The ulitization of durian wood (Durio zibethinus) and corn cob (Zea mays) biochar on corn yields in acid sulphate soil

Biochar addition can be used to overcome the problem of acid sulphate soil. This study was aimed to analyze the effect of biochar dose on plant height and corn yield in acid sulphate soils. Durian wood waste and corn cob biochar used in this study was pyrolyzed for 2 hours at 550 °C temperature and grinded until around 0.4-1.0 mm. The experiment was conducted in a screen house at the Indonesian Swampland Agriculture Research Institute. The experimental design used was a Completely Randomized Design consisting of six doses of biochar treatment of with 3 replications. The total of 18 experimental pots was obtained with the following details: B1 0 t/ha, B2 4 t/ha, B3 8 t/ha, B4 12 t/ha, B5 16 t/ha and B6 20 t ha. Biochar treatment significantly affect plant height age of 2nd, 4th, 6th, 8th, 10th and 12th weeks. The longer the age, the higher the corn plant height. The corn cob length, corn cob diameter, dry weight of seed, and the dry water content significantly different in all treatments. The biochar dose significantly affected the corn yields. The best treatment of biochar in acid sulphate soil was obtained in 12 t ha-1.


Introduction
Biochar is a subtle-grained carbonization product that has a high organic carbon content and low degradation susceptibility, obtained through biomass and biodegradable waste pyrolysis [1]. Biochar can be used for energy-related intention related to agriculture and environmental conservancy. Various kinds of biochar utilization continue to develop, especially in fields such as farming, industry, and operation linked with natural surroundings [2]. A modern approach to biochar production and utilization promising long-range agricultural advantages [3]. Biochar can be returned to the soil to restock nutrients and minerals. Hence it can increase the soil physicochemical features such as density, porosity, and pH. Biochar has also been found to absorb heavy metal and release macro-and micronutrients slowly [4] which can contribute to increasing fertilizer efficiency.
Biochar is produced through pyrolysis, it is heated without enough oxygen for complete combustion, removes various liquids and gases from the feedstock, and leaves a residue as biochar. Slow pyrolysis is the most effective pyrolisis because it results in a high yield of approximately 35.0% by weight of dry biomass [5]. There are many kinds of pyrolysis feedstocks, such as municipal waste, agricultural biomass, and forestry residue. Nowadays, the forestry residues can be used as a sustainable and reliable pyrolysis feedstock. The forestry residue has the most interesting characteristics as pyrolysis biomass since it has a sustainable supply system for large scale base, and raw materials suitability because of its features (low humidity, metal, and ash content) [4]. Biochar ICSTSI 2020 IOP Conf. Series: Materials Science and Engineering 980 (2020) 012027 IOP Publishing doi:10.1088/1757-899X/980/1/012027 2 derived from wood has a large potency to increase C storage in tropical soils because of its high C concentration, aromatic character, and low H/C ratio. The high of aromatic C content is due to the high amount of lignin and cellulose in wood biomass [6].
As soil amendment, biochar has been developed as a sustainable practice that simultaneously can mitigate climate change and improve the marginal soil quality [7]. There are lots of marginal land in Indonesia, such as tidal land, acidic and peat soils. The use of marginal land for crop cultivation has several obstacles that must be faced. Acid sulphate soils have been seen as one of the difficult soil to manage for crop production because of their low fertility, such as low soil pH and available phosphate and high Fe content [8]. The corn cultivation is very potential to be developed in acid sulphate soil. Soil acidity in acid sulphate soils is a main obstacle in the corn cultivation because it needs optimum soil pH at 5.6-7.5 for best growth. The high acidity in the soil will cause a deficiency of macronutrients such as potassium, magnesium, calcium, and phosphorus. The corns begin to suffer at pH 5.6, and can not survive at pH 4.0 [9]. Liming improves soil for the microbe habitat. They accelerate the decay of plant residues and release micronutrients, N, and P in the soil. Liming the acid sulphate soil can reduce the solubility of manganese and aluminum at low pH. Biochar, as liming material, can improve plant growth and crop yield. The fertilizer application can increase the corn yield as 4.4 t ha -1 [10]. Fertilizers that are combined with biochar can numerically increase corn yields. Based on Brantley [11], corn yields at fertile silt loam can increase at a dose of 5 and 10 Mg ha −1 of woodchip biochar in combination with N fertilizer. The addition of cow manure biochar at 15 t ha −1 and 20 t ha −1 in combination with NPK fertilizer significantly increased the corn yield of 150% and 98%, respectively in sandy soil [12]. This study was aimed to analyze the effect of biochar dose on plant height and corn yield in acid sulphate soils.

