Abstract
The effects of different plant nutrients (N, P2O5, K2O, S, Zn, B and Cu) and plant density on the yield, economic return and keeping quality of onion were studied at the Jamalpur Regional Agricultural Research Station (RARS), Bangladesh Agricultural University (BAU) and in some farmers' fields during 1996 to 1999. During the 1996-97 season, effects of different levels of N, P2O5, K20 and S on the performance of onion cvs. Globe Yellow Danvers (exotic) and Taherpuri (local) were observed from 4 independent experiments set at RARS, Jamalpur, one for each nutrient. Different doses of N, P2O5, K20 and S in 4 independent experiments showed significant variation in respect of most of the characters studied. Considering the findings of the experiments on yield, storability and economic return conducted in 1996-97 season, four doses of N (50, 75, 100 and 125 kg/ha), four doses each of P2O5 and K20 (50, 100, 150, 200 kg/ha) and four doses of S (10, 20, 30, 40 kg/ha) were selected for the factorial experiment conducted in the following year. In the 1997-98 season, the performance of 14 selected combinations of N, P2O5, K2O and S on onion cv. BARI Peaj-1 was studied at RARS, Jamalpur and BAU, Mymensingh. The highest bulb yields (18.10 t/ha at RARS and 19.38 t/ha, at BAU) were obtained from the combination of 100- 150-150-30 kg N, P2O5, K2O, S/ha. Bulbs produced in absence or with lower doses of N, P2O5, K2O, S performed better in storage. Four promising N, P2O5, K2O, S treatment combinations were selected for further trial. From another set of experiment conducted during 1996-97 and 1997-98 at RARS, Jamalpur with 10 combinations of Zn, B, Cu and Mg, the combination of 4-1-3-0 kg Zn, B, Cu and Mg/ha appeared to be the best for the variety BARI Peaj-1. In the plant density studies conducted during the 1996-97 and 1997-98 seasons at RARS, Jamalpur, a rectangular planting arrangement (1:2) either at a population of 50 or 80 plants/m2 was found better. Performance of the four combinations of N, P2O5, K2O, S selected earlier, either in presence or absence of the promising combination of Zn, B, Cu on onion cv. BARI Peaj-1 was studied at RARS, Jamalpur in 1998-99. The combination of 100-150-150-30 kg N, P2O5, K2O, S/ha in presence of 4-1-3 kg Zn, B and Cu/ha performed best in respect of yield (16.17 t/ha), economic return (BCR 4.41) and storability (54.41% marketable bulbs after 180 days of storage) of bulbs. A field study with four N, P2O5, K2O, S combinations under two plant populations (80 and 50 plants/m2) in rectangular planting arrangement (1:2) revealed that a combination of either 100-150-150-30 or 125-150-150-30 kg N, P2O5, K20 and S/ha at 80 or 50 plants/m2 population (at 15.80 cm x 7.91 cm, and 20.0 cm x 10.0 cm spacing, respectively) performed better in respect of yield, economic return and storability of onion cv. BARI Peaj-1. An observation trial conducted in farmers' fields at different locations during 1998-99 with four previously selected combinations of N, P2O5, K2O, S either in presence or absence of the promising doses of Zn, B, Cu demonstrated superiority of the combination of 100-150-150-30 kg N, P2O5, K2O, S in presence of 4-1-3 kg Zn, B and Cu/ha in respect of bulb yield of onion.