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Title: SORPTION-DESORPTION AND SOLUTION CONCENTRATION OF PHOSPHORUS IN A FERTILIZED SANDY SOIL

Author
item HE, Z - UNIV OF FLORIDA
item Alva, Ashok
item LI, Y - UNIV OF FLORIDA
item CALVERT, D - UNIV OF FLORIDA
item BANKS, D - UNIV OF FLORIDA

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/1998
Publication Date: N/A
Citation: HE, Z.L., ALVA, A.K., LI, Y.C., CALVERT, D.V., BANKS, D.J. SORPTION-DESORPTION AND SOLUTION CONCENTRATION OF PHOSPHORUS IN A FERTILIZED SANDY SOIL. JOURNAL OF ENVIRONMENTAL QUALITY, 28:1804-1810. 1999.

Interpretive Summary: Phosphorus contamination of surface water has been an environmental issue in some agricultural areas. In poorly drained Alfisols with a hardpan at about 120 cm depth, citrus is grown in raised beds to provide well drained soil conditions for root growth. The leachate from the top of the bed percolorates downwards and reaches the top of the hardpan and then moves laterally into the water furrow, which becomes a part of the return flow. Minimizing nutrient transport in the leachate is important to prevent the potential for nutrient contamination of surface water. This study was conducted in a Riviera fine sand with application of 0 to 30 kg phosphorus per hectare using triple super phosphate in a mixed fertilizer. The phosphorus concentration in the leachate, sampled by using suction lysimeters, varied from 0.031 to 0.976 and from 0.002 to 0.083 mg per liter above and below the hardpan, respectively. This study demonstrated that although hardpan essentially restricts the downward transport of phosphoru in the leachate, the lateral seepage of soil solution, containing high levels of phosphorus, from above the hardpan can potentially contribute to surface water.

Technical Abstract: There has been increasing concern about drinking water contamination and accelerated eutrophication of surface water bodies. A field experiment was conducted to assess leaching potential of PO4-P in a Riviera fine sand (loamy, siliceous, hyperthermic Arenic Glossaqualf) under grapefruit (Citrus paradisi MacFad.) production that received 0 to 30 kg P ha/yr. The PO4-P concentration was measured in soil solution sampled using suctio lysimeters installed above (120 cm) and below (180 cm) the hardpan (argillic horizon). Phosphorus sorption-desorption in soil samples from different depths of the soil profile was determined to understand the transport and leaching of P in the sandy soil. Phosphorus sorption capacity of the argillic horizon was much greater than the soil above and below it. The PO4-P concentrations in soil solution varied from 0.031 to 0.976 and from 0.002 to 0.083 mg P/L at the 120-and 180-cm depths respectively. Solution PO4-P concentrations generally increased with P application rates. The concentrations of P in solution at the 120-cm depth were much greater than those at the 180-cm depths, due to the greater P retention capacity and restricted flow of P through the hardpan. This study demonstrates that leaching of P into groundwater was reduced by the presence of a hardpan in the Riviera fine sand. However, the water drained from the soil above the hardpan contains phosphorus and could be a potential P source to surface waters.