Performance modification of a melt-blown filter medium via an additional nano-web layer prepared by electrospinning

A poly(acrylonitrile) (PAN) nano-web was electrospun on a commercial melt-blown poly(propylene) (PP) filter medium to generate composite filter media. The performance of these media was characterized in terms of filtration efficiency and pressure drop. Quality factors calculated from these parameters were used to evaluate the overall efficacy of the filter media. Structural characterization of the composite media showed that a thin layer of nano-web could improve the overall performance by increasing filtration efficiency without significant increase of pressure drop.     

Comparison of haymaking strategies for cow-calf systems in the Salado Region of Argentina using a simulation model. 3. Exploratory risk assessment

Risk and cost estimates, calculated using a weather‐driven farm simulation model, were used to evaluate the impact of different haymaking strategies in dryland cow‐calf systems such as those in the Salado region of Argentina. Based on a 100‐ha farm, each strategy was simulated using twenty sequences of 50 years of random weather. A risk‐efficiency methodology was used, using calf live weight sold and considering the economic value of the live weight produced per year minus the cost of haymaking, as a simple measure of profit. The analysis highlighted both production and risk advantages in using hay, especially when a flexible hay management approach was implemented, although some haymaking strategies performed worse than not using hay. When calf live weight sold was considered alone, the risk‐efficient set included strategies with large proportions of the areas being harvested (0.42–1.05; paddocks could be cut more that once a year in some of the strategies) and high proportions of hay not being used. The amount of hay for maximizing risk efficiency for profit was notably lower than that for maximizing cattle production. When haymaking costs were included, the proportion of area harvested for risk‐efficient profit ranged from 0.28 to 0.52, depending on the target stocking rate.     

Assessment of regional variation in climate on the management of dairy cow systems in Ireland using a simulation model

A dairy system simulator, Dairy_sim, was designed to assess the interactions between climate and management in spring‐calving milk production systems based on the grazing of grass pastures. The simulator comprises three main components: a grass herbage growth model, an intake and grazing behaviour model, and a nutrient demand model. The simulator was initially parameterized using the Irish National Dairy Blueprint. Sensitivity analysis indicated that the simulator was most sensitive to stocking rate, milk output per cow and nitrogen fertilizer inputs, but less sensitive to other variables. Field data from four grazing systems were used to test the simulator and it was concluded that Dairy_sim was suitable for evaluating the interaction of climate and management for rotational grazing dairy systems based on perennial ryegrass pastures with Friesian cows. The simulator, Dairy_sim, was then used to evaluate the effects of the regional climates of Ireland on system management. The results indicated that, between regions, herbage production at the same input of nitrogen may vary proportionally by 0·10 and that the length of the grazing season may vary by 0·25. It was concluded that the simulator could be a useful tool for developing region‐specific dairy production blueprints.     

The effects of nitrogen and iron fertilization on growth,yield and fertilizer use efficiency of soybean in a Mediterranean-type soil

Poor seed yield of soybean in Mediterranean-type environments may result from insufficient iron (Fe) uptake and poor biological nitrogen (N) fixation due to high bicarbonate and pH in soils. This study was conducted to evaluate the effects of N and Fe fertilization on growth and yield of double cropped soybean (cv. SA 88, MG III) in a Mediterranean-type environment in Turkey during 2003 and 2004. The soil of the experimental plots was a Vertisol with 176 g CaCO₃ kg⁻¹ and pH 7.7 and 17 g organic matter kg⁻¹ soil. Soybean seeds were inoculated prior to planting with commercial peat inoculants. N fertilizer rates were 0, 40, 80, and 120 kg N ha⁻¹ of which half was applied before planting and the other half at full blooming stage (R2). Fe fertilizer rates were 0, 200 and 400 g Fe EDTA (5.5% Fe and 2% EDTA) ha⁻¹. It was sprayed as two equal portions at two trifoliate (V2) and at five trifoliate stages (V5). Plants were sampled at flower initiation (R1), at full pod (R4) and at full seed (R6) stages. Application of starter N increased biomass and leaf area index at R1 stage whereas Fe fertilization did not affect early growth parameters. N application continued to have a positive effect on growth parameters at later stages and on seed yield. Fe fertilization increased growth parameters at R4 and R6 stages, and final seed yield in both years. This study demonstrated an interactive effect of N and Fe fertilization on growth and yield of soybean in the soil having high bicarbonate and pH. There was a positive interaction between N and Fe at the N rates up to 80 kg N ha⁻¹. However, further increase in N rate produced a negative interaction. Fertilization of soybean with 80 kg N ha⁻¹ and 400 g Fe ha⁻¹ resulted in the highest seed yield in both years. We concluded that application of starter and top dressed N in combination with two split FeEDTA fertilization can be beneficial to improve early growth and final yield of inoculated soybean in Mediterranean-type soils.     

