Effect of Integrated Use of Nitrogen on Yield and Nutrient Uptake of Summer Onion

Effect of integrated use of nitrogen on yield and nutrient uptake of summer onion (Allium cepa var. BARI Piaz-2) was assessed in a field experiment carried out in Sher-e-Bangla Agricultural University Farm, Dhaka during the kharif season of 2007. Urea, cowdung (CD) and vermicompost (VC) were combined in a way to supply N at 120 kg ha⁻¹ from the sources and set in twelve treatments such no fertilizer (T₁), 120 kg N ha⁻¹ supplied from urea (T₂), 100 kg N ha⁻¹ supplied from urea with 20 kg from CD (T₃), 100 kg N ha⁻¹ supplied from urea with 20 kg from VC (T₄), 80 kg N ha⁻¹ supplied from urea with 40 kg from CD (T₅), 80 kg N ha⁻¹ supplied from urea with 40 kg from VC (T₆), 60 kg N ha⁻¹ supplied from urea with 60 kg from CD (T₇), 60 kg N ha⁻¹ supplied from urea with 60 kg from VC (T₈), 40 kg N ha⁻¹ supplied from urea with 80 kg from CD (T₉), 40 kg N ha⁻¹ supplied from urea with 80 kg from VC (T₁₀), 120 kg N ha⁻¹ supplied from CD (T₁₁), 120 kg N ha⁻¹ supplied from VC (T₁₂), arranged in a RCBD design with three replications. The results indicated that maximum bulb yield (12.16 t ha⁻¹) and stover yield (5.46 t ha⁻¹) of summer onion were obtained in treatment receiving 80 kg N ha⁻¹ from urea with 40 kg N ha⁻¹ substituted by CD (T₅), followed by the treatment receiving 80 kg N ha⁻¹ from urea with 40 kg N ha⁻¹ substituted by VC (T₆). Comparing with other fertilizer treatments, the yields were significantly lower in treatments where N from urea source was below 50%. Similarly, the N, P, K and S uptake (72.78, 5.53, 55.88 and 28.93 kg ha⁻¹, respectively) by onion plants at harvest stage was also significantly (p<0.01) greater in treatments receiving 80 kg N ha⁻¹ from urea with 40 kg from CD (T₅) followed by treatment T₆. Thus the data suggest that integrated use of N 80 kg from urea with 40 kg from CD or 80 kg from urea with 40 kg from VC has produced maximum yields and is therefore recommended for advantageous onion production.