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Title: NUTRIENT LEACHING POTENTIAL OF MATURE GRAPEFRUIT TREES IN A SANDY SOIL

Author
item HE, Z - UNIV. OF FLA. FT PIERCE
item CALVERT, D - UNIV. OF FLA. FT PIERCE
item Alva, Ashok
item BANKS, D - UNIV. OF FLA. FT PIERCE
item LI, Y - UNIV. OF FLA. HOMESTEAD

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Field- and column- leaching studies were conducted to examine the leaching of nitrate, phosphate, and K in a Riviera fine sand (loamy, siliceous, hyperthermic, Arenic glossaqualf) under grapefruit production that received 0 to 168, 0 to 30,and 0 to 168 kg/ha/yr of N, P, and K, respectively. The concentrations of nitrate, phosphate, and K were measured in soil solution sampled using suction lysimeters installed above (120 cm) and below (180 cm) the hardpan. Column leaching was conducted using soil collected from 0 to 180cm depth, at 30 cm increment. The concentrations of nitrate, phosphate, and K in soil solutions at both 120- and 180-cm depths increased with increasing fertilizer rates. Fertigation tended to enhance leaching of nitrate, phosphate, and K compared with dry soluble granular application. The concentrations of nitrate and phosphate in soil solution were much greater at 120cm depth than those at 180 cm depth, whereas the reverse was true with respect to K concentrations. The average concentrations of nitrate in soil solution at 120- and 180-cm depths and across all fertilizer rates, over 3 years were well below 10 mg/L, the maximum contaminant limit (MCL) for drinking water quality. Solution phosphate concentrations at 120-cm depth (average 0.25 to 0.70 mg/L over 3 years for plots receiving various amounts of fertilizer) were greater than the U.S. EPA criteria for fresh waters (0.025 and 0.05 mg/L for lakes and streams) and may constitute a P contamination for surface waters. A column leaching study demonstrated that the argillic horizon in the Riviera fine sand effectively reduced downward transport of phosphate and K because it had a much greater sorption capacity for phosphate and K, but it had much less effect on the vertical transport of nitrate along the soil profile.

Technical Abstract: