Key soil and topographic properties to delineate potential management classes for precision agriculture in the European loess area

Recent advances in on-the-go soil sensing, terrain modelling and yield mapping have made available large quantities of information about the within-field variability of soil and crop properties. But the selection of the key variables for an identification of management zones, required for precision agriculture, is not straightforward. To investigate a procedure for this selection, an 8 ha agricultural field in the Loess belt of Belgium was considered for this study. The available information consisted of: (i) top- and subsoil samples taken at 110 locations, on which soil properties: textural fractions, organic carbon (OC), CaCO₃ and pH were analysed, (ii) soil apparent electrical conductivity (EC_a) obtained through an electromagnetic induction based sensor, and (iii) wetness index, stream power index and steepest slope angle derived from a detailed digital elevation model (DEM). A principal component analysis, involving 12 soil and topographic properties and two EC_a variables, identified three components explaining 67.4% of the total variability. These three components were best represented by pH, EC_a that strongly associated with texture and OC. However, OC was closely related to some more readily obtainable topographic properties, and therefore elevation was preferred. A fuzzy k-means classification of these three variables produced four potential management classes. Three-year average standardized yield maps of grain and straw showed productivity differences across these classes, but mainly linked to their landscape position. In the loess area with complex soil-landscape interactions pH, EC_a and elevation can be considered as key properties to delineate potential management classes.     

CT diagnosis of occipital condyle fracture in a dog presented for severe cervical hyperesthesia

A 9-month-old male entire Doberman Pinscher presented with acute onset of severe cervical hyperesthesia after a fall. Neurological examination revealed a normal gait with low head carriage and severe cervical hyperesthesia. A CT scan of the cervical vertebral column revealed the presence of a comminuted fracture at the dorsomedial aspect of the right occipital condyle and sclerosis of the underlying bone. Medical management was initiated consisting of an external bandage, strict rest, and pain medication. Due to the lack of clinical improvement, the dog was euthanized 2 months after diagnosis. Histopathology of the lesion was compatible with a healing fracture.     

Improving survival,growth rate,and animal welfare in piglets by avoiding teeth shortening and tail docking

Piglets are subjected to several painful procedures during their first week of life, including ear tagging, teeth clipping or grinding (although routinely prohibited in Europe), tail docking (although routinely prohibited in Europe), needle injections (vaccination and iron injection), and castration might be performed for male piglets. All these management practices cause pain and stress to the newborn piglets. The hypothesis of this experiment was that reducing painful interventions during the first week of life results in better zootechnical performance of the piglets, reduced piglet mortality, and that the overall welfare is improved. To investigate this, the 4 lightest piglets of the experimental group (EE) were not subjected to tail docking and teeth clipping or grinding. The 4 lightest piglets of the control group (CL) and the other piglets of the experimental group (EC) and the control group (CC) received treatments as the common practice. There were differences in behavior, but there were no differences regarding weight at weaning between CL and EE. However, mortality rate was higher in the lightest piglets, that is, CL (34.1%) and EE (23.0%), whereas mortality rate in the other piglets was much lower (9.0% for CC and 9.3% for EC). This information can be useful for a veterinarian to advise farmers on whether painful interventions should be performed.     

Characterization of nitrogen dynamics in a pasture soil by electromagnetic induction

The aim of this study was to investigate how electromagnetic induction can be used to improve the characterization of N dynamics in a 1.2 ha pasture. The soil apparent electrical conductivity (ECa) was measured by electromagnetic induction using an EM38DD. At 116 locations, soil samples were taken according to a clustered sampling design, three times during one winter, and analyzed for the NO₃^––N content in the topsoil (0–60 cm). Management zones were delineated using a fuzzy k-means classification of the interpolated ECa measurements. Two ECa zones were found, reflecting mainly differences in soil texture. Since the mean NO₃^––N content was different for the two ECa zones (24 and 65 kg/ha in November 2002), the residuals were interpolated using stratified simple kriging. This allowed evaluating the NO₃^– dynamics during the winter in both zones; one ECa zone showed a higher risk for NO₃^– losses than the other calling for a site-specific N management. As a validation, NO₃^––N was interpolated using ordinary kriging without stratification. This resulted in similar zones confirming the usefulness of the ECa measurements to assess N-specific management zones, even within small fields.     

