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91.
Viviana Horna Bernhard Schuldt Sarah Brix Christoph Leuschner 《Annals of Forest Science》2011,68(5):1027-1038
• Introduction
We studied stem sap flux density in seven common tree species in a perhumid tropical rainforest at pre-montane elevation in Sulawesi with the aims (1) to analyse the among-species variation in flow patterns, (2) to search for an assumed convergence in the response to controlling environmental factors, and (3) to investigate the effect of tree size on xylem flux. 相似文献92.
The advanced backcross quantitative trait locus (AB-QTL) analysis has proven its usefulness to identify and localize favourable
alleles from exotic germplasm and to transfer those alleles into elite varieties. In a balanced design with up to six environments
and two nitrogen fertilization (N treatment) levels, a 4-factorial mixed model analysis of variance (ANOVA) was used to identify
QTL main effects, QTL × environment interaction effects and QTL × N treatment interaction effects in the spring barley BC2DH population S42. The yield-related traits studied were number of ears per m2, days until heading, plant height, thousand grain weight (TGW) and grain yield. In total, 82 QTLs were detected for all traits.
This finding was compared to a previous QTL study of the same population S42, where the current field data was reduced to
one half through restriction of the analysis to the standard N treatment level (von Korff et al., Theor Appl Genet 112: 1221–1231,
2006). These authors located 54 QTLs for the same traits by applying a 3-factorial mixed model similar to the current model but
excluding the factor N treatment. We found that QTL × environment interaction, alone or in combination, accounted for 24 of
the newly uncovered QTLs, whereas QTL × N treatment interaction was of lesser importance with six new cases in total. A valuable
QTL interacting with N treatment has been identified on chromosome 7H where lines carrying the wild barley allele were superior
in number of ears per m2 in either N treatment. We conclude that in population S42 the extension of the phenotype data set and the inclusion of N
treatment into the mixed model increased the power of QTL detection by providing an additional replication rather than by
revealing specific N treatment QTLs. 相似文献
93.
Validation of a 2-domain-model for the simulation of solute transfer in soils by laboratory and field experiments The simulation of water and solute transfer in the unsaturated zone on the basis of the classical convective dispersive model gives dissatisfactory results in many cases. Especially in the zone of evapotranspiration the observed penetration depths of surface-applied chemicals often exceed calculated values. This has been attributed to preferential flow in domains with accelerated flow. The aim of the investigations presented here was to extend the conventional theory of solute transfer in order to enable improved model predictions without introducing too much complexity to the model which might reduce its applicability. The mobile-immobile-concept of Coats and Smith (1964) was chosen to extend the model FLOTRA (Wagner et al., 1992), which is based on the convective dispersive approach. The model parameters additionally needed by the model are the immobile water content θim and the solute transfer coefficient α. The applicability of the model was tested on the basis of several laboratory and field experiments. It is shown, that with the mobile-immobile-approach modeling results of water and solute transfer in the top soil layers, which are most important in view of soil and groundwater protection, were improved compared to the calculations with the classical convective dispersive model. 相似文献
94.
Adsorption of Water, Ethylene Glycol Monoethyl Ether as well as Nitrogen and its Relation to Properties of German and Israeli Soil Samples To determine the specific surface area, samples taken from 140 soil horizons were selected and the significant physical and chemical properties were investigated. The specific surface area of the samples was determined by adsorption of H2O, ethylene glycol monoethyl ether (EGME) and N2. A comparison of the three methods shows that the specific surface area determined by the adsorption of H2O and EGME does not differ significantly. However, the specific surface determined by N2-adsorption differs markedly from the results obtained using the polar substances. As a dependent variable the specific surface area is mainly influenced by the clay content and clay mineral type. Further, the organic substance content as well as the iron- and manganoxide content have a more significant influence on the specific surface area the lower the clay content is, or the content of three layer minerals. As an independent variable, the specific surface area determined by adsorption of EGME, proved to be the characteristic soil factor which reflects the effective cation exchange capacity as well as the hygroscopicity with the highest degree of accuracy. 相似文献
95.
Mirzakhayot Ibrakhimov Christopher Martius J.P.A. Lamers Bernhard Tischbein 《Agricultural Water Management》2011,101(1):52-61
Salinization of irrigated agricultural land threatens ecological sustainability and livelihoods of people. Salinization is especially severe in the dry lowlands world-wide and in Central Asia where large amounts of salts accumulated in the soil profile, originating from shallow saline groundwater (GW). Analysis of the unique dataset of 2000 monitoring wells of GW table and salinity in lowland Khorezm region of Uzbekistan over the period of 1990 till 2006 showed shallow GW levels of 1.1-1.4 m (±0.48-0.66 m) at start of leaching periods and 0.9-1.4 (±0.43-0.63 m) in July during the annual growing seasons. While leaching efficiency is decreased, shallow GW in July is far above the optimum levels of 1.4-1.5 m. The effects of topography, soil texture, and irrigation and drainage networks were found to favor shallow GW forced by excessive water diversion. The drainage network, which is seen by many specialists as underdeveloped and its improvement necessary to arrest unacceptable GW levels, is being used under its full capacity. The solution to alleviate land degradation is not only an improved drainage, but better controlled and more flexible water management. 相似文献
96.
Modeling irrigated cotton with shallow groundwater in the Aral Sea Basin of Uzbekistan: I. Water dynamics 总被引:4,自引:3,他引:1
I. Forkutsa Rolf Sommer Y. I. Shirokova J. P. A. Lamers K. Kienzler B. Tischbein C. Martius P. L. G. Vlek 《Irrigation Science》2009,27(4):331-346
In Khorezm, a region located in the Aral Sea basin of Uzbekistan, water use for irrigation of predominantly cotton is high
whereas water use efficiency is low. To quantify the seasonal water and salt balance, water application, crop growth, soil
water, and groundwater dynamics were studied on a sandy, sandy loam and loamy cotton field in the years 2003 and 2005. To
simulate and quantify improved management strategies and update irrigation standards, the soil water model Hydrus-1D was applied.
