Abstract-Bean (Phaseolus vulgaris L.) is a crop of great economic and social impacts in
The potential yield of annual crops is affected by management practices and water and energy availabilities throughout the crop season. The current work aimed to assess the effects of plant population, planting dates and soil covering on yield components of maize. Field experiments were carried out during the 2014–2015 and 2015–2016 growing seasons at areas grown with oat straw, voluntary plants and bare soil, considering five plant populations (40,000, 60,000, 80,000, 100,000 and 120,000 plants ha−1) and three sowing dates (15 September, 30 October and 15 December) for the hybrid P30F53YH in Ponta Grossa, State of Paraná, Brazil. Non-impacts of soil covering or plant population on plant height at the flowering phenological stage were observed. Significant effects of soil covering on yield components and final yield responses throughout the 2014–2015 season were detected. An influence of plant populations on yield components was evidenced, suggesting that, from 80,000 plants ha−1, the P30F53YH hybrid performs a compensatory effect among assessed yield components in such a way as to not compromise productivity insofar as the plant population increases up to 120,000 plants ha−1. It was noticed, a positive trend of yield components and crop final yield as a function of plant density increments.
Global solar irradiance (Qg) is an important variable of the physical environment that has been constantly used in agrometeorological models, either for climatic characterization or to give support to radiometric studies developed for irrigation planning and crop weather modeling approaches. The current study aimed to compare measured daily values of Qg with estimates of this variable by means of four different methods. For that throughout the period comprised between March 28 th of 2008 and August 8 th of 2011 at Ponta Grossa, PR, Brazil, a simple linear regression study confronting radiometric data measured by a pyranometer and estimates of Qg was proposed herein. Global transmittance was conditioned by atmospheric cloudiness. The models based on mean global transmittance in daily basis performed more satisfactorily and generated values of Qg with accuracy and exactness at the site in study, as confirmed by the statistical parameters employed to validate the usage of models proposed by Angström-Prescott. However, the performance of the methodologies based on the determination of mean global transmittance under extreme atmospheric conditions, showed the highest Willmott coefficients, which was to be close to 1, reflecting then precision and reliability for the calculated values of Qg, when compared to observed values monitored at an automatic weather station.
The soybean rust (SBR) epidemics are often triggered by weather conditions, which interfere actively on the disease progress. Therefore, weather variables can be used to estimate the risk of occurrence and severity of SBR outbreaks. This research aimed to determine the influence of weather variables on SBR progress in different field trials in Brazil. Field experiments were conducted during 2014-15 and 2015-16 soybean growing seasons in Piracicaba (SP), Ponta Grossa (PR), Campo Verde (MT) and Pedra Preta (MT). For all sites and seasons, a susceptible soybean cultivar was drilled with 0.45 m row spacing and 12 plants per linear meter. No fungicide sprays were applied to ensure natural disease occurrence. In order to create different environmental conditions, sequential sowing dates, of roughly 30-day intervals were carried out. In Piracicaba, Ponta Grossa, Campo Verde, and Pedra Preta the main weather variables influencing SBR were leaf wetness duration - LWD (R = 0.340), air temperature during LWD (R = 0.313), and cumulative rainfall (R = 0.304). The final severity was assessed only at Piracicaba and Ponta Grossa, and it was mainly influenced by LWD (R = 0.643). It is possible to conclude that epidemics of SBR were mainly influenced by leaf wetness duration, accumulated rainfall and air temperature during the LWD. Therefore, future researches aiming to develop a disease warning system for SBR should include the cumulative rainfall, LWD and the air temperature during LWD, together or individually, as inputs.
Na cultura do tomate, a água é um dos principais componentes que contribuem para seu crescimento e produção. Deste modo, é fundamental o manejo adequado através do seu fornecimento durante todas as fases da cultura, de forma a evitar o excesso ou déficit hídrico. Neste contexto, uma alternativa que pode otimizar o uso de água são os hidrogéis, polímeros hidroretentores com capacidade de retenção e absorção de água. Portanto, o objetivo do trabalho foi investigar os efeitos do hidrogel à base de políssacarídeo (HP) no tomate cereja Sweet Heaven. O experimento foi realizado em casa de vegetação, adotando-se delineamento experimental inteiramente aleatorizado, com tratamentos de HP (0 - controle; 0,15; 0,25; 0,50 e 0,70 g célula-1) e quatro repetições, adicionados durante a produção de mudas. Foram avaliados os parâmetros de altura de mudas, número de folhas aos 15 e 30 dias após semeadura (DAS), comprimento de raiz aos 20 DAS, índice de pegamento de mudas, altura e número de folhas de plantas aos 15 e 90 dias após transplante (DAT) e a produtividade média de frutos por planta. Conforme os dados obtidos, verificou-se que as dosagens de hidrogel responderam positivamente na altura de mudas e número de folhas aos 30 DAS e também nos mesmos parâmetros de crescimento aos 15 dias após o transplante das mudas (DAT). Este trabalho mostrou que o fornecimento de hidrogéis naturais pode atuar no melhor aproveitamento de recursos hídricos, principalmente nas fases iniciais de produção da cultura.
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