588-18 Phosphorus in Field Crop Rotations of the Pampas of Argentina: Dynamics of Bray P, P balance and soil P fractions.

Poster Number 523

See more from this Division: S04 Soil Fertility & Plant Nutrition
See more from this Session: Nitrogen and Phosphorus Management (Graduate Student Poster Competition) (Posters)

Monday, 6 October 2008
George R. Brown Convention Center, Exhibit Hall E

Ignacio A. Ciampitti, Latin America Southern Cone, International Plant Nutrition Institute, Acassuso, Buenos Aires, Argentina, Fernando Garcia, Latin America Southern Cone, Intl. Plant Nutrition Inst., Acassuso Buenos Aires, Argentina, Gerardo Rubio, Univ. of Buenos Aires, 1417 Buenos Aires, Argentina and Liliana Picone, Agronomy, INTA-Facultad Ciencias Agrarias Univ. Nacional Mar del Plata, Balcarce, Argentina
Abstract:
A better understanding of the phosphorus (P) cycle is necessary for improved management strategies that enhance P bioavailability to crops. Our objective was to evaluate the effect of continuous P fertilization on 1) P balance, 2) Bray P 1 dynamics, and 3) soil P fractionation, in two crop rotations: corn-double cropped wheat/soybeans (C-W/S; two sites), and corn-full season soybeans-double cropped wheat/soybeans (C-S-W/S; two sites). P balances and Bray P 1 dynamics were determined in four soils, after seven years with or without continuous P application. Soil P was fractionated into Resin-Pi, NaHCO3-Pi and Po, NaOH-Pi and Po, HCl-Pi, Residue-P and P associated to particulate organic carbon (POC-P). Bray P 1 declined with time in the non-fertilized plots and increased in fertilized plots with differences between crop rotations. The changes in P balance between rotations were explained by differences in P removal. In the fertilized treatment, the P budget surplus was converted onto different fractions. All P fractions responded positively to continuous P application. Without considering Residue-P, HCl-Pi appeared to be the most important Pi fraction, in absolute (85 mg P kg-1) and relative (17% of total P) terms. POC-P increased in fertilized P plots and the greatest differences appeared at the superficial layer, 0-5 cm. The ratio of POC to P-POC declined towards the lower soil layers (0-5 cm>5-10 cm>10-20 cm), and the lowest values were obtained in the fertilized treatment. These results were related with an increase in labil P fractions that could be explained by a higher phosphatase activity and, consequently, an enhancement of the rate of P mineralization. At a turn, it would explain the higher values found for NaHCO3-Po and, mainly, for NaOH-Po fractions observed in plots with continuous P application.

See more from this Division: S04 Soil Fertility & Plant Nutrition
See more from this Session: Nitrogen and Phosphorus Management (Graduate Student Poster Competition) (Posters)