Universitas Wiralodra, Jl. Ir. H. Juanda KM 3 Indramayu 2. Lecturer, Faculty of Agriculture, Universitas Padjadjaran 3

The Effect of Steel Slag ….

Jurnal Agrikultura 2015, 26 (2): 68-74 ISSN 0853-2885

The Effect of Steel Slag and Bokashi of Husk to Soil Bulk Density, Soil Aggregate Stability, Soil Porosity and Plant Biomass Broccoli in Andisol Lembang Henly Yulina1,3*, Rina Devnita2 dan Rachmat Harryanto2 Universitas Wiralodra, Jl. Ir. H. Juanda KM 3 Indramayu 2Lecturer, Faculty of Agriculture, Universitas Padjadjaran 3Graduate Student, Faculty of Agriculture, Universitas Padjadjaran *Alamat korespondensi: [email protected] 1

ABSTRACT Andisol soil has very good soil physical characteristic, however it has problem with the P retention. Giving ameliorant to reduce the P retention is expected to maintain, moreover to improve some soil physical characteristics. The objective of this research was to find out the interaction between steel slag and bokashi of husk to bulk density, aggregate stability, soil porosity and biomass of broccoli on Andisol Lembang. This study used a randomized block design factorial with two factors. The first factor was steel slag and the second factor was bokashi of husk. Each of them consisted of 4 levels: 0%, 2.5%, 5.0% and 7.5% with two replications. The result of this research showed there was not interaction between steel slag and bokashi of husk to soil bulk density, soil aggregate stability, soil porosity and biomass of broccoli. The statistical results showed that bokashi of husk influence independently to decreasing soil bulk density until 0.53 g cm-3, decreasing soil aggregate stability until 3.25 and increasing soil porosity until 80.22%, but the provision of steel slag and bokashi of husk didn‟t influence to biomass of broccoli. Keywords : organik matter, silicate, bulk density, agreggate stability, broccoli ABSTRAK Andisol mempunyai sifat fisika tanah yang baik, namun bermasalah dengan retensi P. Pemberian amelioran untuk mengurangi retensi P, diharapkan dapat mempertahankan, bahkan meningkatkan beberapa parameter fisika tanah tersebut. Penelitian bertujuan untuk mengetahui interaksi terak baja dengan bokashi sekam padi terhadap bobot isi, kemantapan agregat, porositas tanah dan biomassa tanaman brokoli pada Andisol Lembang. Penelitian menggunakan Rancangan Acak Kelompok Pola Faktorial dengan dua faktor. Faktor pertama terak baja dan faktor kedua bokashi sekam padi masing-masing 4 taraf: 0%, 2,5%, 5,0% dan 7,5%, diulang dua kali. Hasil penelitian menunjukkan bahwa tidak terjadi interaksi antara terak baja dengan bokashi sekam padi terhadap bobot isi, kemantapan agregat, porositas tanah dan biomassa tanaman brokoli. Hasil statistik menunjukkan bahwa bokashi sekam padi berpengaruh mandiri untuk menurunkan bobot isi tanah sampai 0.53 g cm-3, menurunkan kemantapan agregat tanah sampai 3,25 dan meningkatkan porositas tanah sampai 80,22%, namun pemberian terak baja dan bokashi sekam padi tidak berpengaruh terhadap biomassa tanaman brokoli. Kata kunci : bahan organik, silikat, bobot isi, kemantapan agregat, brokoli

INTRODUCTION

characteristic characterized by C-organic content 25% or less, bulk density 0,9 g cm-3 or less, P retention is more than 85% and amount of Al + ½

Andisol derives from volcanic ash parent material (Devnita, 2010) with andic soil 68



