GB2562275A

GB2562275A - Monitoring of an agricultural product and/or the environment in the vicinity of the agricultural product

Info

Publication number: GB2562275A
Application number: GB1707512.8A
Authority: GB
Inventors: Rutolo Massimo; Covington James
Original assignee: University of Warwick
Current assignee: University of Warwick
Priority date: 2017-05-10
Filing date: 2017-05-10
Publication date: 2018-11-14
Also published as: GB201707512D0

Abstract

A system 1 is used for gas and/or volatile organic compound monitoring of an agricultural product 2 in a storeroom, transportation container or bed or field 3 containing a set of gas sensor units 11. Gas sensors 14 may detect gases, vapours and/or volatile organic compounds which may be indicative of a disease, such as bacterial soft rot, or a disorder such as black heart in the agricultural product or to monitor the condition of the agricultural product, such as freshness or ripeness, or track the level of a chemical used to treat the agricultural product, such as a sprouting suppressant. The agricultural product 2 may be a crop such as a potato, onion or other vegetable. The gas sensors 14 are selected from metal-oxide gas sensors, electrochemical gas sensors, conducting/composite polymer gas sensors, photoacoustic gas sensors, piezoelectric gas sensors(s), infrared gas sensors or photoionization detector gas sensors.

Description

Monitoring of an agricultural product and/or the environment in the vicinity of the agricultural product

Field of the Invention

The present invention relates to gas and/or volatile organic compound (VOC) monitoring of an agricultural product and/or the environment in the vicinity of the agricultural product.

Background

The United Nations Food and Agriculture Organization (FAO) estimates that between 40 to 50 % of root and tuber crops, fruit and vegetables produce is wasted each year. In the United Kingdom, one staple crop that experiences significant losses is potato tubers. The majority of this loss occurs in post-harvest storage and is caused by a bacterial disease known as “soft rot”, with unofficial estimates of circa 5 % of the entire crop. The term soft rot is used for the bacterial disease in stored potatoes, while blackleg is generally used to describe the disease whilst in the growing crop, where the bacterium causes blackening of the plant stems.

The pathogen found most frequently in the UK associated with soft rot (and blackleg) is Pectobacterium carotovorum ssp. carotovorum, but Pectobacterium atrosepticum is also common. Bacterial soft rot in store and blackleg can also be caused by several strains of Dickeya spp., more recently identified as D. Dianthicola, D. dadantii, D. zeae and D. solani as well as by P. carotovorum subsp. brasiliensis and P. wasabiae. Other diseases, namely late blight (caused by the oomycete Phytophthora infestans) and dry rot (caused by fungal Fusarium species) have been reported to provide a means for secondary infection of both subspecies of Pectobacterium.

In the United Kingdom, post-harvest, potato tubers are placed in storage facilities, where they are kept from late September until June of the following year (though this varies with geographic location in other countries). On average, each store room can contain several hundred, one ton boxes of produce. This is the most widespread practice for storing the crop in the UK, although other approaches are also employed worldwide. Monitoring the disease status of potatoes in stores is challenging, due to poor access. However, in an attempt to extend the storage life of these potatoes, stores are environmentally controlled with refrigerated air forced through the tubers. When soft rot is well developed in multiple tubers, a very strong odour is produced that can easily be detected by human olfaction.

Most research into soft rot disease has relied on biological approaches for detection and identification of the causal pathogens Pectobacterium and Dickeya and these techniques are described in R. Czajkowskiet al.: “Control of blackleg and tuber soft rot of potato caused by Pectobacterium and Dickeya species: a review”, Plant Pathology, volume 60, pages 999 to 1013 (2015).