Comparison of haymaking strategies for cow-calf systems in the Salado Region of Argentina using a simulation model. 1. Effect of herbage mass at cutting and cow stocking rate under a rigid system of management

A simulation model was used to compare the long‐term performance of cow‐calf farm systems under different haymaking strategies on a 100‐ha farm. In the simulation, farm management was based on that which had been developed on Reserva 6, an experimental cow‐calf farm established in 1966 at Instituto Nacional de Tecnología Agropecuaria‐Balcarce Experimental Station, Argentina, where different technologies, including haymaking, have been adapted and applied in order to increase productivity of cow‐calf systems in the Salado Region of Argentina. The management of the system is based on a restricted mating season (2 months), early weaning (5–7 months of age) and forage conservation. The simulations showed that the effect of using hay with respect to the strategy without hay, in terms of calf liveweight (LW) production per hectare, was greatest at the cow numbers that maximized production (290–320 cows) with a proportionate increase of 0.25. On the other hand, the advantage of using hay was smallest when the herbage mass at cutting for hay was 6 t dry matter (DM) ha^?1, particularly when more than 0.50 of the farm area was allocated to haymaking. The differences among the haymaking policies increased with cow numbers, especially at high herbage masses at cutting for hay. The analysis also suggested that the LW production per hectare of cow‐calf farms would be maximized by harvesting 0.40–0.50 of the total farm area and aiming to cut hay at a herbage mass of 4 t DM ha^?1 and with medium quality.     

Comparison of haymaking strategies for cow-calf systems in the Salado Region of Argentina using a simulation model. 2. Incorporation of flexibility into the decision rules

In pastoral farming systems, pasture production normally exceeds demand in the spring–summer period. Consequently, conserving forage at this time for use during the following winter is a widespread practice. The objective of this study was to assess the possible advantages of incorporating flexibility into a calendar‐based haymaking policy. A range of flexible haymaking strategies were simulated and compared against a calendar‐based strategy by using a simulation model to estimate long‐term performance of cow‐calf farm systems under each strategy. The results suggest that controlling haymaking in a flexible fashion, basing the decisions of closing, releasing and cutting paddocks on a simple pasture budget, could give the system productive advantages over using a calendar‐based approach. In terms of liveweight production per hectare, compared at the same area harvested, the flexible approach had higher average annual calf liveweight production (an increase of up to 0.15) and lower system variability [a reduction of 0.10 in the coefficient of variation (CV)] depending on the stocking rate. The results indicated that allocating more than 0.50–0.60 of the farm area to conservation would only be advantageous at very high stocking rates. In contrast to the calendar‐based strategy, making more hay than required for the immediate next winter, where possible, can reduce system variability.     

Responses of rainwater conservation, precipitation-use efficiency and grain yield of summer maize to a furrow-planting and straw-mulching system in northern China

In the rain-fed areas of northern China, maize (Zea mays L.) is a main field crop, as it is well adapted to high temperatures and bright sunshine. However, low and variable rainfall and high evapotranspiration rates are common in water-limited environments during the growing season, and often mismatched rainfall events with the critical growth stages, making yield unstable. In this study, the performance of a furrow-planting and straw-mulching system was compared with the conventional flat-planting system in a double-crop culture of winter wheat (Triticum aestivum L.) and summer maize for two consecutive years (2005-2006 and 2006-2007). The four tested treatments were: conventional flat planting (F), furrow planting between ridges (B), flat planting with wheat straw-mulching (FS), and furrow planting between ridges with wheat-straw mulch (BS). Soil water content and leaf area index (LAI) were measured throughout the growing season each year, and grain yield and precipitation-use efficiency (PUE_Y) were determined.On average, ridge tillage combined with furrow planting increased maize yield by 430 kg ha⁻¹ (7.3%) and PUE_Y by 10.7% (1.5 kg ha⁻¹ mm⁻¹), compared with the conventional flat planting; furrow planting coupled with straw mulching increased yield by an additional 16.9% and PUE_Y by 19.4%, respectively. From jointing to maturity, LAI values of BS were significantly higher than those of F-system (55.6% vs. 26.1% in 2006 and 81.4% vs. 21.7% in 2007). Our data suggest that maize production adopted by furrow planting with straw-covered ridges performed best under seasonal average rainfall below 480 mm, which was associated with better synchronization of seasonal soil water supply and crop needs, leading to improved maize yield and PUE_Y.     

