Effects of the application of biochar on soil fertility status, and nutrition and yield of onion grown in a no-tillage system

The study was aimed to evaluate the effect of successive applications of increasing biochar rates along with other mineral fertilizers and poultry manure on onion nutrition and yield. The experiment consisted of 2 (agricultural year) × 11 (treatments) factorial combinations over two cropping years (2017 and 2018). Thus, 11 treatments were tested as follows: C = control; MF = mineral fertilizer; PM = poultry manure; B1+ MF = 1 Mg ha⁻¹ of biochar+MF; B1+ PM = 1 Mg ha⁻¹ of biochar+PM; B2+ MF = 2 Mg ha⁻¹ of biochar+MF; B2+ PM = 2 Mg ha⁻¹ of biochar+PM; B4+ MF = 4 Mg ha⁻¹ of biochar+MF; B4+ PM = 4 Mg ha⁻¹ of biochar+PM; B10+ MF = 10 Mg ha⁻¹ of biochar+MF; B10+ PM = 10 Mg ha⁻¹ of biochar+PM. The highest onion yield (39.9 Mg ha⁻¹) was obtained in 2017 with the biochar rate of 5.9 Mg ha⁻¹ while an increase of 308 kg ha⁻¹ in onion yield was found for each Mg ha⁻¹ of biochar added to soil in 2018. The use of biochar combined with mineral fertilizers increased onion yield; and the use of biochar combined with poultry manure improved soil fertility status.