A role for silicon, nitrogen and reduced bulk density in yield responses to sugar mill ash and filter mud/ash mixtures

Sugar mill ash fractions and a filter mud/ash mixture were compared with various green cane trash management strategies to ameliorate the hard setting fine sandy loam surface of a gleyed podzolic soil. The experiment was established after plant cane harvest and results were obtained for the first and second ratoon crops. Sugar mill waste products reduced bulk density in the surface 10 em of soil, but did not influence pre-harvest soil moisture status. Both mill products had large residual value for phosphorus and the ash increased both exchangeable and non-exchangeable potassium in soil. Yield response to sugar mill waste was confounded with response to reduced bulk density and improved crop nutrition. Nutrient responses were obtained to nitrogen and silicon. There was no apparent response to higher phosphorus or potassium levels. Trash retention did not modify bulk density in this experiment.