Modelling water flow,nitrogen uptake and production for wheat

Soil water and temperature conditions were simulated for three years at three sites in the Netherlands, using a model named SOIL. Observed water table depths from one site with a sandy loam soil indicated bypass flow in macropores. Nitrogen turnover was simulated using the output of SOIL as input to a nitrogen model. To improve the nitrogen model, a crop-growth submodel was introduced, and simulations were compared with measured data for two seasons and three fertilizer treatments at the three sites. Mineral-N in the soil after application of fertilizer was substantially higher in the simulation than indicated by measurements in 4 out of 18 simulations. Regression analyses showed that simulated mineral-N content in the uppermost metre explained 64% of the observed variation. The corresponding values for nitrogen content (N _ta) and biomass (W _ta) of aboveground tissues were 86 and 93%, respectively. With a few exceptions annual values ofW _ta andN _ta were simulated with an accuracy of approximately 20%. A sensitivity test showed that growth parameters and especially the light use efficiency parameter strongly influenced biomass production for fertilized treatments whereas the control of nitrogen uptake from soil was most important for non-fertilized treatments.     

Yield,water use and nitrogen uptake for different water and N levels in winter wheat

In an effort to establish an optimum combination of water and nitrogen for winter wheat a field investigation was carried out on a coarse loamy sand soil during 1984–85 and 1985–86 to assess effects of irrigation regime (IR) and N application on yield, water use and N uptake. The treatments compromised all combinations of three irrigation regimes (IR) based on ratios of irrigation water to cumulative pan evaporation viz.1.2 (I-1), 0.9 (I-2) and 0.6 (I-3) and four rates of N, viz. 0, 60, 120 and 180 kg ha^–1. Grain yield increased with increase in frequency of irrigation. In spite of wide differences in weather during the two years, scheduling of irrigation at IW/CPE = 1.2 gave the highest wheat yield on the coarse-textured soil. During 1984–85, the rainless year, grain yield under I-1 was 20 and 32 per cent higher than I-2 and I-3, respectively. With increasing N rate the yield and water use efficiency increased progressively upto 180 kg N under I-1 and upto 120 kg N ha^–1 under I-2 and I-3 regimes. During 1985–86, the wet year, grain yield response to IR was relatively low. Irrespective of IR, yield increased progressively upto 180 kg N ha^–1 during the wet year. Irrigation water regimes and N application also influenced leaf area index and root growth of wheat. The yield of unfertilized wheat was relatively less affected by seasonal rainfall and IR.Both N uptake and grain yield of wheat were found to increase linearly with increase in water use. Water use efficiency was highest under I-1 regime at all levels of N in the dry season of 1984–85 and under I-3 regime in the wet season of 1985–86. Increase in N uptake with increasing N rates was significantly higher under I-1 than I-2 and I-3 regimes. The N use efficiency being maximum at 60 kg N ha^–1, decreased at higher N levels irrespective of IR.     

Modelling of gas transport properties of polymer electrolytes containing various amounts of water

Gas transport properties of three different PEO-based polymer electrolytes containing PEO sulfonic acid dianions, cations and 90 or 35 or 0 wt% of water are studied by atomistic molecular modelling. The gas molecules studied are H₂, O₂, CO₂ and CH₄. The pair correlation functions are calculated to see the distribution of the gas molecules in the systems. The diffusion coefficients of the gas molecules are calculated and found to be dependent of the amount and distribution of the water in the system and of the size of the penetrant. The motion of the gas molecules is explored in each system. The amount and distribution of water has a strong effect on the motion of the gas molecules. The ionic copenetrants seem not to have any direct influence on the diffusion of the gas molecules in the polyelectrolyte materials. However, ions have an effect on the distribution of the water in the polyelectrolyte materials.     

