Effect of Biochar and Water Level on Increasing Availability and Water Use Efficiency for Maize in Vertisol from Jeneponto South Sulawesi

This study aims to determine the effect of biochar and water level on improving water retention and water use efficiency of corn crops in vertisol. The soil sample was taken from Jeneponto south Sulawesi. This research used split-plot design. The main plot treatment is a soil amendment consisting of two factors ie without biochar and Biochar,sub plot treatment is a water used level consisting of 4 levels ie 100%, 90%, 80%, and 70% field capacity. Observated parameters include field capacity, permanent wilting point, available water, the crops water consumption, crop matter use efficiency, and water use efficiency. The results showed that biochar was able to increase water retention and water use efficiency at low water used level conditions.


INTRODUCTION
Vertisol is one type of soil that is widely used for agricultural because it has a fairly good fertility rate, characterized by high cation exchange capacity, relatively basic saturation, high water holding capacity , with a neutral to alkaline pH ranging from 6-8.5, but water available low for plants (Deckerset al., 2001;Prasetyo, 2007). The high water-binding ability of Vertisol is due to the high clay content that may reaches more than 30% in all horizon with montmorillonite as its main mineral (FAO, 1990). May a montmorillonite is a clay mineral that has a very small in size so that the surface area clay becomes high. According to Foth (1998), the fine grain size of the clay affects the pore space and the adsorptive surface area, thereby increasing water storage capacity. The more surface area the more water and ions can be absorbed, 2: 1 clay mineral has surface area of 700-800 m2 g -1 (smectite) and 57-152 m2g -1 (micasmectiteinterstification), 1: 1 (kaolinite) 7-30 m2 g -1 , while allophane has surface area of 157 -484 m2 g -1 (Tan, 1998). Hanafiah (2007) reported that groundwater content in the field capacity conditions (1/3 atm) in sand, silt, and clay were 15%, 40%, and 55%, respectively. In Vertisol high water content conditions are also followed by high moisture content at the condition of the permanent wilting point, so the high amount of water available does not guarantee adequate availability for the plant. Ouyanget al., 2013). One of the ingredients that can be used as a source of biochar is rice husk. Rice husk is an easy agricultural waste in research location and the surrounding area. Soil improvement in Vertisol is expected to increase water availability for plants and avoid crops from drought. Drought conditions are responsible for 50% crop yield decline in the world (Wood, 2005). Plants with water shortages generally have smaller size compared to normal growing plants (Kurniasariet al., 2010). Lack of water causes a very significant decrease in yield and even the cause of death in plants (Salisbury and Ross, 1992  . So far, further research on how biochar response in improving water availability in various soil moisture conditions has not been done. Based on the above

II. MATERIALS AND METHODS
The study was prepared based on a split-plot design with a completely randomized design baseline design. Where the main plot factor is the soil amandement (A) and the plot factor is the water content level (K).The main plot factor consists of A0: no soil enhancer, A1: Biochar. Sub plot factor is K1: 100% field capacity, K2: 90% field capacity, K3: 80% Field Capacity, and K4: 70% Field Capacity. there are 8 treatment combinations and repeated 3 times, so there are 24 units of an experimental block. Media Planting Preparation Media planting comes from the Punagaya village Bangkala district Jeneponto. The soil is described as the Vertisol soil developed from the limestone parent material. The soil is taken from a depth of 0-20 cm and then dried, mashed and sieved with a 2 mm diameter strainer. The soil is weighed as much as 12 kg and given the soil enhancer according to the treatment of biochar as much as 6 % of the total weight of the soil (Fangfang and Lu, 2014; Gao . Giving water is done by weighing the pot to know the amount of water that should be given according to the treatment. The initial soil properties can be seen in Table 1. Bulk density analysis was done by gravimetric method. Porosity was determined based on weight value of particle type and weight by using gravimetric method as follows:

Tabel.1: Soil characteristics
Porosity (% volume) = (1-BD (Bulk Density) / PD (Particle Density is 2.65) X 100% (1) Where BD is bulk density and PD is partikel density use a value of 2.65 for mineral soil. Water retention analysis using Pressure method Plate apparatus at pF 2.54 and pF 4.2 (Capillarity and pF curve equations) (Richards and Fireman, 1943).Water use efficiency in this study used the amount of water given during plant growth (mm) and dry weight of the plant (g) harvested at 60 days old plants, by the formula: Where WUE is water use efficiency (g.mm-1), EyThe Dry weight of the plant (g), Et is the plant water consumption (mm)

Statistical Analysis
The result were analyzed by using variance analysis and followed by LSD at 5% level using STAR (Statistical Tool for Agricultural Research).

