Phosphorus leaching in sandy soils. II. Laboratory studies of the long-term effects of the phosphorus source

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Australian Journal of Soil Research


phosphorus, superphosphate, rock phosphate, soil test, leaching, sorption, long-term, phosphorus source, fertiliser


Long-term P losses and gains in sandy soils under continuous P fertilization and using simulated mediterranean weather cycles were investigated in laboratory experiments. Phosphorus losses from previously fertilized soils decreased logarithmically with increasing number of cycles. Total inorganic P and resin-extractable P were able to explain 94% of the variation in P losses. Addition of either fertilizer increased the amount of P leached from the soil and 10-40% more P was leached by adding superphosphate rather than coastal superphosphate. The percentage of the cumulative P lost by leaching decreased with increasing application rate of both fertilizers when expressed as a percentage of the cumulative water plus citrate-soluble P added. Addition of either fertilizer increased the amount of acid-extractable P, but coastal superphosphate had a much greater effect than superphosphate. Leaching losses of P were influenced by fertilizer solubility in the short term (<1 >year). In the long term, however, the water plus citrate-insoluble P in the fertilizers also contributed to P losses by leaching.