Results showed that shallow groundwater contributed a substantial share (up to 399 mm) to actual evapotranspiration of cotton
(estimated at 488–727 mm), which alleviated water stress in response to suboptimal quantities of water applied for irrigation,
but enhanced concurrently secondary soil salinization. Thus, pre-season salt leaching becomes a necessity. Nevertheless, as
long as farmers face high uncertainty in irrigation water supply, maintaining shallow groundwater tables can be considered
as a safety-net against unreliable water delivery. Simulations showed that in 2003 around 200 mm would have been sufficient
during pre-season leaching, whereas up to 300 mm of water was applied in reality amounting to an overuse of almost 33%. Using
some of this water during the irrigation season would have alleviated season crop-water stress such as in June 2003. Management
strategy analyses revealed that crop water uptake would only marginally benefit from a permanent crop residue layer, often
recommended as part of conservation agriculture. Such a mulch layer, however, would substantially reduce soil evaporation,
capillary rise of groundwater, and consequently secondary soil salinization. The simulations furthermore demonstrated that
not relying on the contribution of shallow groundwater to satisfy crop water demand is possible by implementing timely and
soil-specific irrigation scheduling. Water use would then not be higher than the current Uzbek irrigation standards. It is
argued that if furrow irrigation is to be continued, pure sandy soils, which constitute <5% of the agricultural soils in Khorezm,
are best to be taken out of annual cotton production. 相似文献
97.
Gi-Tak Chae Seong-Taek Yun Bernhard Mayer Kyoung-Ho Kim Soon-Young Yu 《Agricultural Water Management》2009,96(12):1819-1827
Major ions and stable isotopic (δDwater, δ18Owater, δ15Nnitrate, δ18Onitrate) measurements in concert with hydrochemical modeling were used in order to elucidate the sources and geochemical processes controlling nitrate contamination of shallow alluvial groundwater underneath a riverside agricultural field in the Buyeo area, Korea. Beneath vegetable fields in the sandy soil, the mean nitrate concentration of groundwater was 148.6 mg/L, which is significantly higher than in groundwater (mean 28.8 mg/L) beneath silty soils underneath rice paddy fields. Nitrogen isotope data indicate that synthetic fertilizers are the predominant source of groundwater nitrate in the study area. Denitrification during recharge through rice paddy soils appears to be responsible for the lower nitrate concentrations in groundwater beneath the silty soil zone. The relationship between nitrogen and oxygen isotope data of nitrate also suggests mixing of two different groundwater bodies with nitrates from the silt zone and the sand zone. Geochemical mass balance modeling on hydrochemical data indicates that various agricultural chemicals such as urea, lime, magnesium sulfate and potassium chloride dissolve in vegetable fields of the sandy zone, resulting in significant enrichment of various solutes such as K+, Ca2+, Mg2+, NO3−, SO42− and Cl−. As a consequence of over-utilization of synthetic nitrogen fertilizers, the sand zone is characterized by very high nitrate concentrations in the groundwater. This study suggests that a reduction of over-fertilization especially on vegetable fields in the riverside sand zone is required to minimize the nitrate contamination of groundwater. This study also shows that combination of geochemical and isotopic techniques with simple mass balance modeling provides information about the causes and processes of nitrate contamination of groundwater underneath a riverside agricultural field. The study also provides sustainable measures to optimize fertilization rate as an important basis of eco-friendly agriculture. 相似文献
98.
Bernhard Ericsson 《Forstwissenschaftliches Centralblatt》1896,18(7):389-397
Ohne Zusammenfassung 相似文献
99.
Zainul ABIDEEN Hans-Werner KOYRO Bernhard HUCHZERMEYER Bilquees GUL M. Ajmal KHAN 《土壤圈》2020,30(4):466-477
Soil water and nutrient status are both of major importance for plant appearance and growth performance. The objective of this study was to understand the effect of biochar (1.5%) and a biochar-compost mixture (1.5% biochar + 1.5% compost) on the performance of Phragmites karka plants grown on a synthetic nutrient-poor sandy clay soil (50% sand, 30% clay, and 20% gravel). Indicators of plant performance, such as growth, lignocellulosic biomass, water status (leaf water potential, osmotic potential, and turgor potential), mineral nutrition status, leaf gas exchange, and chlorophyll fluorescence, and soil respiration (carbon dioxide (CO2) flux) were assessed under greenhouse conditions. Biochar-treated plants had higher growth rates and lignocellulosic biomass production than control plants with no biochar and no compost. There was also a significant increase in soil respiration in the treatments with biochar, which stimulated microbial interactions. The increase in soil water-holding capacity after biochar amendment caused significant improvements in plant water status and plant ion (K+, Mg2+, and Ca2+) contents, leading to an increase in net photosynthesis and a higher energy-use efficiency of photosystem II. Biochar-treated plants had lower oxidative stress, increased water-use efficiency, and decreased soil respiration, and the biochar-compost mixture resulted in even greater improvements in growth, leaf turgor potential, photosynthesis, nutrient content, and soil gas exchange. Our results suggest that biochar and compost promote plant growth with respect to nutrient uptake, water balance, and photosynthetic system efficiency. In summary, both the soil amendments studied could increase opportunities for P. karka to sequester CO2 and produce more fodder bio-active compounds and biomass for bio-energy on nutrient-poor degraded soils. 相似文献
100.