Previous work on early detection of potato storage diseases has also been carried out by means of gas or volatile organic compounds (VOCs) analysis over many years, dating back to J. L. Varns and R. Shaw: “An internal standard for rapid analysis of potato sugars by gas chromatography”, Potato Research, volume 16, pages 183 to 187 (1973) and J. L. Varns & Μ. T. Glynn: “Detection of disease in stored potatoes by volatile monitoring”, American Journal of Potato Research, volume 56, pages 185-197 (1979) followed by D. R. Waterer and M.K. Pritchard: “Monitoring of volatiles: A technique for detection of soft rot (Erwinia carotovora) in potato tubers”, Journal Canadian Journal of Plant Pathology, volume 6, pages 165-171 (1984) and D. R. Waterer and M.K. Pritchard: “Volatile monitoring as a technique for differentiating between E. carotovora and C. sepedonicum infections in stored potatoes”, American Journal of Potato Research, volume 61, pages 345-353 (1984). Most of this research has been based on gas chromatography (GC) or gas chromatograph mass spectrometry (GC-MS) in order to identify specific chemical compounds that might be characteristic markers of infected potato tubers and reference is also made to B. P. J de Lacy Costello et al.: “Identification of volatiles generated by potato tubers (Solanum tuberosum CV: Maris Piper) infected by Erwinia carotovora, Bacillus polymyxa and Arthrobacter sp”, Plant Pathology, volume 48, pages 345 to 351 (1999), B. P. J de Lacy Costello etal.: “Gas chromatography-mass spectrometry analyses of volatile organic compounds from potato tubers inoculated with Phytophthora infestans or Fusarium coeruleum”, Plant Pathology, volume 50, pages 489 to 496 (2001), A. C. Kushalappa etal.: “Volatile Fingerprinting (SPME-GC-FID) to Detect and Discriminate Diseases of Potato Tubers”, Plant Disease, volume 86, pages 131 to 137 (2002), L. H. Lui etal.: “Volatile metabolic profiling for discrimination of potato tubers inoculated with dry and soft rot pathogens”, American Journal of Potato Research, volume 82, pages 1 to 8 (2005), D. Lyew et al.: “Changes in volatile production during an infection of potatoes by Erwinia carotovora”, Food Research International, volume 34, pages 807 to 813 (2001) and C. Ratti et al., Proceedings ofthe International Conference on Harvest and Postharvest Technologies, in: Collection and Analysis of Headspace Volatiles for Disease Detection in Stored Potatoes, pages 255 to 261 (1995). A large number of different volatile biomarkers, however, have been identified in many previous studies. These studies differed in hosts, pathogens, environmental factors, methodologies of experimentation, instrument limitations and usage, different analytical and data processing techniques, but above all, the relative time frames under consideration and this has added to the complexity and hampered comparisons of the different approaches employed or the identification of a few key volatiles associated with disease. Furthermore, according to R. A. Dixon “The phenylpropanoid pathway and plant defence-a genomics perspective”, Molecular Plant Pathology, volume 3, pages 371 to 390 (2002) and 0. Fiehn: “Metabolomics - the link between genotypes and phenotypes”, Plant Molecular Biology, volume 48, pages 155 to 171 (2002), plants produce a very large number of volatile metabolites, both before and after harvest. In addition, gas chromatography and gas chromatograph mass spectrometry are expensive, require expert training, specialized infrastructure and, therefore, are unsuitable for continuous monitoring in real stores.

Gas and volatile organic compound (VOCs) analysis with electronic noses in agriculture has been reported for many years, for example in C. Fi et al.: “Gas sensor array for blueberry fruit disease detection and classification”, Postharvest Biology and Technology, volume 55, pages 144 to 149 (2010), F. Torri etal.: “Shelf life evaluation of fresh-cut pineapple by using an electronic nose”, Postharvest Biology and Technology, volume 56, pages 239 to 245 (2010) and A. D. Wilson: “Diverse applications of electronic-nose technologies in agriculture and forestry”, Sensors, volume 13, pages 2295 to 2348 (2013), and early work with electronic noses and potato tuber diseases was done almost two decades ago by B. P. J de Facy Costello et al.: “The development of a sensor system for the early detection of soft rot in stored potato tubers”,

Measurement Science and Technology, volume 11, pages 1685 to 1691 (2000). Their study was based on the fabrication and testing of purpose-built sensors for general monitoring of VOCs associated with soft rot disease development and therefore, not available to the wider community. More recently, a study was completed with both gas chromatography and gas chromatograph mass spectrometry coupled with a commercial electronic nose for the detection of the quarantine potato diseases brown rot and ring rot and reference is made to E. Biondi et al.: “Detection of potato brown rot and ring rot by electronic nose: from laboratory to real scale”, Talanta, volume 129, pages 422 to 430 (2014). In a previous study, M. F. Rutolo etal.: “Early identification of potato storage disease using an array of metal-oxide based gas sensors”, Postharvest Biology and Technology, volume 116, pages 50 to 58 (2016), the inventors reported on the use of use of a commercial electronic nose (Alpha-MOS, Fox 3000) employing metal-oxide gas sensors for early detection of potato soft rot. Although good results were obtained, it still required the use of an expensive commercial electronic nose instrument.

