Effect of cropping systems in no-till farming on the quality of a Brazilian Oxisol

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Qualidade estrutural em latossolos compactados cultivados com milho

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Efeito de dois sistemas de manejo do solo nas propriedades físico-hídricas, desenvolvimento radicular e produtividade do milho

Corn cultivation is part of crop rotation used by irrigation farmers from the southwestern region of São Paulo state, Brazil, who use no-tillage soil management as a kind of sustainable use of soil. The effect of this conservative practice on physical and hydrical properties of the soil, root development and corn crop yield compared to the conventional management was the objective of this work. The experiment was held at the Buriti-Mirim Farm, Angatuba, SP, Brazil, using an irrigated area with a center pivot system and two types of soil management: conventional and no-tillage systems. Although the no-tillage management had higher soil density and less water availability, no significant difference was found for both management systems concerning soil resistance to penetration, root development and crop yield. In both systems of soil management, 90% of roots were concentrated in the first 0-20cm of soil layer.

Spatial variability of soil penetration resistance influenced by season of sampling

O objetivo deste trabalho foi analizar a distribuição espacial da compactação do solo e a influência da umidade do solo na resistência à penetração. Esta última variável foi descrita pelo índice de cone. O solo estudado foi Nitossolo e os dados de índice de cone foram obtidos usando um penetrômetro. A resistência do solo foi avaliada a 5 profundidades diferentes, 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm e mais de 40 cm, porém o conteúdo de umidade do solo foi medido a 0-20 cm e 20-40 cm. As condições hídricas do solo variaram nas diferentes amostragems. Os coeficientes de variação para o índice de cone foram 16,5% a 45,8% e os do conteúdo de umidade do solo variaram entre 8,96% e 21,38%. Os resultados sugeriram elevada correlação entre a resistência do solo, estimada pelo índice de cone e a profundidade do solo. Sem embargo, a relação esperada com a umidade do solo não foi apreciada. Observou-se dependência espacial em 31 de 35 séries de dados de índice de cone e umidade do solo. Esta dependência foi ajustada por modelos exponenciais com efeito pepita variável de 0 a 90% o valor do patamar. em séries de dados o comportamento foi aleatório. Portanto, a técnica das distâncias inversas foi utilizada para cartografar a distribuição das variáveis que não tiveram estrutura espacial. Na krigagem constatou-se uma suavização dos mapas comparados com esses das distâncias inversas. A krigagem indicadora foi utilizada para cartografar a variabilidade espacial do índice de cone e recomendar melhor manejo do solo.

Diagnosis of a compacted area for mining through the mechanical resistance to the penetration using geostatistical methods in the Amazon Forest

The mining process promotes land modification and complete landscape alteration. Those alterations in the surface are shown more obviously in the aesthetical aspect as the visual elements of form, texture, climbs, complexity and color which composes the landscape. As a consequence, mining has impacts on the topography, in the soil, in the vegetation and in the area's drainage, with a direct influence on the enterprise. A quite common problem in the recovery of degraded areas in mineral exploration is the compaction of the soil due to the intense traffic of machines and earth movement. The most common problem of the compaction of a degraded surface is an increase of the mechanical resistance to the penetration of plant roots, a reduction of the aeration, an alteration of the flow of water and heat, also in the availability of water and nutrients. Thus, the present work had the basic objective of diagnosing the compaction of an area degraded by mining in a spacial way, through the mechanical resistance and the penetration, to guide the future subsoiling in the area requiring recovery. Through the studies, it was concluded that the krigagem method in agreement with the space variation allows the division of the area under study into sub areas facilitating a future work to reduce costs and unnecessary interference to the atmosphere. The method was shown to be quite appropriate and it can be used in the diagnosis of compaction in a degraded area by mining, foreseeing the subsoiling requirement.

