Effect of Soil Buffer Capacity on Soil Test Phosphorus Interpretation and Fertilizer Requirement

Labile forms of mineral phosphorus (P) strongly interact with solid phase of soil components. Therefore, soil characteristics may affect the chemical testing and interpretation to assess for the P availability for crops and fertilizer recommendation. A glasshouse trial was conducted with several soil types using wheat as test crop. The soil P availability was estimated by Bray-P, Olsen-P AEM-P and Aslyng-P methods. Results indicated that chemical indices like Bray-P, Olsen-P and AEM-P, appropriately integrates soil factors related with P availability to plants so that its interpretation would not require additional information. However the soil capacity factor, is a key factor for making sound fertilizer recommendations. A quick test of the P adsorption power of soils allow to calculate more precise fertilizer requirements based on the soil sorption power and the P availability.