Fe percentages of more than 2,0% extracted with ammonium oxalate (Soil Survey Staff, 2014). Andisol has a high potential for agriculture because it has excellent some soil physicals and chemical characteristics, such as low soil bulk density, high permeability, high organic matter content and high nutrient content. However, Andisol has problem with high P retention and low P availability. The low availability of P in Andisol is caused by the high afinity. It„s clay minerals like allophane, imogolite, ferrihydrite and Al-humus complexes (Hardjowigeno, 2003). Allophane is highly reactive (Sukmawati, 2011) due to the large specific surface area (Uehara and Gillman, 1982) and active positive charged functional groups (Bohn et al., 1979), that can bind the negative charged of phosphate. It causes the P retention on Andisol is very high, that can be 85% or more. Silicates and organic matter are the anions with high negative charged, therefore they can replace the retain phosphate (Tan, 2001). Silicates and organic matter not only can decrease P retention, but also can decrease bulk density, increase the P availability, aggregate stability and water available (Rashid, 2012; Sukmawati, 2011; Ardiyanto, 2009; Putri, 2010 and Jamil et al., 2006). Steel slag and bokashi of husk can be used as the source of silicate and organic matter. Steel slag is a byproduct of the refining of iron in steel making (Ismunadji et al, 1991). Steel slag has been used for long time for agriculture, as a source of P, Si and lime (Rex, 2002). Silicate can increase the meso pore (Princess, 2010), stimulate the plant growth and also can be an important element for some certain plant (Yukamgo and Yowono, 2007).

Organic matter can improve soil chemical characteristic by increasing the P availability in soil (Stevenson, 1982) and decreasing the P retention through the organic acids as a results of weathering product of organic matter. (Jamil et al. , 2006). Organic matter also can improve physical characteristic by forming and stabilizing soil aggregates. Organic matter is able to bind a single particle into an aggregate to create more pore spaces between the aggregates. Organic matter also can increase plant biomass (Yulnafatmawita, 2006). Broccoli produces flowers and needs P for growth. Phospor is macro nutrient that important for stimulate root growth, plant growth, accelerate the maturity of the fruit and seeds (Suyono et al., 2008) and crop production (Rashid, 2012). Research on the influence of steel slag and bokashi of husk to P retention, P avaibility and chemical characteristics has been found in several publication, but effect of the treatments to the soil physical characteristics has not been found yet. The objective of this research was to find out the effect to physical characteristics, such as bulk density, aggregate stability, soil porosity and biomass. MATERIALS AND METHODS This research was conducted at the Balai Penelitian Tanaman Sayuran (Balitsa) Lembang, on September until February 2014. The research used randomized block design (RBD) factorial with two factors. The first factor was steel slag and the second factor was bokashi of husk each consisted 4 levels: 0%, 2.5%, 5.0% and 7.5% with two replications. Total treatments were 4x4x2 = 32. Steel slag obtained from PT. Krakatau Steel and bokashi of husk has been made in Pedca Unpad. The combination of treatments can be seen in Table 1.

Table 1: Combination Treatment of Steel Slag and Bokashi of husk. Steel Slag (T) t0 t1 t2 t3

Bokashi of husk (B) b1 b2 t0b1 t0b2 t1b1 t1b2 t2b1 t2b2 t3b1 t3b2

b0 t0b0 t1b0 t2b0 t3b0

The soil used in this research taken at some point in the Balitsa with depth of 0-20 cm. The mixtures of soil with defined treatments were then filled into 32 polybags (diameters of 60 cm to a depth of 60 cm) for 4 months while incubating soil was weighed every 1 week 2 times and water levels

b3 t0b3 t1b3 t2b3 t3b3

maintained in field capacity. After incubation of 4 months, broccoli was planted in each polybag. Fertilizer used was 200 kg ha-1 urea, 250 kg ha-1 SP-36 and 200 kg ha-1 KCl with spacing of 60 cm x 40 cm. Broccoli be harvested after the age of 72 days (Wasonowati, 2009), after reaching the end of 69



the generative phase. Soil samples were taken with ring sample and clod. Undisturbed soil samples taken with ring samples were used for measuring bulk density and soil porosity. Soil agreggate stability taken with clod and plants taken to weigh for plant biomass, were the plant roots and vanished. After treatments and incubation, every soils in every treatments were analysed for soil bulk density, soil agreggate stability and soil porosity. Analysed were conducted in the Conservation and Soil Physics Laboratory, Department of Soil Science and Land Resources, Faculty of Agriculture, University of Padjadjaran and Soil Physics Laboratory, Department of Soil Science and Land

Resources, Faculty of Agricultural University.

Agriculture,

Bogor

RESULT AND DISCUSSION Bulk Density Statistical analysis showed that there was no interaction between the steel slag and bokashi of husk to soil bulk density. The statistical results showed that the bokashi of husk independently decreased the bulk density. However steel slag had not influence to the bulk density, as can be seen in Table 2.

