Flávia Aparecida de Alcântara

Adubação verde na recuperação da fertilidade de um Latossolo Vermelho-Escuro degradado

The experiment was conducted at the Empresa de Pesquisa Agropecuaria de Minas Gerais, Nova Baden Experimental Station, in Lambari, MG, Brazil, aiming at evaluating the performance of the green manures pigeonpea (Cajanus cajan (L.) Millsp.) and sunnhep (Crotalaria juncea L.) with and without incorporation of the biomass, on the recovery of fertility of degraded soil cultivated with brachiaria (Brachiaria decumbens Stapf.). Experimental design used was of randomized block in factorial scheme of split plots with three replications, putting the biomass handling in the plots and both the legumes and brachiaria in the subplots. The three crops were cut and handled at the late flowering stage of the legumes, when samplings of the plant material were done for assessing dry matter yield, concentration and amount of nutrient. Evaluations of soil samplings at six depths (0-5, 5-10, 10-20, 20-40, 40-60 e 60-80 cm) and three periods (90, 120 and 150 days after handling) were performed. Pigeonpea stood out in the first evaluation concerning the improvements in soil fertility and sunnhep and slower mineralization, in the second. In the third evaluation, no benefits from the green manure on the chemical properties of the soil were found.

Extraction Methods for Phosphorus and Their Relationship with Soils Phosphorus‐Buffer Capacity Estimated by the Remaining‐Phosphorus Methodology‐A Pot Study with Maize

Abstract This work aimed to calibrate Mehlich 1, Mehlich 3, Bray 1, Olsen, and ion‐exchange resin extraction methods with maize phosphorus (P) responses in a pot study with lowland and upland soils with different P‐buffer capacities and to evaluate whether the calibration can be enhanced through the knowledge of remaining P. The experimental design was completely randomized with four replications in a factorial arrangement involving five P concentrations and four lowland or seven upland soils. The remaining P for each soil was determined, P‐buffer capacity was estimated, and the soils were grouped according to the results. Correlation coefficients showed that the remaining P is strongly dependent on clay and soil organic‐matter content, and its determination was useful to the evaluation of the extractants. The classification and grouping of soils according to their P‐buffer capacity improved the correlations between extracted P and plant response for Mehlich 1 and Bray 1 extractants. The Mehlich 3, Olsen, and resin methods presented better performances, independent of soil grouping.

Characterization of cover crops by NMR spectroscopy: impacts on soil carbon, nitrogen and phosphorus under tillage regimes

The objective of this study was to investigate the chemical composition of cover crops by solid-state CPMAS 13C NMR spectroscopy and its effects on carbon, nitrogen and phosphorus in a Typic Acrustox. Cover crops (Crotalaria juncea, Canavalia brasiliensis, Cajanus cajan, Mucuna pruriens and Raphanus sativus) and natural fallow were studied in rotation with maize under conventional and no-tillage regimes. Tissues of Crotalaria juncea, Canavalia brasiliensis, Mucuna pruriens and Raphanus sativus were analyzed using CPMAS 13C NMR spectroscopy. Soil samples were collected at the end of the growing season of the cover crops (September 2002) and during the grain filling period in corn from 0-5 and 5-10 cm layers. Cajanus cajan presented the lowest content of polysaccharides and along with Mucuna pruriens presented the highest percentage of aromatic carbon compounds, reflecting the slow decomposition of highly lignified material. Carbon stocks were higher in the superficial soil layer and under no-tillage due to the accumulation and slower decomposition of plant tissues under these conditions. Increases in the C/N ratio of the soil with Mucuna pruriens and the C/P ratio with Cajanus cajan in the dry season were also related to slower rates of decomposition, caused by the large concentration of aromatic compounds in the tissues of these species. The higher C/P ratios found at 0-5 cm layer are due to higher values of P (Mehlich-1) at 5-10 cm (25 mg kg-1) layer and the higher concentration of carbon in the superficial soil layer as a result of the accumulation of plant residues.

Effect of management systems and cover crops on organic matter dynamics of soil under vegetables

Vegetable production in conservation tillage has increased in Brazil, with positive effects on the soil quality. Since management systems alter the quantity and quality of organic matter, this study evaluated the influence of different management systems and cover crops on the organic matter dynamics of a dystrophic Red Latosol under vegetables. The treatments consisted of the combination of three soil tillage systems: no-tillage (NT), reduced tillage (RT) and conventional tillage (CT) and of two cover crops: maize monoculture and maize-mucuna intercrop. Vegetables were grown in the winter and the cover crops in the summer for straw production. The experiment was arranged in a randomized block design with four replications. Soil samples were collected between the crop rows in three layers (0.0-0.05, 0.05-0.10, and 0.10-0.30 m) twice: in October, before planting cover crops for straw, and in July, during vegetable cultivation. The total organic carbon (TOC), microbial biomass carbon (MBC), oxidizable fractions, and the carbon fractions fulvic acid (CFA), humic acid (CHA) and humin (CHUM) were determined. The main changes in these properties occurred in the upper layers (0.0-0.05 and 0.05-0.10 m) where, in general, TOC levels were highest in NT with maize straw. The MBC levels were lowest in CT systems, indicating sensitivity to soil disturbance. Under mucuna, the levels of CHA were lower in RT than NT systems, while the CFA levels were lower in RT than CT. For vegetable production, the CHUM values were lowest in the 0.05-0.10 m layer under CT. With regard to the oxidizable fractions, the tillage systems differed only in the most labile C fractions, with higher levels in NT than CT in the 0.0-0.05 m layer in both summer and winter, with no differences between these systems in the other layers. The cabbage yield was not influenced by the soil management system, but benefited from the mulch production of the preceding maize-mucuna intercrop as cover plant.

Hortas urbanas e periurbanas: o que nos diz a literatura brasileira?

O cultivo domestico de hortalicas e hortas comunitarias ganhou importância como uma politica alternativa de reducao da pobreza e melhoria das condicoes alimentares das familias no Brasil desde o final do seculo passado. As experiencias brasileiras foram relatadas em diferentes tipos de publicacoes cientificas, mas ate o momento, esses resultados nao foram avaliados. Assim sendo, publicacoes cientificas brasileiras sobre o tema foram buscadas nas paginas www.google.com.br, www.scielo.com.br, www.periodicos.capes.gov.br e na plataforma Lattes do CNPq para essa avaliacao. Os resultados mostraram que a maioria das publicacoes estavam disponiveis gratuitamente. O numero de publicacoes aumentou entre 1996 e 2009 e a maioria delas foi publicada em Encontros e Congressos. O cultivo de hortalicas contribuiu para aumentar o bem-estar da populacao. No entanto, diversas dificuldades foram relatadas, sendo as mais importantes a falta de organizacao social e a falta de acesso a assistencia tecnica, capital, terra e agua. Ate o momento, a maioria desses projetos foi de curta duracao (menos de tres anos). Assim sendo, e necessario que pesquisas multidisciplinares e de longo prazo sejam conduzidas a fim de que sejam melhor avaliados e compreendidos os beneficios e dificuldades dos projetos e as formas encontradas para superar essas dificuldades.