Interferência de plantas daninhas na cultura do milho: I - efeito do número de repetições sobre a precisão dos resultados obtidos

Foi conduzido um experimento com o objetivo de determinar o mínimo de repetições para que níveis preestabelecidos de precisão sejam alcançados sobre a matointerferência na produtividade da cultura do milho mantida na presença ou na ausência das plantas daninhas até 0, 10, 20, 30, 40, 50, 60 e 120 dias após a emergência. O experimento foi conduzido no período de dezembro de 1997 a abril de 1998, correspondendo à safra de verão, na Fazenda Experimental Marcelo Mesquita Serva, Universidade de Marília - UNIMAR, município de Marília, Estado de São Paulo - Brasil. A precisão experimental avaliada pela diferença mínima significativa (dms) mostrou-se continuamente crescente com a adição de novas repetições, observando-se, contudo, reduções menores acima de seis repetições. Os valores médios do quadrado médio do resíduo (QMR) e do coeficiente de variação (CV) e o F dos tratamentos não foram alterados pelo aumento do número de repetições.

Exchangeable basic cations and nitrogen distribution in soil as affected by crop residues and nitrogen

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

Phosphorus and potassium balance in soil under crop rotation and fertilization

The use of crop rotation and manure application can provide sustainability for an agricultural production system by improving soil quality and increasing nutrient use efficiency. This study aimed to evaluate the effect of mineral, organic and mineral+organic fertilization on grain yield and on soil phosphorus and potassium balance, in two crop systems under no-till, with and without rotation of cover crops. The experiment was carried out from 2006 to 2008 on a clayey Rhodic Hapludox in Marechal Candido Rondon, Parana State, Brazil. The cropping sequence in the rotation system involving cover crops was black oat + hairy vetch + forage turnip/corn/pigeon pea/wheat/mucuna + brachiaria + sunn hemp, and in the succession system was wheat/corn/wheat/soybean. Organic and mineral+organic fertilizations consisted of the application of solely manure and manure combined with mineral fertilizer, respectively. Soil P and K balances were calculated after the second year of the experiment, up to a depth of 0.40 m. First year corn yields were higher in the crop succession system accompanied by mineral fertilization. In the second year, wheat and soybean yield did not vary between crop systems and nutrient sources, demonstrating the residual effect of crop rotation and manure use. Crop rotation with cover crops resulted in an increase in soil K levels by promoting the recycling of this nutrient in the soil. In both crop systems, the application of mineral and organic fertilizers - either in isolation or in combination - resulted in a negative soil P and K balance in the short term. This represents a threat to the sustainability of the agricultural production system in the long term, due to the depletion of soil nutrient reserves.

Nitrogen content identification in crop plants using spectral reflectance and artificial neural networks

The accurate identification of the nitrogen content in crop plants is extremely important since it involves economic aspects and environmental impacts. Several experimental tests have been carried out to obtain characteristics and parameters associated with the health of plants and its growing. The nitrogen content identification involves a lot of nonlinear parametes and complexes mathematical models. This paper describes a novel approach for identification of nitrogen content thought spectral reflectance of plant leaves using artificial neural networks. The network acts as identifier of relationships among pH of soil, fertilizer treatment, spectral reflectance and nitrogen content in the plants. So, nitrogen content can be estimated and generalized from an input parameter set. This approach can be form the basis for development of an accurate real time nitrogen applicator.

Viscosity measurement of Newtonian liquids using the complex reflection coefficient

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

The temperature coefficient of the optical path length as a function of the temperature in different optical glasses

An interferometric technique was used to determine the temperature coefficient of the optical path length (dS/dT) as a function of the temperature in several optical glasses. The temperature range was between 25degreesC and 180degreesC. The studied samples included undoped and doped oxide glasses, such as low silica calcium aluminosilicate, phosphates, borates and also chalcogenides. The oxide glasses had dS/dT between 10 X 10(-6) K-1 and 20x10(-6) K-1, while for the chalcogenides, these were around 70 x 10(-6)K(-1). The results showed that dS/dTs increased with the temperature in all samples. For samples doped with Nd the dS/dT values were found to be independent of concentration. on the other hand, for the phosphate glass doped with Cr, dS/dT increased about 5% when compared with the Nd doped one. In conclusion, the used interferometric method, which is a considerably simpler and a lower cost technique, and is a useful tool to measure dS/dT in semi-transparent glasses as a function of the composition and temperature. (C) 2004 Elsevier B.V. All rights reserved.

