Phosphorus behavior in flooded-drained soils. III. Phosphorus desorption and availability
1989
Sah, R.N. | Mikkelsen, D.S. | Hafez, A.A.
Four California soils that showed wide variability in soil properties and P sorptivity under flooded-drained (FD) conditions were selected for this study. The soils were flooded for 0 to 90 d at two levels of organic matter (OM, 0 and 10 g kg-1) and two temperatures (23 and 35 degrees C). They were subsequently drained and used for P-sorption studies at 0.3, 1.2, and 2.0 mM initial P concentrations. The P desorption from P-sorbed soils were carried out in three consecutive extractions with 0.1 M NaCl. The effect of FD conditions on P availability to corn (Zea mays L.), was studied at three levels of P (0, 5, and 20 mg P kg-1 soil). Without OM treatment, FD conditions decreased P desorption in three of four soils examined. Added OM and higher temperature further decreased P desorption and the period of flooding (FP) required to reach the minimum P desorption. Organic matter markedly decreased P desorption even in Soil 3, which was unaffected by FD conditions. Under FD conditions, plant-tissue P concentration of corn was decreased to a variable extent depending on soil type. The desorption of added fertilizer P in a given FD soil correlated well with changes in the amorphous FeA fraction under comparable conditions. Phosphorus sorption and desorption were controlled by the changes in amorphous FeA and, in some cases, amorphous FeB fractions.
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