Summary

According to a first aspect of the present invention there is provided a system for gas and/or volatile organic compound monitoring of an agricultural product (such as potatoes), for example to detect a disease (such as bacterial soft rot) or a disorder in the agricultural product (such as black heart) and/or to monitor the condition of the agricultural product (such as freshness or ripeness), and/or of the environment in the vicinity of the agricultural product, for example to track the level of a chemical used to treat the agricultural product (such as a sprouting suppressant). Herein, for brevity, the term “gas and/or volatile organic compound monitoring” is also simply referred to as “gas monitoring”.

The system comprises a set of one of more gas and/or volatile organic compound sensor units disposed in a bed or field, storeroom or container for transportation (such a ship or lorry container) for sensing gas(es) and/or volatile organic compound(s) (herein also referred to as “vapour(s)”) generated by the agricultural products or provided to treat the agricultural product. Herein, for brevity, the term “gas and/or volatile organic compound sensor unit” is also simply referred to as a “gas sensor unit”.

The one or more gas sensor units each comprise at least one respective gas sensor. The gas sensor(s) comprise metal-oxide gas sensor(s), electrochemical gas sensor(s), conducting/composite polymer gas sensors(s), photoacoustic gas sensor(s), piezoelectric gas sensors(s), infrared gas sensor(s) and/or photoionization detector gas sensor(s). Herein, for brevity, the term “gas and/or volatile organic compound sensor” is also simply referred to as a “gas sensor”.

Thus, the system can be used for symptomatic and pre-symptomatic detection of one or more diseases and disorders or the condition of the agricultural product, and/or for monitoring the level of one or more chemicals used to treat the agricultural product by, for example, sensing carbon monoxide, ethylene oxide, an alcohol, nitric oxide and/or other gases or volatile organic compounds.

The gas sensor unit may contain two or more gas sensors. If the gas sensor unit contains two or more gas sensors, then the gas sensors may contain gas sensors of different types and/or gas sensors of the same type, but configured to or used to detect different gases or vapours.

The vicinity of the agricultural product may include a space (or “volume”) surrounding the product (typically of the order of tens or hundreds of centimetres from the surface of product) in, or through which, gaseous atmosphere sits, circulates or flows. The vicinity of the agricultural product may include headspace above or adjacent to the headspace the agricultural product, which may be more than tens or hundreds of centimetres from the surface of product.

Gaseous atmosphere maybe collected or drawn in the vicinity of or near to the agricultural product (e.g. in the headspace above the product) and carried via a duct, pipe or conduit to a gas sensor unit. Thus, the gas sensor unit need not necessarily be located in the close to the agricultural product.

The one or more gas sensors units may each comprise communication module(s) for transmitting a signal to a remote base unit and, optionally, receiving a signal (e.g. signal configuration instructions or threshold values) from the base unit. The communication module(s) may include a wired network interface, such as Ethernet, and/or a wireless network interface, for example, to a WiFi, Bluetooth (RTM) or other type of wireless network. The wireless network may be a proprietary wireless network.

Each gas sensor unit may be configured to transmit a signal carrying a value of a measurement. Each gas sensor unit may be configured to determine whether the measurement value exceeds a predetermined threshold and to transmit a signal signalling an outcome of the determination. The gas sensors maybe configured to transmit a signal periodically, for example every 5,10, 30 or 60 minutes. Each gas sensor unit may be configured to transmit the signal signalling an outcome of the determination in response to a positive determination. The gas sensors maybe configured to transmit in response to a predetermined condition, such as detection of a given analyte (i.e. gas, vapour and/or volatile organic compound generated by the agricultural products).

The system may include one or more temperature, humidity, barometric, accelerometer, light and/or flowmeter sensors. The system may include another gas sensor, such as a CO2 sensor, for monitoring store conditions.

