Acta agriculturae Slovenica, 116/2, 253–260 Ljubljana 2020 doi:10.14720/aas.2020.116.2.1322 Original research article / izvirni znanstveni članek Effect of soil conditioner enriched with biofertilizers to improve soil fer- tility and maize (Zea mays L.) growth on andisols Sinabung area Mariani SEMBIRING 1, 2 , Tengku SABRINA 1 , Mukhlis MUKHLIS 1 Received November 13, 2019; accepted October 25, 2020. Delo je prispelo 13. novembra 2019, sprejeto 25. oktobra 2020. 1 Universitas Sumatera Utara, Faculty of Agriculture, Padang Bulan, Medan 20155, Indonesia 2 Corresponding author, e-mail: mariani.sembiring29@yahoo.com or marianisembiring@usu.ac.id Effect of soil conditioner enriched with biofertilizers to im- prove soil fertility and maize (Zea mays L.) growth on andis- ols Sinabung area Abstract: Andisol soil contains a lot of heavy metals Al and Fe, which results in P being unavailable to plants and can cause low soil pH, this will inhibit plant growth. One effort that can be made to increase the availability of nutrients in the soil is by utilizing soil enhancing ingredients enriched with biological fertilizers. The research design used was factorial randomized block design (RBD) consisting of: Factor I: (biological fertiliz- ers) M0 = without application, M1 = Talaromyces pinophilus (Hedgecock), M2 = Azotobacter sp, M3 = Mycorrhizae, M4 = Talaromyces pinophilus + mycorrhizae + Azotobacter sp. Fac- tor II Soil enhancing ingredients, namely P0 = Without Soil Improvement, K1 = Zeolite 50 g, K2 = Humic acid 50 ml, K3 = compost / manure fertilizer for agriculture 50 g. From the results the combination of microbial treatment and soil condi- tioner can increase nitrogen in the soil by 2-40.81 %, cation ex- change capacity by 1.7-44.29 % and P available by 1.3-49.36 %. Soil conditioner combined with biological fertilizers can im- prove soil quality in general, the best treatment is a combina- tion treatment of T. pinophilus + mycorrhizae + Azotobacter sp. with coffee skin (M4P4). Key words: andisol; biological fertilizers; maize; soil con- ditioner; soil fertility Dodatek izboljševalcev tal obogatenih z biognojili izboljša rodovitnost tal in rast koruze (Zea mays L.) na andisolih na območju Sinabung, Indonezija Izvleček: Andisoli vsebujejo veliko težkih kovin, Al in Fe, kar povzroča nedostopnost P rastlinam in lahko zniža pH tal in s tem zavira rast rastlin. Eden od načinov za povečanje razpoložljivosti hranil v takšnih tleh je uporaba talnih izbolj- ševalcev obogatenih z biognojili. Poskus v raziskavi je bil po- polni naključni bločni poskus, ki je obsegal naslednja obrav- navanja: obravnavanje I: (biognojila) M0 = brez gnojil, M1 = Talaromyces pinophilus (Hedgecock), M2 = Azotobacter sp., M3 = mycorrhiza, M4 = Talaromyces pinophilus + mycorrhizae + Azotobacter sp. Obravnavnaje II- z dodatki izboljševalcev tal: P0 = brez izboljševalcev tal, K1 = zeolite 50 g, K2 = humin- ska kislina 50 ml, K3 = kompost / kurji gnoj 50 g. Rezultati so pokazali, da je kombinacija obravnavanja z mikrobi in talnimi izboljševalci povečala vsebnost dušika v tleh za 2 do 40,81 %, kationska izmenjevalna kapaciteta se je povečala za 1,7-44,29 % in vsebnost dostopnega fosforja za 1,3 do 49,36 %. Izboljševalci tal v kombinaciji z biognojili lahko na splošno izboljšajo kvali- teto tal. V poskusu je bilo najboljše obravnavanje T. pinophilus + mycorrhizae + Azotobacter sp. z dodatki ostankov iz pridela- ve kave (M4P4). Ključne besede: andisol; biognojila; koruza; izboljševalci tal; rodovitnost tal Acta agriculturae Slovenica, 116/2 – 2020 254 M. SEMBIRING et al. 1 INTRODUCTION The accumulation of organic matter and the oc- currence of organic matter complexes with Al are char- acteristic of some andisol soils. The research results of Ritonga et al (2015) and Sembiring et al. (2016), stated that the pH of andisol soil affected by the eruption of Mount Sinabung ranges from 3.7 to 4.7 which is in the very acidic category. The low pH of the soil affected by the eruption of Mount Sinabung results that the availabil- ity of P in the soil can be hampered. One