Pathways of Phosphorous Fraction Dynamics in Field Crop Rotations of the Pampas of Argentina.

CIAMPITTI, I.A., PICONE, L.I., RUBIO, G. AND GARCÍA, F.O.

SOIL SCIENCE SOCIETY OF AMERICA JOURNAL

SOIL SCI SOC AMER

Año: 2011 vol. 75 p. 918 - 926

0361-5995

The study of labile and non-labile forms of phosphorus (P) might contribute to advances in soil test procedures and provide insights into management strategies to enhance P bioavailability to crops. Our objective was to evaluate the effect of continuous P fertilization on inorganic (Pi) and organic (Po) fractions to improve the understanding of soil P dynamics. For this purpose, four on-farm experiments were analyzed over a 6-year period. Two sites followed the corn-double cropped wheat/soybean (C-W/S) rotation and two sites followed the corn-soybean-double cropped wheat/soybeans (C-S-W/S) rotation. Phosphorus fertilization levels were 0 (Wp treatment) and 34 kg yr-1 (Fp treatment). The following soil P fractions were analyzed: anion exchange membrane (AEM)-Pi, bicarbonate (NaHCO3)-Pi and -Po, sodium hydroxide (NaOH)-Pi and -Po, chloridic acid (HCl)-Pi and residual-P. Path analysis of relationships between all P forms revealed that the main P fertilizer sinks were NaOH-Po and HCl-Pi fractions, accounting for approximately 50% of total applied P. The pathways for the Wp treatment showed the importance of inorganic P pools for the replenishment of available P, represented by the AEM-Pi and NaHCO3-Pi fractions, and the role of NaOH-Pi along with HCl-Pi as major inorganic P sources. When P fertilizer addition exceeded plant P removal, the pathway analysis showed that the Pi fractions tend to reorganize into more stable Po fractions. Path analysis was a practical tool to elucidate the roles of different Po and Pi pools in the transformations induced by differences in nutrient inputs and crop removal.