At least one of the at least one gas sensor units may be integrated into refrigeration or ventilation system, for example, in an appliance, in a duct, pipe or conduit, or in a port, outlet or grille.

The system may further comprise a base unit comprising a computer system configured to receive a value of measurement from at least one of the one or more gas sensors units, to determine whether the measurement value exceeds a predetermined threshold, and, in response to a positive determination, to signal the positive determination.

The computer system may be configured to receive an outcome of a determination whether the measurement value exceeds a predetermined threshold from at least one of the one or more gas sensors units, and, in response to the determination being a positive determination, to signal the positive determination.

The system may further comprise a base unit comprising a computer system configured to receive an outcome of a determination whether the measurement value exceeds a predetermined threshold from at least one of the one or more gas sensors units, and, in response to the determination being a positive determination, to signal the positive determination.

At least of the one or more gas sensor units may be portable, for example, taking the form of a hand-held gas sensor.

The system may be configured to monitor the presence or onset of a disease or disorder. Additionally or alternatively, the system may be configured to monitor the condition of the agricultural product, for example, its freshness or ripeness.

Additionally or alternatively, the system may be configured to the level of chemicals used to treat the agricultural product (which maybe held in an enclosure or may still yet to be harvested), such as a sprouting suppressant, a preservative, a fungicide or the like.

According to a second aspect of the present invention there is provided an installation comprising a storeroom and a system according to the first aspect of the present invention, wherein the set of one or more gas sensor units are installed in the storeroom.

According to a third aspect of the present invention there is provided an installation comprising a transportation container and a system according to the first aspect of the present invention, wherein the set of one or more gas sensor units are installed in the transportation container.

According to a fourth aspect of the present invention there is provided an installation comprising a bed or field and a system according to the first aspect of the present invention, wherein the set of one or more gas sensor units are installed in the bed or field.

The installation may be a building, greenhouse or type of enclosure covering or housing the bed or field (such as a polytunnel). The enclosure maybe provided with heating/cooling, irrigation and/or environmental control.

The installation may include the agricultural product. The agricultural product may be stored in rigid containers (such as boxes), flexible containers (such as bags or sacks) or loose.

According to a fifth aspect of the present invention there is provided a method of gas monitoring of an agricultural product and/or the environment in the vicinity of the agricultural product using a set of one or more gas sensor units disposed in a storeroom, a transportation container or a bed or field, for sensing gas(es) and/or volatile organic compound(s) generated by the agricultural product or provided to treat the agricultural product, wherein the one or more gas sensors units each comprise at least one respective gas sensor, wherein the gas sensor(s) comprises metal-oxide gas sensor(s), electrochemical gas sensor(s), conducting/composite polymer gas sensors(s), photoacoustic gas sensor(s), piezoelectric gas sensors(s), infrared gas sensor(s) or photoionization detector gas sensor(s).

According to a sixth aspect of the present invention there is provided a system for gas monitoring of an agricultural product and/or the environment in the vicinity of the agricultural product. The system comprises at least one gas sensor unit, disposed in packaging, for sensing gas(es) and/or volatile organic compound(s) generated by the agricultural products or provided to treat the agricultural product. The one or more gas sensors units each comprise at least one respective gas sensor. The one or more gas sensor(s) comprise metal-oxide gas sensor(s), electrochemical gas sensor(s), conducting/composite polymer gas sensors(s), photoacoustic gas sensor(s), piezoelectric gas sensors(s), infrared gas sensor(s) and/or photo ionisation detector-gas sensor(s).

The packaging may be primary packaging (for example, plastic wrapping, in direct contact with the product), secondary packaging (for example, cardboard boxes), or tertiary packaging (for example unit loads).

Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is schematic diagram of a system for detecting disease in an agricultural product stored in containers in a storeroom, silo or transport container comprising a set of one or more sensors units;

Figure 2 is schematic diagram of a system for detecting disease in an agricultural product stored loose in a storeroom, silo or transport container comprising a set of one or more sensors units;

Figure 3 is schematic diagram of a system for monitoring onset and/or development of rotting of a crop in a field;

Figure 4 is a schematic diagram of a metal-oxide gas sensor;

Figure 5 is a schematic diagram of an electrochemical gas sensor;

Figure 6 is a schematic diagram of an infrared- type gas sensor;

Figure 7 is a schematic diagram of a photo ionisation detector gas sensor;

Figure 8 is schematic diagram of a conducting polymer gas sensor;

Figure 9 is a schematic diagram of a piezoelectric based gas sensor;

Figure 10 is a schematic diagram of a photoacoustic spectroscopy based gas sensor; Figure 11 is a process flow diagram of a first method of operating a gas sensor; and Figure 12 is a process flow diagram of a second method of operating a gas sensor.

Detailed Description of Certain Embodiments

In the following like parts are denoted by like reference numerals.

Referring to Figures 1 and 2, a system 1 is shown for detecting disease or disorder in a quantity of agricultural product 2 (herein also referred to as “crop”) which is stored or held in an enclosure 3.

An individual item or part of the agricultural product 2 may be referred to as an “item” or “piece”, or by the name normally given to an individual item, such as, for example, in the case of potato maybe “a potato” or “a tuber”, in the case of an onion maybe “an onion” or “a bulb” and so on. Individual items maybe grouped, for example, into bunches.

The agricultural product 2 may take the form of potatoes or other type of root and tuber, such as sugar beets, cassavas, onions, carrots, parsnips, or swedes. The agricultural product 2 may be a fruit or vegetable, cereal, oilseed or other crop, such as rapeseed.

The agricultural product 2 may be stored in rigid or flexible containers 4, such as boxes, for example ι-ton boxes, bags or sacks which maybe stacked in one or more towers 5, or loose. Different types of product 2 may be stored in the same in the enclosure 3.

The enclosure 3 can be used for storing or transporting the agricultural product 2. The enclosure 3 may take the form of a storeroom, grain store, silo, shed, barn, or other form of agricultural building. The enclosure 1 may take the form of shipping container, lorry trailer cargo holder or other transportation container.

The enclosure 3 may be provided with one or more appliances 6 for controlling temperature and/or humidity, e.g. air-conditioning, chiller units, and/or for providing ventilation. Particularly in the case of bulk storage, the enclosure 3 may be provided with a network of horizontal and/or vertical ducts 7 (having ventilation holes) on the crop 2 is stored. The enclosure 3 may have walls 8, which include thermal insulation (not shown). The enclosure 3 may have a volume of between 1 to 10,000 m3 or more.

In some cases, for example in transportation, the enclosure 3 may have a volume of between 20 to 500 m3. In other cases, for example for storage, the enclosure 3 may have a volume of between 500 to 10,000 m3.

The system 1 can be used for symptomatic and pre-symptomatic detection of soft rot or other diseases or disorders in agricultural products 2, such as potatoes, carrots, parsnips and other roots and tubers, and in onions and other bulbs, or the condition of the agricultural product, for example, to determine freshness or ripeness of the product, and/or for monitoring the level of one or more chemicals used to treat the agricultural product. A chemical used to treat the product may include sprouting suppressant, such as chlorpropham (or “CIPC”), a preservative, a fungicide or the like. Thus, the system 1 can be used, for example, to monitor distribution of the chemical throughout the enclosure and/or to determine whether concentration of the chemical falls below a threshold.

The system 1 includes a set of one or more gas and/or volatile organic compound (VOC) sensor units n (herein, for brevity, simply referred to as “gas sensor units”) disposed in the enclosure 3 for sensing gas, vapour and/or volatile organic compounds 12 generated by the agricultural product 2. The system 1 may also include a temperature and/or humidity sensor unit 13, or any other relevant sensor.

Each gas sensor unit 11 comprises a respective gas and/volatile organic compound (VOC) sensor 14 (herein, for brevity, simply referred to as “gas sensor”), a microcontroller-based control unit 15 (or “controller”) and a communications module 16. Each gas sensor unit 11 may include more than one gas sensor, which may be of the same type or of different types, for detecting different analytes (e.g. different VOCs).

The gas sensor unit(s) 11 may be fixed, for example, depending from the ceiling or roof of the enclosure 3, for instance above each tower 5 or in an array having a separation, s, of, for example, between 1 and 5 m. Thus, each gas sensor unit 11 is used to monitor a given volume 18 of the enclosure 3. If ducts 7 are provided, the gas sensor unit(s) 11 may also be disposed in the ducts 7.

