Propriedades físicas do solo e sistema radicular do cacaueiro, da pupunheira e do açaizeiro na Amazônia oriental

Abstract

Physical properties of soil and root system of cocoa, peach palm and açai in the eastern AmazonThe knowledge on the relationship between roots of crop plants and soil physical properties is very important. This article evaluates the distribution of the root systems of cocoa, palm peach and açai and their relationships with the soil physical properties. The research was carried out in an alic Yellow Latosol and root and soil samples were obtained from 10 cm to 40 cm depth. The experiment was arranged in a randomized block in the factorial design (four depth soils and three root class), with four replications. The açai root amount is twice of the palm peach and ten times more that of cacao. No difference was verified in the amount of roots of peach between the distances of the plants. The roots were collected in two distances of the plant stem in monolith samples and separated in three diameter class: < 1.0 mm, 1.0-3.0 mm e > 3.0 mm. The roots amount of the three plants was directly correlated with the coarse sand content and inversely correlated with clay content and bulk density. The large pores size was also directly correlated with the amount of cacao and açai roots in the three classes of diameter. The açai showed the most abundant root system and it the greatest number of correlations between the amount of roots and the physical properties of soil involving the three diameter root classes.

Influence of hydrological pathways on dissolved organic carbon fluxes in tropical streams

“…This indicates higher water movement in the soil profile of the PF, so DOC is transported to greater depths and consumed before reaching the stream, as found by Shibata et al (2001) in the temperate forest, where the high hydraulic conductivity is attributed to the sand content. According to Augusto et al (2004) and Martins and Augusto (2012) During the rainy season, DOC transport by the streams was five and ten times higher (PF and CP, respectively) in comparison with the dry season in both areas; however, the annual flows in the PF accounted for a third of what was recorded in the CP. In contrast, DOC flows in the dry season were the same in the microbasins.…”

“…This reflects the SOM content transported from the infiltration to the outflow into the stream throughout, which is dependent on the dynamics of the litter and the biomass above ground. In a comparison between cacao and other tropical crops, Theobroma cacau showed a concentration of roots with a diameter <3 mm at a depth of 0–10 cm, which affects the presence of pores with decreasing hydraulic conductivity and can contribute to the increase in DOC in this soil layer (Augusto, Martins, & Góes, ; Martins & Augusto, ). According to Jansen et al.…”

“…According to Augusto et al. () and Martins and Augusto (), in sandy soils, macropores promote better drainage, enabling thicker and deep roots, while in clay soils, the predominance of micropores allows for thin and shallow roots that reduce hydraulic conductivity. Therefore, we suggest that higher DOC concentrations in the CP at SS90, when compared to the PF, are also influenced by the presence of sand, which has a low potential for adsorption, and are influenced by the deep DOC sources derived from OM transport in the soil matrix or the roots.…”

Soil organic matter and CO2 fluxes in small tropical watersheds under forest and cacao agroforestry

“…The predominance of cacao trees ( Theobroma cacao ) in both systems (MC and UC) may provide a thick litter layer and a greater concentration of roots in the first centimeters of soil compared to PF [ 71 ]. The change in composition of SOM in MC and UC can be explained by higher concentrations of nutrients such as Ca 2+ and Mg 2+ , as well as the dynamics of DOC and DIC in the soil profile.…”

Oil palm agroforestry shows higher soil permanganate oxidizable carbon than monoculture plantations in Eastern Amazonia

“…The AFS studied were composed of several species that contribute to C and soil nutrients via the following two mechanisms: (1) decomposition of the layer of plant material formed by litterfall (mainly T. cacao) and pruning (mainly T. cacao and G. sepium) (Dawoe et al, 2010; Fontes et al, 2014; Schneidewind et al, 2019) and (2) diverse root systems (in terms of morphology, architecture, association with microorganisms, and chemical composition) that incorporate C into the soil by root cycling and release of exudates in different amounts and depths (Hombegowda et al, 2016) and exploit soil resources better. Forest tree species generally have deeper root systems, resulting in the exploration of deeper layers of the soil, enabling them to access nutrients that are out of the reach of plants with rather superficial root systems as in agroforestry, such as T. cacao and E. oleracea (de Mendonça Góes et al, 2004; Martins & Augusto, 2012), which are then returned to the soil through litterfall (Das & Chaturvedi, 2008; Montagnini & Nair, 2004). In general, AFS is more efficient than monocultures in incorporating C into the soil because of the higher production and quantity of litter (Schneidewind et al, 2019) and roots (Niether et al, 2019; Rajab et al, 2016) owing to the higher density and diversity of plants in AFS.…”