Resumo

MARTINS, J. C. et al. Experimental evaluation of runoff and erosion in an Haplic Luvisol of Mértola: impacts of fertilization in pastures. Rev. de Ciências Agrárias [online]. 2007, vol.30, n.2, pp.278-290. ISSN 0871-018X.

In a experimental area located in a hillside of Mértola region, Alentejo, with an Haplic Luvisol (FAO, 2001) and a mean slope of 15%, soil loss by erosion and surface runoff after rainfall occurrence were evaluated in small erosion plots, from October 2001 until June 2004, in 3 field experiments (A, B, and D) with a sown pasture mixture under different fertilization treatments. The experiments A (improved pasture) and B (sown pasture) were established in 1997, but the experiment D (sown pasture) was only installed in 2001. The sown mixture consisted of ryegrass, cocksfoot, some clover species, bisserula, and bird’s foot. In both experiments A and B, the erosion plots (4 × 1 m²) were superimposed on 6 plots. These experiments had three treatments (1 - without fertilization, 5 - inorganic fertilization; 7 - organic fertilization (8 t/ha of urban sewage sludge - SS applied in 1997, plus inorganic fertilizer in the beginning of each growing period) and two replications. In D experiment, the erosion plots were also superimposed on 6 large plots with three SS application rates (L0 = 0, L1 = 12, and L2 = 24 t/ha) and two replications. In each erosion plot, the volume of discharged water was measured and the amount of sediments was estimated when the infiltration capacity was exceeded by the amount of the rainfall occurring for one or several consecutive days of rainfall. The lowest observed runoff coefficient corresponded to the SS treatment, in B experiment. The highest values of that coefficient were reached at the treatment without fertilization in both A and B experiments. In D experiment, all treatments showed low values, between 0.07 and 0.10. The lowest soil loss values in the 3 years occurred in experiments A and B for the treatment with 8 t/ha of SS. In the experiment D, the highest values of soil loss were observed at the plots with L0 treatment.

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