A. C. Gomes

Comportamento de diferentes sistemas de manejo como fonte ou depósito de carbono em relação à vegetação de Cerrado

Carbon storage and its distribution in the profile of clayey Oxisols were studied to evaluate the role of the soil as a sink or source of atmospheric CO2 in the center of the cerrado region, Federal District, Brazil. Evaluations were carried out in six different management systems: a native cerrado type vegetation (CE), eucalypt reforestation (EU), introduced pasture (PA), heavy disk harrow tillage (GP), disk plow tillage (AD), no-tillage (PD), all of them having been established for more than twelve years. Organic carbon was analyzed in soil samples taken at a 100 cm depth. Carbon storage in all other five agroecosystems was compared to CE in order to analyze soil behavior as a source or sink of C-CO2. The main important dynamic features related to C, such as additions and losses, were observed in the upper soil layers. Compared with CE, the agroecosystems without soil disturbance like PD, PA and EU showed higher carbon accumulation, thus working as a soil sink for atmospheric C-CO2. Those with soil disturbance (AD and GP) showed lower carbon accumulation, thus working as a source of C to the atmosphere.

Reação às doenças e produtividade de onze cultivares de maracujá-azedo cultivadas sem agrotóxicos

The objective of this work was to evaluate the reaction to diseases and the yield of eleven sour-passion fruit cultivars during the first six months of harvesting in the Federal District, Brazil. Weeds were controlled using a polyethylene black cloth (mulching) with 1.20 m large on the tape of dripping irrigation along the planting line. The hybrid EC-RFM (Passiflora edulis f. flavicarpa x P. edulis) had the best yield and it was less susceptible to woodiness virus (PWV), fruit-anthracnose and septoriose. All cultivars were susceptible to fruit-scab and bacterial spot. All cultivars evaluated presented low genetic variability to disease resistance.

Sistemas de manejo na absorção de nitrogênio pelo milho em um Latossolo Vermelho no Cerrado

The objective of this work was to evaluate the effect of different management systems on nitrogen absorption by corn in an Oxisol in the Cerrado. Total nitrogen (Ntotal), soil and mineral fertilizer derived nitrogen (Ndsolo and Ndfm, respectively), and N-fertilizer recovery efficiency (ERNF) taken by corn were determined. Eight management systems comprised by different implements and crop residues incorporation times were studied. The sampling plan was accomplished by simple random sampling. The soil was the main N source. Under no-till or minimum tillage, corn grains showed greater N content (Ntotal, Ndfm, and Ndsolo), as well as ERNF, than under moldboard plow with crop residues incorporated after harvesting treatment. The disk and moldboards action plows on soil properties as well as crop residues incorporation time, before planting and after harvesting, did not affect the N content in the corn grains (Ntotal and Ndfm), although they presented differences in the absorption dynamics related to N fertilizer broadcasting periods .

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.

Utilização de calcário em plantio direto e convencional de soja e milho em Latossolo Vermelho

Cerrado soils are acid with toxic levels of aluminum and, in order to overcome these conditions to grow crops, lime is necessary. This experiment evaluated the effects of lime levels and methods of lime application on the grain production of soybean and corn in rotation, under conventional (disk plowing and harrowing) and no-tillage planting systems in a Red Latosol (Oxisol). Cover crops were planted in the dry season; mucuna was cultivated after soybean and millet after corn. One lime treatment was included without cover crop under the conventional system. The occurrence of a dry spell period caused reduction in soybean yield in the first crop, but yield increases were observed due to lime application, under both systems, in the third crop. In the second and fourth crops, corn grain yields increased with lime levels, and were higher in the conventional system in the second crop. In no-tillage system, lime levels without incorporation produced less corn grain yield compared to incorporated lime. The corn response to split lime application was proportional to the incorporated lime levels. The exclusion of cover crops under the conventional system promoted corn grain yield reduction. Surface lime applications affected the soil chemical characteristics mainly at the 0-5 cm depth.

Adubação da cana-de-acúcar: XIV. Adubação NPK em latossolo roxo

Nineteen 33 NPK factorial experiments with sugar cane were carried out in 1958/59 on dusky red latosol soils of various sugar plant owned lands, in the State of Sao Paulo, Brazil. The amounts of nutrients applied corresponded to: 0, 90 and 180 kg/ha of N; 0, 80 and 160kg/ha of P205; and 0, 100 and 200kg/ha of K2O. The experiments were separated in two types of areas, based on former soil use: one group in areas where sugar cane was cultivated over ten years, and the other group in areas where which sugar cane had never been cultivated. The results were in accordance with former management, indicating residual effect of phosphorus applications and potassium depletion on the areas former cultivated with sugar cane. However, responses to nitrogen could not be related to former soil usage. Responses of sugar cane to nitrogen were related to soil organic matter (r = 0.695**) and to phosphorus with resin extractable P (r = 0.709**), but the response to potassium fertilizer was not related to soil K (r = 0.284 n.s). With adjusted response functions, the optimal economical amount of nutrients were shown to be in general, higher than the current recommendations. Yield increases promoted by NPK were directly related to the maximum economic yield (r = 0.773**).

AVALIAÇÃO DE SETE PORTA-ENXERTOS MONO E POLIEMBRIÔNICOS SOB QUATRO CULTIVARES DE MANGUEIRA NO CERRADO BRASILEIRO

O melhoramento, visando a selecao de porta-enxertos com tendencia ananicante para mangueira nas condicoes dos Cerrados, e de grande importância. As cultivares de manga para exportacao Tommy Atkins e Haden, embora muito produtivas e com frutas de coloracao excelente e polpa sem fibras, sao muito vigorosas e de porte muito elevado, o que dificulta os tratos culturais e a colheita. O objetivo do trabalho foi obter o efeito interativo da copa x porta-enxerto sobre a altura da planta, sua produtividade e qualidade de frutas.