effort that could be made to increase nutrient availability and andisol soil fertility is by applying soil conditioner enriched with biological agents, namely organisms that are useful in in- creasing the availability of nutrients for plants. According to Sembiring et al. (2016; 2017a; 2017b), application of phosphate solvent microbes (Talaromyces pinophilus) can increase the availability of P by 9.63 to 49.78 % in andisol soil. Observations of Marbun et al. (2015), shows that ap- plication of phosphate solvent fungi and organic matter can increase P uptake and potato plant growth on andi- sol soil affected by the eruption of Mount Sinabung. Ac- cording to Sembiring et al. (2018), Hijikata et al. (2010), Kikuchi et al. (2014) application of mycorrhizae can im- prove plant growth. Application of Azotobacter can in- crease plant growth (Kizilkaya, 2009; Patil et al., 2011; Ponmurugan et al., 2012). Agricultural development in Indonesia is faced with soil quality problems which are generally classified as low, characterized by problems with poor nutrients and organic matter, high soil acidity, and soil physical proper- ties that do not support plant growth. High soil fertility shows high soil quality (Biswas and Kole, 2017; Doran and Parkin, 1994). Soil quality is the capacity of the soil which functions to maintain crop productivity. Good soil quality will support soil function, working as a medium for plant growth, regulate and divide water flow and sup- port a good environment (Krener, 2013; Pal, 2016). Soil conditioner is a material that can be used to ac- celerate the recovery / improvement of soil quality. Or- ganic matter, besides being able to function as a source of nutrients, s functions as a soil conditioner has also been widely proven. In addition to organic soil condi- tioner, there are mineral soil conditioner that can be used to improve soil quality. Zeolite is a mineral mate- rial that can be used as a soil conditioner (Suwardi and Goto, 1996; Juarsah, 2016). Application of zeolite can increase the efficiency of fertilization, cation exchange capacity (CEC), soil potassium, P availability and plant growth (Juarsah, 2016; Balqies, et al., 2018). Cover crops that produce organic materials play an important role in improving soil quality because they protect the soil from erosion, and create suitable environmental conditions for microbial habitats that play a role in nutrient cycling (Marzaioli et al., 2010; Krener, 2013). Maize is a plant that can be used as an indicator because it requires fer- tile soil to produce properly. This is because maize plants need nutrients, especially nitrogen (N), phosphorus (P) and potassium (K) in large quantities. In general, maize plants require loose soil, fertile and rich in organic mat- ter. Therefore this study aims to improve soil fertility and growth of maize using a soil conditioner and biofertiliz- ers. 2 MATERIALS AND METHODS Research was carried out in Kuta Rayat Village, Karo Regency. Indicator plant used was maize variety Super Sweet. The research was conducted for 3 months. The andisol soil characteristics used were: pH 4.56, 4.8 % organic C (Walkey and black titration method) P availa- bility is at 67.28 ppm (Bray II method), soil N is at 0.55 % (Kjedahl-Titrimetry Method) and CEC 19.87 %me kg -1 . Materials used were: T.pinophilus (Hedgecock) Samson et al., Azotobacter sp. and mycorrhiza (Glomus sp.) used were obtained from the Laboratory of Soil Biology, Fac- ulty of Agriculture, University of Sumatera Utara. The research design used factorial randomized block design (RBD) with two factors and three replica- tions. Factor I was biofertilizers consisting of treatments M0 = without application, M1 = 30 g T.pinophilus (18 x 10 9 CFU g -1 ), M2 = 30 g mycorrhiza (Glomus sp.), M3 = 30 g Azotobacter sp. (18 x 10 9 CFU g -1 ) and M4 = 10 %g T. pinophilus + 10 g mycorrhiza + 10 g Azotobac- ter sp.. Factor II: material for soil conditioner (applica- tion 50 %g/plant, equivalent to 1t ha -1 ), P0 = without soil conditioner, P1 = zeolite, P2 = humic