The fact of, present is the key of the past, will help us to use paleosols properties as indicators of the ecological characteristics of past .time, particularly the paleoclimate. In this respect the micro- morphologi...The fact of, present is the key of the past, will help us to use paleosols properties as indicators of the ecological characteristics of past .time, particularly the paleoclimate. In this respect the micro- morphological properties showed to be a very good indicator. Therefore, for investigating of climate change in Ardakan-Yazd plain, Central Iran 9 pedons were digged and described. Yazd has an arid climate with less than 100 mm annual precipitation and more than 22℃ mean annual temperature （Aridic-hyper thermic soil moisture and temperature regions, respectively）. Based on the morphological and physicochemical analysis Arglic, Calcic and Gypsic diagnostic horizons have been distinguished in these soils. Thin section studied showed that the illuviated form of clay includes, infillings on channel, coating on pendant, on nodules and on grains, at lower depths and also juxtaposed calcite needles on void argillan at upper part of the profiles. Mineralogical result showed fine clay in arglic horizon, too. Considering depth and forms of these pedofeatures, we concluded that, the observed illuviated clays at lower depth must be the result of the more humid climate of the past, where the carbonates have been removed completely as pendant, nodules or coating to considerable depth, following processes, clay has been dispersed and also trans located to these depths. In contrast to these features, the juxtaposed needle calcite at the shallower depth is probably the result of drier climate of today.展开更多
A greenhouse pot experiment was conducted to study the effect of drought induced at different phenological stages on growth, biomass production and yield performance of grain amaranth Amaranthus cruentus G6. After eme...A greenhouse pot experiment was conducted to study the effect of drought induced at different phenological stages on growth, biomass production and yield performance of grain amaranth Amaranthus cruentus G6. After emergence seedlings were exposed to different soil water regimes： constant adequate moisture （W1） and drought （W2） throughout the growing period, drought initiated at crop inflorescence formation （W3）, drought condition during pre-inflorescence formation （W4） and treatment W5 where drought condition occurred in the period from the beginning of inflorescence formation to the beginning of flowering. Crop samples were taken at the maturity. The growth and yield performance of amaranth were assessed by measuring root length, stem height and inflorescence length, and by evaluating fresh and dry weight of plant parts, grain yield and harvest index. Drought stress initiated at different phenological stages affected the evaluated morphological parameters, assimilate allocation and grain yield. Drought throughout the growing period resulted in grain and biomass yield reduction for 51% and 50%, respectively. Water deficit during inflorescence formation appears to be critical growing stage influencing grain yield, while soil drying in the vegetative growth stages improve the assimilate allocation to the above-ground biomass and particularly to the grain.展开更多
基金supported by the Soil Science department, faculty of Soil & Water, University College of Agriculture & Natural Resources, University of Tehran
文摘The fact of, present is the key of the past, will help us to use paleosols properties as indicators of the ecological characteristics of past .time, particularly the paleoclimate. In this respect the micro- morphological properties showed to be a very good indicator. Therefore, for investigating of climate change in Ardakan-Yazd plain, Central Iran 9 pedons were digged and described. Yazd has an arid climate with less than 100 mm annual precipitation and more than 22℃ mean annual temperature （Aridic-hyper thermic soil moisture and temperature regions, respectively）. Based on the morphological and physicochemical analysis Arglic, Calcic and Gypsic diagnostic horizons have been distinguished in these soils. Thin section studied showed that the illuviated form of clay includes, infillings on channel, coating on pendant, on nodules and on grains, at lower depths and also juxtaposed calcite needles on void argillan at upper part of the profiles. Mineralogical result showed fine clay in arglic horizon, too. Considering depth and forms of these pedofeatures, we concluded that, the observed illuviated clays at lower depth must be the result of the more humid climate of the past, where the carbonates have been removed completely as pendant, nodules or coating to considerable depth, following processes, clay has been dispersed and also trans located to these depths. In contrast to these features, the juxtaposed needle calcite at the shallower depth is probably the result of drier climate of today.
文摘A greenhouse pot experiment was conducted to study the effect of drought induced at different phenological stages on growth, biomass production and yield performance of grain amaranth Amaranthus cruentus G6. After emergence seedlings were exposed to different soil water regimes： constant adequate moisture （W1） and drought （W2） throughout the growing period, drought initiated at crop inflorescence formation （W3）, drought condition during pre-inflorescence formation （W4） and treatment W5 where drought condition occurred in the period from the beginning of inflorescence formation to the beginning of flowering. Crop samples were taken at the maturity. The growth and yield performance of amaranth were assessed by measuring root length, stem height and inflorescence length, and by evaluating fresh and dry weight of plant parts, grain yield and harvest index. Drought stress initiated at different phenological stages affected the evaluated morphological parameters, assimilate allocation and grain yield. Drought throughout the growing period resulted in grain and biomass yield reduction for 51% and 50%, respectively. Water deficit during inflorescence formation appears to be critical growing stage influencing grain yield, while soil drying in the vegetative growth stages improve the assimilate allocation to the above-ground biomass and particularly to the grain.
