Maria Lucrécia Gerosa Ramos

Nitrogênio da biomassa microbiana em solo cultivado com soja, sob diferentes sistemas de manejo, nos Cerrados

The aim of this study was to quantify soil microbial biomass carbon in a soybean crop under different soil management systems: no-tillage, single harrowing, subsoiling and two harrowing, on a clay Red-Yellow Latossol in the Cerrado region. Soils were studied at five depths: 0-5, 5-10, 10-20, 20-30 and 30-40 cm. Four periods were observed: before soil preparation; 30 days after germination; flowering stage and after harvesting soybean plants. The same measurements were taken under the same conditions in an area of native cerrado vegetation, adjacent to the experiment (Cerrado sensu strictu). Subsoiling showed highest carbon values 30 days after germination (865.7 mg kg -1 of soil). This was reduced to less than 10% (80.3 mg kg -1 ) at flowering. The carbon values were more stable in the no-tillage system, mainly in the 0-20 cm layer. The layers 0-5 cm and 5-10 cm showed significantly higher carbon values compared with other layers in most of the studied periods and depths. Subsoiling showed the lowest soil organic carbon level after soybean harvesting. Only in the system with subsoiling there was no significant correlation between the microbial carbon:organic carbon index and soil nutrients.

Carbono e nitrogênio da biomassa microbiana em resposta a diferentes sistemas de manejo em um latossolo vermelho no Cerrado

The microbial biomass is a living component of the organic matter responsive to changes caused by different soil management systems. The objective of this long-term study was to determine microbial biomass carbon and nitrogen in response to different management systems in a clayey Red Latosol cultivated with corn in the Cerrado. The field experiment was conducted on an experimental area of Embrapa Cerrados, Planaltina, in the Federal District. Eight soil management systems with different implements and periods of crop residue incorporation were compared. Soil samples were collected from five layers: 0-5, 5-10, 10-20, 20-30, and 30-40 cm, with three replicates and in three sampling periods: before corn planting, 30 days after germination and at corn flowering. Treatments under no-till differed from each other regarding the microbial biomass Cmic and Nmic contents: while in one no-till treatment the soil cultivated by moldboard plow in the first year (PDAV) had a higher Cmic content, in the other no-till treatment the soil cultivated by disk plow in the first year (PDAD) had a higher Nmic content. This indicates that the effects in the soil profile caused by disk and moldboard plowing are still measurable, even after 22 years under no-till. In general, the greatest differences between no-till (PDAD and PDAV) or minimum tillage (chisel plow), and those with greater soil disturbance (disk and moldboard plow) were observed before planting, that is, before soil plowing and fertilization for the crop.

Seleção de matrizes e clones de mangabeira para o cultivo in vitro

High tax of mortality of mangabeira (Hancornia speciosa) seedlings in greenhouse conditions hinders its use on the reversion of the degradation of the natural vegetation, as well as on the preservation of the production and environmental integrity. The objective of this work was to select better mother plants and clones from sexual and assexual propagation, with potential to survive in vitro, for producing mangaba seedlings. Fruits were collected from 11 mother plants and from each plant, 24 seeds without aparent diseases were selected. After superficial desinfection, seeds were inoculated in MS medium without growth regulators and having a germination of 92.4% without significant difference between mother plants. On multiplication phase, with MS medium, with growth regulators BAP (6-benzilaminopurine) and IBA (indol-3-butiric acid), both at concentration of 1.28 mg L-1; the better mother plant was C1 and better clone was C1 15. During all phases of this work there was a high variability, mainly among clones. The selection must be made mainly among clones in mother plants.

Indicadores de qualidade de Latossolo Vermelho sob diferentes usos

The evaluation and monitoring of soil quality, in the micro-drainage basins which contribute directly to the Rio Descoberto reservoir, in the Rio Descoberto drainage b asin, Distrito Federal (DF), Brazil, are necessary, due to its disordered rural occupation. Thus, this study aimed at evaluating the quality indicators of Red Latosol (RL), in micro-drainage basins located in the northern Rio Descoberto drainage basin , under diversified uses and managements: Savannah (SA), reforestation (RF), native pasture (NP), cultivated pasture (CP), agriculture with covered soil (AC) and agriculture with partial soil covering (AP). Soil density (SD) presented the lowest value for SA and the highest one for AP. The CP area showed the highest values for soil resistance to penetration, reflecting the effect of animal trampling. The highest value for organic matter (OM) was 55.5 g kg -1 , in the CP, and the lowest one was observed in the AC (37.5 g kg -1 ), where decomposition processes are favored. The cation exchange capacity varied from 7.80 cmol c dm -3 (NP) to 9.75 cmol c dm -3 (RF), pointing out the liming effect . The values obtained for microbial biomass carbon and basal respiration showed positive effects of the grass root system in the development of microorganisms. Among t he soil quality attributes evaluated, the OM and SD stood out, confirming that a more intensive agricultural activity is directly related to the quality reduction of the RL evaluated.

Matéria orgânica e infiltração da água em solo sob consórcio milho e forrageiras

Infiltration is a process by which water penetrates through the soil by its surface, and its dynamics can be influenced by several factors, among them, the soil management system adopted. The objective of this work was to estimate water infiltration rate and soil organic matter content in maize and forage intercropping systems. The experiment was conducted in a randomized block design with three replications. Five treatments under no-tillage management were evaluated: 1) Corn (Zea mays L. ), 2) Brachiaria humidicola (Brachiaria humidicola), 3) Corn and Brachiaria humidicola intercropping, 4) Aruana grass (Panicum maximum cv. Aruana), 5) Corn and Aruana grass intercropping. The double ring infiltrometer method was used to determine the basic infiltration rate (VIB). Soil physical properties and soil organic matter were evaluated and correlated with VIB values. Results revealed high VIB values for no-tillage. The highest VIB values were observed in the corn treatment. VIB values decreased with the inclusion of forages. All cultivation systems showed a decrease of organic matter with depth.