Release of angiotensin I converting enzyme (ACE) inhibitory activity during in vitro gastrointestinal digestion: from batch experiment to semicontinuous model

Gastrointestinal digestion is of major importance in the bioavailability of angiotensin I converting enzyme (ACE) inhibitory peptides, bioactive peptides with possible antihypertensive effects. In this study, the conditions of in vitro gastrointestinal digestion leading to the formation and degradation of ACE inhibitory peptides were investigated for pea and whey protein. In batch experiments, the digestion simulating the physiological conditions sufficed to achieve the highest ACE inhibitory activity, with IC(50) values of 0.076 mg/mL for pea and 0.048 mg/mL for whey protein. The degree of proteolysis did not correlate with the ACE inhibitory activity and was always higher for pea than whey. In a semicontinuous model of gastrointestinal digestion, response surface methodology studied the influence of temperature and incubation time in both the stomach and small intestine phases on the ACE inhibitory activity and degree of proteolysis. For pea protein, a linear model for the degree of proteolysis and a quadratic model for the ACE inhibitory activity could be constituted. Within the model, a maximal degree of proteolysis was observed at the highest temperature and the longest incubation time in the small intestine phase, while maximal ACE inhibitory activity was obtained at the longest incubation times in the stomach and small intestine phase. These results show that ACE inhibitory activity of pea and whey hydrolysates can be controlled by the conditions of in vitro gastrointestinal digestion.     

Modes of Action of Pantoea agglomerans CPA-2, an Antagonist of Postharvest Pathogens on Fruits

Pantoea agglomerans CPA-2 is an effective antagonist against the postharvest pathogens Penicillium digitatum and Penicillium italicum on citrus fruits but its mode of action is unknown. Possible mechanisms studied in this work were antibiosis, induced resistance, competition and production of chitinolytic enzymes. P. agglomerans CPA-2 was unable to produce antibiotics or chitinolytic enzymes under the conditions tested. Induction of resistance by P. agglomerans CPA-2 was studied in oranges by measuring phenylalanine ammonia lyase and peroxidase enzyme activity in the orange peel at different time points after inoculation with the antagonist and/or the pathogen. No significant augmentation of enzyme activity after inoculation of oranges with P. agglomerans CPA-2 in the presence or absence of the pathogen was observed. P. agglomerans was effective only when it is in close contact with the pathogens. Competition for nutrients was studied using tissue culture plates with cylinder inserts, which allowed competition for nutrients to be studied without competition for space since physical contact between pathogen and antagonist was avoided. The presence of P. agglomerans in the tissue culture wells clearly decreased the germination of Penicillium conidia present in the cylinder when diluted orange peel extract or diluted potato dextrose broth was the nutrient source. Germination of Penicillium conidia, however, was almost completely inhibited when pathogen and antagonist were in physical contact. These results indicate that competition for nutrients is one of the modes of action of P. agglomerans CPA-2, but that physical contact between pathogen and antagonist is important for effective control.     

A floating sensing system to evaluate soil and crop variability within flooded paddy rice fields

Continuous paddy rice cultivation requires fields to be flooded most of the time limiting seriously the collection of detailed soil information. So far, no appropriate soil sensor technology for identifying soil variability of flooded fields has been reported. Therefore, the primary objective was the development of a sensing system that can float, acquire and process detailed geo-referenced soil information within flooded fields. An additional objective was to determine whether the collected apparent electrical conductivity (EC_a) information could be used to support soil management at a within-field level. A floating sensing system (FloSSy) was built to record EC_a using the electromagnetic induction sensor EM38, which does not require physical contact with the soil. Its feasibility was tested in an alluvial paddy field of 2.7 ha located in the Brahmaputra floodplain of Bangladesh. The high-resolution (1 × 1 m) EC_a data were classified into three classes using the fuzzy k-means classification method. The variation among the classes could be attributed to differences in subsoil (0.15–0.30 m below soil surface) bulk density, with the smallest EC_a values representing the lowest bulk density. This effect was attributed to differences in compaction of the plough pan due to differential puddling. There was also a significant difference in rice yield among the EC_a classes, with the smallest EC_a values representing the lowest yield. It was concluded that the floating sensing system allowed the collection of relevant soil information, opening potential for precision agriculture practices in flooded crop fields.     

Identifying potential management zones in a layered soil using several sources of ancillary information

Variation in soil texture has a profound effect on soil management, especially in texturally complex soils such as the polder soils of Belgium. The conventional point sampling approach requires high sampling intensity to take into account such spatial variation. In this study we investigated the use of two ancillary variables for the detailed mapping of soil texture and subsequent delineation of potential management zones for site‐specific management. In an 11.5 ha arable field in the polder area, the apparent electrical conductivity (EC_a) was measured with an EM38DD electromagnetic induction instrument. The geometric mean values of the EC_a measured in both vertical and horizontal orientations strongly correlated with the more heterogeneous subsoil clay content (r = 0.83), but the correlation was weaker with the homogenous topsoil clay content (r = 0.40). The gravimetric water content at wilting point (θg_{(?1.5 MPa)}) correlated very well (r = 0.96) with the topsoil clay content. Thus maps of topsoil and subsoil clay contents were obtained from 63 clay analyses supplemented with 117θg_{(?1.5 MPa)} and 4048EC_a measurements, respectively, using standardized ordinary cokriging. Three potential management zones were identified based on the spatial variation of both top and subsoil clay contents. The influence of subsoil textural variation on crop behaviour was illustrated by an aerial image, confirming the reliability of the results from the small number of primary samples.