João Ambrósio de Araújo Filho

Impactos de sistemas agroflorestais e convencional sobre a qualidade do solo no semi-árido cearense

The environmental benefits of agroforestry system are well documented in many regions of the globe. However, works documenting the advantage of this kind of soil management system on soil quality in the cearense semi-arid region are very scarce. The aim of this work was to evaluate the impact of agroforestry and conventional systems on the physical and chemical soil characteristics, after five years of experimentation in the semi-arid region, Ceara, Brazil. The experiment consisted of seven treatments: agrosilvopasture (AGP), silvopasture (SILV), traditionally cultivated in 1998 and 1999 (TR98), traditionally cultivated in 2002 (TR02), intensive cropping (CI), and two native forests (MN-1 and MN-2). Soil samples were collected at four depths: 0-6, 6-12, 12-20 and 20-40cm. Soil quality was evaluated by the following physical and chemical characteristics analyzed: granulometry, clay dispersion, aggregate stability, exchangeable elements, soil pH and total organic carbon (COT). The treatments AGP, TR98 and CI reduced the COT content due to intensive soil management.

Characterization of condensed tannins from native legumes of the Brazilian northeastern semi-arid

Despite the possible influence of tannins on the nutritional value of the forages from Caatinga vegetation, there are few studies that evaluated their tannin concentration. This study was conducted to characterize condensed tannins present in the legumes species Mimosa hostilis (Jurema Preta), Mimosa caesalpinifolia (Sabia) and Bauhinia cheilantha (Mororo), at three stages of their phenological cycle. The concentration of soluble tannin (ST), bound tannin (BT) and total tannin (TT) were determined using the butanol-HCL method; astringency was by the radial diffusion method, and the monomeric composition of purified tannins by a high-performance liquid chromatograph with delphinidin, cyanidin and pelargonidin as standards. Concentration and astringency of purified condensed tannins, as well as their monomeric composition varied between species, and in some cases among phenological cycles. The values observed were always above the limits considered beneficial for ruminal digestion (i.e. 5%). Jurema Preta presented the highest values (30.98% TT and 22% astringency at full growth stage), and Mororo the lowest (10.38% TT and 14% astringency during fructification). Jurema Preta presented a mean relationship prodelfinidin (PD): procyanidin (PC) of 97:3, which did not vary during the phenological cycle, showing the high astringent capacity of these tannins. Sabia presented a relationship of 90:20 during full growth and flowering stages, decreasing to 40:50 at fructification. In Mororo the PD:PC relationship was more equilibrated, around 40:50 during full growth and flowering stages, decreasing to 35:60 During fructification. Propelargonidin was not detected or was present at low concentration in the three species.

Efeitos da Manipulação da Vegetação Lenhosa sobre a Produção e Compartimentalização da Fitomassa Pastável de uma Caatinga Sucessional

The research was carried out at the Centro de Assessoria e Apoio aos Trabalhadores e Instituicoes Nao-Governamentais, Alternativas (CAATINGA) in the Ouricuri county, state of Pernambuco, Brazil, in the period of 1989-1994, with the objective of comparing different practices of woody vegetation manipulation, as alternatives of sustainable pastoral management of caatinga and determining their viability to the small producers. Plots measuring 25 x 100 m had the woody vegetation submitted to the following experimental treatments: deforestation, thinning, thinning-lowering, lowering and control. The results indicated that the total availability and compartimentalization of the aerial phytomass of caatinga (woody species foliage and herbaceous vegetation) were affected by the manipulation methods of the trees and shrubs, and by the annual variations of the rainfall. The vegetation treatments substantially increased the participation of the grass species on the floristic composition of the herbaceous phytomass. The lowering and the thinning-lowering of the woody vegetation are the recommended methods for the pastoral management of caatinga to the sites similar to that of this research.

