Pathways of Soil Phosphorus Transformations after 8 Years of Cultivation under Contrasting Cropping Practices
- Zhiming Zhenga,
- Régis R. Simard *b,
- Jean Lafondc and
- Léon E. Parenta
The knowledge of P transformations is essential to understand the P behaviour in soils. Organic (Po) and inorganic (Pi) P fractions were obtained from the 0- to 30- and 30- to 90-cm layers of a Labarre silty clay (fine, mixed, frigid, Humic Cryaquept) by a sequential extraction. Barley (Hordeum vulgare L.) monoculture and 3-yr barley-forage rotation as main plots, and two nutrient sources (mineral fertilizer and liquid dairy manure) as subplots were studied. Path analysis was used to describe soil P transformations between the falls of 1989 and 1997. Nutrient source was the main factor affecting P transformations in the 0- to 30-cm soil layer, whereas crop rotation predominated in the subsoil. Pathways differed more for Po than for Pi pools. In the 0- to 30-cm soil layer, 86 to 97% of the variation in resin-P was the direct effect of added Pi The NaHCO3-Pi and Po were sensitive to crop rotations and nutrient sources, and were transitory pools of soil P. The NaOH-Pi was a sink for added Pi and a source of NaHCO3-Pi Labile Pi tended to store as NaOH-Po, which was the sink for added Po and immobilized soil Pi in the mineral fertilizer systems. Conversely, the NaOH-Po was mineralized and contributed to labile Pi in dairy manure systems. The NaOH-Po acted as store of subsoil Po in the monoculture but was the main source of labile P in the rotation systems. The P transformations in this Cryaquept were strongly influenced by nutrient sources and crop rotations.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2002. Published in Soil Sci. Soc. Am. J.66:999–1007.