Differential growth and yield by canola (Brassica napus L.) and wheat (Triticum aestivum L.) arising from alterations in chemical properties of sandy soils due to additions of fly ash.

BACKGROUND: There is a need for field trials on testing agronomic potential of coal fly ash to engender routine use of this technology. Two field trials were undertaken with alkaline and acidic fly ashes supplied at between 3 and 6 Mg ha⁻¹ to acidic soils and sown to wheat and canola at Richmond (Eastern Australia) and to wheat only at Merredin (Western Australia). RESULTS: Ash addition marginally (P< 0.10) raised the pH in the top soil layers at both sites. The exceptionally dry season at both sites constrained yields and thwarted any likelihood of gaining yield benefits from ash-induced improvements in soil conditions. Yield improvements due to ash addition were absent at Merredin and only marginal at Richmond, where no elevated accumulation of B, Mo, Se, P or S in either the straw or seeds of wheat was observed; canola increased accumulation of Mo and Se in its shoot with acidic fly ash, but it was well below phyto toxic levels. Simulations of wheat using APSIM at Richmond over a 100-year period (1909-2008) predicted yield increases in 52% of years with addition of ash at 3.0 Mg ha⁻¹ compared with 24% of years with addition of ash at 6.0 Mg ha⁻¹. The simulated yield increases did not exceed 40% over the control with addition of 6 Mg ha⁻¹ ash, but was between 40% and 50% with an addition rate of 3 Mg ha⁻¹. CONCLUSION: We found no evidence of phytotoxicity in either crop in this unusually dry year and there is still a need for further field assessment in years with favourable rainfall to enable development of clear recommendations on fly ash rates for optimum yield benefits.

Phytase supplemented poultry diets affect soluble phosphorus and nitrogen in manure and manure-amended soil.

Understanding P and N dynamics in manure-amended soil is essential for estimating the environmental impact of manure utilization in land applications. A laboratory incubation study was conducted to assess, (i) the effect of feeding a standard Australian commercial diet, and diets modified with phytase supplementation and reduced nonphytase phosphorus (NPP), on the concentrations of P and N (total and soluble) in the manure derived from layer hens (Gallus domesticus L.), and (ii) the change in water-soluble phoshorus (P(WSP)) and mineral N (NH(4)-N and NO(3)-N) when used as a soil amendment, applied at rates equivalent to 200 kg ha(-1) (200N) and 400 kg ha(-1) (400N). Phytase supplementation increased %P(WSP) by 8 to 12% in the manures, regardless of the levels of NPP in the diets, and in the manure-amended soils by 27 to 30% at the 200N application rate, and up to 54% at the 400N rate. Phytase significantly (P < 0.05) reduced total nitrogen (TN) content (by 12-31%) of the manures but generally produced greater nitrate accumulation in the manure-amended soils. Net nitrification, which commenced 4 wk after incubation, was accompanied by a simultaneous decrease in soil pH (by one pH unit) and a concomitant decline in %P(WSP). The decline in %P(WSP) was primarily attributed to P retention by the soil as it became more acidic. This study suggests that phytase addition not only reduces manure total N content, and increases water-soluble P, but its effects on manure total phosphorus (TP) and 2 mol L(-1) KCl extractable mineral N is influenced by the NPP level in the diet.