Experimental location: The experiment was conducted to study the effects of fertilizer and plant spacing on the growth and yield of onion at the On-Farm Research Division (OFRD), Agricultural Research Station, Bangladesh Agricultural Research Institute (BARI) Daulatpur, Khulna.
Physical and chemical properties of soil: The experimental area was medium high land and the soil was sandy to clay loam. The nutrient status of the soil of the experimental plot was analyzed at SRDI, Daulutpur, Khulna prior to cultivation.
Climate: The experimental area was under the sub-tropical climate zone, which is characterized by heavy rainfall, high humidity, high temperature, and relatively long day during the kharif season and hardly rainfall, low humidity, low temperature and short day period during the rabi season. Details of the meteorological data during the experimental period are listed below. Monthly mean temperature, total rainfall, relative humidity and sunshine during crop period at the experimental site.
Variety: BARI Piaz 1, a high yielding variety was considered for this study as a test material. Thirty five days old seedlings were collected from Spices Research Station, BARI, Magura. The variety produces plant of 50-60 cm tall with 10-12 leaves per plant. The average weight of individual bulb is 20-30g and the diameter is 3-4 cm. The bulbs are rhombic and highly pungent with pinkish red skin and most of the bulbs are single type, mature at 130-140 days, bulbs have long shelf life and the yield is about 12-16 t/ha.
Land preparation: The land was first ploughed in the 12th December, 2011 with power tiller. After that the land was exposed to sunlight for five days. The ploughing was followed by laddering to obtain good tilth and this process was repeated until getting a loose soil. During land preparation weeds and stubbles were collected and removed from the field and the clods were broken. Seedlings were transplanted on 26th December, 2011.
Treatment and layout of the experiment: The experiment comprised three different plant spacing and three different fertilizers.
Factor A: Spacing
- Close: 10 × 10 cm (S1)
- Medium: 15 × 10 cm (S2)
- Wide: 15 × 1 5 cm (S3)
Factor B: Fertilizer
- F1 - Soil test based fertilizer dose (N 30 kg/ha; P 18 kg/ha; K 30 kg/ha and S 5 kg/ha).
- F2 - IPNS ((N 7.5 P 0.5 Kg/ha) based fertilizer dose + cow dung 5 ton/ha.
- F3 - Farmers’ practice (N 115 kg/ha; P 82 kg/ha and K 125 kg/ha).
Experimental design: The two factor experiment was laid out in a randomized completely block design (RCBD). The whole field was first divided into 3 blocks each containing 9 plots. In total there were 27 unit plots. The treatment combinations were assigned randomly in each unit plot so as to keep one treatment only in each block. The size of each unit plot was 1.5 × 1.2 m. The space left between plots and replication was 1 m.
Fertilizer application: During land preparation all the fertilizer except urea were applied according to the recommended experimental design as a basal dose. The selected 3 fertilizer combinations were applied in the treatment of unit plots. Top dressing with urea was applied in two equal splits, at 20 and 50 days after transplanting .
Intercultural operation: Various kinds of intercultural operations were accomplished for better growth and development of the plants.
Gap filling: Gap filling was d one using healthy plants as per requirement .
Weeding and mulching: Weeding and mulching were accomplished as and when required to keep the crop free from weeds and to conserve the soil moisture.
Irrigation: Irrigation was given by both watering can and ho se pipe as and when needed. Seedlings were first irrigated just after transplanting and then they were irrigated whenever required to conserve the optimum moisture level to the soil.
Plant protection: To avoid pest and fungal infection seedlings were spray ed with Antracol @ 0.2% after 1 month of sowing and sprayed with Rovral @ 0.2% and Tilt @ 0.2% after 45 days of transplanting.
Harvesting: The crop was harvested on 23 rd March, 2012 when more than 75% of the tops had fallen over. The tops were removed by cutting off the pseudo - ste m keeping 2.5 cm with the bulb.
Data collection: Data of the following parameters were recorded from the sample plants. Ten plants were selected randomly form each plot in such a way so that the border effect could be avoided. Plant population per square meter. The total number of plants in a square meter area were counted and recorded.
Bulb length (cm): The length of bulb was measured with a centimeter scale from pseudo - stem to the bottom of the bulb taken from 10 randomly selected plants from each plot.
Bulb diameter (cm): The diameter of bulb at harvest was measured at the middle portion of bulb taken from 10 randomly selected plants with slide calipers. Individual bulb weight (g) Ten plants were selected from each unit plot. The top was removed by cutting the pseudo-stem keeping only the 2.5 cm from the bulb (A - AS - Saqui, 1994). Ten bulbs were weighed by a simple balance and the average was taken.
Yield of onion (t/ha): The yield of bulb per unit plot was converted into to ns per hectare.
Statistical analysis: The collected data on various parameters were statistically analyzed. The mean for all the treatments were calculated and analysis of variance for the all the character were performed by F-test. The significance of the difference between the pairs of means was evaluated by Duncan’s new Multiple Range Test (Gomez and Gomez, 1984)