III. RESULT AND DISCUSSION Bulk Density and Soil Porosity
Statistical analysis showed no interaction between the treatments of soil amendment with the water level. Biochar is able to decrease bulk density and increase soil porosity significantly, whereas biochar treatment decreases bulk density from 0.897 to 0.775 gcm -3 and increases porosity from 66.13% to 70.72%. Biochar's ability to decrease bulk density and soil porosity was also reported by Jaceket al.
(2017) in the HaplicPodzol research in which biochar 4,5 and 3 t.ha-1 significantly reduced bulk density after 2 years of application. Biochar 2.5 to 5 t.ha-1 was found to decrease bulk density from 1.41 to 1.3 g.cm -3 compared to the application of manure on Alfisol soil (Pandianet al., 2016). Castelliniet al. (2015) reported that biochar administration significantly balances the amount of liquid phase and gas in the soil and reduces the solid phase in the soil. The treatment of moisture level showed that the K3 treatment (80% FC) gave the best result against the decrease of bulk density and porosity increase of 0.788 g.cm -3 and 70.25%, which was significantly different with K1 treatment (0.877 g.cm-3 and 67.04 %) and K2 (0.867 g.cm -3 and 67.30%) and differed from K4 treatment (0.818 g.cm-3 and 69.12%). The treatment of K1 (100% FC) and K2 (90% FC) caused the soil to become more humid and the air in the soil decreased, whereas on the soil K3 and K4 treatment were drier and the pore of soil was filled with air. In the condition of K3 and K4 is the development of plant roots to be better and affect the decrease of bulk density and increased porosity of the soil.

Water Retention
The results of the analysis of variance indicate that there is an interaction between the treatment of soil enhancer and moisture level to field capacity, permanent wilting point, and available water.

Field Capacity
Comparison of soil amendment factor (A) at various levels of water content (K) showed that treatment A0 (control) was significantly different from treatment A1 (Biochar) at high water content levels K1 (100%) and K2 (90%), how ever at water content of K3 (80%) and K4 (70%) there is no real difference between A0 (control) and A1 (Biochar). The comparison of water content (K) factor at soil amendment level (A) shows the field capacity at the highest A0 (control) treatment achieved at K1 treatment (100%) of 0.597% followed by K2 treatment (90%) of 0.56% and significantly different with K3 (80%) and K4 (70%). In Treatment A1 (Biochar) there was no significant difference between the various levels of water content (Table 3).

Water available
Comparison of A at level K shows a significant difference between A0 (control) and A1 (biochar) occurring at treatment K1 (100%) and K2 (90%) but not significantly different at K3 and K4.
Comparison of K at level A indicated that the highest available water A0 (control) was achieved at the treatment of K1 and K2 and was significantly different from the treatment of K3 and K4. While treatment A1 (Biochar) showed no significant difference in water available at various levels of water content (table 5). The result of statistic analysis for field capacity, permanent wilting point and water available on the comparison of soil enhancer (A) to water content level (K) showed that there was a significant difference between treatment A0 and A1 at water level K1 and K2, while on treatment K3 and K4 is not significantly different. This shows that at high levels of water content, A0 (control) treatment is able to bind water better than in treatment A1 (Biochar), but in low water content treatments, biochar is able to bind water better than control treatment. This result is in line with the Devereux et al. (2012) study which states that the addition of real biochar increases the water holding capacity when soil conditions dry out.
Comparison of moisture level (K) to the soil enhancer (A), indicating that the field capacity, permanent wilting point, and water available at the A0 treatment (control) decreased as water supply decreased. While in treatment A1 (Biochar) showed no real difference in field capacity, permanent wilting point, and water available at all levels of water content. The results of this study are in line with the results of the Fangfang and Shenggao (2014) study which stated that rice bran biochar on vertisol increases groundwater content in field capacity, permanent wilting point, and water available to plants. The results of statistical analysis showed no interaction between treatment of soil amendment (A) with water level (K), but there was significant difference between the influence of soil amendment (A) and water content level (K), in which biochar administration increased the amount of water 163.43 mm in maize compared with A0 treatment (125.49 mm). For the comparison of the treatment of moisture content, the largest amount of water consume by corn crops was achieved at K1 treatment (216.72 mm) followed by K2 (146.04 mm), K3 (113.91 mm), and K4 (101.18 mm) respectively. This is in line with Handayani (2004) study which states that the lower the moisture level of the soil during watering, the less water it will be. The reduced water the treatment responds to the plant by adjusting for water use during its growth phase. The plant responds to drought conditions in two ways by changing the distribution of new assimilates and regulating the level of stomatal opening to reduce the loss of water through transpiration (Mansfield and Atkinson, 1990).

