A comparison of mixed and band applications on the dissolution of North Carolina phosphate rock and on bicarbonate-soluble soil phosphorus

Abstract

The effect of mixed and band placement in soil on the dissolution of reactive North Carolina phosphate rock (PR) and the consequent increase in available P was investigated in a laboratory incubation study. The dissolution of PR in the soil was estimated from the increase in soil exchangeable Ca. The increase in available P was measured with the Olsen bicarbonate extractant. At the same level of application greater PR dissolution occurred for mixed than for band application. For both methods of PR application the amount of dissolution increased with the level of application and incubation period. The increase in the amount of PR that dissolved with increasing incubation period was greater for band than for mixed application due to the influence of unfertilized soil adjacent to the band. However, a higher proportion of dissolved P was soluble in bicarbonate solution for band than mixed PR.