Avaliação tecnológica de semeadoras e/ou adubadoras: tratamento de dados de ensaios e regularidade de distribuição longitudinal de sementes Seed drill technological evaluation: test data treatments and seed longitudinal distribution uneveness

Normas, procedimentos de ensaio e trabalhos de pesquisa apontam a regularidade de distribuição longitudinal de sementes como uma das características operacionais de semeadoras que mais contribuem para a obtenção de um stand adequado de plantas e, conseqüentemente, boa produtividade. Dois parâmetros são utilizados para essa avaliação: o coeficiente de variação (CV) das populações de espaçamentos e as porcentagens de ocorrência de espaçamentos aceitáveis ou de sementes "normalmente semeadas". Como tais textos preconizam o emprego de diferentes procedimentos para o cálculo daqueles parâmetros de avaliação, o presente estudo visou aos efeitos dos diferentes tratamentos de dados nos resultados e na sua interpretação. Aplicaram-se tratamentos - DEA, ISO, ABNT e INTA ADAPTADO - às populações de espaçamentos de sementes, resultantes de ensaios de bancada com três tipos de mecanismos desadores (disco horizontal, disco inclinado e disco vertical com dispositivo pneumático). Para dois deles, observaram-se diferenças expressivas entre os resultados da aplicação dos tratamentos, tanto no tocante aos coeficientes de variação (CV) quanto às ocorrências de espaçamentos definidos como aceitáveis. Dependendo do tratamento, corre-se o risco, num processo de avaliação de desempenho, de aprovar-se um mecanismo que, como máquina, apresenta resultados satisfatórios, sem, no entanto, atender aos requisitos agronômicos, sua função básica.<br>Standards, test procedures and research works appoint the regularity of seed longitudinal distribution as one of the seed drills operational characteristics that contributes for attainment of an adequate plant stand and good productivity. Coefficient of variation (CV) of the spacing population and the percentage of acceptable spacings of seeds "normally sown" are the parameters used for that evaluation. This study was conducted to test different procedures recommended to calculate the coefficient of variation and the percentage of acceptable seed spacings. Four treatments (DEA, ISO, ABNT and INTA adapted) were applied to seed spacing populations resultant of bench tests with three types of metering mechanisms - horizontal plate, inclined plate and pneumatic device. For two of these mechanisms, the results of the application of the different treatments were quite different with respect of both evaluation parameters. Depending on the treatment, mistake should be made in the performance evaluation process with approval of a mechanism, that is perfect as a machine, but completely incapable to satisfy the agricultural requirements, its basic purpose

Application of Spectral Remote Sensing for Agronomic Decisions

Remote sensing has provided valuable insights into agronomic management over the past 40 yr. The contributions of individuals to remote sensing methods have lead to understanding of how leaf reflectance and leaf emittance changes in response to leaf thickness, species, canopy shape, leaf age, nutrient status, and water status. Leaf chlorophyll and the preferential absorption at different wavelengths provides the basis for utilizing reflectance with either broad-band radiometers typical of current satellite platforms or hyperspectral sensors that measure reflectance at narrow wavebands. Understanding of leaf reflectance has lead to various vegetative indices for crop canopies to quantify various agronomic parameters, e.g., leaf area, crop cover, biomass, crop type, nutrient status, and yield. Emittance from crop canopies is a measure of leaf temperature and infrared thermometers have fostered crop stress indices currently used to quantify water requirements. These tools are being developed as we learn how to use the information provided in reflectance and emittance measurements with a range of sensors. Remote sensing continues to evolve as a valuable agronomic tool that provides information to scientists, consultants, and producers about the status of their crops. This area is still relatively new compared with other agronomic fields; however, the information content is providing valuable insights into improved management decisions. This article details the current status of our understanding of how reflectance and emittance have been used to quantitatively assess agronomic parameters and some of the challenges facing future generations of scientists seeking to further advance remote sensing for agronomic applications

Daytime sprinkler irrigation effects on net photosynthesis of maize and alfalfa

14 Págs., 5 Tabls., 11 Figs.During sprinkler irrigation some water is lost due to drift and evaporation. After irrigation, plant-intercepted water is lost due to evaporation. The water loss causes microclimatic changes, which may involve positive or negative plant physiological responses. We studied the changes in net photosynthesis of maize (Zea mays L.) and alfalfa (Medicago sativa L.) associated with irrigation with a solid-set sprinkler system. For each species, measurements were made simultaneously in two plots, one being irrigated and the other not being irrigated. Two automatic canopy chambers connected to two CO2 infrared gas analyzers were used. Sprinkler irrigation decreased air temperature (1.5°C on maize, 1.7°C on alfalfa), air vapor pressure deficit (VPD) (0.44 kPa for both crops) and canopy temperature (5.1°C on maize, 5.9°C on alfalfa). Sprinkler irrigation decreased maize net photosynthesis on 80% of the days and the mean reduction was 19%. Sprinkler irrigation increased alfalfa net photosynthesis on 36% of days, decreased it on 14% of days, and had no effect on half of the days. The decrease of maize net photosynthesis during sprinkler irrigation was linked to the high leaf wettability (water contact angles from 60–80°) and the decrease in temperature below the optimum range for photosynthesis. The higher hydrophobicity of alfalfa leaves (water contact angles >120°) and the wide range of optimum temperature for alfalfa photosynthesis may be the reasons why photosynthesis remained unaffected by sprinkler irrigation. The results suggest that daytime sprinkler irrigation with solid-set should be avoided for maize but can be used for alfalfa.This work was supported by the projects AGL2007-66716-C03-01 and AGL2010-21681-C03-01 (Ministerio de Economía y Competitividad) of Spanish Government. Y.F. Urrego-Pereira had a FPI grant of the Spanish government.Peer reviewe

Winds of Change: A Century of Agroclimate Research

Climate has been of primary concern from the beginning of agricultural research. Early in the 20th century, climatology and agronomy evolved separately, focusing primarily on production agriculture and crop adaptation. Concepts developed include thermal units and water use efficiency. The integrated discipline of agroclimatology developed in the mid-20th century. As theoretical understanding evolved, numerous papers related to agroclimatology were named Citation Classics. Spectral properties of plants and soils were identified that underpin today’s remote sensing technologies. Commercialization of instrumentation enhanced our ability to efficiently collect data using standardized methods. Private and public-sector partnerships advanced research capacity. Later in the 20th century, research focus shifted toward integrating knowledge into crop growth and agronomic models. Remote sensing provided capacity to gain theoretical and practical understanding of regional scale processes. In the early 21st century, recognition of earth as a system along with inter-related human systems is driving research and political agendas. There is a pressing need to change our data-rich to an information-rich environment. The emerging cyberinformatics field along with natural resource and agricultural system models allow us to apply climate information to assessments and decision support related to water supply, production, environmental management, and other issues. Solutions to today’s problems require interdisciplinary and multi-sectoral teams. While needs have never been greater, fewer universities maintain critical mass required to off er advance degrees in agroclimatology. It will be increasingly important that agrclimatology attract top students and provide training and practical experience in conducting integrated systems research, communications, and team skills