Agricultural Management Systems Impact on Soil Phosphorous Partition and Stratification

摘要

Our objective was to evaluate the impact of land use change, from natural forest to tillage-based systems, on the distribution of P pools and their stratification in soils under both no-till (NT) and conventionally tilled (CT) corn (Zea mays)-soybean (Glycine max) with and without cover crops, CT alfalfa (Medicago sativa), chicken and dairy manure, organic, and adjacent natural deciduous forest ecosystems (control). Results showed that residual P (RP) accounted for 68.7% followed by 13.3% calcium- and magnesium-bound P (CaMgP), 9.6% particulate organic P (POP), 8% iron- and aluminum-bound P (FeAlP), 0.3% soluble reactive P (SRP), and 0.1% exchangeable P (EP) of the total P. While the concentration of all P pools increased, the POP decreased at 0-10 cm depth under both CT and NT compared to the forest. The SRP increased threefold under NT, 2.6-fold under CT, sevenfold under alfalfa, and more than fourfold under organic, chicken and dairy manure systems. In contrast, the POP decreased by 63 to 73% under CT and 41 to 58% under NT. Likewise, the POP decreased under CT dairy and chicken manure, alfalfa, and organic systems. A similar tillage and cover crop impact on SRP and POP was observed at 10-20 cm depth. All P pools except POP have shown various degrees of stratification. An integration of cover crops under NT reduced the SRP stratification (by 41%), when compared to NT alone. Our results suggested that the SRP concentration and stratification in all agricultural systems are prone to edge-of-field loss either by drainage under NT or surface runoff under CT.