Table 2. Influence Bokashi of Husk and Steel Slag to Bulk Density. Treatment Bulk Density Bokashi of husk (B) and Steel Slag (T) b0 (without bokashi of husk / control) 0.79 a b1 (2.5 % bokashi of husk) 0.69 b b2 (5.0 % bokashi of husk) 0.59 c b3 (7.5 % bokashi of husk) 0.53 d t0 (without steel slag / control) 0.65 a t1 (2.5 % steel slag to the growing media) 0.64 a t2 (5.0 % steel slag to the growing media) 0.68 a t3 (7.5 % steel slag to the growing media) 0.63 a Remarks: Figures followed by the same letter, are not significantly different according to Duncan's Multiple Range Test at the 5% level. Data in Table 2 showed that the bokashi of husk influenced in the decreasing of soil bulk density. The increasing dosage of bokashi of husk, caused the decreasing of the soil bulk density. The lowest bulk density (0.53) was obtained at the dosage of 7.5% bokashi of husk. However, the dosage of 2.5% and 5.0% had already decreased the soil bulk density compared to the control. Bulk density was an indication of the density of the soil. The more dense the soil, the higher bulk density, make the root more difficult to penetrate the soil. Increasing soil organic matter content can maintain the quality of soil physics to help the development of plant roots (Hairiah, 2000). The increasing of roots will improve the absorbtion of the nutrients (Wigati et al, 2006). Plant roots also contributed to the abundance of organic matter in the soil that acted as an adhesive (binder) of soil particles, therefore the

aggregation in soil would be stable, pore space would be increase and bulk density would be decrease. This was in line with Mariana (2006) mentioned that the organic matter when applied to the soil would create pore space and reduce the soil bulk density. In this research, steel slag didn‟t influence the soil bulk density. Because the steel slag volumetrically was less than bokashi of husk. Soil Aggregates Stability Statistical analysis showed that there was no interaction between the steel slag and bokashi of husk to soil aggregate stability. The statistical results showed that the bokashi of husk independently improve the soil aggregate stability, steel slag had not influence to the soil aggregate stability, as can be seen in Table 3.

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Table 3. Influence Bokashi of Husk and Steel Slag to Soil Aggregate Stability. Treatment Soil Aggregate Stability Bokashi of husk (B) and Steel Slag (T) b0 (without bokashi of husk / control) 6.75 a b1 (2.5 % bokashi of husk) 3.75 b b2 (5.0 % bokashi of husk) 3.25 b b3 (7.5 % bokashi of husk) 3.25 b t0 (without steel slag / control) 4.13 a t1 (2.5 % steel slag to the growing media) 4.25 a t2 (5.0 % steel slag to the growing media) 4.25 a t3 (7.5 % steel slag to the growing media) 4.38 a Remarks: Figures followed by the same letter, are not significantly different according to Duncan's Multiple Range Test at the 5% level. Data in Table 3 showed that the bokashi of husk increased the soil agreggate stability. The smaller value of soil agreggate stability formed the more stable soil agreggation. The increasing dosage of bokashi of husk caused the more stable soil agreggation. The lowest soil agreggate stability (3.25) obtained at the dosage of 5.0% and 7.5% bokashi of husk. However, the dosage of 2.5% have already increased the soil agreggate stability compared to the control. Bokashi of husk influenced independently on the soil aggregate stability. Due to bokashi of husk volumetrically more than steel slag,caused by the less of bulk density (bulk density of bokashi of husk 0.3 g cm-3 and bulk density of steel slag 1.7 g cm-3) Bokashi of husk contains organic carbon that had a high positive and negative charged. The negative charged of organic matter (carboxyl) that would bind to the negative charged clay domains

with intermediate cations Ca, Mg, Fe and hydrogen bonding, while the positive charged of organic matter (amine, amide and amino) would bind with the clay domains negative charged (Sarief, 1989), so it would form a stable soil aggregates. Plant roots also contributed to the abundance of soil organic matter (Watts et al., 1993) that played a role in stabilizing soil aggregates by binding soil particles into aggregates. Soil Porosity Statistical analysis showed that there was no interaction between the steel slag and bokashi of husk to soil porosity. The statistical results showed that the bokashi of husk influenced increase the soil porosity. Steel slag had not influence, as can be seen in Table 4.

