Effects of ammonium lignosulphonate and diammonium phosphate on soil organic carbon, soil phosphorous fractions and phosphorous uptake by corn

Low P fertilizer efficiency can be attributed to a reduction in solubility due to P reactions with soil components. Added organic material may reduce such reactions and improve P fertilizer efficiency. Lignosulphonate (LS), a by-product of the pulp and paper industry, could have beneficial effects on fertilizer P. Effects of ammonium lignosulphonate (ALS) and diammonium phosphate (DAP) on corn (Zea mays L.) P uptake, extractable P and P fractions were measured. Soil P fractions were determined using a field incubation technique to simulate banded P applications in two Humic Gleysols, a Ste. Rosalie clay soil and an Ormstown silty clay loam soil. Soil organic C increased with increasing ALS addition and decreased with DAP additions. ALS had little effect on native soil P fractions. When applied with DAP, increasing rates of ALS increased Mehlich-III extractable P, 0.5 M NaHCO 3 and 0.1 M NaOH extractable inorganic P, reduced 1.0 M HCl extractable P and had no effect on organic P extractable in 0.5 NaHCO 3 and 0.1 M NaOH. Applying ALS at rates up to 300 kg ha −1 with P at 60 kg P 2 O 5 ha −1 may improve uptake by corn of fertilizer P, but using ALS alone does not improve native soil P availability. Key words: Lignosulphonate, phosphorous fractions, field incubation, organic carbon, Zea mays L.