Comparison of outputs of a biophysical simulation model for pasture growth and composition with measured data under dryland and irrigated conditions in New Zealand

Simulation models have a role in predicting and understanding the consequences of weather and management perturbations to biophysical systems. One such model is EcoMod – a biophysical simulation model of a pastoral ecosystem. It comprises a range of sub-models that form the main components of pastoral ecosystems – namely plants, soils and ruminant livestock. These component models are integrated to simulate the complex interactions occurring within such systems. The purpose of this study was to test how well EcoMod simulated the changes in growth rate and plant composition of dryland and irrigated pasture production in a temperate climate through comparison with a long-term (1966–2003) data set measured in New Zealand. The general behaviour of the modelled pastures was similar to those of the observed pastures. There was also close agreement between the measured and modelled total annual and monthly growth rates of dry matter (DM), particularly after modifying some of the parameters of plant growth to better represent the characteristics of dominant species present under dryland and irrigation pastures. There was greater discrepancy between measured and modelled pasture composition but in the case of the simulation of the dryland pasture, the proportional differences in species composition were much greater than the absolute differences in species composition. In addition to comparing the outputs of EcoMod to data from actual pasture production, model testing issues and potential sources of error between model outputs and data were also examined.     

Effect of water saving management practices and nitrogen fertilizer rate on crop yield and water use efficiency in a winter wheat–summer maize cropping system

Deficit irrigation (DI) is a water-saving irrigation strategy in which irrigation water is applied at amounts less than full crop-water requirements. Some researchers have suggested that greater increases in water use efficiency (WUE) could be realized if DI was used in combination with water conservation or rainwater harvesting techniques. The objective of this six-year field study was to determine the effect of DI in combination with straw mulch (SM) or plastic film-mulched ridge and straw-mulched furrows (RF) on grain yield and WUE in a winter wheat-summer maize rotation. Interactive effects between the water-saving management practices and N fertilizer rate were also investigated. Results indicated that maize yields in the RF + DI and SM + DI treatments were as much as 1.6 times those in the DI and conventional furrow irrigation (CFI) treatments. Over the six-year study, total maize yield in the RF + DI treatment was 5580 kg/ha more than in the CFI treatment and 6500 kg/ha more than in the DI treatment. Wheat yields in the RF + DI and SM + DI treatments were similar to the CFI treatment but slightly more than in the DI treatment. At harvest, there was no significant difference in water storage in the 0-200 cm soil profile among the RF + DI, SM + DI, DI, and CFI treatments. Nitrogen fertilizer application significantly increased maize and wheat yield compared to the unfertilized treatment; however, there was no further yield response when the N application rate exceeded 120 kg N/ha. In summary, these results indicated that DI in combination with SM or RF practices increased crop yield and WUE in the winter wheat-summer maize crop rotation. Compared to CFI practices, the SM + DI and RF + DI practices reduced the amount of irrigation water applied over a six-year period by about 350 mm.     

Effects of free air carbon dioxide enrichment and nitrogen supply on growth and yield of winter barley cultivated in a crop rotation