acid, P3 = chicken manure and P4 = coffee shell. Plot size 0.6 x 4.20 m, the distance between plots within a block was 30 cm and spacing between blocks was 50 cm. Soil conditioner ap- plication was carried out 2 weeks before the corn plant was planted by applying it to the planting hole and then mixed evenly. Application of biofertilizers was carried out after 1 week of plant growth by applying it around the plant roots. Basis fertilizers used were urea 3 g, super phosphat 36 (SP 36) and KCl 5 g/plant application was carried out 2 day before the corn plant was planted by applying it to the planting hole and then mixed evenly. 2.1 DATA COLLECTION Phosphorus analysis (P) availability in soil with Bray II method, soil N nutrient content, soil K nutrient content in 25 % HCl, cation exchange capacity (CEC), Acta agriculturae Slovenica, 116/2 – 2020 255 Effect of soil conditioner enriched with biofertilizers to improve soil fertility and maize (Zea mays L.) growth on andisols Sinabung area soil pH, microbial population, nutrient content of N, P, K of plants and plant dry mass all parameters observed at the end of the vegetative period. Soil and plant sam- ples were taken after plant growth for 45 days. By taking 1 sample/plot where the sample is randomly determined at the beginning of plant growth. 2.2 STATISTICAL ANALYSIS Statistical analysis used to see the effect of treatment was carried out on F test at the level of 5 % and continued with LSD test at 5 % level (Gomez and Gomez, 1984). 3 RESULTS AND DISCUSSION 3.1 RESULTS The results of observations and statistical analysis of soil conditioner applications and biological agents on all parameters of observation, can be seen in Table 1 and Table 2. Application of biological fertilizers had no significant effect on increasing soil pH, soil total N, soil K and soil CEC but had significant effect (p < 0.05) on available P in soil (Table 1). Application of biological agents (M) can increase the availability of phosphorus (P) in soil. Soil conditioner have a significant effect (p ≤ 0.05) on the soil K content and plant dry mass, zeolite treatment (P1) increases soil K levels for 24.34 % when compared with no application (P0). The treatment com- bination of soil conditioner and biological fertilizers can increase cation exchange capacity for 44.29 % when compared with control (Figure 1), soil N content, the best treatment was T.pinophilus and coffee peels (M1P4) increased soil N content by 40.81 % (Figure 2) and avail- able P for 49.36 % when compared to control ( Figure 3). Application of biofertilizers increases nutrient con- tent of N, P , K in plants and plant dry mass (Table 2). The application of T. pinophilus + mycorrhizae + Azotobacter sp. (M4) increases the nutrient P content in plants by 19.81 % and plant dry mass by 25.94 % when compared with the control. Application of mycorrhiza and zeolite (M3P1) can increase potassium (K) content in soil by 19.10 % (Figure 4). The treatment combination of soil conditioner and biological fertilizers can increase nutri- ent K content in plants (Figure 5), Treatment of T. pino- philus + mycorrhizae + Azotobacter sp. (M4) and coffee skin increase nutrient K content in plants by 28.83 % and plant dry mass by 25 % when compared to control. Treatment Soil pH Microbial Popula- tion (10 8 CFU g -1 ) Soil N (%) P-Available (mg kg -1 ) Soil K (mg kg -1 ) CEC (mol kg – 1 ) Biofertilizers (M) M0 5.46±0.24 33.53±11.48a 0.58±0.05 93.69±27.64a 601.19±54.07 19.38±2.34 M1 5.41±0.13 44.87±9.80bcd 0.56±0.08 118.07±15.26ab 581.46±52.72 19.81±2.39 M2 5.53±0.05 44.13±8.35ab 0.53±0.04 84.86±8.34a 563.24±110.07 18.12±1.60 M3 5.47±0.17 38.93±8.74a 0.56±0.06 101.99±19.16a 610.20±168.77 19.87±2.72 M4 5.61±0.10 44.47±13.24abc 0.55±0.03 100.63±26.02a 611.74±71.06 19.27±1.73 Soil conditioner (P) P0 5.5±0.17 39.53±10.93a 0.52±0.05 101.34±19.76 562.93±59.10a 18.44±1.22a P1 5.46±0.18 41.80±7.78a 0.57±0.05 103.83±20.48 700.74±115.48b 21.16±2.84ab P2 5.45±0.21 39.6±11.86a 0.56±0.05 103.84±17.26 567.23±73.34a 19.96±1.86a P3 5.59±0.07 45.07±11.70ab 0.56±0.04 