Modelling of the nitrogen cycle in farm land areas

The authors propose a method of modelling the cycles of water and nitrogen in the soil in order to simulate the drainage flow of water and the flow of leached nitrate, the main inputs into a model of transfer in aquifers. The processes of the N cycle included here are: mineralization, nitrification, ammonium adsorption-desorption, immobilization of N from ammonium and nitrate, N uptake by plants and leaching of nitrate. The results of a limited test of the model using data from Dutch experimental farms showed that, on the whole, measured and simulated values were in reasonably good agreement, in spite of the relative simplicity of the model. However, the simulations do not give detailed information concerning the dynamics of nitrogen in the various layers in the soil.     

The effect of nitrogen on root growth and nutrient uptake of young tea plants (Camellia sinensis L.) grown in sand culture

Root growth and nutrient uptake of a tea clone were studied in a sand culture experiment using ammonium sulphate, ammonium nitrate and urea each at 35, 70 and 105 ppm N. Results show that increasing N levels regardless of forms increased the proportion of white roots and decreased brown root weight.As to the composition of the aerial parts (plant tops) enhanced N supply increased concentrations of Ca and NO₃, while K and H₂PO₄ concentration decreased. Use of ammonium sulphate increased the sulphate levels. Increased N level through urea increased Cl concentration, while the reverse was true with both ammonium sulphate and ammonium nitrate. Concentrations of Mg and Na remained unaffected by N fertilization, though the former tended to increase with increased level of N irrespective of forms. The organic acid concentration measured as the difference of sum equivalents of cations and that of anions increased with an increase supply of N in any of the three forms.The white:brown root ratio was correlated positively with growth, Ca:K ratio and organic acid content of plant tops.     

Modelling the motion of cylindrical particles in a nonuniform flow

The models currently used in computational fluid dynamics codes to predict solid fuel combustion rely on a spherical shape assumption. Cylinders and disks represent a much better geometrical approximation to the shape of bio-fuels such as straws and woods chips. A sphere gives an extreme in terms of the volume-to-surface-area ratio, which impacts both motion and reaction of a particle. For a nonspherical particle, an additional lift force becomes important, and generally hydrodynamic forces introduce a torque on the particle as the centre of pressure does not coincide with the centre of mass. Therefore, rotation of a nonspherical particle needs to be considered. This paper derives a model for tracking nonspherical particles in a nonuniform flow field, which is validated by a preliminary experimental study: the calculated results agree well with measurements in both translation and rotation aspects. The model allows to take into account shape details of nonspherical particles so that both the motion and the chemical reaction of particles can be modelled more reasonably. The ultimate goal of such a study is to simulate flow and combustion in biomass-fired furnaces using nonspherical particle tracking model instead of traditional sphere assumption, and thus improve the design of biomass-fired boilers.     

SKALAR San++连续流动分析仪同时检测水源水中总氮和总磷

实验建立了采用SKALAR San++连续流动分析仪同时检测水源水中总氮和总磷的分析方法,其中总氮方法检出限为0.05 mg/L,纯水加标回收率为94.0%~104%,相对标准偏差RSD为0.0%~0.07%;总磷方法检出限为0.009mg/L,纯水加标回收率为91.0%~106%,相对标准偏差RSD为0.0%~0.7%,均符合工作要求。通过对比分析,该方法较传统手工方法具有明显优势:可以直观图谱查看结果,可以连续监测水源水中总氮和总磷的变化,实现快速检测,对提高水源水质监测预警具有重要意义。     

Yield,water use,and nutrient uptake of corn hybrids under varied irrigation and nitrogen regimes

