Microclimate of grass canopies and biomass accumulation are influenced by the use of caged exclosures in grazing research.

Exclosure cages are often used for estimating biomass accumulation on continuously stocked pastures in grazing experiments. The microclimate inside the cages may affect the estimates of biomass accumulation, but this has not been previously identified or quantified. We evaluated how the exclusion from grazing for 21 days in Mulato II brachiariagrass (Brachiaria brizantha × Brachiaria decumbens × Brachiaria ruziziensis) pastures affected canopy air temperature (T) and relative humidity (RH) and how this related to biomass accumulation. We also evaluated the effect of the exclosure cage on wind speed (WS) and incoming solar radiation (SR), and how these impacted evapotranspiration (ET) and estimates of biomass accumulation on grazed canopies maintained at 20- and 30-cm height under continuous stocking. Regardless of canopy height, changes in canopy structure during the exclusion period up to 21 days did not affect T and RH (averages of 24.3 °C and 88.7%, respectively), indicating that the air circulation was not affected by the exclusion. The cage structure reduced SR by 5%, although there were times during clear days when SR was slightly greater inside the cage than outside. The cage also reduced WS by 4.4%. Smaller SR and WS resulted in less ET inside the cages than outside, although with close values (2.9 vs. 3.0 mm day-1; P = 0.0494). The biomass accumulation rate was greater inside than outside the cages for both canopy heights. This overestimation would be 5.8 and 9.7% greater if the structure of the cage did not reduce the SR, WS, and ET.

Vineyard microclimate and yield under different plastic covers.

The use of plastic cover in vineyards minimizes effects of adverse weather conditions. The northwest of São Paulo State is one of the largest grape producing regions in Brazil; however, few studies investigate the effects of different plastic covers on vineyards in this region. This study compared the effect of black shading screen (BSS) and braided polypropylene film (BPF) on BRS Morena vineyard microclimate, grown on an overhead trellis system in the northwestern São Paulo. The experiments were carried out during three growing seasons (2012-2014). BSS allowed superior incoming solar radiation (SR) transmissivity, resulting in higher net radiation (Rn), and higher ratio between photosynthetically active (PAR) and SR. No differences were observed between the average air temperatures (T) and relative humidity (RH) of covered environments (BPF and BSS) and outside condition (automatic weather station-AWS), due to high air circulation, despite wind speed (WS) reduction caused by plastic covers. BPF provided better conditions for vineyard growth with higher fruit yield than vineyard under BSS regarding the number of shoots with bunches per plant, bunch and stem weights, longitudinal diameter of berries, quantity of fertile buds per shoot, and yield per shoot and per plant. BPF covers also influenced leaf size and growth speed of plants in vineyards.

Cherry tomato yield in greenhouses with different plastic covers / Produção de tomate cereja em ambientes protegidos com diferentes coberturas plásticas

ABSTRACT: The objective of the present study was to evaluate the influence of different plastic covers on microclimate and cherry tomato yield in greenhouses. The experiments were carried out in Piracicaba, state of São Paulo (Brazil), during three growing periods (2008/2009/2010). A greenhouse was divided in: Environment I (EI) - covered with plastic film anti-UV and thermo-reflective shading screen, and Environment II (EII) - covered with diffusive plastic film; monitored with automatic weather sensors; and cultivated with cherry tomato ('Sweet Grape' and 'Sweet Million'). Use of diffusive plastic in greenhouses provides a better inside distribution of solar energy without causing major changes in air temperature and relative humidity, resulting in higher yield (kg plant-1), fruits quantity (number plant-1) and fruits average weight than those obtained under thermo-reflective shading screen.

RESUMO: O objetivo do presente estudo foi avaliar a influência de diferentes coberturas plásticas no microclima e rendimento do tomate cereja em casa-de-vegetação. Os experimentos foram realizados em Piracicaba, Estado de São Paulo, durante três períodos de produção (2008/2009/2010). A casa-de-vegetação foi dividida em Ambiente I (EI) - coberto com filme plástico anti-UV e tela de sombreamento termo-refletora, e Ambiente II (EII) - coberto com filme plástico difusor; monitorados com sensores meteorológicos automáticos; e cultivados com tomate cereja ('Sweet Grape' e 'Sweet Million'). O uso do plástico difusor em casas-de-vegetação proporcionou melhor distribuição da energia solar sem causar grandes mudanças na temperatura e umidade relativa do ar, resultando em maiores rendimento (kg planta-1), quantidade de frutos (número planta-1) e peso médio dos frutos do tomateiro, em comparação ao ambiente coberto com tela termo-refletora.