Resumo

SERRAO, M. G.; PEDRA, F.  e  DOMINGUES, H.. Comparison between two organic amendments on phosphorus availability for ryegrass . Rev. de Ciências Agrárias [online]. 2007, vol.30, n.2, pp.109-121. ISSN 0871-018X.

Municipal solid waste compost (MSW) and urban sewage sludge (SS) applied to soils, containing phosphorus (P) in organic and inorganic forms, can affect the element dynamics in soil, with subsequent reflexes on plant nutrition. This work aimed to evaluate the effects of the application of a MSW and a biologically treated SS on P uptake by a test plant and soil “available” P concentration as determined by the Egnér-Riehm method (Riehm-P). The study fell upon soil and plant samples deriving from a pot trial with multiple aims. It had two pot series, one maintained with annual ryegrass (Lolium multiflorum) during approximately seven months, and the other one without plants until the end of the same period. The treatments of each series, in triplicate, referring to the combinations of two soils and four MSW and SS rates (equivalent to 0, 15, 30, and 60 t/ha) were compared. Topsoil samples of a Haplic Podzol (PZha) and of a Calcic Vertisol (VRcc), with low Riehm-P concentrations, were used. A basal fertilisation including P was applied at the beginning of the trial, in the series cropped with annual ryegrass. Total P uptake, evaluated in six harvests of the aboveground biomass, and soil Riehm-P contents at the last harvest were determined. A single P sorption index (Bache & Williams, 1971) was also determined to compare the initial soils P sorption capacity. The highest total P uptake value (378 mg/pot) was achieved in the VRcc soil at the 60 t/ha SS rate (P ? 0.001). In this soil, total P uptake increased with the MSW and SS application, with the exception of the 15 t/ha MSW rate. However, soil Riehm-P concentration only raised at the 60 t/ha SS rate, in the series without plant test, and at the 60 t/ha MSW rate, in the series with annual ryegrass. Differently, in the PZha soil, total P uptake values were not higher than the control but at the highest MSW and SS rate, where they did not differ (P? 0.001). This agreed to the much higher positive effect of the same MSW and SS rate on soil Riehm-P concentration, in both series. The highest SS rate was as or more efficient than the same MSW rate in increasing P availability in these soils, in part due to its higher total P content. Other specific soil P studies will help to clarify the different soil behaviour, namely the soil pH evolution and P sorption capacity variation as influenced by the residue application.

        · resumo em Português     · texto em Português     · Português ( pdf )