The experiment was carried out during January to April, 2014.
Experimental materials
Feedstock
Sawdust was used for feedstock or raw materials. The sawdust was collected from woodcuts from a local sawmill. The raw materials were spread on a polythene sheet for sun drying to decrease the water content for two days. Time for drying depended on the materials and when drying completed, this feedstock was used for biochar production.
Biochar stove:
The biochar has been produced in biochar stove developed by Mia et al. (2012).
Production of biochar
Biochar used for the field experiment was produced from sawdust by pyrolysis. The average residence time was (5 hours) and the highest temperature was >350 0 C. Fifteen (15) kg dry sawdust were pyrolysed each time by 5 kg fuel (dry wooden stem) and produced biochar was 3.3 kg on an average. (Appendix IV). (Figure 3.1(b))
Seed collection
The seeds of three soybean varieties (BARIsoybean-5, BINAsoybean-1, Shohag (PB-1) were used as planting materials.
Soil
The top soil of newly developed agronomy field was used for this experiment. The soil of the experiment was silt clay loam having pH > 8.5. It was mildly alkaline and non saline.
Experimental treatments
The experiment was included two factors.
Factor A:Soil amenders
C= Non-fertilized soil without biochar(Control)
BC = Non-fertilized soil with biochar
BC+ N = Biochar + N-fertilizer
BC+ P = Biochar + P-fertilizer
BC+ K = Biochar +K-fertilizer
BC+ NPK= Biochar + Normal dose of fertilizers
NPK = Recommended rate of N, P and K
Factor B:Variety : 3
V1 : BARIsoybean-5
V2 : BINAsoybean-1
V3 : Shohag (PB-1)
Experimental design and layout
The experiment consisted of three Soybean varieties and seven soil treatments and was laid out in a RCBD (Completely Randomized Block Design) with three replications. The line to line distance of pot arrangement was 40cm .The total pots were 63 (varieties 3 × soil amenders 7 × replications 3). All pots were arranged using excel randomization program.
Preparation of soil and pot trials
The top soil layer (0-15 cm depth) from Research field of Agronomy Department, Patuakhali Science and Technology University, was used for the experiment. The land was filled with sand soil in the previous from unknown source.The soil samples were air-dried and moved out all sort of stones and bigger particles by manually. The soil was sieved with 10 mm sieve. The properties of soil are under analysis supported by project of Biochar Production and Development. Earthen pot with 22 cm × 28 cm × 30 cm was used for the experiment. Each pot received a uniform weight of 8kg soil or a soil and biochar mixture. Biochar was applied at a rate of 25 t ha-1. Inorganic fertilizers were applied as 60-175-120 kg ha-1 N-P2O5-K2O through urea, triple super phosphate, muriate of potash as the recommendation of (KrishiProzuktiHaatBoi; BARI, 2005). Biochar and all fertilizers were added during final soil preparation for pot filling (Appendix-1). For each pot 153 gm biochar is applied. The required amount of biochar or biochar and fertilizers dose for each application rate was combined with the soil on a floor by manually until that mixer was homogenous. A total of sixty three (63) pots were filling-up by soil or soil with different soil amendments. Then all pots were placed in outside to simulate nature or at field condition. The moisture content of soil was maintained at 60% water holding capacity by a manual test (3.5.3 section).Then pots were kept for 10days before seed sowing and watered on every alternate day
Crop sampling and Data collection
Data were collected on plant height and leaves number plant-1 at 30 DAS, 60 DAS and 90 DAS respectively. Plant height, root length, number of branches plant-1, Nodules plant-1, pod numbers plant-1, number of seeds pod-1were collected at harvest time. Similarly, weight of stem, leaves, pod shell, root, seeds plant-1 and 100-seed weight were collected also at harvest time on fresh and dry weight basis. Different parts of plant were separated and those samples were oven-dried to a constant weight at 700Cfor 72 hours.
Chlorophyll content of leaves (SPAD value)
Chlorophyll content of leaves was measured by SPAD (model: 502 plus) (Soil Plant Analysis Development) meter. SPAD reading were taken from 5 randomly selected youngest and fully expanded leaves of each soybean plant. This reading was taken one side of the midrib of leaf blade, mid way between the leaf blade and tip and average SPAD reading was recorded from each plant.
Harvest index
Harvest index (HI) was calculated by dividing economic yield to biological yield of plant by multiplying with 100 and expressed in percentage.
Harvest index (HI) = 
×100