The system 1 may include one or more portable (e.g. hand-held) gas sensor unit 11.

This may be used to verify readings, carry out spot checks

The system 1 also includes a base station 19, which comprises a computer system (not shown). The gas sensor units 11 and the base station 19 are interconnected via wireless local area network, for example a wireless network based on IEEE 802.11 standard or Bluetooth (RTM) standard.

As will be explained in more detail later, the gas sensors 14 comprises metal-oxide gas sensor(s), electrochemical gas sensor(s), conducting/composite polymer gas sensors(s), photoacoustic gas sensor(s), piezoelectric gas sensors(s), infrared gas sensor(s) or photo ionisation detector gas sensor(s) is shown.

Referring to Figure 3, a system 1’ is shown for detecting disease or disorder in an agricultural product 2 which being grown or harvested in a bed or field 20.

The system 1’ comprises one or more gas sensor units 11 which are housed, for example, in a stake or pole 21 driven into the ground 22. The stake or pole 21 includes holes 23 to allow air to reach the gas sensor unit 11. The gas sensor 14 of the gas sensor unit 11 lies a distance, d, from the surface of the ground 22. The distance, d, may be between 0 and 5 cm.

The system 1’ can be used for symptomatic and pre-symptomatic detection of rotting in the tuba 2 or in the stem 24 or the condition of the tuba 2 or in the stem 24.

As explained earlier, certain types of gas sensor are preferred. In some cases, only one type of gas sensor may be used in a given enclosure 3. In other examples, more than one type of gas sensor may be used. For example, a gas sensor unit may include two or more gas sensors, each sensor being of different types.

Simple examples of suitable gas sensors will now be briefly described with reference to Figures 4 to 9.

Metal-oxide gas sensor

Referring to Figure 4, a metal-oxide (or “MOX”) gas sensor 31 is shown.

The MOX gas sensor 31 comprises a strip 32 of tin oxide, tungsten oxide, zinc oxide, chromium titanium oxide or other suitable metal oxide having first and second spaced-apart electrodes 33. The metal oxide may also be doped with a metal, including platinum, gold, silver, palladium, copper and/or iron. The metal oxide strip 32 is supported on a substrate 34 formed of, for example silicon or alumina. The substrate 34 may take the form of a membrane, for example, having a thickness of a few hundreds of nanometres or a few micrometres. The gas sensor can also take the form of a bead/tube. The gas sensor 31 also includes a heater 35. The MOX gas sensor 31 is controlled by a controller 36 for applying a bias across the metal oxide strip 32 and measuring current, and for driving current through the heater 35. Resistance of the metal oxide strip 32 varies when the surface 37 of the metal oxide is exposed to given gas, vapour and/or volatile organic compounds 12.

Examples of suitable metal-oxide gas sensors include the FIS Gas Sensor SP-53B model available from FIS Inc., Itami, Hyogo, Japan, and TGS 2602, TGS 2610, TGS 2611 and 2620 models available from Figaro Engineering Inc., Mino, Osaka, Japan.

Electrochemical gas sensor

Referring to Figure 5, an electrochemical gas sensor 41 is shown.

The electrochemical gas sensor 41 comprises first and second metal electrodes 42, 43 (referred to a working electrode and counter electrode respectively) formed from platinum or other suitable material in contact with an electrolyte 44. The sensor 41 may include a third, reference electrode (not shown). The electrochemical gas sensor 41 is controlled by a controller 46 which applies a voltage between the electrodes 42, 43. When a gas, vapour and/or volatile organic compound 12 comes into contact with the working electrode 42 it is oxidized which results in generation of protons (not shown) at the working electrode 41 which flow towards the counter electrode 43 through the electrolyte 44.

Examples of suitable electrochemical gas sensor include the CO-A4 Carbon Monoxide Sensor, ETO-Ai Ethylene Oxide Sensor and NO-Ai Nitric Oxide Sensor available from Alphasense Ltd, Great Notley, Essex, UK.

Infrared gas sensor

Referring to Figure 6, an infrared gas sensor 51 is shown.