The increase in atmospheric CO₂ concentration [CO₂] has been demonstrated to stimulate growth of C₃ crops. Although barley is one of the important cereals of the world, little information exists about the effect of elevated [CO₂] on grain yield of this crop, and realistic data from field experiments are lacking. Therefore, winter barley was grown within a crop rotation over two rotation cycles (2000 and 2003) at present and elevated [CO₂](375 ppm and 550 ppm) and at two levels of nitrogen supply (adequate (N2): 262 kg ha⁻¹ in 1st year and 179 kg ha⁻¹ in 2nd year) and 50% of adequate (N1)). The experiments were carried out in a free air CO₂ enrichment (FACE) system in Braunschweig, Germany. The reduction in nitrogen supply decreased seasonal radiation absorption of the green canopy under ambient [CO₂] by 23%, while CO₂ enrichment had a positive effect under low nitrogen (+8%). Radiation use efficiency was increased by CO₂ elevation under both N levels (+12%). The CO₂ effect on final above ground biomass was similar for both nitrogen treatments (N1: +16%; N2: +13%). CO₂ enrichment did not affect leaf biomass, but increased ear and stem biomass. In addition, final stem dry weight was higher under low (+27%) than under high nitrogen (+13%). Similar findings were obtained for the amount of stem reserves available during grain filling. Relative CO₂ response of grain yield was independent of nitrogen supply (N1: +13%; N2: +12%). The positive CO₂ effect on grain yield was primarily due to a higher grain number, while changes of individual grain weight were small. This corresponds to the findings that under low nitrogen grain growth was unaffected by CO₂ and that under adequate nitrogen the positive effect on grain filling rate was counterbalanced by shortening of grain filling duration.     

Effects of competition between phase separation and ester interchange reactions on the phase behavior in a phase-separated immiscible polyester blend: Monte carlo simulation

The effects of rate ratio of phase separation to ester interchange reactions and the repulsive pair interaction energy on the phase behavior in a phase-separated immiscible polyester blend are investigated using a Monte Carlo simulation method. The time evolution of structure factor and the degree of randomness are monitored as a function of homogenization time. When the phase separation is dominant over ester interchange reactions, the domain size slowly increases with homogenization time. However, when the pair interaction becomes less repulsive, the domain size does not significantly change with homogenization time. On the other hand, when ester interchange reactions are dominant over the phase separation, the homogenization proceeds without a change in the domain size. The higher the extent of phase separation, the lower the increasing rate of the DR. However, when the phase separation is sufficiently dominant, the effect of the extent of phase separation on the increasing rate of the degree of randomness become less significant.     

Numerical prediction of suspended sediment concentrations in the Ariake Sea, Japan, using a time-dependent sediment resuspension and deposition model

The Ariake Sea, a typical semi-closed bay located in Kyushu Island, western Japan, has a maximum tidal range of 6 m in spring tide, and its vast tidal flats are composed of both sandy bottom areas and muddy bottom areas. In this study, two-dimensional depth-averaged finite difference numerical models have been developed for predicting the tidal flow velocity and suspended sediment concentration in the Ariake Sea. In the suspended sediment transportation model, a time-dependent sediment resuspension and deposition process was modeled as a response to the tidal flow by considering the presence of cohesive bottom sediment. The shifting-particles method, known as an operator-splitting technique, was used for time integration of the convective-dispersion equation. The model results were compared with in situ measurements of suspended sediment concentration and tidal flow velocity at several points in Isahaya Bay—located at the western part of the Ariake Sea—and also with the estimated suspended sediment concentration distribution via a Landsat Thematic Mapper image. The results indicated that the models were able to predict the measured values for suspended sediment concentration and tidal flow velocity, as well as the spatial distribution pattern of the suspended sediment concentration as estimated by the Landsat Thematic Mapper image.     

Productivity and residual benefits of grain legumes to sorghum under semi-arid conditions in south-western Zimbabwe: Unravelling the effects of water and nitrogen using a simulation model

The APSIM model was used to assess the impact of legumes on sorghum grown in rotation in a nutrient-limited system under dry conditions in south-western Zimbabwe. An experiment was conducted at Lucydale, Matopos Research Station, between 2002 and 2005. The model was used to simulate soil and plant responses in the experiment. Sequences of cowpea (Vigna unguiculata), pigeonpea (Cajanus cajan), groundnut (Arachis hypogaea) and sorghum (Sorghum bicolor) were used in the rotations. Legumes accumulated up to 130 kg of N ha⁻¹ which was potentially available for uptake by sorghum in the following season. The APSIM model predicted total biomass, grain and N yields of the legume phase within the experimental error and performed well in predicting sorghum yield and N supplied in the rotation after cowpea and groundnut. The model generally under-predicted sorghum total biomass and grain yield after pigeonpea. Observed patterns of crop water use, evaporative losses during the dry season and re-charge of soil profile at the start of the rainy season were generally well predicted by the model. An assessment of output on sorghum N and water stresses in the rotation indicated that the legume–cereal rotation is more driven by soil nitrogen availability than water availability even under semi-arid conditions. Further legume–cereal rotation analysis using the model will assist in the understanding of other processes in the rotations in dry environments.