Phosphorus fractions and correlation with soil attributes under no-tillage and crop-livestock integration systems in Cerrado of Goias

The objectives of this study were to evaluate the fractions of organic phosphorus (P) and inorganic soil, and to determine the remaining phosphorus (Prem) and correlate the fractions of P with some soil attributes in areas with different land use systems in the Cerrado region, Goias State. The farming systems were used: crop-livestock integration - CLI (Brachiaria+corn/beans/cotton/soybean), no-tillage system - NTS (sunflower/millet/soybean/corn) and as a reference, the natural Cerrado (Cerradao). In a completely randomized design in Oxisol and relief, were collected soil samples in the layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m depth. Were determined organic P - Po (H+, OH- and labile-L), inorganic P - Pi (H+, OH-, and L), P-total (Pt) and Prem. Through Pearson correlations estimated the dependency between P fractions and some soil attributes (clay, fractions of soil organic matter - SOM, soil chemical attributes - via fertilization, and iron oxides). In general, the highest levels of PiH(+), PoH+, PtH+, PiOH(-) , PtOH- , PiL, PoL, PtL and Prem (0.00-0.10 m) were found in the CLI system compared to the NTS. Regarding depth, the highest levels of P fractions were observed in the surface layer. The cultivated areas had higher values of P fractions when compared to Cerrado area. It was observed dependence of the fraction PiH(+) with clay and fertility (fertilizer); fraction PoH+ is related to iron oxides (Fe-d and Fe-o) and SOM fractions, the fraction PiOH(-) was dependent on iron oxides and carbon of fulvic acid fraction (C-FAF) and P, while the fraction PoOH- related with the carbon of humic acid fraction (C-HAF) and Mg, Al and K. The fraction is related PiL clay and fertilizer, while the PoL, to iron oxides, the C-FAF and C-HAF and fertilizing. CLI system, due to the increased plant intake brachiaria, bovine manure randomly left in the area and fertilization performed, carries the greater availability of Pi and Po fractions than compared to SPD, without brachiaria.