Chemical retardation of phosphate diffusion in simulated acid soil amendedwith lignosulfonate

The availability and movement of inorganic phosphate fertilizer is usually low due to precipitation and adsorption reactions in soil. Lignosulfonate ( LS), which is produced from acid sulfite pulping processes, has similar cha racteristics to soil organic materials. An experiment was designed to study the effects of LS on P movement in a simulated acid soil containing alumin um-saturated cation exchange resin and acid-washed fine sand. The resulting simulated soil had a cation exchange capacity of 22 cmol(c) kg(-1) and eit her no or 10 g kg(-1) gibbsite. Movement of surface-applied monopotassium p hosphate was studied in soil columns, either with 20 g kg(-1) LS or without LS. Lignosulfonate reduced phosphate fixation and sustained a higher water extractable phosphate concentration near the surface of the columns, but h ad no effect on downward phosphate movement in the columns with gibbsite. L ignosulfonate reduced the solution concentration of P near the surface and reduced downward phosphate movement in the columns without gibbsite. The re sin-sand column with gibbsite closely reflected an acid soil, and this rese arch showed that adding LS would increase fertilizer P availability in a gi bbsite-rich acid soil. Adding Ca-LS to AI-rich soil is beneficial for anoth er reason, improving Ca nutrition, which is poor for these soils.