Abstract

HORTA, Carmo; LUPI, Samuel; ANJOS, Ofélia  and  ALMEIDA, José. Assessement of two residues from forestry industry as fertilizers. Rev. de Ciências Agrárias [online]. 2010, vol.33, n.2, pp.147-159. ISSN 0871-018X.

Forestry industry originates residues with distinct properties which can have also differences in its management reutilization. This study aimed at evaluating the fertilizer potential of forestry biomass burning ashes and causticizing lime mud from pulp and paper industry process, which are both residues from forestry industries. In a pot trial we evaluated the effect on ryegrass biomass production and on soil properties due to soil application of increasing amounts of the two forestry industry residues. These amounts corresponds to soil incorporation of 0, 0.5, 1, 3 and 5 t per ha of the residues. It was observed that ashes from biomass burning can be applied to soil without any negative effects, neither on productivity, nor on soil proprieties. This residue might supply some nutrients as K and Ca. In the case of soils with a high Ca to Mg ratio the simultaneous supply of ashes and Mg might be necessary. The other residue (causticizing lime mud) should be incorporated into soil long before seeding, due to its caustic effect. It should not be applied on perennial crops. As a fertilizer it might be used for alkali effect. As it has high Na content it induced a significant increase in electrical conductivity and exchangeable Na. Therefore, its application to soil should not be higher than 1 t per ha.

Keywords : Ashes; causticizing lime mud; fertilization; forestry biomass; residues.

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