Geographically the experimental site was located at Noldanga mouza, Jhenidah sadar upazila at 23°26' to 23°36' N latitude & 88°57' to 89°20' E longitude and was situated in High Ganges River floodplain (AEZ11). Red amaranth was used as the test crop for the experimental field. This particular variety has gained popularity among the farmers of Bangladesh for its high yield potential. Red amaranth can be grown throughout the year and can he harvested in a very short time. For vegetables and seed production red amaranth is best grown in winter. The seeds were collected from Bangladesh Agricultural Development Corporation (BADC). The experimental field was first opened in 5th June, 2009. The land was ploughed several times to obtain good tilth condition and finally prepared seven days before planting the seed. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. The total numbers of plots were 24. The size of the unit plot was 1.0 m x 1.0 m. Inter block and inter plot spacing were 0.25 m and 0.25 m, respectively. Eight treatments were conducted in the experiment viz. no fertilizer or manure, poultry manure, biogas residue, vermicompost, poultry manure in combination with inorganic N, P and K fertilizer, biogas residue in combination with inorganic (N, P, K) fertilizer and vermicompost in combination with inorganic NPK fertilizer and only inorganic N, P, K fertilizer. The treatments were as follows- TO: Control, T 1: Vermicompost + NPK, T2: Biogas Residue + NPK , T3: NPK•, T4: Biogas Residue, T5: Poultry Manure + NPK, T6: Vermicompost, T7: Poultry Manure.
According to BARI (1991) biogas residue, vermicompost and poultry manure were applied at the rate of 10 t ha-1, 7 t ha-1 and 5 t ha-1, respectively. Urea, TSP and MoP were as the source of N, P and K, respectively in traditional farming. Biogas residue, vermicompost and poultry manure were incorporated in the plots as per treatment at 4 days before sowing and were mixed thoroughly with the soil. All the fertilizers were applied during the final land preparation of plot, because red amaranth is a short duration crop. The seeds were planted in 26th June, 2009. The seeds were sown thoroughly as it was possible to keep uniformity and then the seeds were covered by soils. The seed rate was 1 kg ha-1 (BARI, 2005). Intercultural operations such as weeding, irrigation, fertilization and necessary observations were done. The experimental crop was harvested after 30 days of sowing on 27th July, 2009. The harvested plants were tagged separately, weighed, oven dried at 65°C to 70°C temperature for 48 hours until moisture content reaches to minimum condition. The dried material of each treatment was weighed. The parameters recorded and their mean values were calculated from the sample plants during experiment were plant height, shoot length, root length, leaves per plant, yield per plot, fresh weight per plant, dry weight per plant, moisture content (%) and dry matter content (%).
Initial soil samples were collected randomly from 10 different spots at 0-15 cm depth before manuring and fertilization and all samples were composite(' to make a single sample for analysis. After crop harvest, soil samples were collected again from each plot. After getting weeds and other unwanted things removed, the samples were air-dried, grind, sieved (through a 2 mm sieve) and tagged in plastic bag for physical and chemical analysis. The methods were used for analyzing the different parameters of soil samples are as follows: Soil color - munsell color chart, soil texture - sieving and hydrometer method, soil moisture - gravimetric method, soil reaction or soil pH - pH meter method, organic carbon -Walkley and Black's wet oxidation method, total nitrogen - micro-kjeldahl method, exchangeable potassium - extraction with NH4OAc., available phosphorous- Bray- II method. The collected data were compiled and tabulated in proper form and were subjected to statistical analysis. CRD studies were done following the standard method of computer programme (SAS).