Water Evaporative Demand Research Articles

Will temperature and rainfall changes prevent yield progress in Europe?

AbstractConcerns about the effects of global warming on crop yields have been raised due to stagnating yield progress in recent years. However, an understanding of the effects of changes in temperature and rainfall throughout the crop cycle on historical yield progress is lacking in Europe (EU). In this study, positive wheat, barley, rice, and maize yield progress in the EU (1961–2019) was significant, with rates of 0.05, 0.04, 0.05, and 0.07 Tha−1year−1, for the four crops respectively. Much of this progress has been sustained by Eastern European countries (EE), which had the highest yield progress rates. On average, in the case of wheat and barley, a temperature increase of 1°C in the winter resulted in yields increasing by +0.33 Tha−1 in EE. This was potentially due to decreasing cold damage and improved photosynthesis and vegetative growth, supporting positive yield progress. Recent historical (2001–2019) rates of wheat, barley, rice, and maize yield progress were positive in all EU regions except Western Europe (WE), barley in Southern Europe (SE) and wheat in Northern Europe (NE). Stagnated wheat, barley and rice yields in WE were not explained by temperature or rainfall using direct correlations of observed data. However, May and July temperatures were associated with wheat yields in NE (−0.30 Tha−1°C−1), barley in SE (−0.14 Tha−1°C−1) and maize in WE and SE (−0.42 and −0.39 Tha−1°C−1). With increasing temperatures becoming less than optimal for photosynthesis, reducing grain filling duration and increasing drought episodes, crop yields have stagnated for wheat in NE and barley in SE. With consistent increases in temperature and water evaporative demand expected in the future, the interplay among genetic adaptation, increased crop cycle duration, drought tolerance, sowing dates, smart irrigation and sustainable practices may require thorough regional testing to maximise the yields of wheat, barley and maize in Europe.

Estimation of Aerodynamic and Canopy Resistances in a Mediterranean Greenhouse Based on Instantaneous Leaf Temperature Measurements

Aerodynamic and canopy resistances have long been considered to be of key interest in model equation parameterization, particularly for the accurate estimation of crop evapotranspiration. However, model parameters applied in greenhouses showed variation affected by the micrometeorological environment. Three experiments were carried out in a plastic greenhouse to evaluate microclimate effects on resistances of a soilless cucumber crop. The regression analysis of canopy-to-air temperature (Tc − Ta) difference on air vapor pressure deficit (VPD) was substituted into the energy balance equation for the estimation of aerodynamic and canopy resistance values. As expected, a fan and pad evaporative cooling system proved to be the more efficient method of decreasing crop temperature (Tc) compared to the forced air ventilation system. The estimated transpiration by the Penman–Monteith model based on calculated aerodynamic and canopy resistance values successfully validated values measured with lysimeters in different growing periods. In this article, we report for the first time the calculation of aerodynamic and canopy resistance values inside a greenhouse based on equations for an open field that were found in the literature. Results may be helpful in Mediterranean greenhouses for direct determinations of plant water evaporative demand and smart climate control systems.

Phytochrome A increases tolerance to high evaporative demand

Stresses resulting from high transpiration demand induce adjustments in plants that lead to reductions of water loss. These adjustments, including changes in water absorption, transport and/or loss by transpiration, are crucial to normal plant development. Tomato wild type (WT) and phytochrome A (phyA)-mutant plants, fri1-1, were exposed to conditions of either low or high transpiration demand and several morphological and physiological changes were measured during stress conditions. Mutant plants rapidly wilted compared to WT plants after exposure to high evaporative demand. Root size and hydraulic conductivity did not show significant differences between genotypes, suggesting that water absorption and transport through this organ could not explain the observed phenotype. Moreover, stomatal density was similar between genotypes, whereas transpiration and stomatal conductance were both lower in mutant than in WT plants. This was accompanied by a lower stem-specific hydraulic conductivity in mutant plants, which was associated to lower xylem vessel number and transversal area in fri1-1 plants, producing a reduction in water supply to the leaves, which rapidly wilted under high evaporative demand. PhyA signaling might facilitate the adjustment to environments differing widely in water evaporative demand in part through the modulation of xylem dimensions.

Influência da cobertura de resíduos de culturas nas fases da evaporação direta da água do solo

No presente trabalho, analisou-se a influência dos resíduos de culturas do milho e do trigo nas fases de evaporação da água do solo para duas classes texturais. Os tratamentos constaram de três taxas de resíduo de culturas, 0, 50 e 100% da matéria seca e de três demandas evaporativas. A taxa de evaporação da água do solo descoberto apresentou comportamento distinto para as três demandas evaporativas utilizadas. Para a demanda evaporativa de aproximadamente 3 mm d-1, o tratamento com solo descoberto permaneceu no primeiro estágio de evaporação, pelo período de 21 dias do experimento. O conceito U, estabelecido por Ritchie (1972) para definir o final do primeiro estágio, não foi observado para as demandas evaporativas de 5,2 e 3 mm d-1. Para essas demandas, o solo permaneceu no primeiro estágio de evaporação durante o período de coleta de dados de 21 dias. Para a taxa de resíduos de 100% da matéria seca, para as culturas do milho e do trigo, a demanda evaporativa teve pequena influência na redução na evaporação da água do solo que, em média, variou de 28% da evaporação ocorrida no tratamento com solo descoberto, havendo diferença significativa entre as taxas de resíduo, mas não ocorreu diferença entre as duas classes de solo, para a lâmina d'água evaporada em 21 dias.

Efeito da cobertura de resíduos de culturas na evaporação direta da água do solo

The influence of corn, bean and wheat crops residues used as soil surface mulching to control the water evaporation demands, for two soils textural classes, was analyzed in the present work. The treatments consisted of three layers of crop residues, corresponding to 0, 50 and 100% of dry matter produced by irrigated cropping systems, and three water evaporative demands of 3, 6 and 8mm d-1, for two soil textural classes, silty sand and heavy loamy soils, with 84% of sand and 76% of clay, respectively. The experiment was carried out in laboratory, with the soil sample conditioned in a 45-cm high and 20-cm nominal diameter PVC pipes columns. The water evaporation rate from the bare soil column presented different behavior for the three water evaporation demands tested. For water evaporative demand of approximately 3mm d-1, the treatments with corn and wheat crops residues, which represented mulching layer of 50 and 100% of dry matter, the water evaporation rate reached only the first evaporation stage. For treatment with 50% of dry matter with residues produced by bean crop, the evaporation stage moved beyond the first evaporation stage. Finally, for mulching with 100% of bean crop dry matter, the rate of soil water evaporation was influenced by the evaporative demand tested. The relationship among evaporation rate for treatment with 100% of dry matter and the water evaporative demands of 7,0, 5,0 and 2,5mm d-1 were 46, 41 and 47%, respectively