Combining inorganic fertilizer with poultry manure for sustainable production of quality protein maize in Ghana

Abstract

Field studies were used, in the major and minor seasons of 2002 and 2003 at Fumesua (forest zone) and Ejura (transition zone), to determine the effects of combining inorganic fertilizer with poultry manure on grain yieldstability and economic benefits of quality protein maize (QPM) production. The experimental design was a randomized complete block with four replicates. The treatments were (i) recommended inorganic fertilizerrate (IFR) (76 kg N ha-1); (ii) recommended poultry manure (PM) (3 t PM ha-1); (iii) 57 kg N ha-1 + 0.75 t PM ha-1 (i.e. ¾ IFR + ¼ PM); (iv) 38 kg N ha-1 + 1.5 t PM ha-1 (i.e. ½ IFR + ½ PM); (v) 19 kg N ha-1 + 2.2 t PMha-1 (i.e. ¼ IFR + ¾ PM); and (vi) no fertilizer (control). An open-pollinated QPM variety Obatanpa was used. Averaged over all seasons and locations, grain yield for the recommended IFR was 3.31 t ha-1, similar to grain yields of 3.22 and 3.10 t ha-1 for the ½ IFR + ½ PM and ¼ IFR + ¾ PM treatments, respectively. However, these treatments together yielded 7-14 per cent higher than the yields produced at 3 t PM and ¾ IFR + ¼ PM; and 32- 38 per cent higher than the control. The yields at ¼ IFR + ¾ PM and recommended IFR were most stable across all environments, with mean yields above the grand mean and regression coefficients less than but close to 1.0. The ¼ IFR + ¾ PM and ½ IFR + ½ PM recorded the highest net benefits and marginal rate of returns (MRR)of 187 - 349 per cent over 3 t PM ha-1. The recommended IFR and ¾ IFR + ¼ PM treatments had lower net benefits, but higher total variable costs than the ¼ IFR + ¾ PM and ½ IFR + ½ PM; and, therefore, were dominated by the latter.