Abstract
A series of experiments were undertaken to study the effect of planting time, spacing, seedling age and plant nutrient on the performance of summer onion cv. BARIpiaj-3. The experiments were conducted for three consecutive years, two years at Bangladesh Agricultural University, Mymensingh and one year at TCRSC, BARI, Bogra during the early Kharif season of 2003-05. On the basis of these findings, the fourth experiment was conducted with three summer onion cultivars at varying panting dates during the late Kharif season of 2006 at ARS, Burirhat, Rangpur. The results showed that in early Kharif season, earlier planting (16 March) out-yielded (producing 8.81 t to 9.58 t/ha) the later plantings (26) March, 05 April and 15 April) in terms of bulb yield having the highest values for most of the yield parameters. The closest spacing (10cmx9cm) produced the highest bulb yield (from 9.17t to 10.15t/ha) having non-marketable smallest bulb size. The moderate spacing (15cmx8cm), on the other hand, gave the second highest bulb yield (from 8.49 t -9.40 t/ha), which was statistically similar (from 8.23 t -9.12 t/ha) to next higher spacing (15cmx10cm). But on account of high seedling requirement in the former, the later spacing (15cmx10cm) was acceptable in terms of marketable bulb yield and productivity. The widest spacing (20cmx9cm), although had the heaviest individual bulb weight, gave the lowest bulb yield because of the lowest number of plants accommodated per unit area. The seedling age (60, 50, 40 and 30-day old) study indicated that seedlings of 40-day old produced the highest bulb yield, ranging from 8.56 t to 9.31 t/ha over seasons. The aged seedling of 60 days had some advantages of quick bulbing with early maturing, but it did not perform well in respect of bulb yield. The effect of fertilizer and manure on summer onion production revealed that the treatment with 100% STB fertilizers + cowdung @ 7.5 t/ha gave the highest bulb yield, ranging from 8.63 t to 9.41 t/ha, which was statistically identical to that of 100% STB fertilizers + poultry manure @ 5.0 t/ha. A quantum of raised bulb yield (7.09 t to 7.68 t/ha) was noted when 75% STB fertilizers was applied compared to the control treatment (3.83 t to 4.38 t/ha). This big yield difference proved that the soil was deficit of plant nutrients and that there was remarkable effect of fertilizers. The experiment in the late Kharif season with planting date and variety revealed that the cv. Agrifound Dark Red produced the highest bulb yield (37.6 t/ha) with no bolting from planting on 16 September followed by 26 September (33.6 t/ha), 06 September (30.9 t/ha) and 27 August (28.7 t/ha). The yielding pattern with respect to late Kharif planting date for the other two varieties was however different, BARIpiaj-3 gave the best yield from 16 September planting (14.08 t/ha) and BARIpiaj-2 had the highest yield from 06 September planting (13.78 t/ha). It was observed that the later varieties suffered from bolting by 2-3% when planted after 16 September and therefore, planting of these two varieties is not recommended beyond mid September.