Phosphorus solubility changes with time in organically amended soil in a mediterranean environment

Abstract

As in other areas of the world, in the Middle East, phosphorus (P) is also a vital element in agricultural production. Laboratory studies have shown how inorganic P changes with time after application. With increased interest in the use of organic wastes, the extent to which seasonal change, characteristic of the Mediterranean climate, affects transformation of organic P alone and in combination with fertilizer P has been given attention. This preliminary pot experiment, conducted under outdoor conditions, examined changes in sodium bicarbonate (NaHCO3)‐extractable P over a 19‐month period in soil amended with organic matter as farmyard manure (5%) and superphosphate (100 mg/kg P). During the initial cool winter season's incubation, there was no change in available P. With the onset of the warmer dry season, NaHCO3‐extractable P declined rapidly. The rate of decrease was greater, and the onset earlier with inorganic P alone. Organic matter reduced the P Sorption maxima and increased desorption. Thus, organic matter, whether added or as accumulated root biomass, enhances the longevity and potential plant availability of P in soils of a xeric moisture regime. Future field research should focus on monitoring, with time, the various organic and inorganic P fractions as well as detailed moisture and temperature measurements.