The phosphorus supply to crops in tropical soils is deficient due to its somewhat insoluble nature in soil, and addition of P fertilizers has been necessary to achieve high yields. The objective of this study was to examine the mechanisms through which a cover crop (Congo grass – Brachiaria ruziziensis) in rotation with soybean can enhance soil and fertilizer P availability using long-term field trials and laboratory chemical fractionation approaches. The experimental field had been cropped to soybean in rotation […]

In highly weathered tropical soils phosphorus (P) bioavailability to plants is closely associated with soil organic P forms, which in turn are influenced by the vegetation cover. The aim of this study was to evaluate total organic P (Po), labile P fractions and microbial biomass P in soils under Acacia auriculiformis and Mimosa caesalpiniifolia stands, secondary forest and pasture. The clay-adjusted average content of total Po and labile Po were 375 mg kg-1 P and 40.2 mg kg-1, respectively. The […]

Soil management systems affect the P dynamics in content and forms. The aim of this work was to measure the effect of several cultivations systems in the long term (16 years) on the different soil P forms. The treatments consisted of combinations of the two cultivation systems: sole corn (C) and corn-bean intercrop (CB), with two levels (0 and 1) of organic fertilizer (OF), at rates of 0 and 40 m3 ha-1 year-1 and three levels (0, 1, 2) of mineral fertilizer (MF) […]

Most soils in semi-arid Northeastern Brazil are considered phosphorus deficient. The great diversity of orders they belong to, however, indicates that they are not similar in relation to the concentrations of their different P forms. The distribution of phosphorus forms in 69 soils of the most common soil orders in the semi-arid region was evaluated in samples from the 0-20 and 20-40 cm soil layers. Phosphorus was determined by Mehlich-1 and by a sequential fractionation, through extractions with resin, NaHCO3, […]