth involves an increase in the volume, number, shape and size of vegetative organs such as leaves, stems, and diameter.Generative growth involves the growth of the generative organs starting from the formation of the initial flower.
Analysis of variance showed that the use of varieties significantly affected stem diameter, flowering age, and dry weight of stover.In contrast, the use of biochar had a significant effect on stem diameter (Table 1).The Dena 1 variety treatment showed the highest plant height growth at 10 WAP of 38.78 cm but not significant if compared to the Demas 1 and Gepak Kuning varieties; meanwhile, rice husk biochar gave the highest results on plant height of 40.06 cm but not significant if compared to other types.According to [9], genetic factors include plant innate characteristics such as tolerance and adaptation, and environmental factors such as climate, physical, biological conditions, and nutrient availability in the soil.Applying rice husk biochar can provide nitrogen nutrients plants need and encourage plant growth mechanisms [10].1).The application of rice husk biochar significantly affect stem diameter of 9.19 mm compared to the other types of biochar (Table 1).Stem diameter rises with increased water and nutrient absorption, as stated by [11].According to [12], nitrogen and hosphorus nutrients can help in the vegetative growth of plants, especially in plant stems.[13] stated that adding rice husk biochar increases soil nitrogen content, promoting plant growth.Optimal plant growth occurs with the right biochar quantity, demonstrating its crucial role.
The Gepak Kuning variety had the highest number of leaves with 108.00 leaves, but not significantly different from the Demas 1 variety, with 98.97 leaves.The type of biochar did not significantly affect the number of leaves, but the type of rice husk gave results on the number of leaves of 104.30 leaves, not significant if compared to the treatment of the type of sugar palm fiber biochar and without biochar (Table 1).Genetics influence leaf formation.[14] stated it as a factor shaping adaptability and organ development.Leaf number depends on photosynthate production influenced by nitrogen, impacting assimilated yield [15].Table 2 below shows the effect of biochar application on flowering time and stover dry weight of several soybean varieties.
Table 2.The effect of biochar application on flowering time and stover dry weight of several soybean varieties.
Numbers followed by the same notation in the same column group show no significant difference at the DMRT level of 5%.
The Demas 1 variety had the longest flowering age compared to other varieties, around 7.33 WAP, while the application of biochar did not have a significant effect on the flowering period of the three soybean varieties ( flower appearance [16].Genetics and environment influence flowering age through vegetative growth and development [17]. The Demas 1 variety had a significantly different dry weight of stover of 39.95 g compared to Dena 1 of 20.41 g and Gepak Kuning of 17.35 g.The application of biochar type did not have a significant effect on the dry weight of the stover (Table 2).Genetic and environmental factors, unique to each plant, mutually influence stover dry weight due to varying photosynthetic abilities and conditions [18].Soybean varieties adapt differently to the same environment based on their genetics, altering physical and biological traits for optimal growth [19].

