RESUMO Em aplicações de herbicidas em pré-emergência sobre palha, o tipo e a quantidade desse material e as características físico-químicas dos herbicidas são determinantes na eficácia. O objetivo desse trabalho foi avaliar a eficácia do herbicida flumioxazin aplicado em pré-emergência de Euphorbia heterophylla quando aplicado sobre diferentes quantidades de resíduos culturais e simulações de chuva. O delineamento experimental foi inteiramente casualizado, 4 repetições, no esquema fatorial 7x3, sendo sete tipos e quantidades de palha - sem palha; Brachiaria ruziziensis com 3 t ha-1 e 5 t ha-1; B. ruziziensis+Zea mays com 3 t ha-1 e 5t ha-1; Z. mays com 3 t ha-1 e 5 t ha-1 -, três volumes de chuva - 10, 25 e 40 mm -, e uma dose de flumioxazim (120 g i.a. ha-1). A avaliação da eficácia foi efetuada aos 7, 14, 21, 28, 35 e 45 dias após emergência (DAE) e a massa seca da parte aérea da infestante aos 45 DAE. As maiores porcentagens de controle ocorreram na aplicação de flumioxazin sobre 3 t ha-1 e 5 t ha-1 de B. ruziziensis e 3 t ha-1 Zea mays, com 86,3, 82,1 e 80,4% respectivamente. A chuva de 10 mm resultou na menor porcentagem de controle de Euphorbia heterophylla. Portanto, o tipo de palha e a quantidade interferem na eficácia do controle.

ABSTRACT In the spread of pre-emergent herbicides on straw, the type and quantity of this material and the physical-chemical characteristics of the herbicides, are decisive in the effectiveness of weed control. The objective of this work was to evaluate the efficacy of the flumioxazin herbicide in the pre-emergence control of the weed Euphorbia heterophylla , when applied over different straw types and quantities and rain simulations. The experimental design was completely randomized, with four replications, organized in a 7x3 factorial scheme, with seven straw managements - (without straw; Brachiaria ruziziensis with 3 t ha-1 and 5 t ha-1 ; B. ruziziensis+Zea mays with 3 t ha-1 and 5 t ha-1; Z. mays with 3 t ha-1 and 5t ha-1 -, and three amounts of rain - 10, 25 and 40 mm -, and the herbicide flumioxazim(120 g a.i. ha-1). The control evaluation was carried out at 7, 14, 21, 28, 35 and 45 days after emergence (DAE) and the dry mass of the aerial part at 45 DAE. The highest percentages of control occurred in the application of flumioxazin on 3 t ha-1 and 5 t ha-1 of Brachiaria ruziziensis and 3 t ha-1 of Zea mays, with 86.3, 82.1 and 80.4%, respectively. The 10 mm rain resulted in the lowest percentage of control of Euphorbia heterophylla. Thus, the type and quantity of straw interfere in the control effectiveness.

RESUMO A cana-de-açúcar é uma cultura muito importante para o Brasil, usada para a produção, tanto de alimentos, quanto de biocombustíveis, provendo 18% do total de energia primária no país. Um importante requisito para uma produtividade alta é uma boa uniformidade do canavial, a qual é comprometida devido a falhas que aparecem nas linhas de cana causadas por falhas no plantio, danos durante a colheita, tráfego de máquinas, pragas e doenças entre outros fatores. O objetivo deste estudo é desenvolver um sistema baseado em um sensor fotoelétrico para examinar o canavial, georreferenciando as falhas e apresentando-as em um mapa. Um coletor de dados integrou um sensor fotoelétrico, um encoder um Sistema de Navegação Global por Satélites (GNSS em inglês) mensurando a distância entre as plantas, definindo as falhas. Testes em situação controlada, utilizando estacas, mostraram erros entre 0,02 e 0,03 m variando a velocidade de 1,3 a 3,0 m s-1 e as estacas de 0,1 a 1,0 m de espaçamento, os resultados encontrados foram próximos aos mensurados manualmente. Testes em campo utilizando amostras de 6,0 x 6,0 m (quatro linhas de cana) em cana planta e soqueira, também mostraram uma boa relação com a mensuração manual. Os dados brutos fornecem o tamanho de cada falha individualmente ou em porcentagem e uma interpolação entre falhas pontuais produz um mapa que evidencia áreas com baixa ou alta densidade de falhas, criando uma ferramenta útil no gerenciamento da cultura de cana-de-açúcar para que sejam tomadas as medidas necessárias a manutenção do canavial.

ABSTRACT Sugarcane is a very important crop in Brazil, used as food production and biofuel, providing 18% of the total primary energy in the country. An important requirement to high yield is a good uniformity in the sugarcane field, which is impaired due to row gaps that appear since the first year of sugarcane crop caused by planting failures, harvesting damages, machinery traffic, pests, diseases and others. The aim of this study is to develop a system based on a photoelectric sensor to scan the field, georeferencing gaps representing them as a map. A data logger integrates the data from the photoelectric sensors, an encoder and a Global Navigation Satellite System (GNSS) and measures the distance between plants, defining the gaps. Tests under controlled conditions, using regular obstacles simulating stalks, showed errors between 0.02 and 0.03 m under speeds varying from 1.3 to 3.0 m s-1 and obstacles ranging from 0.1 to 1.0 m of gap. Results of tests performed at sugar cane rows were close to manual measurement. Field tests were performed using sampling plots of 6.0 x 6.0 m (four crop rows) along the area, on newly planted and on ratoon areas, showed a good relation with manual measurements. The raw data provides the length of the individual gaps or its local percentage and the interpolation among punctual gaps produces a map highlighting areas with low and high gap intensity as a useful tool in the sugarcane management for decision making for local or integral replanting.

The amount of energy required to produce a commodity or to supply a service varies from one production system to another and consequently giving rise to differing levels of environmental efficiency. Moreover, since energy prices have been continuously increasing over time, this energy amount may be a factor that has economic worth. Biomass production has a variety of end-products such as food, energy, and fiber; thus, taking into account the similarity in end-product of different crops (e.g.: sunflower, peanuts, or soybean for oil) it is possible to evaluate which crops require less energy per functional unit, such as starch, oil, and protein. This information can be used in decision-making about policies for food safety or bioenergy. In this study, 23 crops were evaluated allowing for a comparison in terms of energy embodied per functional unit. Crops were grouped as follows: starch, oil, horticultural, perennial and fiber, to provide for a deeper analysis of alternatives for the groups, and subsidize further studies comparing conventional and alternative production systems such as organic or genetically modified organisms, in terms of energy. The best energy balance observed was whole sugarcane (juice, bagasse and straw) with a surplus of 268 GJ ha−1 yr−1; palm shows the highest energy return on investment with a ratio of approximately 30:1. For carbohydrates and protein production, cassava and soybean, respectively, emerged as the crops offering the greatest energy savings in the production of these functional foods.