Abstract
The investigation was performed during 2005-2008 growing season at the experimental field of Regional Agricultural Research Station, BARI, Jamalpur to determine an optimal combination of organic and chemical fertilizers for yield maximization of garlic. Eight experiments were conducted during the rabi seasons of 2005- 06, 2006-07 and 2007-08. Four single factor independent experiments, one for each of N, P, K and S were conducted for two consecutive years (2005-06 and 2006-07). Three more separate experiments for Mg, Zn and B were also conducted for one year (2006-07) to find out an optimum dose of the studied nutrients independently. The nutrients and the treatments were: N (0, 50, 100, 150, 200 and 250 kg ha1), P (0, 15, 30, 45, 60 and 75 kg ha1), K (0, 40, 80, 120, 160 and 200 kg ha1), Mg (0, 10, 20, 30, 40 and 50 kg ha1), Zn (0, 2, 4 and 6 kg ha1) and B (0, 1, 2 and 3 kg ha1). The yield potential of the garlic cultivar Jamalpur local was evaluated with these nutrients. Nutrient rates were distributed as RCB design with three replications. A blanket fertilizer dose and one control treatment were used for each experiment. Results from seven independent experiments revealed that the cultivar and different nutrient rates had a significant effect on yield. The highest yields (average of 2 years) obtained in different fertilizer treatments were: 6.97, 7.13, 7.18, 7.14, 7.18, 7.18 and 7.03 t ha1 due to Niso, P60, K120, S45, Mg10, Zn, and B, kg ha', respectively. Based on the findings of 7 independent experiments, an optimal combination of chemical fertilizers was estimated from regression equations which were: 152.5, 60.6, 126.5, 44.0, 11.5, 4.08 and 1.36 kg ha" of N, P, K, S, Mg, Zn and B, respectively. With the selected doses of nutrients, an optimal combination of chemical fertilizers was formulated as N152.5 P60.6 K120 S44.0 Mg11.5 Zn4.08 B1.36 kg ha1 which used later in third year (2007-08) experiment along with different organic manures at various rates. The organic manures were: cowdung (CD) at 10 and 15 t ha', poultry manure (PM) at 2 and 3 t ha' and mustard oil cake (MOC) at 1 and 2 t ha'. So, in total 10 fertilizer treatments (including one farmers' practice (FP) and one control (addition of no fertilizer and manure) viz.: T1: 100% optimum fertilizer dose (OFD) as N152.5P60.6 K126.5 S44 Mg11.5 Zn4.08 B1.36, T2: 50 % of the OFD, T3: T2 + CD at 10 t ha', T4: T2 + CD at 15 t ha', Ts: T2 + PM at 2 t ha', T6: T2 + PM 3 t ha ̈1, T7: T2+ MOC 1t ha', Tg: T2+ MOC 2 t ha', T, FP at N75 Po Ks2 S15 DAP 300 kg ha1 + CD 12 t ha'', and T10 Control. Two garlic varieties BARI Rasun-1 and Jamalpur local were evaluated with the 10 fertilizer treatments through experiment no. 8. Treatments were also distributed in RCB design under factorial arrangement. Results from experiment 8 (2007-08) revealed that the garlic cultivars, the nutrient fertilization rates, and the interaction between cultivars and nutrient fertilization rates were significant. BARI Rasun-1 performed much better than Jamalpur local in respect of yield and yield components and also growth parameters and produced 10.93% higher yield (7.04 t ha') than Jamalpur local (6.27 t ha''). The highest bulb yield (7.83 t ha1) was obtained with T6 treatment (50 % of the optimum fertilizer dose, OFD + 3 t PM ha1) which was statistically identical to that recorded in T4 treatment receiving 50 % of the OFD + 15 t CD ha1 (7.68 t ha1) and both the yields being significantly higher over yields obtained from rest of the treatments. The yield benefit for To treatment over control (T10) and 100 % optimum fertilizer dose (T1) were 48.53 and 8.56% higher, respectively. This finding indicated that 50% of the OFD with 3 t PM ha or 15 t CD ha1 may compensate the requirement of 50% of the OFD. Maximum marginal benefit cost ratio, MBCR (10.62) was in To treatment (50% of the OFD + 3 t PM ha1), which was followed by that in Ts treatment (8.69) receiving 50 % of the OFD + 2 t PM ha'. The highest gross return (Tk. 2,74,050.00) and gross margin (Tk.2,61,529.19) were also observed in the same treatment. The highest bulb yield (8.54 t ha1) was obtained from T6 treatment with BARI Rasun-1 which was statistically similar to that recorded in T4 treatment (8.06 t ha1) with the same variety, while the lowest (3.94 t ha'') was in control treatment (T10) with Jamalpur local variety. A fertilizer package of N76P30K63S22Zn2B0.65kg ha1 along with 3 t poultry manure ha' may be the best combination for the yield maximization of garlic in Old Brahmaputra Floodplain Soil under Jamalpur region, Bangladesh and similar environment else-where.