The infrared gas sensor 51 comprises an infrared (IR) source (e.g. a lamp) 52 and a detector 53 and an enclosure 54 through which air can pass. The infrared gas sensor 51 is controlled by a controller 56. When a gas, vapour and/or volatile organic compound 12 passes into the enclosure 54 between the source 52 and detector 53, IR light 55 at a characteristic frequency is absorbed. Absorption is detected by the detector 53.

Examples of suitable infrared gas sensor include the Cirius 1 and Cirius 2 available from Clairair Ltd, Witham, Essex, UK.

Photo ionisation detector gas sensor

Referring to Figure 7, a photoionization detector gas sensor 61 is shown.

The photoionization detector gas sensor 61 comprises an ultraviolet source (e.g. a lamp) 62 which illuminates a space between and first and second electrodes 63, 64 through which air can pass. The photo ionisation detector gas sensor 61 is controlled by a controller 66. When a gas, vapour and/or volatile organic compound 12 passes between the first and second electrodes 63, 64, UV light 65 ionises the analyte which generates ions and electrons 67 thereby generating a photocurrent.

Examples of suitable infrared gas sensor include the PID-AH2 Photo Ionisation Detector available from Alphasense Ltd, Great Notley, Essex, UK.

Conducting polymer/polymer composite gas sensor

Referring to Figure 8, a conducting polymer or polymer composite gas sensor 71 (herein referred to collectively as a “polymer-based gas sensor”) is shown.

The polymer-based gas sensor 71 comprises of a strip 72 of semiconducting polymer material 72 having first and second spaced apart electrodes 73, 74. The semiconducting polymer strip 72 is supported on a substrate 75. The polymer-based gas sensor 71 is controlled by a controller 76 for applying a bias across the polymer strip 72 and measuring current. Resistance of the strip 72 varies when the surface 77 of the polymer is exposed to given gas, vapour and/or volatile organic compounds 12.

The semiconducting polymer material maybe, for example, polypyrrole, polyaniline and polybithiophene (which maybe doped or be undoped). The semiconducting polymer material may take the form of a composite of an electrically-conductive and electrically -insulating components. For example, the semiconducting polymer material may take the form of a composite of an electrically-insulating polymer matrix and electrically-conductive particles (preferably particles having a characteristic dimension less than 1 pm, i.e. nanoscale) embedded in the matrix. The polymer may be, for example, polystyrene or polyethylene, and the conductive particles maybe formed from carbon, gold or silver nanoparticles.

Examples of suitable polymers and sensors are described in Hua Bai and Gao Guan: “Gas Sensors Based on Conducting Polymers”, Sensors, volume 7, pages 267 to 307 (2007).

Piezoelectric based gas sensor

Referring to Figure 9, a piezoelectric based gas sensor 81 is shown.

The sensor 81 comprises a substrate 82 comprising a piezoelectric material and first and second spaced apart transducers 83,84 (for example, in the form of interdigital transducer) for generating and detecting acoustic waves 85 in the substrate 82. A surface 86 of the substrate 82 supports a gas-sensitive layer 87, e.g. a polymer or metal oxide, which can absorb a given chemical species.

The piezoelectric- or acoustic wave-based gas sensor 81 is controlled by a controller 88 which applies a time-varying signal to one transducer 83 and detects a signal at the other transducer 84. Propagation of the acoustic wave 85 when the surface 89 of the gas-sensitive layer 87 is exposed to given gas, vapour and/or volatile organic compounds 12.

Reference is made to Chapter 13 “Materials for Piezoelectric-Based Gas Sensors” of “Handbook of Gas Sensor Materials: Properties, Advantages and Shortcomings 307 for Applications Volume 1: Conventional Approaches, Integrated Analytical Systems”, by G. Korotcenkov (Springer Science 2013).

Photoacoustic spectroscopy based gas sensor

Referring to Figure 10, a piezoelectric based gas sensor 91 is shown.

The.sensor 91 comprises a measurement chamber 92 (or “cavity”) and at least one microphone 93 (for example, comprising a piezoelectric diaphragm) for detecting vibrations of gas 94 in the chamber 92.