88.49±24.95 568.21±77.67a 18.76±2.01a P4 5.47±0.15 39.93±13.59a 0.57±0.08 101.72±30.37 568.74±85.46a 19.13±2.20a M NS * NS * NS NS P NS * NS NS * * MxP NS NS * * * * CV% 6.38 27.67 10.34 27.8 10.17 11.89 Table 1: Average of soil pH, microbial population, levels of N, P , K soil and CEC treatment of soil conditioner enriched with biofer- tilizers Description: *significant at p ≤ 0.05 and NS Not significance. Means in a column followed by a common letter are not significantly different at the level 0.05 level by LSD. M0 = without application, M1 = Talaromyces pinophilus, M2 = Mycorrhizae, M3 = Azotobacter sp., M4 = T. pinophilus + Mycorrhizae + Azotobacter sp., P0 = without soil conditioner, P1 = zeolite, P2 = humic acid, P3 = chicken manure and P4 = coffee skin. Acta agriculturae Slovenica, 116/2 – 2020 256 M. SEMBIRING et al. 3.2 DISCUSSION The application of T. pinophilus (M1) increases the P availability by 26.02 % when compared to without appli- cation (M0) and can increase the P available by 102.32 % when compared with the initial soil analysis (67.28 %). This is because T.pinophilus used is an environment- specific microbe isolated from areas affected by Mount Sinabung eruption (Sembiring and Fauzi, 2017). Rao (1999) argues that the mechanism of releasing P-bound from Al, Fe, Ca and Mg can be carried out in the pres- ence of organic acids through chelating processes so that P becomes available and be absorbed by plants. Soil conditioner increases soil K content and plant dry mass, zeolite treatment (P1) can increases soil K nu- trient levels by 24.34 %. According to Suwardi (2009), zeolite as an enhancer given to the soil with sufficient quantities can improve soil physical, chemical and bio- Treatment N nutrient content in plant (%) P nutrient content in plant (%) K nutrient content in plant (%) Plant dry mass (g) Biofertilizers (M) M0 1.32±0.11 0.222±0.06a 2.42±0.23 206.46±41.69b M1 1.52±0.23 0.256±0.03a 2.31±0.14 211.19±37.95c M2 1.34±0.18 0.257±0.02b 2.44±0.28 236.53±45.45d M3 1.32±0.13 0.261±0.02ab 2.22±0.34 200.02±33.20a M4 1.42±0.21 0.266±0.02bc 2.34±0.33 260.02±28.06e Soil conditioner (P) P0 1.35±0.22a 0.241±0.03a 2.21±0.39a 207.69±43.19a P1 1.23±0.11a 0.251±0.02a 2.36±0.25ab 205.14±36.20a P2 1.38±0.17a 0.266±0.03a 2.45±0.21bcd 230.77±49.94d P3 1.49±0.19bc 0.273±0.01ab 2.28±0.17a 210.53±35.29bc P4 1.47±0.13ab 0.231±0.05a 2.43±0.27abc 260.09±27.22e M NS * NS * P * * * * MxP NS NS * NS CV 18.4 15.9 9.74 22.09 Table 2: Average of N, P , K nutrient content in plants and plant dry mass in soil conditioner treatment enriched with biofertilizers Description: *significant at p ≤ 0.05 and NS Not significance. Means in a column followed by a common letter are not significantly different at the level 0.05 level by LSD. M0 = without application, M1 = Talaromyces pinophilus, M2 = Mycorrhizae, M3 = Azotobacter sp, M4 = T. pinophilus + Myc- orrhizae + Azotobacter sp, P0 = without soil conditioner, P1 = Zeolite, P2 = Humic acid, P3 = Chicken manure and P4 = Coffee skin. Figure 1: Interaction of soil conditioner and biofertilizers to CEC in the soil (mol kg – 1 ) Acta agriculturae Slovenica, 116/2 – 2020 257 Effect of soil conditioner enriched with biofertilizers to improve soil fertility and maize (Zea mays L.) growth on andisols Sinabung area Figure 2: Interaction of soil conditioner and biofertilizers to soil N nutrient content (%) Figure 3: Interaction of soil conditioner and biofertilizers to P available in the soil (mg kg -1 ) Figure 4: Interaction of soil conditioner and biofertilizers to K in the soil (mg kg -1 ) Acta agriculturae Slovenica, 116/2 – 2020 258 M. SEMBIRING et al. logical properties so that agricultural production can be increased. According to Ahmed et al. (2010), zeolite is able to increase the availability of nutrients in the soil and soil nutrient uptake from fertilizers that are used to improve the efficiency of the availability of nutrients in the soil and reduce soil bleaching so that nutrients can be used for corn plant growth. The treatment combination of soil conditioner and