Biochar production and properties
The method of biochar production was adopted from Setiawati [13]. Durian wood waste and corn cob as feedstock were collected from Banjarbaru, South Kalimantan, Indonesia. The feedstock was airdried to remove moisture. Dry wood waste was then pyrolyzed at 550 °C with a holding time of 2 hours. The hot biochar was then quickly immersed by water. The biochar produced was then air-dried and grinded until around 0.

Experimental design
The experimental design used in this study was a Completely Randomized Design (CRD) consisting of 6 (six) doses of biochar treatment of DWB and CCB with 3 replications. The analysis of data used SAS 9.1 software for windows by using the analysis of variance at the level of confidence at 5 %. Difference between treatments for each parameter was analyzed by the Duncan's Multiple Range (DMRT) Test with a 5% confidence level [14] . Table 1 showed that the moisture content of corn cob durian (6.18%) was lower than the durian wood biochar (7.66%). The value of water content in biochar could be influenced by the drying process of biochar just after being immersed in water. Biochar for agricultural purposes should have a low water content because it could accelerate the absorption of nutrients and/or water [15]. The value of water content affected the ability of biochar to hold water. Biochar had the high ability to retain water to maintain soil moisture and create environmental carrying capacity [16].

Biochar characteristics
Some research results concerning the pH value of biochar stated that biochar used as a soil conditioner should have an alkaline pH or above 7 [17,18]. These alkaline pH values indicated that both durian wood and corn cob biochars could also be used to reduce soil acidity. The corn cob biochar had a higher pH than that of durian wood (9.35 vs. 8.93, respectively), as well as a much higher CEC (25 vs. 24 me 100g -1 , respectively). The high pH was due to the nutrient content of corn cob was higher than durian wood. Furthermore, high ash content of corn cob biochar also played a vital role in increasing the pH of biochar. High CEC in biochar indicated the ability to retain nutrients and water so that the water availability of plants was sufficient, especially for the process of plant physiology which necessary for plant height growth [19].
In biomass, volatile matters were methane, hydrocarbons, hydrogen, carbon monoxide, and noncombustible gases such as carbon dioxide and nitrogen. The content of VM durian wood biochar and corn cob biochar was (15.21 and 17.13)%. The VM in biochar was composed of compounds other than water, ash, and carbon. It was consists of elements of hydrogen, hydrocarbons, CO2, CH4, methane, and carbon monoxide [15]. Therefore, the high or low value of VM in biochar was based on the chemical composition of extractive substances from its feedstock. Fixed-C showed that carbon had been converted to a more stable carbon which cannot be easily degraded. In line with the previous studies [13,15,20], the biochar FC of durian wood and corn cob was 71.9% and 70.37%.
The higher C concentration with a rise in pyrolysis temperature was due to a higher polymerization rate, resulted in a more condensed carbon structure in biochar. A similar result was reported for biochar produced by Domingues [6], biochar C contents in durian wood and corn cob were 79.88% and 81.13%. Yang [21] and Khodadad [22] found that biochar derived from wood at higher temperatures was more stable because it contains large amounts of aromatic organic matter compared to biochar made from agricultural residues when pyrolyzed at high temperature. An increase in the aromatic character of biochars was associated with dehydration reactions and removal of O and H functional groups, as well as the formation of aromatic structures [23]. The durian wood biochar had a higher H content than durian wood (11.09% vs. 10.23%, respectively), as well as a much higher O content (3.41% vs. 1.61%, respectively). As seen in figure 1, there was the similarity of functional groups between durian wood biochar and corn cob biochar, which consisted of conjugated C-H bend (aromatic) at 862.88 cm -1 -758.74 cm -1 , while the other peaks showed the presence of cluster C=O stretch (in ketone) 1686.43 cm -1 , C=C stretch (aromatic) at 1570.71 cm -1 -1481.99 cm -1 , -CH3 bend (in alkane) at 1481.99 cm -1 , and C-O stretch (in ether, esther, carboxylic acid, alcohol) at 1385.56 cm -1 -111.68 cm -1 . The higher number of C-H bend in durian wood biochar than corn cob biochar indicated that the durian wood biochar was more aromatic. The aromatic carbonyl (C-O) and carboxyl groups (C=O) were attributed to retained oxygen-containing organic groups in biochar produced. The broad peak of durian wood biochar at 3472.39 cm -1 came from the feedstock, which was commonly found in lignin of phenolics (O-H stretch) [24].