Defined relationships among grain yields, water-use efficiencies (WUE) and nutrient uptake of different genotypes under varied irrigation and nitrogen (N) regimes would be invaluable for optimizing production of corn (Zea mays L.). Our objective was to evaluate these factors for six popular corn hybrids grown in Nebraska. The procedure involved measuring the effects of three supplemental irrigation rates and two N rates on yields, consumptive water use (ET), water-use efficiency, and nutrient uptake of these hybrids in one field experiment. A second field experiment evaluated effects of irrigation timing on the same characteristics of the six hybrids. Soils employed for the field experiments were Sharpsburg sicl, a typic Argiudoll, and Zook sicl, a cumulic Haplaquoll. In addition, two greenhouse experiments measured above-ground and root yields, water use, and nutrient uptake of the six hybrids under limited and high soil moisture levels.From 30–40 percent reductions in grain and stover yields occurred by limiting moisture supply in the greenhouse but with no reduction in root yields. There was only a small benefit to grain and stover yields from the higher soil moisture levels provided in the field experiments because of very favorable rainfall amount and distribution in 1979. Light, frequent irrigation was advantageous to yield and WUE over the same total amount of water applied in larger, less frequent intervals explainable in part by a N use efficiency factor. Genotype B73xMo17 produced significantly higher grain, stover, root and total yields than the other hybrids under all moisture and N regimes. Amounts of water consumed by the six hybrids in the field experiments were similar, but because of higher yields B73xMo17 had the highest WUE values. This hybrid had greater root development in the field and took up disproportionately more P, Ca, S, Fe, Cu, and Zn and less Mn and Cl than the other hybrids suggesting that its superior yielding capacity may be related to efficiency in mobilizing and utilizing certain nutrients.Contribution of the Nebraska Agric Exp Stn, Lincoln, NE as paper No. 7041 Journal Series.     

A model to predict changes in soil moisture,NO3-N content and N uptake by wheat

A simulation model to predict fertilizer N behaviour in a soil-plant (wheat) system has been developed and tested. The model predicts components of field water balance (evaporation, transpiration, drainage and run-off) and changes in soil nitrogen amounts due to N transformations (urea hydrolysis, mineralization, nitrification and volatilization), N movement and plant N uptake using information on N transformation coefficients for the soil, atmospheric evaporative demand (E_pan), leaf area development and root growth characteristics of the crop. The model predicts N uptake by wheat through mass flow using a new simplified crop cover function. The coefficients of correlation between the measured and predicted N uptake by wheat grown under three different moisture regimes in the two years (1987–88 and 1988–89) approached unity. The computed amount of residual NO₃-N in the soil profile at wheat harvest matched well with the measured amount with a root mean square error of 13.7 percent. The close matching of the measured and model predicted components of nitrogen and water balances under three widely different set of irrigation treatments suggests of model's capabilities to help in on-farm N management both under irrigated and rainfed conditions.     

Response of wheat to nitrogen fertilization,a data set to validate simulation models for nitrogen dynamics in crop and soil

A data set originating from winter wheat experiments at three locations during two years is described. The purpose is to provide sufficient data for testing simulation models for soil nitrogen dynamics, crop growth and nitrogen uptake. Each experiment comprised three different nitrogen treatments, and observations were made at intervals of two or three weeks. The observations included measurements of soil mineral nitrogen content, soil water content, groundwater table, dry matter production and dry matter distribution, nitrogen uptake, nitrogen distribution and root length density.     

Effect of nitrogen and water uptake on yield of wheat

For 2 years, field experiments were conducted to study the direct and interactive effects of water and nitrogen uptake at different growth stages on grain yield of wheat, grown on coarse textured alluvial soil of Ludhiana. Twelve treatments comprising 3 irrigation regimes and 4 rates of N were imposed. The N and irrigation regimes showed significant interaction, especially during the drier year. Grain yield was better explained with water uptake and N uptake, when partitioned over different growth stages than with total uptake. The sensitivity factor for water uptake was higher at the reproductive stage ( = 1.60) than at the vegetative ( = 1.05) and maturation ( = 0.38) stages. Contrary, yield was more sensitive to N uptake during the vegetative stage than the reproductive and the maturation stages. Sensitivity of grain yield to water uptake was higher at higher N application rates. Yield predictability was much better (R² = 0.98) when N and water uptake at different growth stages were combined.     

