J De Smet

Phosphate enrichment in the sandy loam soils of West-Flanders, Belgium

The last three decades, pig breeding has evolved towards a specialised, large scaled, land independent bio-industry in the province of West-Flanders. Subsequently, in certain regions, very high amounts of liquid pig manure are produced each year. This pig slurry is used as a fertilizer at a rate which very often exceeds normal agricultural practices. Because of the nonequilibrium between the phosphorus crop requirements and the P-inputs, phosphates accumulate in the soil. However, the phosphate sorption capacity of a soil is limited. Once the sorption capacity is exceeded, phosphates will start leaching through the soil profile. Since, during winter, in these areas, the groundwater table is situated at a depth of less than 1.0 m, phosphate breakthrough might take place. In the sandy loam soil region (± 1000 km2) of the province, an inventory of the P status of the soil was made. The region was sampled according to a regular grid with 2 km intervals. At random, some sample points were only 500 m apart. This resulted in a total of 296 samplings. In view of fertilizer recommendations, lactate extractable P of the plough layer (0–30 cm) was determined. A maximum value of 101 mg P 100 g-1 of air dry soil, a minimum value of 6 mg P 100 g-1 and a median value of 31 mg P 100 g-1 were found, indicating that for half of the spots monitored, the P status of the soil is high to very high. An oxalate extraction was done to investigate the phosphate saturation of the soil profile (0–90 cm). Based on a critical phosphate saturation degree of 30%, more than half of the soil profiles are phosphate saturated. Phosphate leaching at a rate higher than 0.1 mg ortho-P l-1 at a depth of 90 cm can be expected. Therefore, a restriction of the P fertilization should be highly recommended. The geostatistical processing of the data using block kriging resulted in a spatial continuous estimate of the phosphate saturation degree. A good agreement was found between the pig density and the phosphate saturation degree of the soil profile.

Design and Wrinkling Behavior of a Contact Lens With an Integrated Liquid Crystal Light Modulator

A new design of a spherically molded liquid crystal cell intended for embedding in a contact lens is proposed. Wrinkle formation in these cells was investigated and a correlation was found between the total thickness of the cell and its smoothness. Smooth cells with minimal thickness were obtained by using an asymmetric configuration with a thin layer at the convex side and a thicker but threshold dependent layer at the concave side. Active liquid crystal cells filled with a guest-host liquid crystal mixture exhibited uniform light modulation along their surface, paving the way towards a modulation-based contact lens display.

Effect of soil properties on the kinetics of phosphate release

Abstract The kinetics of the phosphate release by 35 non‐calcareous soil samples were investigated by consecutive extraction of the soil. The soil samples covered a wide range of texture, pH and degree of phosphate saturation. For all soils, phosphate release initially followed first order kinetics. With time, the process became linear to the logarithm of time. These relationships were used to distinguish between the initial fast process of phosphate desorption and the much slower diffusion‐dissolution process. The influence of physico‐chemical soil properties on the parameters describing the two processes was investigated using multiple regression analysis. The total amount of reversibly adsorbed phosphate was highly significant correlated to the oxalate extractable phosphate of the soil: the former approximated 33 % of the latter. The rate constant of the initial desorption process was mainly influenced by the pH of the soil: increasing the pH positively affects the desorption rate. The kinetics of the ...

Variability of the phosphate saturation degree of the sandy loam soils in west‐flanders, Belgium

