An experiment was conducted on Gazipur (23°59′21.584′′N, 90°24′34.999′′E) belonging to the acidic soil during two rabi season of 2018-2019 and 2019-2020.The soil at the site of the experiment is under chiata soil series, brown hill soil type classified as Inceptisols.Initial soil samples (0-15cm) collected from arable fields and analyzed some important soil physical and chemical parameters of the experimental soil are presented.
Biochar preparation and analysis:
The poultry litter was collected from suburb of Gazipur region. Poultry litter was air-dried at room temperature and make small pieces then placed in biochar making device (made in Soil Science Division, BARI) and pyrolyzed under oxygen-limited conditions. The pyrolysis temperature was raised to the selected value of 700°C at a rate of approximately 20°C per minute and held constant for 2 h, then the biochar was allowed to cool to room temperature and ground to pass a 0.25 mm sieve. All biochar samples were examined to determine their main characteristics without further treatment, and their characteristics are described. After being thoroughly mixed with deionized water at a ratio of 1:20 and equilibrated for 1 h, the pH of the biochars was measured by Metler Toledo S220 with a combine electrode. The CEC of the soil samples was measured by ammonium acetate compulsory displacement method. Exchangeable base cations were extracted with 1.0 M ammonium acetate (pH 7.0) (Pansu and Gautheyrou, 2006). Ca2+ and Mg2+ were measured with AAS, and K+ and Na+ with flame photometre. The phosphorus was determined colorimetrically after digesting the biochars with sulphuric acid and hydrogen peroxide.
Fertilizer and Treatments:
The experiment was laid out in a randomized complete block design with three replications. The unit plot size was 3m ´ 2m and plant spacing was 60 cm ´ 20 cm. “BARI Khoibhutta” maize seeds were placed into experimental field on January, 2018. The experiment consisted of eight treatments, viz. T1 = Poultry litter @ 3 t ha-1, T2 = Poultry litter @ 6 t ha-1, T3 = Poultry litter @ 9 t ha-1, T4 = Poultry litter biochar @ 3 t ha-1, T5 = Poultry litter biochar @ 6 t ha-1, T6 = Poultry litter biochar @ 9 t ha-1, T7 = Agricultural lime 1 t ha-1, T8 = control. Recommended dose of fertilizer for the crop was N255 P50 K120 S40 Zn5 B2 kg ha-1. Urea, TSP, MoP, gypsum and boric acid were used as a source of N, P, K, S and B, respectively. All P, K, S, B and boichar, and 1/3 N were applied at the time of final land preparation and the remaining 2/3 N was applied in two equal installments at 25 and 50 days after transplanting. All the intercultural operations such as irrigation, weeding, insect control etc. were done as and when necessary. Harvesting of maize was done when the cob became mature and turned reddish color.
Soil sampling:
Initial soil samples were taken from the site at the depth of 0–15 cm before the experiment. The soil samples were thoroughly mixed to form a composite soil sample and used for the determination of the soil physical and chemical properties. Also, core soil samples were collected from 24 plots at the depth of 15 cm in each plot at 90 d and used for the determination of soil bulk density.
Pop corn Yield and Yield Components:
Plant height was measured on five random plants per plot. Thousand grain weight was determined by counting a hundred maize grains and weighing (Cerhulst et al., 2013). Grain yield (t ha−1) was corrected to 12.5% moisture level.
Soil and Plant analyses:
Soil bulk density was determined using the core method (Blake and Hartge, 1986) in which a stainless steel core (5 cm in diameter and 10 cm in height) was used to collect soil core to determine soil bulk density (Bd) in each sampling time during incubation. Total porosity (TP) was calculated from bulk density using the formula:
TP= 100 × {1- (Bd/Pd)}………………………………..(1)
where Bd = bulk density, Pd = Particle density, and Pd is assumed to be 2.65 g cm–3 (Obi, 2000). Soil organic carbon was determined by the Walkley–Black oxidation method (Nelson and Sommers, 1982). Total nitrogen was measured by the Kjeldahl method (Bremner and Mulvaney, 1982) and soil pH by a pH meter with soil to water ratio of 1:2.5 (Sahilemedhin and Taye, 2000). Exchangeable acidity (Al3+ and H+) was titrated using 0.01 M NaOH by extracting 4.0 g soil with 50 mL of 1.0 M KCl (Wang et al., 2012). Available phosphorus was determined by Bray-1 method, while potassium was measured with the flame photometry method (Sparks et al., 1996). The CEC of the soil samples was measured by ammonium acetate compulsory displacement method, exchangeable base cations were extracted with 1.0 M ammonium acetate (pH 7.0) (Pansu and Gautheyrou, 2006). Ca2+ and Mg2+ were measured with AAS, and K+ and Na+ with flame photometre. Carbon stock and C sequestration were calculated using the following equation 1 and 2, respectively.
Carbon stock (t ha-1) = Carbon concentration (%) x bulk density (g cm-3) x depth (cm).... (2)
Carbon accumulation (t ha-1) = Final C stock (t ha-1) – Initial C stock (t ha-1)................ (3)
The clean plant samples were air-dried and placed in an electric oven, dried at 105ºC for 24 h, weighted for dry biomass. Again, place it in the oven at 105ºC for 2h. Cool it in a desiccator and weight it again. Repeat drying, cooling and weighing until the weight become constant. The dried plant samples were homogenized by grinding using willey mill and used for nutrient analysis. Then, the grains were ground and N, P, K, Ca, Mg, S, B and Zn contents were determined according to the method described by described by Jones and Case (2018). Atomic absorption spectrophotometer (Thermo Scientific - SOLAAR S Series AA spectrometer) was used for metal ion and spectrophotometer (Agiland Technologies, cary 60 UV-Vis) for anion analysis. The accumulation of nutrients in the grains was estimated by multiplying nutrient content by dry grain weight.
Statistical analyses:
Software package, Statistix-10 (Analytical Software. Tallahassee, Fla, USA) was used for the statistical analysis of data. A one-way analysis of variance was undertaken for each time interval of the incubations to determine significant differences among treatments. The significant effects for various treatments were detected using t-test.