Study on phosphorus desorption and availability to soybean (Glycine max L.) in two phosphorus rich Gleysolic soils under different tillage and fertilization practices

Soil phosphate is essential for the development and maturity of crops. Plants absorb phosphate from the soil solution which is continuously replenished by fertilizer application and/or desorption from the soil solid phase. Anion exchange membranes (AEMs), act in a similar way to plant roots, adsorbing P from soil solution. Desorption of available P was studied in 1997 on two Gleysolic soils rich in P, a Ste. Rosalie clay soil and a Duravin sandy loam soil, using fluoride-saturated AEMs let in soil suspension for various contact periods. Determination of available P using these AEMs was compared to P extraction using the Mehlich III extractant for predicting P availability to soybean (Glycine max L.). Desorption from both soils, and subsequent adsorption by AEMs was found to decrease with time. A high P desorption rate was calculated for both soils with the Elovich equation. Different chemical and physical characteristics such as pH, Mehlich III extractable Al, Fe and Ca, sand and clay content were in some cases, positively correlated and in other cases, negatively correlated with various contact periods for both soils. The use of AEMs better predicted P availability than the Mehlich III extractant, although the most important asset of using AEMs is that they showed the desorption effect over time on P availability. It was observed that P remobilization from the vegetative part to the grain was reduced due to the high P concentration in both soils