EFFECTS OF LIGNOSULFONATE-FERTILIZER APPLICATIONS ON SOIL RESPIRATIONAND NITROGEN DYNAMICS

Lignosulfonate (LS) has been used as a carrier for micronutrients and has the potential to improve macronutrient fertilizer efficiency, but little is known about the behaviour of LS fertilizer mixtures in soil. A laboratory study was conducted using ammonium lignosulfonate (2.67% wt wt-1) in combination with diammoniumphosphate (DAP), urea (U) and U + DAP incubated in a silty clay loam soil. The experiment monitored CO2 evolution and NH3-N volatilization for 69 d and extractable soil N periodically for 38 d. Addition of LS initially increased CO2 evoluti on, but only a small proportion (10-22%) of the LS-C was evolved as CO 2. Lignosulfonate decreased urea hydrolysis slightly and reduced the p roportion of added N volatilized from the LS+U treatment. Lignosulfona te treatments accumulated N in the form of NH4+, suggesting that LS ma y inhibit nitrification. A larger proportion of added inorganic N was recovered in the LS + fertilizer treatments, indicating that LS may in crease fertilizer N availability.