Laboratory studies on the enhancement of nematicidal activity of ammonia-releasing fertilisers by alkaline amendments

The effect of manipulating soil pH on the nematicidal activity of ammonia-releasing fertilisers was tested with cement kiln dust (CKD) and alkaline stabilised biosolid (ASB) as alkaline amendments. The nematicidal activity of chicken litter (1.0, 2.0 and 4.0 g kg−1) or ammonium sulphate (50 mg N kg−1) was enhanced by combination with CKD at 1.0 and 2.0 g kg−1 or ASB at 5, 10 and 20 g kg−1. The amendment of soil with alkaline amendments or fertilisers alone did not reduce, or reduced only moderately, Meloidogyne javanica infection of the plant roots. The application of CKD and ASB increased the soil pH from ca 8.5 to ca 11.0, and converted ammonium (NH+4) released from the fertilisers into nematicidal ammonia (NH3). Increased ammonia concentrations by 5.2- to 6.7-fold in the soil were probably the major factor responsible for nematode suppression, whereas increased soil pH was less detrimental to the nematodes. Combination of ammonia-releasing fertilisers with alkaline amendments to soil may serve as a nematode control method.