Inversion in the temperature coefficient of the optical path length close to the glass transition temperature in tellurite glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Straw decomposition of nitrogen-fertilized grasses intercropped with irrigated maize in an integrated crop-livestock system

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Variabilidade espacial de atributos químicos do solo sob diferentes usos e manejos

O uso e manejo do solo e da cultura são importantes condicionadores da variabilidade de atributos do solo. O trabalho foi desenvolvido em Selvíria (MS), com o objetivo de avaliar a variabilidade espacial do pH, potássio (K), cálcio (Ca), magnésio (Mg) e saturação por bases (V) em Latossolo Vermelho sob diferentes usos e manejos. Os solos foram amostrados em malha, com intervalos regulares de 2 m, perfazendo o total de 64 pontos, nas profundidades de 0,0-0,1 e 0,1-0,2 m, nas seguintes áreas: vegetação natural (Cerrado), plantio direto, plantio convencional e pastagem. As maiores variabilidades, medidas por meio do coeficiente de variação, foram observadas para K, Mg e Ca; o pH apresentou o menor coeficiente de variação nos diferentes usos e manejo do solo, e o atributo V, coeficiente de variação médio. Os sistemas preparo convencional e pastagem apresentaram os menores alcances quando comparado aos sistemas Cerrado e plantio direto.

Nitrogen fertilization and soil management of winter common bean crop

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

Evapotranspiração da cultura da melancia irrigada com água de diferentes salinidades

Sabe-se que a determinação precisa da evapotranspiração da cultura (ETc) é de grande importância para o uso eficiente da água, principalmente em regiões áridas e semiáridas onde se faz necessária a utilização de água salina para irrigação. O objetivo deste trabalho foi determinar a evapotranspiração da melancia, cultivar Mickylee, com o uso de diferentes níveis de salinidade da água de irrigação. O experimento foi conduzido na Fazenda Experimental da Alagoinha, pertencente à Universidade Federal Rural do Semiárido, Mossoró - RN. Os níveis de salinidade da água de irrigação foram: S1 = 0,55; S2 = 1,65; S3 = 2,35; S4 = 3,5, e S5 = 4,5 dS m-1, sendo os tratamentos dispostos no delineamento de blocos ao acaso, com quatro repetições. A determinação da evapotranspiração de referência (ETo) foi realizada pelo método FAO-Penmam-Monteith, e a ETc, pelas leituras obtidas em lisímetros de pesagem, instalados nos tratamentos S1 e S5. Os resultados mostraram que a ETc da melancia diminui com o aumento da salinidade da água aplicada e que a evapotranspiração total durante o ciclo foi de 245 e 214 mm, respectivamente, para os tratamentos S1 e S5. Os valores médios de Kc obtidos para cada fase fenológica foram 0,23; 0,68; 1,12; 0,90 e 0,24; 0,61; 0,98 e 0,78, respectivamente, para as águas S1 e S5.

Analysis and functional annotation of an expressed sequence tag collection for tropical crop sugarcane

To contribute to our understanding of the genome complexity of sugarcane, we undertook a large-scale expressed sequence tag (EST),program. More than 260,000 cDNA clones were partially sequenced from 26 standard cDNA libraries generated from different sugarcane tissues. After the processing of the sequences, 237,954 high-quality ESTs were identified. These ESTs were assembled into 43,141 putative transcripts. of the assembled sequences, 35.6% presented no matches with existing sequences in public databases. A global analysis of the whole SUCEST data set indicated that 14,409 assembled sequences (33% of the total) contained at least one cDNA clone with a full-length insert. Annotation of the 43,141 assembled sequences associated almost 50% of the putative identified sugarcane genes with protein metabolism, cellular communication/signal transduction, bioenergetics, and stress responses. Inspection of the translated assembled sequences for conserved protein domains revealed 40,821 amino acid sequences with 1415 Pfam domains. Reassembling the consensus sequences of the 43,141 transcripts revealed a 22% redundancy in the first assembling. This indicated that possibly 33,620 unique genes had been identified and indicated that >90% of the sugarcane expressed genes were tagged.

Determination of the optimal quantity of crop residues for energy in sugarcane crop management using linear programming in variety selection and planting strategy

The aim of this work was to present organizational models for optimizing the reduction of crop residue generated by the sugarcane culture. The first model consisted of the selection of varieties of sugarcane to be planted meeting the mill requirements and, at the same time, to minimize the quantity of residue produced. The second model discussed the use of residue to produce energy. This is related to the selection of variety and quantity to be planted, in order to meet the requirements of the mill, to reduce the quantity of residue, and to maximize as much as possible the energy production. The use of linear programming was proposed. The two models presented similar results in this study, and both may be used to define the varieties and areas to be cultivated. (C) 2001 Published by Elsevier B.V. Ltd.

Game theory in sugarcane crop residue and available energy optimization

This work proposes a mathematical model to aid variety selection and planting quantity of sugarcane in order to reduce crop residues, maximize energy generated by this residue, and satisfy all the supply of the mill. We propose Linear Programming with two objective. The conflict between these objectives allows the use of the Nonzero-sum Game Theory. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Identification and expression analysis of microRNAs and targets in the biofuel crop sugarcane

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