Growth and Residual nutrients in soil of intercropped stand of Khaya senegalensis and Orthosiphon stamineus treated with paper mill biosludge

The effect of soil amendment with biological sludge from the paper mill on growth of khaya senegalensis forest tree and orthosiphon stamineus medicinal shrub was studied. both crops received nutrient input early,i.e. after transplanting. growth data were taken at fixed intervals for up to 1 year. orthosiphon stamineus was measured for aboveground dry matter yield at four crop cycles. residual nutrient level in soil after 1 year of application was evaluated. comparison was made with inorganic fertiliser application and untreated soil. khaya senegalensis responded positively to raw and composted biosludge applications,outperforming the widely used inorganic fertiliser. biosludge application resulted in greater height increment,diameter growth and total plant biomass than the control and inorganic fertiliser. orthosiphon stamineus also produced greater biomass with biosludge application and the trend remained the same for all crop cycles except for the relatively lower yield at the second,third and fourth crop cycles. soil fertility parameters were most affected at the topsoil layer with overall accreting tendency under k. senegalensis tree with sludge application. exchangeable k was the most limiting nutrient for k. senegalensis while p and k limited growth of o. stamineus. © forest research institute malaysia.