
%0 Journal Article
%A Zhang, Xike 
%A Rengel, Zdenko 
%T Role of soil pH, Ca supply, and banded P fertilisers in modulating ammonia toxicity to wheat
%J Australian Journal of Agricultural Research
%D 2000/08/07
%V 51
%N 6
%P 691-699
%K banding, di-ammonium phosphate, gypsum, liming, mono-ammonium phosphate, root growth, Triticum aestivum.
%R https://doi.org/10.1071/AR99071
%U https://www.publish.csiro.au/paper/AR99071 
%X Di-ammonium phosphate (DAP) and mono-ammonium phosphate (MAP) banded close to seed may cause ammonia (NH 3 ) toxicity by inhibiting seed germination and early seedling growth. A pH increase around the fertiliser band and/or limited Ca supply may exaggerate ammonia toxicity. In the current study, wheat growth and gradients of pH, electrical conductivity (EC), ammonium (NH 4 + ), and P concentration in soil were studied by comparing banded DAP + urea or MAP + urea fertilisers in control or gypsum- or CaCO 3 -treated Lancelin soil. After 21 days of wheat growth, visual symptoms of ammonia toxicity appeared in the gypsum-treated and control plants, but not in the CaCO 3 -treated plants. The symptoms were more severe in the MAP treatments than in DAP treatments. An addition of CaCO 3 increased soil pH CaCl2 from 5.1 to 7.3, and the ammonium concentration was lower than that in the gypsum-treated and control soils. In the gypsum-treated and control soils, pH increased by nearly 1 unit in the vicinity of the DAP or MAP band. In contrast, soil pH decreased in the location of the DAP or MAP band in the CaCO 3 -treated soil. Banding of MAP or DAP in the gypsum-treated soil caused an increase in soil EC. The good plant growth on the soil amended with CaCO 3 might have been related to the low ammonium concentration in the soil and the high concentration of Ca. Gypsum and CaCO3 decreased the availability of P supplied in the MAP or DAP band. It was concluded that increased pH and higher Ca content in sandy soil may alleviate ammonia toxicity to wheat. 