Spatial variability of soil water content and mechanical resistance of Brazilian ferralsol

The spatial variability of mechanical resistance to penetration (PR) and gravimetric moisture (GM) was studied at a depth of 0-0.40 m, in a ferralsol cropped with corn, and under conventional tillage in llha Solteira, Brazil (latitude 20 degrees 17'S, and longitude 52 degrees 25'W). The purpose of this study was to analyse and to try explaining the spatial variability of the mentioned soil physical properties using geostatistics. Soil data was collected at points arranged on the nodes of a mesh with 97 points. Geostatistics was used to analyse the spatial variability of PR and GM at four depths: 0-0. 1, 0.1-0.2, 0.2-0.3 and 0.3-0.4 m. PR showed a higher variability of data, with coefficients of variation of 52.39, 30.54, 16.91, and 15.18%, from the surface layers to the deepest layers. The values of the coefficients of variation for GM were lower: 9.99, 5.13, 5.59, and 5.69%. Correlation between GM and PR for the same soil layers was low. Penetration resistance showed spatial structure only in the 0.30-0.40 m layer, while gravimetric moisture showed spatial structure at all depths except for 0-0. 10 m. All the models of fitted semivariograms were spherical and exponential, with ranges of 10-80 m. Data for the variable 'GM' in the 0.20-0.30 and 0.30-0.40 m layers revealed a trend in data attributed to the occurrence of subsurface water flow. (C) 2005 Elsevier B.V. All rights reserved.

Sensitivity of cotton cultivars to soil compaction

Cotton is one of the most sensitive crops to soil compaction, but there may be genetic variability for this trait. The objective of this study was to evaluate cotton cultivars sensitivity to soil compaction. Soil columns were built with three pvc rings with internal diameter of 10 cm and filled with an alfisol. The heights of the top and bottom rings were 15 cm, and the intermediate ring, in which the soil was compacted, was 3.5 cm high. The levels of compression used in the subsurface were characterized by penetration resistances of 0.41, 0.93, 1.41 and 1.92 MPa. The cultivars 701 FMT, FMT 705, FMT 707, FMX 951 LL and FMX 966 LL were grown up to 23 days after plant emergence, when the dry matter of shoots and roots, root length density and root diameter were determined. The cotton cultivars have variability in their sensitivity to resistance to penetration. The cultivar 707 FMT is more sensitive to soil compaction, while the FMT 701 is more tolerant. Penetration resistance of around 0.92 to 1.06 MPa reduce 50% cotton root growth, but resistance to penetration of 1.92 MPa did not totally prevent growth.

Spatial variability of forage yield and soil physical attributes of a Brachiaria decumbens pasture in the Brazilian Cerrado

The objective of this study was to analyze variability, linear and spatial correlations of forage dry mass yield (FDM) and dry matter percentage (DM%) of Brachiaria decumbens with the bulk density (BD), gravimetric (GM) and volumetric (VM) moisture, mechanical resistance to penetration (RP) and organic matter content (OM), at depths 1 (0-0.10 m) and 2 (0.10-0.20 m), in a Red Latosol (Oxisol), in order to select an indicator of soil physical quality and identify possible causes of pasture degradation. The geostatistical grid was installed to collect soil and plant data, with 121 sampling points, over an area of 2.56 ha. The linear correlation between FDM × DM% and FDM × BD2 was low, but highly significant. Spatial correlations varied inversely and positively, respectively. Except for DM% and BD, at both depths, the other attributes showed average to high variability, indicating a heterogeneous environment. Thus, geostatistics emerges as an important tool in understanding the interactions in pasture ecosystems, in order to minimize possible causes of degradation and indicate better alternatives for soil-plant-animal management. The decrease in FDM and increased BD1 are indicators of physical degradation (compaction) of Red Latosol (Oxisol), particularly in the places with the highest concentration of animals and excessive trampling, in Cerrado conditions, in the municipality of Selvíria, Mato Grosso do Sul State, Brazil.

Inheritance of resistance to powdery mildew in pea and pathogenesis-related aspects

A herança da resistência ao oídio na cultivar de ervilha MK-10 e alguns aspectos histológicos da infecção foram estudados. Para o estudo da herança, as gerações F1, F2, retrocuzamentos e geração F3 de MK-10 com duas populações suscetíveis foram avaliadas. Nas avaliações histológicas observou-se a porcentagem de conídios germinados, porcentagem de conídios que formaram apressório, porcentagem de conídios que estabeleceram colônia e número de haustórios por colônia. Para comparar as razões de segregação obtidas no estudo da herança da resistência, adotou-se o teste do Qui-quadrado (X²) e para os dados das análises histológicas, utilizou-se o teste Tukey a 5% de probabilidade. Concluiu-se que a resistência de MK-10 ao oídio é devida a um par de alelos recessivos e que a resistência é expressa na fase de pré-penetração, completada por uma morte celular localizada pós-penetração, característica da presença do par de alelos recessivos er1er1.