The variability of the phosphate sorption capacity (PSC) and the phosphate saturation degree (PSD) of the soil profile was studied in the sandy loam soil region (+/-1000 km(2)) of West-Flanders at different scales. In the frame of a regional inventory, the soil profile was sampled at 2000 m intervals on a square grid. In total, 296 observations were made. Additionally, in this area, 21 fields were sampled in detail: 15 augerings per field were made. Finally, on one field, seven observations were made at the micro scale: five augerings within a circular area of 30 m(2). All soil samples were analyzed for ammoniumoxalate extractable Fe, Al and P and the PSC and the PSD were calculated. The coefficient of variation (CV) of the PSC of the whole soil profile 0-90 cm was found to be 7% on the micro scale, 20% on the field scale and 28% on the regional scale. The CV of the PSD was found to be 9%, 21%, and 48% respectively. This means already quite a proportion? about 20%, in variation in PSC and PSD is situated at short distances (< 5m) Most of the variability in PSC is already found at the field level. On the contrary, the CV of the PSD is twice as high on the regional scale compared to the field scale. This may be explained by the regional structure of the P inputs, due to the local intensification of pig breeding activities. The criterion phosphate saturation is stochastically approached at the field scale. In the study area, the mean field averaged CV of the PSD was 21%. Taking into account the uncertainty when sampling, supposing a lognormal distribution of the PSD, the critical PSD of 24% is translated into a practical threshold PSD of 26% if 15 measurements per field are taken and a probability of 95% is pursued.

Residual soil nitrate under intensive agriculture

Abstract From November 1991 until January 1992, a 956 km2 area of the loamy sand to sandy loam region of West‐Flanders (Belgium) was sampled for residual soil nitrate, i.e. the amount of nitrate nitrogen in the soil profile at the end of the growing season. In total, 296 soil samples were taken to a depth of 90 cm (in layers of 30 cm) on arable land only. On basis of the rate of the mineral nitrogen losses occuring during this extended period, all residues present on the date of 21 November 1991 were estimated. This date corresponded with the start of the sampling campaign and is close to the end of the growing season. The residues were lognormally distributed around a mean of 177 kg NO3 ‐‐N/ha with a minimum of 24 and a maximum of 881 kg NO3 ‐‐N/ha. Classifying the residues into groups according to the preceding crop, the lowest residues appeared after beets (a median of 59 kg NO3 ‐‐N/ha). Between cereals, maize, potatoes, and vegetables, no significant differences were found. Each of these four groups h...

Slat collimated multipinhole human brain SPECT

A new brain SPECT system based on multipinhole collimation has been designed and the properties have been studied with Monte Carlo simulations. Results show the system has better resolution and acceptable sensitivity compared to commercial SPECT systems.

Effect of application of pig slurry on soil penetration resistance and sugar-beet emergence

Abstract The effect of the application of 50, 100 and 200 t ha−1 of pig slurry on soil penetration resistance, and sealing of the soil surface as a result of rainfall, was studied for a sandy loam soil in the field and under laboratory conditions, respectively. In the field, after slurry application and ploughing, a somewhat higher penetration resistance in the ploughed layer was noticed on the plots that had been fertilized with the liquid pig manure. In the laboratory, a superficial application of the pig manure resulted, after simulated rainfall, in lower penetration resistance of the soil surface. However, mixing the slurry with the soil gave a higher penetration resistance. Additionally, the emergence of sugar beet seeds and the oxygen diffusion rate in the soil under laboratory conditions was monitored. The emergence of the sugar beet seeds was much slower in the soil that received pig manure, but final emergence was similar in all treatments. The oxygen diffusion rate showed no difference at all among treatments. An application of 200 t ha−1 pig slurry increased the soil salinity from 1 to 6 mS cm−1.

SiGe micromirrors for optical applications

Micromirrors are a typical example of Micro-Electromechanical Systems (MEMS) with many applications including optical scanners, optical switching, projection displays, etc. We have succeeded in producing MEMS micromirrors in a SiGe structural layer, which can be used to realize CMOS-integrated MEMS structures. Several pixel designs were simulated using COMSOL multiphysics and subsequently verified in hardware. They differ in mirror size, hinge length and number of attracting electrodes (two or four). One particular mirror design enables variable Pulse Width Modulation (PWM) addressing. In this design, the mirror switches between two extreme states with a variable duty cycle determined by two generic high voltage signals and two CMOS-compatible pixel-specific DC voltages applied to the four attracting electrodes. The processed arrays were subjected to Laser Doppler Vibrometer (LDV) measurements in order to verify the simulation results. The simulated and measured pull-in voltages are compared for 8, 10 and 15μm mirrors. The agreement between simulation and measurement lies within the expectations, which is an encouraging result for future designs.