The Dry weight of the plant
For the dry weight component of the plant, the statistical analysis shows that there is an interaction between the soil amandment (A) and the water content (K) level ( Figure 2). For comparison A at level K, it was seen that treatment A1 (biochar) gave the highest yield and was significantly different from treatment A0 (control). Comparison of water level (K) at soil amendment level (A) shows that the dry weight of the plant decreases in line with the decreasing amount of water administered both on treatment A0 (control) and A1 (Biochar). Maize is a very sensitive plant with soil moisture, where water is the limiting factor. The Khalili et al. (2014) study showed that the weight of plant biomass treated with drought stress significantly decreased compared to the control treatment. Previous research also proves that the decline in plant biomass is closely related to the decrease in soil moisture (Stone et al., 2001, Osborne et al., 2002.

Water Use Efficiency
There is an interaction between the treatment of soil enhancer and the level of water content to the efficiency of water use in corn crops. The comparison of the median treatment of factor A at level K showed that treatment A1 (Biochar) gave the highest yield and was significantly different at different levels of water content than the A0 (control) treatment. Biochar's ability to increase the efficiency of plant water use caused biochar to increase the availability of plant nutrients, improve cation exchange capacity so as to improve crop growth and yield (Atkinson et al., 2010;Mukherjee and Lal, 2013). This is in line with Yeboah's (2016) study which stated that 5 ton/ha biochar significantly increased corn yield by 2.5 ton H-1 compared to without biochar. Previous studies also suggest that Biochar can provide nutrients for plants, especially cations such as K, Ca and Mg (Daniket al., 2011) and ensure nutrient availability for plants (Zhang et al., 2016). For the treatment of water level (K) ratio at soil enhancer level (A) showed that the efficiency of water use in the K3 treatment gave the best result for corn corp on treatment A0 (control) and K4 level gave the best result of 36.69% for treatment A1 (Biochar) was significantly different from K2 treatment (32.35%) and was not significantly different with K1 and K3 treatment. The high efficiency of water usage at K3 level for treatment A0 (control) and K4 level on treatment A1 (Biochar) showed that under high humidity conditions (K1 and K2 levels) nutrient absorption did not run optimally, so that water content is appropriate for treatment A0 (Control) is at the level of K2 80% of the field capacity, under the condition of the moisture content the availability of nutrients decreases as the permanent wilting point increases. Provision of biochar is proven to increase the efficiency of water use at low levels of water content.
IV. CONCLUSION 1. Biochar is able to increase field capacity, reduce permanent wilting points and increase the amount of water available at all levels of water content. 2. Bbiochar feeding increases the amount of water consumption of the plant. 3. There is an interaction between the soil enhancer and the moisture content of the dry weight of the plant. The biochar treatment (A1) gave the best results compared to the treatment without biochar (A0). The dry weight of the plant decreases as the amount of water is decreased. 4. Biochar (A1) was able to increase the efficiency of water use compared to without biochar treatment (A0), and the highest result was obtained in combination of biochar treatment and lowest moisture content (K4).