TY - JOUR
T1 - The influence of potassium and defoliation of ryegrass on the formation of acidic subsurface layers in stock urine patches
AU - Condon, Jason
AU - Black, Archibald
AU - Conyers, Mark
N1 - Imported on 12 Apr 2017 - DigiTool details were: Journal title (773t) = Australian Journal of Soil Research. ISSNs: 0004-9573;
PY - 2005
Y1 - 2005
N2 - This study examined the influence of simulated urine solutions containing various KCl and urea-N rates on the formation of acidic subsurface layers in soil columns. A factorial design was implemented with application rates equivalent to 0, 21, 42, 63, and 84 g urea-N/m2 and 0, 12.5, 25, and 37.5 g KCl-K/m2. The addition of N caused the formation of acidic subsurface layers at depths between 0.02 and 0.10 m. The magnitude of the resultant net acidification and the depth of the most acidic layer increased with N rate. More acidification occurred at depth at the higher N rates due to the downward movement of NH4+-N. The inclusion of K in the simulated urine produced less acidity in the surface layers and more acidity at depth as the K application rate increased owing to competition between K+ and NH4+-N for exchange sites, allowing more NH4+-N to move to depth. The residual acidity in the soil at the completion of the experiment was found to be greater than the alkalinity of plant material. Therefore, acidic subsurface layers are likely to persist after plant death and decomposition. We also examined the impact of defoliation on the resultant pH profiles formed following simulated urine addition. Defoliation accentuated the magnitude of acidic subsurface layers, possibly due to changes in the rate of N uptake. The influence of defoliation was minor compared with the main effects of N addition.
AB - This study examined the influence of simulated urine solutions containing various KCl and urea-N rates on the formation of acidic subsurface layers in soil columns. A factorial design was implemented with application rates equivalent to 0, 21, 42, 63, and 84 g urea-N/m2 and 0, 12.5, 25, and 37.5 g KCl-K/m2. The addition of N caused the formation of acidic subsurface layers at depths between 0.02 and 0.10 m. The magnitude of the resultant net acidification and the depth of the most acidic layer increased with N rate. More acidification occurred at depth at the higher N rates due to the downward movement of NH4+-N. The inclusion of K in the simulated urine produced less acidity in the surface layers and more acidity at depth as the K application rate increased owing to competition between K+ and NH4+-N for exchange sites, allowing more NH4+-N to move to depth. The residual acidity in the soil at the completion of the experiment was found to be greater than the alkalinity of plant material. Therefore, acidic subsurface layers are likely to persist after plant death and decomposition. We also examined the impact of defoliation on the resultant pH profiles formed following simulated urine addition. Defoliation accentuated the magnitude of acidic subsurface layers, possibly due to changes in the rate of N uptake. The influence of defoliation was minor compared with the main effects of N addition.
U2 - 10.1071/SR04077
DO - 10.1071/SR04077
M3 - Article
SN - 0004-9573
VL - 43
SP - 213
EP - 223
JO - Australian Journal of Soil Research
JF - Australian Journal of Soil Research
IS - 2
ER -