
%0 Journal Article
%A Evans, C. M. 
%A Conyers, M. K. 
%A Black, A. S. 
%A Poile, G. J. 
%T Effect of ammonium, organic amendments, and plant growth on soil pH stratification
%J Soil Research
%D 1998/06/30
%V 36
%N 4
%P 641-654
%K soil acidity, mineral nitrogen, sucrose, ammonium sulfate, lucerne hay.
%R https://doi.org/10.1071/S97100
%U https://www.publish.csiro.au/paper/S97100 
%X We studied the development of soil layers of different pH (strata) within the surface 10 cm of soil. Substrates which affect nitrogen transformations (ammonium sulfate, sucrose, and lucerne hay) were added to the soil to determine the effect of amendment on the development of pH stratification. A glasshouse experiment used soils of 3 different initial pH(0&#183;01 CaCl2; pHCa) values: 4, 5, and 6. At the end of the experiment, soil was sampled in depth intervals of 0&#183;5 cm between 0 and 2 cm depth and then 1-cm intervals between 2 and 10 cm depth. Soil pHCa decreased over time and pHCa changes could be explained by variations in the concentration of ammonium and nitrate, which were brought about by changes in the rate of mineralisation, nitrification, and plant uptake of nitrogen. Little stratification in soil pHCa was found within the 0&#8211;10 cm layer. This minimal stratification was considered to be due to the soil in the pots being a closed system where nitrate was not lost through leaching. A field trial was rotary hoed to a depth of approximately 10 cm to achieve adequate mixing of soil and amendments. Soil pHCa decreased over the 6 months of the growing season, ranging from 0&#183;1 pHCa units in the control to 0&#183;4 pHCa units in the hay amendment. Between the initial and final sampling times there was little change in soil pHCa in the surface 0&#8211;2 cm. The pHCa decreased in the layers between 2 and 10 cm, thus producing the stratification of soil pHCa. The growth of oats had little effect on the development of pHCa stratification. Decreases in the soil pHCa from the 0&#8211;2 cm to the 8&#8211;10 cm layer in the absence of plants were 0&#183;22, 0&#183;27, 0&#183;30, and 0&#183;51 for the control, added sucrose, added ammonium sulfate, and added hay amendments, respectively. The processes of mineralisation and nitrification were considered to be the major causes of change in soil pHCa. Stratification of pHCa in the field trial was attributed to nitrification followed by nitrate leaching in the open system. 
