The effect of 2 organic amendments (lignite and compost) on wheat growth and phosphate fertiliser efficiency (triple superphosphate, TSP; di-ammonium phosphate, DAP) in an acid soil was investigated in a glasshouse experiment. Organic amendments were incorporated into the top 40 mm of soil at rates resulting in a 1% and 2.5% increase in soil C, and fertilisers were banded within the seed row at rates equivalent to 5, 10, and 25 kg P/ha. When no P was applied, addition of both organic amendments increased shoot height, with greatest growth recorded in the compost-amended treatments. Addition of organic amendments and P fertiliser resulted in additive effects, with increased shoot height, tiller number, and shoot dry matter (DM) in both the lignite- and compost-amended soils with fertiliser addition. The addition of 1% C resulted in plant growth equal to that measured at a higher rate of addition (2.5% C), resulting in a higher relative efficiency of application. Tissue P uptake was significantly increased when soil amendment was combined with 25 kg P/ha DAP addition. Significant differences in nutrient uptake were also measured for other important plant nutrients. As the addition of organic amendments resulted in increased DM compared with untreated soil per unit of P fertiliser applied, it is feasible that this growth response may translate into increased yield. However, further study is required to define the agronomic and economic feasibility of broad-scale application of such amendments for production gains.