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

Studies have proven that the agroforestry systems in the semi-arid region of the State of Ceara, Brazil, induce an increase in soil organic C levels. Notwithstanding, there is no information if this increase also results in qualitative changes in different pools of soil organic matter. The objective of this study was to verify the possible chemical and structural alterations in fulvic and humic acids of a Luvisol in areas adopting agroforestry, traditional intensive cultivation and native forest in a long-term experiment conducted in the semi-arid region of Ceara State, Brazil. The study was conducted in an experimental area of the National Goat Research Center (Embrapa) in Sobral, CE. The following treatments were evaluated: agrosilvopasture (AGP), silvopasture (SILV), intensive cultivation under fallow (ICF), and areas with native forest (NF). Soil fulvic and humic acids fractions were extracted from the 0-6 and 6-12 cm layers and characterized by elemental composition, thermogravimetry and infrared spectroscopy analyses. The elemental composition analysis of humic acids confirmed the data found for fulvic acids, showing reduction in the C, H and N levels, followed by an increase in O contents in the AGP and ICF treatments over SILV and NF. In all treatments, except to SILV in the 0-6 cm layer, the percentage of mass loss was highest (300-600 °C) for humic acids in the thermally most stable region. Despite the similarity between infrared spectra, soil fulvic acids in the SILV treatment extracted from 6-12 cm depth decrease the absorption bands at 1708 and 1408 cm-1 followed by an increase in the absorption band at 1608 cm-1 attributed to aromatic C=C groups. This behavior suggests an increase in the aromatic character of the structure. The AGP and ICF treatments, which increase the soil tilling, favored the maintenance of humic substances with a more aromatic character in the soil than SILV and NF. The less aromatic humic substances in the SILV treatment resulted in an increase of exchange sites of soil organic matter, indicating improved nutrient cycling and maintenance of productivity in the system.

Efeito do corte da parte aérea na sobrevivência do marmeleiro (Croton Sonderianus Muell.Arg.)

The research was conducted at the EMBRAPA - National Center for Goat Research, in Sobral, Ceara, Brazil, to evaluate the effects of cutting of the above ground parts in relation at regrowth height of marmeleiro on its survival, persistence, regrowth vigor and subsequent production of herbaceous understory phytomass. The plants were cut at 10.0 cm above ground, when the regrowth reached four different heights (25, 50, 75 and 100 cm). The cutting treatments were applied on plots of 5 m x 30 m. The evaluation of the mortality of the plants was accomplished by the count of the total number of dead and alive plants of the experimental plots. Data were analyzed by means of the chi-square nonparametric test. It was observed dependence between mortality of the plants and regrowth cutting, where all treatments were different. Best results were obtained when regrowth plants were cutting to a medium height of 75 cm, which decreased marmeleiro density by 96%. The reduction of density provided a significant increase on herbaceous understory phytomass in relation to control treatment.

Pastoreio de curta duração com ovinos em caatinga raleada no sertão cearense

The experiment was carried out in Sobral, Ceara, Brazil, from January 1992 to July 1994, with the objective of determining the productive performance of lambs, forage production, and frequency of the species of the herbaceous layer of a thinned caatinga, under organic fertilization and short duration grazing, with two stocking rates. The stocking rates were 3.3 (light) and 10.0 heads/ha (heavy), with (5.0 ton/ha of goat manure) and without fertilization. A complete randomized design was followed, with a factorial distribution of 2 x 2 x 3 (stocking rate x fertilization x year), with two repetitions. Sheep grazing resulted in total disapearing of the grass species and an increasing of the forbs, along the period of study. The organic fertilization did not show significant effects (P>0.05) on the animal and pasture performances. The best animal performance (P<0.01) was observed on the padocks under light stocking rate (3.3 head/ha), with 108.0 g/head/day, and the best performance (P<0.01) of the pasture was obtained on the areas under heavy stocking rate (10 head/ha), with 71.2 kg/ha/year. Although, the short duration grazing with sheep presented high performance by the animals and by the pasture, it should not be recommended for the thinned caatinga, because it unbalances the herbaceous layer composition, the principal source of the diet of those ruminants. Possibly, the alternate grazing with other herbivorous of different grazing habit and diet composition may result on a beter sustainability of the exploration.