Biochar, poultry manure and NPK fertilizer: sole and combine application effects on soil properties and ginger (Zingiber officinale Roscoe) performance in a tropical Alfisol

Biochar has a low chemical composition and is recalcitrant to degradation. For good soil fertility and nutrient use efficiency of crops it becomes imperative that addition of a fast releasing nutrient source to biochar be sought. Therefore, studies were conducted in 2017 and 2018 to evaluate the effects of biochar with poultry manure (PM) and NPK fertilizer on soil properties, growth and yield of ginger. Treatments evaluated were: biochar applied alone at 15 t ha-1 , PM applied alone at 15 t ha-1, NPK fertilizer applied alone at 200 kg ha-1, biochar applied at 15 t ha-1 with poultry manure applied at 15 t ha-1 (B+PM), biochar applied at 15 t ha-1 with NPK fertilizer applied at 200 kg ha-1 (B+NPK) and a control with no amendment whatsoever. The experimental design was a randomized complete block design with three replications. Biochar, PM, NPK fertilizer alone or B+PM and B+NPK improved soil physical and chemical properties, growth and yield of ginger compared to no amendment (control). NPK fertilizer did not improve soil physical properties nor increased pH, OM, Ca and Mg significantly. B+PM and B+NPK improved soil physical and chemical properties, growth and ginger yield compared to their sole forms. Although B+PM had better soil physical properties, B+NPK increased yield and growth of ginger compared to B+PM. B+NPK increased the yield of ginger by 12.2% and 10.6% in 2017 and 2018, respectively compared with B+PM. B+NPK also increased the yield of ginger by 49.2% and 50.3% in 2017 and 2018, respectively compared to biochar alone. This was related to high presence of nutrients in B+NPK especially N and K which are important for ginger rhizome formation