Sediment, nutrient and water losses by water erosion under agroforestry systems in the semi-arid region in northeastern Brazil

Abstract

Inadequate soil management practices adopted in the Brazilian semi-arid region contribute to erosive processes. Agroforestry systems (AFs) have been considered an alternative to reduce water erosion. This study aimed to evaluate the impact of two alternatives AFs, a traditional and an intensive cropping system on the losses of sediments, water, organic carbon and nutrients caused by water erosion in comparison to the natural vegetation (caatinga) in a semi-arid region of northeastern Brazil. The agroecosystems studied were: agrosilvopasture (AGP) which consisted of an alley cropping system, cultivated with Leucaena leucocephala and maize, within an area composed by 22% of native trees (200 native trees per hectare) which was grazed during the dry season; silvopasture (SILV) that was composed by 38% of native trees (260 trees per hectare) with a stocking rate of 20 ewes during whole year; traditional agrosilvopasture (TRAG) being managed as following: total deforestation, burning of the residues, cropped with maize for 2 years (1998 and 1999) and fallow during 8-10 years; and intensive cropping (IC) system which was deforested and burned in 1997 followed by cultivation of maize from 1998 to 2002, and thereafter by a fallow period of 8-10 years similar to TRAG. Two areas of native forest (NF1, NF2) known as 'caatinga', used as grassland during the dry season and as a source of wood, were selected and used as reference of steady state in the comparative study in relation to the cultivated sites. Sediment and water losses as a result of erosion were collected during two rainy seasons, i.e. 2003 and 2004, and nutrients and organic carbon contents were determined. Soil samples were collected and organic carbon, pH in water, pH in KCl, water dispersible clay (WDC) and hydraulic conductivity (K 0 ) were measured. In 2003, sediment and water losses did not differ significantly among all treatments. However, in 2004, TRAG (0.70 Mg ha -1 ) and NF1 (1.37 Mg ha -1 ) showed the highest sediment losses, whereas TRAG and IC presented the highest water losses. On average, nutrients losses in cropped areas were lower than in natural vegetation (NF1, NF2).

Carbon sequestration and nutrient reserves under differen t land use systems

“…In the experimental area (3°41'S, 40º20'W), the average annual rainfall over the past 10 years was 989 mm. The soil in the area consists of patches of typical Ortic Chromic Luvisol and typical Hypochromic Luvisol (AGUIAR et al, 2010). The vegetation is a thorny deciduous savannah, regionally known as Caatinga (COLE, 1960).…”

“…Studies by Aguiar et al (2010), Iwata et al (2012), Maia et al(2006;, Nogueira et al (2008), and Silva et al (2011) demonstrated the beneficial effects of agroforestry systems on the soil chemical, physical and biological properties, as well as on the preservation of the plant diversity (ALMEIDA et al, 2009;CAMPANHA et al, 2011). Some of the above studies were developed in experimental areas of the National Goat and Sheep Research Center (CNPCO), in the northern part of the Ceará State, Brazil, where agroforestry systems are being studied as an alternative to the traditional management of family farming.…”

Chemical and structural characterization of soil humic substances under agroforestry and conventional systems

“…Solo, 35:1597Solo, 35: -1608Solo, 35: , 2011 In the semi-arid Northeastern region of Brazil, AGF may be considered a promising alternative to restore the soil quality of areas degraded by intense soil cultivation (Araújo Filho & Carvalho, 2001). These agroecosystems can improve nutrient cycling and enhance soil structure (Maia at al., 2006), reducing water erosion (Aguiar et al, 2010) and increasing soil organic C stocks (Maia et al, 2007).…”

Dinâmica de Sistemas Integrados de Manejo de um Solo no Desenvolvimento da Cultura do Milho

“…O sistema iLPF auxilia no aumento das interações biológicas entre os cultivos agrícolas, árvores e animais e reduz os riscos de erosão mantendo ou elevando os estoques de matéria orgânica quando comparado com outros modelos agrícolas (AGUIAR et al, 2010;MOLUA, 2005). Outra importante opção é o sistema Santa Fé pelo cultivo de culturas anuais, especialmente o milho, consorciado com forrageiras, principalmente as do gênero Brachiaria.…”