Case Study: Application of the Observational Method Using High Strain Dynamic Tests

In-situ High Strain Dynamic Testing (HSDT) was developed more than 40 years ago. When a hammer or drop weight strikes the top of a pile, a compressive stress wave travels down its shaft at a speed that is a function of the elastic modulus and mass density. The impact induces a force and particle velocity at the top of the pile that can be measured using accelerometers and strain gauges. This paper discusses the theory behind using HSDT instruments and the procedures to calculate the capacity of the pile. The role of selecting the proper instrument to record them is also discussed. Finally, a case history involving the use of HSDT as an instrument for the observational method is presented

Selectivity of saflufenacil applied alone or mixed to glyphosate in maize.

The use of selective herbicides is important for weed management in agricultural crops. Selectivity studies of new molecules are really important to expand the control options of glyphosate-resistant and -tolerant eudicotyledons in corn. The objective of this work was to evaluate the selectivity of the herbicide saflufenacil applied alone in different doses in post-emergence of corn and in a mixture with glyphosate. The design used was randomized blocks, with four replications, with treatments consisting of five doses of saflufenacil, applied alone and in a mixture with a fixed dose of glyphosate, in addition to the weeded control and only glyphosate. At 7, 14, 21 and 28 days after application (DAT), the phytotoxicity of the herbicides to the crop was evaluated. The physiological variables were measured at 35 DAT. At harvest, yield components were determined, in addition to the mass of 1,000 grains and grain yield. The application of the mixture of glyphosate with saflufenacil increases phytotoxicity symptoms and yield losses. Doses of up to 70 g ha-1, applied alone, caused low phytotoxicity to corn and did not interfere in yield. The use of glyphosate + saflufenacil tank mixtures caused decreases in yield of 43.96 and 40.81% when compared, respectively, with the weeded control and the averages of the applications of the herbicides alone. Saflufenacil has the potential to be used in the management of eudicotyledonous weeds, as long as it is not mixed with glyphosate and the dose limit is respected

Periods of weed interference in cowpea crop in the semi-arid of Minas Gerais, Brazil.

Weed interference is one of the main limiting factors in the cowpea yield. In this sense, we aimed to determine the periods of weed interference in the cowpea crop in the semi-arid region of Minas Gerais. The treatments were arranged in a 2 x 10 factorial scheme, with two factors: coexistence and control of weed and ten periods: 0, 7, 14, 21, 28, 35, 42, 49, 56 and 63 days after emergence (DAE) subjected to control and coexistence. The evaluated characteristics were dry weight of weeds and the cowpea, weight of 100 grains and yield, which was fitted to the exponential model and the periods of interference of the weed community were determined. The period before interference (PBI) occurred up to 20 DAE, with weed control having to be performed up to 32 DAE. The critical period for weed control (CPWC) was from 21 to 32 days after emergence of the crop. The cowpea bean yield reduced 73.5% with the weed interactions during the whole cycle, under conditions of the semi-arid of Minas Gerais

Weed management in raw sugarcane

Nos ?ltimos anos, o processo de colheita da cana-de-a??car vem sendo modificado, passando da tradicional queima do canavial para a colheita da cana-crua, seja por imposi??es da legisla??o ou conscientiza??o ambiental e tamb?m por press?es da sociedade. A ado??o desse novo sistema de colheita da cana-de-a??car tem resultado em importantes modifica??es nas t?cnicas de cultivo, como o uso de maiores espa?amentos entre as linhas e a deposi??o de palha ? superf?cie do solo, as quais influenciam diretamente a ocorr?ncia e o manejo de plantas daninhas e a fertilidade dos solos. Mudan?as da flora t?m sido observadas em ?reas cultivadas com a cana-crua em consequ?ncia do favorecimento de esp?cies com maior capacidade de germina??o sob espessa cobertura de palha, em compara??o com outras que t?m a germina??o impedida por a??o f?sica ou alelop?tica da palhada. Al?m disso, herbicidas utilizados em pr?-emerg?ncia nessa cultura t?m apresentado redu??es na sua efic?cia, pelo fato de que grande parte deles fica retida na palha e n?o atinge o solo na concentra??o necess?ria para o controle das plantas daninhas. Nesta revis?o foram descritos os principais resultados envolvendo a pesquisa relacionada ao manejo de plantas daninhas em ?reas com cana-crua, com o objetivo de disponibilizar informa??es aos pesquisadores para implementar t?cnicas e pesquisas no desenvolvimento do manejo integrado de comunidades infestantes na cultura da cana-de-a??car. Os resultados mostram que h? possibilidade de redu??o da depend?ncia do uso de herbicidas e melhoria real da qualidade dos solos como consequ?ncia do maior ac?mulo da palha oriunda da colheita da cana-de-a??car.Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG)Empresa de Pesquisa Agropecu?ria de Minas Gerais (EPAMIG)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)In the last years, the sugarcane harvesting process has undergone changes imposed by law, environmental awareness or social pressure, leading to the exclusion of the traditional slash and burn before harvesting and inclusion of crude sugarcane harvest. This process is denominated crude harvesting. The adoption of this new harvesting system promoted alterations in the entire sugarcane tillage system, including wider row spacing and the formation of a mulching layer due to the deposition of sugarcane residues on the soil surface. This new crop management system affects directly the weed dynamics in these areas and soil fertility as well. Weed shifting has been observed, producing weed species with higher germination and emergence capacity under a thicker straw layer, compared to those unable to germinate due to the physical or allellopathic action of the straw. In addition, pre-emergence herbicides are usually less efficient under this system due to their retention in the straw, not reaching the soil in sufficient concentrations to promote weed control. In this literature review, the major results involving weed management in crude sugarcane areas are described to provide information to researchers, extension workers, and farmers on how to improve sugarcane integrated weed management, mainly under this new harvesting process. The results show that reduction of herbicide dependence is feasible, leading to improved soil quality in these fields

Época de emergência de azevém e nabo sobre a habilidade competitiva da cultura da cevada.

Objetivou-se com o trabalho avaliar os efeitos de épocas de emergência das plantas daninhas, azevém e nabo, sobre a cultura da cevada. O experimento foi conduzido em delineamento de blocos casualizados, arranjado em esquema fatorial 2x5, com três repetições. No fator A, foram alocadas as plantas competidoras (azevém e nabo) e no B as épocas de emergência (14 e 07 dias antes, no mesmo dia, 07 e 14 dias depois da emergência da cultura). No início da floração da cevada, foram mensuradas as variáveis: estatura das plantas, número de colmos ou caules, área foliar e matéria seca da parte aérea da cultura e das plantas daninhas. Todas as variáveis avaliadas da cevada apresentaram aumento de valor com o atraso da emergência das plantas daninhas. As espécies, cultivada ou daninhas, que emergiram antes, apresentaram maior habilidade competitiva, dominando o ambiente quando emergiram 14 dias antes uma da outra. Quanto mais tarde ocorrer a emergência das plantas daninhas com relação à cultura, menor é a interferência e, desse modo, maior é a habilidade da cevada em competir com a espécie daninha pelos recursos disponíveis no meio