Phosphorus retention on soil surface of tilled and non-tilled soils

GUTIERREZ BOEM, F. H.; ALVAREZ, C. R.; CABELLO, M. J.; FERNÁNDEZ, P. L.; PRYSTUPA, P.; TABOADA, M.A.

SOIL SCIENCE SOCIETY OF AMERICA JOURNAL

Soil Science Society of America

Lugar: Madison, Wisconsin; Año: 2007

0361-5995

Decreasing phosphorus buffer capacity of soil surface in non-tilled soils has been attributed to enrichment of both, phosphorus and organic matter. As soil surface enrichment with phosphorus and organic matter usually occurs simultaneously in non-tilled soils, it is not clearly established whether the increase of soil organic matter affects the capacity of soils to retain phosphorus. A study was conducted to assess whether the variations in soil organic matter (total and particulate) at soil surface affects phosphorus retention capacity. Thirty five soils from the Rolling Pampa (17 tilled and 18 non-tilled) were selected. All soils had medium to low levels of available phosphorus (PBray1<20 mg kg-1). Soil samples were taken from the top 5 cm, and several soil characteristics determined: available and total phosphorus, phosphorus sorption index, organic matter, particulate organic matter (>53 µm), particle size distribution, and pH. Tilled and non tilled soils did not differ in soil texture, pH, total and available phosphorus content. On the contrary, non-tilled soils had more organic matter (+13%) and particulate organic matter (+56%) than tilled soils. The capacity of soils to retain added phosphorus was not different in both groups of soils. Phosphorus sorption index was not related to soil content of total or particulate organic matter. Variation in phosphorus sorption index was only related to soil clay content (R2=0.44). This study provides evidence contradicting the long held assumption that the reported decrease in phosphorus sorption at the surface of non-tilled soils was caused in part by organic matter enrichment.