The research work was done in the rabi season during October 2010 to March 2011 at the Allium Field Laboratory, Horticulture Farm, Bangladesh Agricultural University, Mymensingh. Materials used and methodologies followed in this investigation have been described below:
2.1. Study materials Twenty five germplasm of garlic were collected from different parts of Bangladesh (Nilphamari, Dinajpur, Ishurdi, Magura, Rajshahi and Mymensingh district) also different parts of the world (Tunisia, Turkey, Florida, China and Vietnam).
2.2.1. Climate and Soil condition The experimental area was under a sub-tropical humid climate which is characterized by heavy rainfall, air temperature, sunshine hour, annual average rainfall and relative humidity and have been presented. The soil of the experimental area of Bangladesh Agricultural University Farm was sandy loam and belongs to the Old-Brahmaputra Flood-Plain Alluvial Tract. The soil samples collected at a depth of 0-30 cm from the, experimental area were analyzed in the Humboldt Soil Testing Laboratory, Department of Soil Science, Bangladesh Agricultural University, Mymensingh. Description of the characteristics of soil of the experimental plot have been presented. The morphological characteristics of the soil of the experimental plot are given below. AEZ: Old Brahmaptura Flood Plain Soil series: Sonatala series General soil: Non calcareous dark grey Parent material: Old Brahmaptura River-borne deposits.
2.2.2.1 Land preparation The experimental land was first opened by tractor one month before planting. Several ploughing and cross ploughing followed by laddering were done until the desired tilth was achieved for planting the cloves. Weeds and stubbles were then removed from the field. Finally, the land was divided into blocks in which small plots (plot size were mentioned in individual experiment) were made as an experimental unit according to the design of the experiment.
2.2.2.2 Manure and fertilizer The crop received manures and fertilizers at the rate of cowdung 5 tons, Urea 217 kg, T.S.P. 267 kg, M.P. 333 kg and Zypsum 111 kg per hectare respectively. The entire amount of cowdung and TSP were added to the soil at the time of final land preparation 7 days before planting. Urea and MP were top dressed in three equal installments at 25, 50 and 75 days after planting of cloves or transplanting of seedlings.
2.2.2.3 Planting materials Cloves were separated from the bulb, and only the healthy large sized ones were planted. Date of planting: 10 Nov, 2010 Plant spacing: 20 cm x 10 cm 2.2.2.4 Intercultural operation Weeding and pulverizing of soil were done regularly whenever necessary to keep the plots free from weeds and to ensure good aeration in soil.
2.2.2.5 Plant protection Ridomil MZ 72 WP and Rovral at the rate of 25g and 45g in 10 litre of water was applied at an interval of 15 days from 30 DAP up to one month before harvesting to prevent the purple leaf blotch disease caused by Alternaria porii.
2.2.3 Harvesting The garlic plants when the tops turn yellowish or light brownish and show signs of drying up indicate the symptom of maturity. The bulbs were lifted, freed from earth and the leaves were tied at the top. The bulbs were cured for 2 to 3 days in t he shade before storing them in an ordinary room. Thoroughly cured garlic bulbs store well in ordinary well-ventilated room/store.
2.2.4 Laboratory works At the experimental site, a laboratory for weighing and sample drying was used. A good electrical weighing balance and oven were used.
2.2.5 Collection of data The following data were recorded on the base of physio- morphological growth parameters after planting as well as on yield. 2.2. 5.1 Number of leaves per plant The number of leaves per plant was counted from 5 randomly selected plants. The mean number of leaves was calculated by dividing total number of leaves observed from 5 plants by 5. 2.2.5.2 Height of plant (cm) Plant height was measured from the base of the leaf sheath to the tip of the longest leaf of 5 randomly selected plants and mean was calculated in cm. 2.2.5.3 Length of leaf (cm) Length of leaf was measured from the base to top of the leaf of 5 randomly selected leaves in centimeter and mean was calculated. 2.2.5.4 Fresh leaf weight (g) Fresh weight of leaves of 5 randomly selected plants was taken and their average was calculated in gram as fresh weight of leaves of individual plant. 2.2.5.5 Dry leaf weight (g) Fresh weight of leaves of 5 randomly selected plants was taken and the average was considered in gram as fresh weight of leaves per plant. The leaves were cut into small pieces, dried in the sun for 3 days and kept in an oven at 80°C for 72 hours, till a constant weight was achieved. Average dry weight of leaves per five plants was estimated. 2.2.5.6 Number of clove/plant The cloves were counted from 5 plants and their average was taken as a number of cloves per plant. 2.2.5.7 Bulb diameter (cm) Diameter at the widest part of 5 randomly selected bulbs was measured in centimeter and then average diameter of each bulb was calculated. 2.2.5.8 Fresh weight of bulb (g) Fresh weight of bulb of 5 randomly selected plants was taken and their average was calculated in gram as fresh weight of bulb of individual plant. 2.2.5.9 Dry weight of bulb (g) Fresh weight of bulb of 5 randomly selected plants was taken, and the average was considered in gram as fresh weight of bulb per plant. Bulbs were cut into small pieces, dried in the sun for 3 days and kept in an oven at 80°C for 72 hours, till a constant weight was achieved. Average dry weight of bulb per plant was estimated. 2.2.5.10 Yield of bulb per plot (kg) The yield of bulb per plot was taken in kilogram (kg) by harvesting all the bulbs of each plot after removing the roots and pseudo stem. 2.2.5.11 Yield of bulb per hectare (t) Per plot yield of bulb was converted into yield per hectare and expressed in ton (t).
2.2.6 Design and layout of the experiment The experiment was laid out in a Randomized Completely Block Design (RCBD) with three replications. The whole plot was divided into three blocks, each containing 25 unit plots of 1 square meter and one germplasm represented one treatment.
2.2.7 Statistical analysis Data collected from the experiment were statistically analyzed as per design of the experiment followed in the field using PLABSTAT computer package programmer [30-34]. The means for all treatments were calculated and the analyses of variances for all the characters under consideration were performed by 'F' variance test. The significance of difference between pair of means was performed by Least Significant Difference (LSD) test taking 5% probability level as the minimum unit of significance.