Yield and uptake response of lettuce to cadmium as influenced by nitrogen application

A screen house experiment was conducted to determine the effect of N (0, 50, 100 and 150 mg N kg^–1) and Cd (0, 5, 10, 25 and 50 mg Cd kg^–1) on growth and concentration and uptake of N and Cd in lettuce grown for 70 days. Nitrogen application increased significantly fresh yield, dry matter yield, N concentration and uptake, whereas these parameters were significantly decreased by Cd application at all levels of N. The concentration and uptake of Cd were significantly increased by Cd application at all levels of N. This increased Cd uptake was related to increased availability of Cd in soil. Application of N upto 100 mg N kg^–1 increased Cd uptake, whereas there was sharp reduction in Cd uptake at 150 mg N kg^–1 treatment at all levels of Cd. The plant dilution effects and reduced translocation of Cd from roots to tops or the competition at the root absorption sites at highest level of N seem to be the mechanisms responsible for N suppressed Cd uptake in this study.     

Role of water states on water uptake and proton transport in Nafion using molecular simulations and bimodal network

Using molecular simulations and a bimodal-domain network, the role of water state on Nafion water uptake and water and proton transport is investigated. Although the smaller domains provide moderate transport pathways, their effectiveness remains low due to strong, resistive water molecules/domain surface interactions. The water occupancy of the larger domains yields bulk-like water, and causes the observed transition in the water uptake and significant increases in transport properties.     

微污染水源水中氨氮的危害与现代处理技术

在我国微污染水源水中,氨氮污染问题尤为突出,而目前自来水厂大多采用传统工艺,主要针对悬浮物、细菌和病毒,对氨氮的去除效果差,所以必须进行工艺改造。针对我国的微污染水源水中氨氮的污染现状,对当下去除微污染水源水中氨氮的常见物化法、生物法和联合处理法进行综述,介绍了它们的原理和优缺点,并对未来微污染水源中氨氮的去除技术进行了展望。     

Effect of irrigation and nitrogen fertilizer on yield,oil content,nitrogen accumulation and water use of canola (Brassica napus L.)

Effects of N application and water supply on yield, oil content and N accumulation by canola, cultivar Marnoo, grown on a heavy clay soil in the Goulburn Murray Irrigation Region were investigated. Treatments were rainfed (R_f) or watered at a deficit of 50 mm (40–60 mm, I₅₀) beginning in the spring. N treatments were 0, 50, 100 or 200 kg N ha^–1 at sowing or as split applications of 20/80, and 50/50 kg N ha^–1 at sowing and rosette, respectively.Yield (Y_g) ranged from 170 to 520 g m^–2. Irrigation and N increased yield in both years. Grain yields were increased by N application on the irrigated treatments when 100 or 200 kg N ha^–1 was applied. Oil concentrations ranged from a maximum of 46.4% in treatment N₀ to a minimum of 40.6% in treatment N₂₀₀ and was inversely related to seed N concentration. Although fertilizer N decreased oil concentration, it increased the yield of oil.Nitrogen accumulation (N_b) limited yield of all treatments and was described by the equation, Y_g = 806[1-EXP(–0.039*N_b)]. This implied a decrease in yield per unit of N_b at the higher rates of fertilizer addition with consequent increases in grain N concentration.The efficiency of water use in the production of grain (WUE_g) and biomass (WUE_b) were 7.5 and 23 kg ha^–1 mm^–1 respectively. Nitrogen additions increased WUE_g and WUE_b in both seasons. Maximum values of 8.9 (WUE_g 1986) and 26.8 (WUE_b 1987) were measured from treatment N₂₀₀. These data suggest that the crops made efficient use of the applied water.     

Effect of rates and sources of nitrogen application on yield and nutrient uptake of Citronella Java (Cymbopogon winterianus Jowitt)

Two field experiments were conducted for two crop cycles each of two years (1985–87 and 1986–88) on an entisols to study the effect of rate and sources of N application on yield and nutrient uptake of Citronella Java (Cymbopogon winterianus Jowitt). Fresh herbage and essential oil yields were significantly influenced by application of N up to 200 kg ha^–1 yr^–1, while tissue N concentration and N uptake increased only to 150 kg N ha^–1. The oil yields with Neem cake coated urea (urea granules coated with Neem cake) and urea super granules were 22 and 9% higher over that with prilled urea and urea supergranules were significantly increased up to 200 kg N ha^–1 while with Neem cake coated urea, response was observed only to 150 kg N ha^–1! Estimated recovery of N during two years from Neem cake coated urea, urea supergranules and prilled urea were 38, 31 and 21%, respectively.     

