Partial substitution of phosphorus fertiliser by farmyard manure and its localised application increases agronomic efficiency and profitability of maize production

In sub-Saharan Africa (SSA), maize production is not only constrained by the limited use of P fertilisers, but also by the strong P fixation (on Fe- and Al-oxides) which consequently lowers the amount of bioavailable P in the soil solution. We hypothesise that substitution of triple super phosphate (TSP) fertiliser with farmyard manure (FYM) and its localised application in the planting row increases the agronomic use efficiency (AE) of the P fertiliser applied. Field experiments were conducted during the 2009 long rains (LRs) and short rains (SRs) at three sites (Sega, Bokoli and Teso) located in western Kenya, to assess (i) the effect of concentrating FYM in different areas of the planting rows, (ii) FYM and TSP applications at different substitution rates and (iii) the effect of FYM and TSP additions and/or their combinations on soil pH, available P. maize yields, AE and economic benefits. Treatments included substitutingTSP by FYM at 0,25,50,75 and 100% of the 26 kg P ha(-1) recommended rate. Further, 13 kg P ha(-1) FYM was either applied to 100% of planting area (i.e. broadcast) or localised in only 50% or 25%, of the planting area of the maize row. Results show that FYM and TSP combinations increased maize grain yields by over 200% in Sega, 90-150% in Teso and 20-50% in Bokoli relative to the control. The AE largely depended on the relative fertility of the soils but increased with an increase in FYM in the substitutions. Soil pH and available P were improved by FYM applications only in the second season (2009 SRs). Maximising P from FYM in the substitutions increased net benefits by over 33% with gross benefit cost ratios > 4.5 $ $(-1) relative to sole TSP application at 26 kg P ha(-1). Concentrating FYM in 25% of the planting area gave over 32% increases in net benefits relative to broadcast. This study confirms that it is possible to reduce the quantity of FYM if it is applied only in the planting row but its profitability largely depends on the quality of the material selected. (C) 2012 Elsevier B.V. All rights reserved.