biological agents can increase soil N content for 40.81 % and P available for 49.36 %. The research results of Sem- biring et al., 2017b; Masdariah et al., 2019; Siswana et al., 2019 stated that the application of phosphate solubilizing microbes and organic matter can increase the P avail- ability in andisol. Phosphate solubilizing microbes and organic matter are able to produce organic acids so that the availability of nutrient elements in the soil increases (Richardson, 2001; Gyaneshwar et al., 2002). Application of mycorrhiza and zeolite (M3P1) can increase potassi- um (K) content in soil and cation exchange capacity. The ability of zeolites which can improve the physical, chemi- cal and biological properties of soil combined with my- corrhiza applications is expected to increase the cation exchange capacity of the soil as observed from the results of Suwardi and Wijaya (2013). The application of T. pinophilus + mycorrhizae + Azotobacter sp. (M4) increases the nutrient P content in plants and plant dry mass. The application of T. pinophi- lus (M1) can increase the P available for 26.02 % when compared to without application (M0) and can increase the P available for 102.32 when compared with the ini- tial soil analysis (67.28 %). This is because T.pinophilus used is an environment-specific microbe isolated from areas affected by Mount Sinabung eruption (Sembiring and Fauzi, 2017). According to Al-Karaki (2000; 2006); Gamper et al., 2004; Chiou et al., 2001) application of mycorrhizae can increase nutrient P uptake of plant. The research results of Sembiring et al, (2018); Farzaneh et al. (2011) stated that the application of mycorrhizae could increase nutrient P uptake for 67.83 % and plant growth for 59.45 %. According to Redman et al., 2002; Lewis 2004, the presence of mycorrhizae in plant roots can im- prove the ability to absorb nutrients so that plant growth becomes elevated. Soil conditioner can increase soil nutrient content. Chicken manure treatment (P3) increases the nutrient N content in plants for 10.37 % and the nutrient P content in plants for 13.27 % when compared to control (P0). Sembiring and Fauzi (2017) stated that the application of chicken manure could increase the P uptake of plant for 6 % when compared to without application. Applica- tion of humic acid (P2) can increase the nutrient K con- tent in plants for 28.83 % when compared to control. The treatment combination of soil conditioner and biological agents can increase nutrient K content in plants, treat- ment of T. pinophilus + mycorrhizae + Azotobacter sp. (M4) and coffee skin can increase nutrient K content in plants, plant dry mass. This is because the ability of each microbial is different and so if put together will expected to increase plant growth. This finding is in consistence with the findings of Sembiring et al. (2016). Soil conditioner and biological agents can improve soil quality, namely pH 4.56 to 5.61 in this case ∆pH is 1.05. The effect of the increasing P available in the soil, the initial soil was 67.28 ppm to 118.07 ppm the increase in p available was at ∆50.76 ppm. The soil N parameters observed increased with the treatment, the initial soil analysis of soil N content was 0.55 % to 0.57 increase in soil N by ∆N 0.02 and CEC 20.87 increased to 21.16 me kg -1 so that ∆CEC 0.29 was obtained. From the results of this research we observe that the treatment applications improve soil quality which is in line with the findings of according to Kirener (2013); Marzioli (2010). Figure 5: Interaction of soil conditioner and biofertilizers to nutrient K content in the plant (%) Acta agriculturae Slovenica, 116/2 – 2020 259 Effect of soil conditioner enriched with biofertilizers to improve soil fertility and maize (Zea mays L.) growth on andisols Sinabung area 4 CONCLUSIONS This study found superior soil repairers and mi- crobes that can increase soil fertility and plant growth. This research will help researchers and farmers to over- come the low soil fertility in andisols. 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