A carregar...
Projeto de investigação
Sem título
Financiador
Autores
Publicações
Water use, soil water balance and soil salinization risks of Mediterranean tree orchards in southern Portugal under current climate variability: Issues for salinity control and irrigation management
Publication . Ramos, Tiago B.; Darouich, Hanaa; Oliveira, Ana R.; Mohammad, Farzamian; Monteiro, Tomás; Castanheira, Nádia; Paz, Ana; Alexandre, Carlos; Gonçalves, Maria C.; Pereira, L.S.
Secondary salinization has long been reported in the Roxo irrigation district (RID), southern Portugal, due to the
use of saline-prone irrigation water and the existence of poorly structured soils. This study assessed the soil water
and salt budgets in nine commercial orchards located in the RID using the multiple ion chemistry module
available in the HYDRUS-1D model during the 2019 and 2020 growing seasons. The studied crops were almond,
olive, citrus (orange, mandarin, and clementine), and pomegranate. The model successfully simulated soil water
contents measured in the different fields but there was a clear underestimation of the electrical conductivity of
the soil saturation paste extract (ECe) in some locations, while simulations of the sodium adsorption ratio (SAR)
were generally acceptable. Modeling errors were mostly associated with missing information on fertigation
events rather than related to the effects of irrigation water quality. The water and salt balances were also
computed for the 1979–2020 period. Considering the probability of non-exceedance of salt accumulation during
this period, the risk of salinity build-up was high to very high for the very dry years in most fields, except in the
citrus sites. The factors influencing the salt accumulation were the irrigation strategy, the seasonal irrigation and
rainfall depths, the duration of the crop growth period, the rainfall distribution in the late and non-growing
stages, the soil drainage conditions, and the irrigation water quality. For the current climate conditions and
irrigation water quality, the risk of soil salinity levels affecting crop development and yields was found to be
minor. This means that, despite salts tended to accumulate in the rootzone over a season, under current conditions the salinity stress did not reach harmful levels for plants. Only in two of the study sites, there was a need
to promote salt leaching. Hence, this study shows that soil salinization risks in the study area are low but, for
given locations during drier seasons, there is a need for tailored irrigation solutions aimed at the conservation of
soil and water resources.
Salts dynamics in maize irrigation in the Hetao plateau using static water table lysimeters and HYDRUS-1D with focus on the autumn leaching irrigation
Publication . Ramos, Tiago B.; Liu, Meihan; Paredes, Paula; Shi, Haibin; Feng, Zhuangzhuang; Lei, Huimin; Pereira, L.S.
Soil salinization problems are widespread in the Hetao plain, Inner Mongolia, resulting from arid climate con-
ditions, a shallow saline water table, poor irrigation water management, and insufficient drainage. This study
follows previous research aimed at evaluating crop water use and controlling the salinity build-up in the region,
namely using weighing and static water table lysimeters to parameterize a water balance model aimed at the
development of appropriate irrigation scheduling. Two sets of five static water table lysimeters, which fixed
depths ranged from 1.25 to 2.25 m, were used over two maize crop seasons. The mechanistic HYDRUS-1D model
was further used to daily predict measured data on soil water contents, boundary fluxes in the interface between
the saturated and unsaturated zones, the electrical conductivity of the soil saturation paste extract (ECe), and the
actual crop evapotranspiration (ETc act). The soil water balance helped quantify the combined effect of water and
salinity stresses on root water uptake as well as groundwater fluxes into the rootzone. The salt balance showed
that the salinity build-up was much related to irrigation and capillary fluxes, and that the autumn irrigation
carried out during the non-growing season was essential for controlling soil salinity. The efficiency of the autumn
irrigation much depended on groundwater depth and the amount of water applied for salt leaching, with the best
results found for the lysimeters with water table depths at 2.0 and 2.25 m (85–100%) for irrigation depths ≥ 220
mm. The lysimeters with shallower water tables never showed a leaching efficiency higher than 88%. This
research shows that the sustainability of irrigation in Hetao depends on finding adequate solutions for controlling
the depth of the saline groundwater, minimizing capillary fluxes to the rootzone, and developing consequent
approaches for autumn irrigation leaching.
Development and functional evaluation of pedotransfer functions for estimating soil hydraulic properties in Portuguese soils: Implications for soil water dynamics
Publication . Ramos, Tiago B.; Darouich, Hanaa; Gonçalves, Maria C.
Accurate knowledge of soil hydraulic properties is essential for effectively simulating soil water dynamics in field
plots. However, determining these properties directly can be challenging, especially when a large amount of data
is required. Therefore, the primary objective of this study was to develop four hierarchical pedotransfer functions
(PTFs) to estimate the soil hydraulic parameters of the Mualem-van Genuchten model. The PTFs that were
developed ranged from utilizing a limited set of variables to those comprising a more comprehensive set of
variables. These included particle size distribution, soil bulk density, soil depth, and soil water contents at matric
potentials of − 33 and − 1580 kPa. The functional performance of these PTFs was also assessed in simulations of
the soil water balance in ten agricultural fields over two growing seasons using the HYDRUS-1D model. The
simpler PTFs exhibited moderate accuracy in estimating soil water contents at different matric potentials, while
the more complex PTFs with a greater number of variables yielded increasing accuracy. However, estimation
errors were more noticeable in the drier range of the soil water retention curve. The inclusion of bulk density as a
predictor only affected the wetter range of the same curve. Estimation of log Ks improved from the simpler to the
more complex PTFs, but the statistical indicators were consistently modest. The functional performance of the
PTFs showed increased errors in simulating soil water contents in the ten study sites compared to reference
simulations. The more complex PTFs with the greatest number of variables provided the best predictions in most
cases. The PTFs primarily affected flow conditions in the soil profile, resulting in increased soil water storage and
impacting predictions of deep percolation the most. Water availability in the soil profile then influenced actual
transpiration, alleviating stress in some cases but causing waterlogging in one situation. The study emphasizes
the cautious use of the PTFs and the need for additional information on clay-rich soils and hydraulic conductivity
data to enhance their performance.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
2022.03921.PTDC