Uso das terras da parte norte da bacia do Rio Descoberto, Distrito Federal, Brasil

This work had the objective to evaluate the land use in the northern region of the Environmental Protection Area of Descoberto River, which encompasses the watersheds of the streams Barrocao, Bucanhao and Capao da Onca, accomplished with the support of geoprocessing techniques. A land use map of the area was produced through analysis and treatment of SPOT 4 satellite images, obtained in 2003, using the software ENVI 3.6. Then, the adequation of land use was checked using cross-tabulation between the maps of present and potential use for agriculture, with the software ArcView 8.3, allowing development of a map of land use suitability. The results showed that most of the area has been used under its agricultural potential, characterizing sustainability in the use of the natural resources, particularly of the soils.

Qualidade físico-hídrica de um latossolo sob irrigação e braquiária em lavoura de café no cerrado

The objective of this study was to evaluate the effect of irrigation and cultivation of brachiaria among coffee trees lines on physical-hydric Oxisol quality at Brazilian central plateau. The experiment was carried out in five randomized blocks in a factorial design 2 x 2, with two water treatments, irrigated and rainfed systems, and two management systems, with and without brachiaria between coffee trees lines. The research strategy was based on studying soil water storage based on porosity distribution due to the behavior of physical parameters in different water and management treatments. Soil samples were collected in duplicate in each plot at depths from 0.0 to 0.05, 0.05 to 0.10, 0.10 and 0.20 m. The irrigation regime increased soil bulk density in the surface layer without reducing its readily available water that, due to presence of brachiaria was increased by 18%. In general, irrigated brachiaria had a positive effect on the physical-hydric soil characteristics of the soil and promoted an increase in readly available soil microporosity from the redistribution of pore diameter characterized by increasing retention curve amplitude in the soil water tension range corresponding to the readily-available water.

Qualidade de Organossolo sob diferentes usos antrópicos em áreas de preservação permanente no Distrito Federal

The use and occupation of soil should be planned in a rational way to avoid negative environmental impacts on natural resources, particularly in areas environmentally protected by law. This study aimed to evaluate quality attributes of soil in permanent preservation areas of a Ribeirao do Gama Watershed, Distrito Federal, Brazil, to verify the influence of anthropic use. The physical, chemical and biological attributes of Histosol quality were assessed in five areas of diversified use and soil occupation: three areas under cultivation (vegetables, eucalyptus and cassava) and two preserved areas (native pasture and gallery forest). Soil samples were collected in 0-10 and 10-20 cm depth. The data obtained for physical, chemical and biological analysis of the soils were statistically evaluated using the Sisvar 4.6 software. The results obtained showed the influence of different uses and soil occupation in relation to the attributes of soil quality. The adopted management in these areas was considered the main factor of change in the physical, chemical and biological attributes, highlighting the compaction of soils under native vegetation and decrease of organic matter in the soils under cultivated systems.

Propriedades microbiológicas do solo e disponibilidade de nitrogênio para milho em monocultura e em consórcio com forrageiras

The objective of this work was to evaluate the effects of corn (Zea mays) in monoculture and intercropped with forage on soil microbiological properties and nitrogen availability under no-tillage in the Cerrado (Brazilian savanna). The experiment was carried out from the 2007/2008 to the 2010/2011 crop season, in a Latossolo Vermelho-Amarelo distrófico (Typic Haplustox). A randomized complete block design with three replicates was used, with the following treatments: corn in monoculture; corn intercropped with Panicum maximum; corn intercropped with Urochloa humidicola; P. maximum in monoculture; and U. humidicola in monoculture. Soil samples were taken at 0.00–0.05, 0.05–0.10, 0.10–0.20, and 0.20–0.30-m soil depths, in the begining and in the end of the last crop season. The intercropping systems of corn increased soil nitrogen availability, but did not alter total nitrogen and organic carbon contents in the soil, when compared to corn in monoculture. Corn intercropped with P. maximum increased soil microbial biomass nitrogen and microbial nitrogen quotient, in comparison to corn in monoculture, as well soil as microbial biomass carbon in the surface soil layer, when compared to corn intercropped with U. humidicola.

Nitrogen uptake efficiency of maize in monoculture and intercropped with Brachiaria humidicola and Panicum maximum in a dystrophic Red-Yellow Latosol of the Brazilian Cerrado

Abstract. No-tillage systems associated with intercropping practices of grains and forages as cover crops are increasing in the Cerrado agricultural areas. The aim of this study was to quantify the nitrogen (N) uptake efficiency of maize (Zea mays L.) grown as monoculture and intercropped with tropical forages under a no-tillage system by using the 15N isotope tracer in conjunction with measurements of soil microbial biomass N and available soil N. The experiment was conducted in the 2010–11 growing season, in a Dystrophic Red-Yellow Latosol (Typic Haplustox) in the Cerrado. The experiment was established in a complete randomised block design with three replicates with the following treatments: maize monoculture; maize intercropped with Panicum maximum Jacq. cv. Aruana; and maize intercropped with Brachiaria humidicola (Rendle) Schweick. Nitrogen was applied as ammonium sulfate at a rate of 100 kg ha–1 (30 kg N ha–1 was applied at planting and 70 kg N ha–1 as a side-dressing). The N-fertiliser uptake efficiency in maize and grain yield was not affected by the presence of the intercropped forages. The intercropped B. humidicola and P. maximum recovered 2.08% and 3.71% of the N fertiliser applied, respectively. The soil was the main N source for maize. Maize intercropped with P. maximum showed higher values of microbial biomass N and available N in the soil.