A novel technique to produce polygenic resistance to anthracnose in Stylosanthes capitata

An improved cultivar, based on 17 genotypes of S. capitata and six of S.macrocephala, was developed at the wEmbrapa Beef Cattle Research Center, Campo Grande, Brazil. The aim was to create durable, race non-specific resistance to anthracnose controlled by polygenic factors. A mass hybridisation technique was employed to produce a high degree of genetic diversity and sizeable quantities of seed of hybrid-derived progenies of Brazilian and Venezuelan genotypes of S. capitata. Outcrossing resulted in a significant improvement in the forage production of progeny of Venezuelan accessions. The multicross was evaluated in multilocational trials, each representing a large tract of country in the Cerrados ecosystem along a north-south transect from lat.6degrees S to 20degrees S. The genetic shift that occurred in S. capitata was a key element in the formation of the new cultivar. It is a complex mixture of two species, and a recombination of much desired forage traits of Brazilian x Venezuelan genotypes, high forage and seed yields coupled with anthracnose resistance. The new cultivar with its diverse genetic make-up has a wide application in the acid-soil savannas of tropical America. It was released by Embrapa for the Cerrados in 2000.

An alternative field method for screening soybean genotypes for resistance to Heterodera glycines

The soybean cyst nematode (Heterodera glycines) has become an increasingly severe problem in soybean production areas in Brazil. The development and use of resistant cultivars is the most efficient method of minimizing losses due to this pathogen. Our objective was to test the efficiency of an alternative method for screening soybean genotypes for resistance to H. glycines in field plots. The alternative method was compared to the standard method of sowing the test genotypes in fields found to be infested during the previous crop season. In the alternative method, the test genotypes are sown in the furrow following the uprooting of 45-day-old infected plants. The alternative method resulted in twice the cyst population and fewer escapes, and more consistent results than the standard method. The major advantage of the alternative method is that it permits screening in a more homogeneous distribution of H. glycines in the soil.

The effects of land use and soil management on the physical properties of an Oxisol in Southeast Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

RAPD marker use for improving resistance to Helicoverpa zea in corn

Helicoverpa zea is responsible for great losses to the corn, Zen mays L., crops final productivity, and the best way to control it is by improving genetic resistance. In collaboration with corn improvement and increasing resistance to insects through molecular marker assisted selection, this work had as an objective the selection of resistant (RP) and susceptible progenies (SP) to H. zea based on the RAPD technique. Molecular markers were Found, among the resistant progenies and it is suggested that linkage of these within the Zapalote Chico corn race, be used to extract resistance genes from this race as a donor. The progenies were selected from a population of half-sibs exhibiting a broader genetic base (FCAVJ-VF14). After DNA extraction, two sample bulks were formed; one made up of the six most resistant plants, the other of the six least resistant plants. Eighty-six primers were tested for PCR reactions with the resistant and susceptible bulks and analyzed on agarose electrophoresis for the detection of RAPD band polymorphism. The results of the banding patterns and similarity values indicated a nucleotide sequence amplified by the primer OPC-2 as a possible molecular marker for the identification of resistant progenies and a homology region between them and the Zapalote Chico corn race.

Spatial variability of physical attributes of an alfisol under different hillslope curvatures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comportamento espacial da demanda energética em semeadura de amendoim em latossolo sob preparo convencional

A mecanização desempenha papel fundamental na produção agrícola e, consequentemente, na composição dos custos. Os adequados planejamento e gerenciamento dos sistemas mecanizados contribuem para a racionalização e redução dos gastos e melhoria do produto final. O objetivo deste trabalho foi estudar e caracterizar a variabilidade espacial da resistência mecânica do solo à penetração, da demanda energética e do desempenho operacional do conjunto trator-semeadora-adubadora em semeadura de amendoim, atuando com 5% de biodiesel etílico destilado de amendoim, em solo sob preparo convencional. As variáveis avaliadas neste estudo foram: força e potência requeridas na barra de tração, capacidade de campo efetiva, consumo de combustível, consumo de energia, patinhagem dos rodados e resistência mecânica do solo à penetração. Pelos resultados obtidos, concluiu-se que a variabilidade espacial das variáveis ligadas ao conjunto mecanizado depende principalmente da direção de deslocamento e que a resistência mecânica do solo à penetração não apresentou correlação com as outras variáveis. O consumo específico de combustível demonstrou correlação negativa com a força de tração, indicando que houve melhor aproveitamento da energia disponibilizada pelo combustível para maior exigência de tração.