Status and management of excessive phosphorus fertilizer application under durian orchard soils in Eastern Thailand.

Durian growers believed that phosphorus (P) is direct a contribution for crop flowering and fruit set, therefore it has been applied profligately, being particularly overused, even though, it reaches excess range especially in durian orchard soils in Eastern Thailand. The purpose of this investigation was to study the status and management of P in order to enhance efficiency fertilizer used. The soil samples (topsoil and subsoil) and durian leaf samples were collected from 6 orchards depended on soil suitability (high, moderate and low suitability) for analysis. The leaf samples were collected 5 times during the growing season (first leaf flushing, second leaf flushing, flowering, young fruit and mature fruit). The result indicated that available P (Bray II) of soil was an average 192 and 88 mg/kg for top soil and sub soil, respectively in which 68% of top soil and 35% of sub soil were classified as a very high range. Moreover, 4% of soil samples accumulated P higher than 500 mg/kg. Most of the P content of leaf tissue varied within a range of critical value (0.15-0.25%), where the highest concentration was found in flowering and young fruit stages (0.24-0.26%). The antagonism between P and Zn was found in 1 of the 2 orchards with high soil suitability (r =-0.507**); P and Cu were found in 4 orchards with moderate and low soil suitability (r =-0.423**, -0.330*, -0.851**, and -0.352*). The farmers normally applied 630-1200 g of P₂O₅/tree/year, which could be decreased P fertilizer by 10-39% or more for a very high available P in the soil. [ABSTRACT FROM AUTHOR]