Effects of ferulic acid,an allelopathic compound,on net P,K, and water uptake by cucumber seedlings in a split-root system

Since distribution of allelopathic compounds in soils is highly variable, injurious effects by such compounds should be related to the frequency of contact with roots. Experiments were conducted to determine how P, K, and water uptake of cucumber seedlings were affected as the fraction of roots in contact with ferulic acid (FA) was increased. Seedlings were grown in Hoagland's nutrient solution for 14 days and then transferred to 0.5 mM CaSO₄ solution for 24 hr before being placed into a split-root culture system. The containers in the system were filled with 0.5 mM concentrations of KH₂PO₄ and CaSO₄ or 0.5 mM concentrations of KH₂PO₄, CaSO₄, and ferulic acid (FA). Net uptake of P by seedlings (milligrams per seedling) decreased in a curvilinear (concave) manner as the fraction of the roots in contact with FA increased. Net uptake of K (milligrams per seedling) and water (milliliters per seedling) by seedlings decreased linearly as the fraction of the roots in contact with FA increased. Net uptake of P, K, and water by seedlings was reduced 57, 75, and 29%, respectively, when the whole root system was exposed to FA. Net P and K uptake of roots (milligrams per gram root fresh weight) not in contact with FA decreased in a linear and curvilinear (convex) manner, respectively, as the fraction of roots in contact with FA increased. Net P and K uptake of roots in contact with ferulic acid increased in a linear and curvilinear (convex) manner, respectively. Net water uptake of roots (milliliters per gram root fresh weight) not in contact with FA increased in a curvilinear (concave) manner as the frequency of the roots in contact with FA increased. Net water uptake of roots in contact with FA did not show a trend. Transpiration (milliliters per square centimeter) was reduced in a linear manner as the fraction of roots in contact with FA increased. A very slight compensation by roots not in contact with FA for roots in contact with FA was observed for net water uptake rates. No compensation for P and K uptake rates was observed.Paper Mo. 12421 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned.     

Transport parameters for the modelling of water transport in ionomer membranes for PEM-fuel cells

The water transport number (drag coefficient) and the hydraulic permeability were measured for Nafion. The results show a significant increase of both parameters with increasing water content indicating that they are strongly influenced by the membrane microstructure. Based on these experimental studies a new model approach to describe water transport in the H₂-PEFC membrane is presented. This approach considers water transport by electro-osmosis caused by the proton flux through the membrane and by osmosis caused by a gradient in the chemical potential of water. It is parametrized by the measured data for the water transport number and the hydraulic permeability of Nafion. First simulation results applying this approach to a one-dimensional model of the H₂-PEFC show good agreement with experimental data. Therefore, the developed model can be used for a new insight into the dominating mechanisms of water transport in the membrane.     

An experimental, numerical and analytical investigation of gas flow characteristics in concrete

A series of tests are reported which used existing pressure cell apparatus to measure nitrogen gas flow in concrete. A finite difference numerical model is described which is used to investigate the time to reach steady state and the long-term transient response of the experimental system. An analytical solution is derived for the cell-pressure-time function from which a formula is derived for the intrinsic permeability coefficient. The permeabilities calculated from the experimental data have variations consistent with those from other investigations. The analytical solution matches the experimental pressure-time decay curves closely in the range of interest but there is a tendency for the curves to diverge for lower cell pressures. This is attributed to gas slippage and modifications to both the numerical and analytical solutions are described to account for this factor. Revised formulae are derived which give both the intrinsic permeability and Klinkenberg factor. These are then applied to the present experimental data and results compared with those from the literature.