Table 4. Influence Bokashi of Husk and Steel Slag to Soil Porosity. Treatment Soil Porosity (%) Bokashi of husk (B) and Steel Slag (T) b0 (without bokashi of husk / control) 70.04 a b1 (2.5 % bokashi of husk) 73.88 b b2 (5.0 % bokashi of husk) 77.52 c b3 (7.5 % bokashi of husk) 80.22 d t0 (without steel slag / control) 75.49 a t1 (2.5 % steel slag to the growing media) 75.81 a t2 (5.0 % steel slag to the growing media) 74.28 a t3 (7.5 % steel slag to the growing media) 76.08 a Remarks: Figures followed by the same letter, are not significantly different according to Duncan's Multiple Range Test at the 5% level. Data in Table 4 showed that the bokashi of husk increased the soil porosity. The increasing the dosage of bokashi of husk, caused the increasing of

the soil porosity. The highest soil porosity (80.22) obtained at the dosage of 7.5% bokashi of husk. However, the dosage of 2.5% and 5% had already

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increased the soil porosity compared to the control. Hasanah (2009) showed that the value of soil would be optimal if soil porosity was greater than 50%. The increasing meso pore would increase the air-filled pores and lower the water-filled pores, therefore would improve aeration in the soil. Organic matter would improve the total of soil pore and decreased soil bulk density (Wiskandar, 2002). Soil porosity also could not be separated from other soil physical characteristic, like soil bulk density and aggregate stability. These physical characteristic were also closely associated with plant roots as a growing medium. Soil bulk density was

one reflection of the differences in soil aggregate size, which indirectly affect the growth and yield of, due to its influence to soil porosity, water availability, aggregate stability and movement of roots in the soil (Alexander and Miller, 1991). Plant Biomasss Statistical analysis showed that there was no interaction between the steel slag and bokashi of husk to biomass. The statistical results showed that steel slag and bokashi of husk had not influence to biomass as can be seen in Table 5.

Table 5. Influence Steel Slag and Bokashi of Husk to Plant Biomass . Treatment Biomass Steel Slag (T) and Bokashi of husk (B) Plant Broccoli t0 (without steel slag / control) 146.00 a t1 (2.5 % steel slag to the growing media) 130.50 a t2 (5.0 % steel slag to the growing media) 138.88 a t3 (7.5 % steel slag to the growing media) 126.88 a b0 (without bokashi of husk / control) 130.75 a b1 (2.5 % bokashi of husk) 135.50 a b2 (5.0 % bokashi of husk) 138.00 a b3 (7.5 % bokashi of husk) 138.00 a Remarks: Figures followed by the same letter, are not significantly different according to Duncan's Multiple Range Test at the 5% level. Data in Table 5 showed that the steel slag and bokashi of husk had not influence to plant biomass. Broccoli had fibrous root (radix primaria) with root branches elliptic shape (cillindris), spread in all directions at a depth between 30-50 cm (Haryanto et al., 2003). So cation and anion in the steel slag and bokashi of husk could be evenly absorbed by plants. This result also indicated that the improvement of soil physical characteristics like soil bulk density, soil agreggate stability and soil porosity with steel slag and bokashi of husk had not able to increase the biomass of broccoli yet, soil bulk density was low, soil aggregate stability was stable and soil porosity was great. Limited of space in a polybag caused the roots growth was not optimal, although growing media had a low bulk density. The used of polybag could make the soil was deeper be solid. In a solid soil contact between the roots and the soil was greater, but root growth was hampered by the large of soil resistance, the ability of roots to grow in the soil was limited, so the lack of water or nutrients for

plants (Pasioura, 1991; Bengough and Mullins, 1990) causes plant growth was reduced. CONCLUSION The results of this research showed that there was not interaction between the steel slag and bokashi of husk to soil bulk density, soil aggregate stability, soil porosity and biomass of broccoli. The statistical results showed that there was the influenced independently bokashi of husk to soil bulk density, soil aggregate stability and soil porosity at dosage of 2.5%, but the provision of steel slag and bokashi of husk didn‟t influence to biomass of broccoli. ACKNOWLEDGEMENT I would like to thank my guide, Dr. Rina Devnita, Ir., MS., M.Sc whose has financed my research. I thank to Dr. Rachmat Harryanto, Ir., MS whose has guided to finish my thesis and we are grateful to Balai Penelitian Tanaman Sayuran

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(Balitsa) Lembang for permission to use the land for research.

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Universitas Wiralodra, Jl. Ir. H. Juanda KM 3 Indramayu 2. Lecturer, Faculty of Agriculture, Universitas Padjadjaran 3

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