Management Practices Impact Soil Phsophorus Speciation.

Phosphorus (P) is the second most important essential macronutrient vital for crop growth. The objective of the study was to measure the distribution of P in different fractions and the fate of stratified P in soil under different management practices. Composite soils (at 0 to 10, 10 to 20, and 20 to 30 cm depth) were collected from chemically fertilized, manure applied, cover cropped, CT and NT fields, organic experiments, continuous corn and soybeans, corn-soybean and corn-soybean-wheat rotations. Soil samples were processed and analyzed for P contents in different pools by sequential extraction including soluble reactive P (SRP), exchangeable P (EP), iron- and aluminum-bound P (FeP), calcium- and magnesium-bound P (CaP) and residual P. Results showed that management systems significantly influenced the distribution and concentration of in various fractions. Other than RP, most of the P in soil was extracted as FeP and CaP fractions. A small amount of P remained in the soil in a soluble reactive form. Organic production had higher concentration of soluble reactive P (SRP) than conventional system. Likewise, soils under filter strip had the highest concentration of SRP followed by forest and alfalfa, compared to lowest values of SRP in soils under corn-soybeans-wheat (C-S-W) and continuous soybeans. No-till (NT) had a significantly higher concentration of SRP than that of conventional-tillage. Cover crops significantly reduced the SRP as compared to soils without cover crops. The concentration of SRP was higher in chicken manure (CM) amended soil, followed by dairy manure (DM) amended soil, compared to soils under without any manure amendments. The concentration of P fractions under different management systems decreased with increased depth. The organic system had higher P stratification than the conventional system. The stratification of SRP, EP, and RP was higher under NT when compared with CT. The stratification of SRP was lowest in soil under cover crops compared with soil under control. Results showed that the stratification of SRP was highest in CM amended soil followed by DM amended soil compared with soil under control. The P stratification in soil under different management systems decreased with depth.