Distribution and Adsorption Characteristics of Phosphorus at A Headwater Wetland in Ichikawa City, Chiba Prefecture, Japan

<p>The distribution and adsorption characteristics of phosphorus were investigated in a typical headwater wetland in Ichikawa City, Chiba Prefecture, Japan. Total dissolved phosphorus (TDP) was the main phosphorus fraction in the waters, ranging from limit of quantification (0.002 mg/L) to 0.059 mg/L in spring water, from limit of quantification to 0.128 mg/L in groundwater and from 0.012 to 0.048 mg/L in river water. TDP in 33% water samples were higher than the environmental quality standard for eutrophication (0.020 mg/L). Next, phosphorus adsorption experiment was conducted to study phosphorus distribution in the aquifer where the equilibrium phosphorus concentration (C_EPC) is the key to access the phosphorus in the waters. In addition, the amount of TDP releasing from the wetland through river was 20.9 g/day.</p>

Mineral nutrition of soybeans grown in the South Burnett region of south eastern Queensland. 2. Prediction of grain yield response to phosphorus with soil tests

Grain yield response of soybean (Glycine max cv. Bragg) to applied phosphorus was measured at 19 experimental sites in the South Burnett region. The soil phosphorus supply factors of quantity, intensity, buffer capacity and rate were estimated by various soil chemical tests, and relative yield [(yield at nil applied phosphorus/maximum yield) x 100] regressed against these tests. The equilibrium phosphorus concentration-the intensity measure-accounted for the greatest percentage variation in relative yield (80%) and at 90% maximum yield was 0.014 �g P/ml. Phosphorus extracted by 0.01 M CaCl2 was highly correlated with the equilibrium phosphorus concentration (r2=0.93) and accounted for 73% of the variation in relative yield. Soil levels of calcium chloride-extractable phosphorus were interpreted as follows: < 0.044 �g P/g, response to phosphorus probable; 0.044 �g P/g to 0.058 �g P/g, response uncertain; > 0.058 �g P/g, response unlikely

ADSORPTION OF PHOSPHORUS BY FOUR SASKATCHEWAN SOILS

The adsorption of phosphorus by four soils of differing colloid content showed close agreement with the Langmuir isotherm when final phosphorus solution concentrations were less than 20 μg. P/ml. Calculated adsorption maximum for the four soils were 79.1, 87.7, 150.4 and 164.4 μg. P per g. of soil. The average value of the constant k, related to the bounding energy of the soil for phosphorus, was 0.141.The percentage phosphorus saturation of the adsorption maximum was closely correlated with the equilibrium phosphorus concentration in the soil suspension. At an equilibrium concentration of 28.7 μg. P/ml., 100 per cent saturation of the adsorption capacity of the four soils was obtained; the total adsorbed phosphorus on the four soils was not related to the phosphorus concentration of the soil solution but varied considerably depending on the colloid content of the respective soils.Carbonated water extractable phosphorus, and 'surface' phosphorus measured by P32 equilibrium studies, were not related to the equilibrium concentration of phosphorus of the soil solution. It appears that the percentage phosphorus saturation of the adsorption maximum may prove a more reliable measure of the capacity of the soil to supply phosphorus to the soil solution than either of the 'quick' tests used.Organic matter appeared to be equally as important as the inorganic colloids in determining the phosphorus adsorption capacity of the soils. Differences in exchangeable calcium were not closely related to the adsorption maximum.