Soil pH and growth plant height
Based on the results of a variety of analysis, it showed that the various doses of durian wood biochar and corn cob biochar on corn plants significantly affected the height of corn plants aged 2 nd , 4 th , 6 th , 8 th , 10 th and 12 th weeks of observation. The longer the observation, the higher the corn plant height. It could be stated that biochar addition can significantly influence plant growth [25]. The obtained results of plant growth indicated that the ameliorative effect of biochar was largely related with pH increase (table 2). The soil pH increased at biochar dose starting from 4 t ha -1 (B2). In accordance with Manickam [7], the application of 4 t ha -1 biochar combined with bio-fertilizer yielded a high increase in soil pH and crop yields. 5.39 a 5.60 a 6.02 a 6.12 a 6.10 a 6.51 a Remarks: Numbers followed by the different letter within each column were significantly different based on DMRT α = 5% Table 3 [26], the low dose of biochar was not significantly different from the zero dose in plant height. During the first 1-2 weeks after planting, seeds provided food reserves for plant growth. In line with the development of the root system and decrease in food reserves in the seeds then the roots were immediately obtained following their functions. The growing point was 2-3 cm below the surface of the soil in the 3-4 week planting periods. In the first growing season at 3-4 week periods, plant height increased with the application of biochar.

Corn yield
Based on the study results, it showed that the corn cob length, corn cob diameter, dry weight of seed, and dry water content significantly different in all treatments. The biochar dose significantly affected The biochar could increase crop yield. The presence of cow manure as compost could improve productivity. The compost showed the existence of microbiological characteristics that the potential to be used as a soil conditioner. The combination of compost and biochar seemed to increase added value. It was proved in this study, which B2-B6 had a better yield performance than B1. In line with Trupiano [27] which stated that a combination of biochar and organic fertilizers (compost) which provides important nutrients for plants could increase soil fertility and crop yield. Compared to B1, the increasing of corn cob length was 12.28% -26.5% for DWB and 25.3%-33.6% for CCB (figure 2a), the corn cob diameter was 1.8%-13.1% for DWB and 8.4%-13.6% for CCB (Figure 2b), the dry weight of seed was 13.1-89.3% for DWB and 27.2-88.6% for CCB (Figure 2c), while the dry water content of corn was decreased by 5.6%-15.1% for DWB and 4.0%-9.1% for CCB.  showed that the highest dry weight of seed in acid sulphate soil was obtained from 12 t ha -1 (B4) biochar dose, which increased by 89.3% for durian wood biochar and 88.6% for corn cob biochar, compared with the treatment without biochar (B1). Ngongo [28] state that the optimum dose of bamboo biochar on dry weight of seed was 10.44 t ha -1 . Bamboo biochar on 10 t ha -1 could increase the growth of corn crops in dryland [29]. 10

Conclusion
Biochar treatment significantly affected plant height age of 2 nd , 4 th , 6 th , 8 th , 10 th and 12 th weeks. The longer the age, the higher the corn plant height. The corn cob length, corn cob diameter, dry weight of seed, and the dry water content significantly different in all treatments. The biochar dose significantly affected the corn yields. The cornob length was (11.20-14.14) cm for DWB treatment and (10.98-114.67) cm for CCB treatment. The diameter of corn cobs was (3.14-3.55) cm for DWB and (3.23-3.67) cm for CCB. The dry weight of seed was (26.77-50, 68) gr for DWB and (27.17-51.23) gr for CCB. The dry water content was (13.17-15.50) % for DWB and (13.24-14.56) % for CCB. The best treatment of biochar in acid sulphate soil was obtained in 12 t ha -1 .