Soybean yield components
Soybean yield components is one of the indicator to determine soybean productivity.Soybean yield components observed were number of pods per plant, number of seeds per pod, 100 seed weight, number of root nodules, and harvest index.Table 3 below shows the effect of biochar application on number of pods per plant, number of seeds per pod, and 100 seed weight of several soybean varieties.
Table 3.The effect of biochar application on number of pods per plant, number of seeds per pod, and 100 seed weight of several soybean varieties.
Numbers followed by the same notation in the same column group show no significant difference at the DMRT level of 5%.
The results of the analysis of variance showed that the use of varieties had a significant effect on the number of pods per plant, the number of seeds per pod, the weight of 100 seeds, and the yield index, while the type of biochar had a significant effect on the number of pods per plant and the number of pods per seed (Table 3).The Demas 1 variety produced the highest number of pods per plant with 122.41 pods, but was not significantly different from the Gepak Kuning variety with 96.89 pods.The application of rice husk biochar gave the highest number of pods per plant of 117.37 pods, significantly different from the treatment without biochar of 77.44 pods but not significantly different from sugar palm fiber of 117.37 pods (Table 3).Number of pod per plant rises due to favorable environmental conditions and enhanced photosynthetic processes, leading to increased assimilation production [20].[21] stated that nitrogen plays a vital role in the formation of pods in plants.
The Dena 1 variety with rice husk biochar gave the highest yield on the number of seeds per pod compared to other treatment combinations.The Dena 1 variety had a significantly different number of seeds per pod of 1.94 seeds compared to the Gepak Kuning variety of 1.60 seeds and the Demas 1 variety of 1.21 seeds.The treatment without biochar addition had a significantly different effect on the number of seeds per pod of 1.74 seeds compared to rice husk and sugar palm fiber biochar (Table 3).The ability of plants to form seeds in pods is determined predominantly by the adequate nutrient status of plants [22].
The Dena 1 variety had a significantly different weight of 100 seeds of 4.23 g compared to the Gepak Kuning and Demas 1 variety, which were 2.53 g and 2.06 g.The type of biochar did not significantly affect the weight of 100 soybean seeds (Table 3).Seed weight indicates seed size, influenced by each variety's unique photosynthetic ability, impacting overall production [23].Dena 1 seeds fall into the large category, with a weight of ± 14.3 g, while Demas 1 and Gepak Kuning seeds are in the medium category, weighing ± 13 g and ± 8.25 g, based on variety descriptions [24].Table 4 below shows the effect of biochar application on number of root nodules and harvest index of several soybean varieties.
Table 4.The effect of biochar application on number of root nodules and harvest index of several soybean varieties.
Numbers followed by the same notation in the same column group show no significant difference at the DMRT level of 5%.
Treatment of varieties and types of biochar significantly affected the number of root nodules.The Demas 1 variety significantly affected the number of root nodules of 25.26, not significant if compared to Gepak Kuning of 18.44.Sugar palm fiber biochar led to 25.67 nodules, significantly different from the control of 11.33, but not from rice husk biochar of 18.04 (Table 4).Root nodule formation varies due to soil nutrient availability, aeration, root size, and plants nitrogen-fixing ability, leading to differences between varieties [25].Rhizobia facilitate biological nitrogen fixation in root nodules, converting nitrogen into usable forms [26].
The Dena 1 variety gave a significantly different harvest index of 0.82 compared to the Gepak kuning and Demas 1 varieties, which were 0.82 and 0.25.Biochar treatment did not significantly affect harvest index (Table 4).Genetic differences cause differences in yield index between varieties.[27] stated that the effect of crop production is influenced by genetic factor of the soybean.Each soybean has a different size and seed weight so it can affect the yield.Sugar palm fiber has a larger fiber texture and pores compared to rice husk, so the resulting aeration is also better.According to [28], this allows nitrogen-fixing bacteria to adapt and work better.

Conclusion
Climate change can have a negative impact on soil fertility, which could threaten global food security.Low soil fertility resulted from climate change could also negatively affect soybean growth and yield, especially in alfisol soils that are already poor in nutrients and organic matter.Biochar can be used as a sustainable solution to overcome the problem with its soilfixing abilities.Based on the results of the research, the use of Demas 1 variety significantly affects growth and yield with biochar addition compared to Dena 1 and Gepak Kuning.The addition of rice husk biochar can increase the growth and yield of 3 soybean varieties, compared to the addition of sugar palm fiber biochar and without the addition of biochar.

Table 1 .
The effect of biochar application on plant height, stem diameter, and number of leaves of several soybean varieties at the age of 10 week after planting.Numbers followed by the same notation in the same column group show no significant difference at the DMRT level of 5%.Demas 1 variety and rice husk biochar gave the highest stem diameter on 10 WAP of 9.19 mm compared to other treatment combinations.The Demas 1 variety had a significantly different stem diameter of 9.69 mm compared to the Dena 1 variety of 8.04 mm and Gepak Kuning of 7.81 mm (Table