An infra-red source 95 (for example in the form of laser) is used to generate pulse light 96 which passes through an optical window 97 into the chamber 92 and is used to excite molecules in the chamber. Different molecules have different resonant frequencies and so by tuning the wavelength of the light 96, different analytes can be detected. By measuring the magnitude of vibration, the concentration of gas or vapour 12 can be determined.

Reference is made to C. Haisch and R Niessner: “Fight and sound - photoacoustic spectroscopy”, Spectroscopy Europe, volume 14, page 10 (2012).

The controllers 36 (Figure 4), 46 (Figure 5), 56 (Figure 6), 66 (Figure 7), 76 (Figure 8), 88 (Figure 9), 98 (Figure 10) may be implemented at least in part by the control unit 15 (Figure 1). In some cases, an additional front end module (not shown) may be used.

Commercially-available gas sensors intended to be used in industrial safety or air quality monitoring may be used.

Operation

Referring to Figures l and ll, each gas sensor unit 11 may carry out a measurement (step Si) and transmit the measurement to the base unit 19 for analysis (step S2). After each measurement, the gas sensor unit 11 may wait a given period, which may be, for example, between 5 minutes to an hour (step S3). During this period, the gas sensor unit 11 may enter into a low-power, sleep mode.

Referring to Figures 1 and 12, in an alternative approach, each gas sensor unit 11 may carry out a measurement (step Si) and locally analyse the measurement (step S4). If the presence of a given analyte is positively determined, then the measurement and/or the determination is transmitted (step S2). Optionally, the gas sensor unit 11 may wait a given period (step S3).

Diseases and other disorders

The system can be used to detect the onset of one or more types of bacterial, fungal, viral, viroid, nematode, and phytoplasmal diseases and other disorders found in haulm, stems, sprouts, tuber or other plant parts.

Examples of diseases found in potatoes and other roots, tubers and bulbs (such as onions) include blight, ring rot, brown rot, verticillium wilt, common scab, powdery scab, stem canker and black scurf, spraing, potato virus Y, potato virus X, potato cyst nematode, rust spot, blackleg, and black dot. Disorders (including defects) include, for example, black heart, hollow heart, brown heart and the like.

Examples of bacterial diseases include leaf streak and bulb rot, soft rot, centre rot, Enterobacter bulb decay, slippery skin, sour skin and xanthomonas leaf blight.

Examples of fungal diseases include basal rot, black mould, black stalk rot, blue mold rot, botrytis brown stain, botrytis leaf blight, damping-off, downy mildew, leaf blotch, neck rot, phytophthora neck and bulb rot, pink root, powdery mildew, purple blotch, rust, smudge, smut, southern blight, stemphylium leaf blight, twister, white rot white tip and yeast soft rot.

Modifications

It will be appreciated that various modifications may be made to the embodiments hereinbefore described. Such modifications may involve equivalent and other features which are already known in the design, manufacture and use of gas sensors and component parts thereof and which maybe used instead of or in addition to features already described herein. Features of one embodiment maybe replaced or supplemented by features of another embodiment.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combination of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

1. A system for gas and/or volatile organic compound monitoring of an agricultural product and/or of the environment in the vicinity of the agricultural product, the system comprising: a set of one or more gas and/or volatile organic compound sensor units, disposed in storeroom, transportation container or a bed or field, for sensing gas(es) and/or volatile organic compound(s) generated by the agricultural product or provided to treat the agricultural product; wherein the one or more gas and/or volatile organic compound sensor units each comprise at least one respective gas and/or volatile organic compound sensor, wherein the gas sensor(s) comprises metal-oxide gas sensor(s), electrochemical gas sensor(s), conducting/composite polymer gas sensors(s), photoacoustic gas sensor(s), piezoelectric gas sensors(s), infrared gas sensor(s) or photoionization detector gas sensor(s).

2. A system according to claim l, wherein the one or more gas sensors units each comprise communication module(s) for transmitting a signal to a remote base unit.

3. A system according to claim 2, wherein the communication module(s) includes a wired network interface.

4. A system according to claim 2 or 3, wherein the communication module(s) includes a wireless network interface.

5. A system according to any preceding claim, wherein each gas sensor unit is configured to transmit a signal carrying a value of a measurement.

6. A system according to claim 5, wherein each gas sensor unit is configured to determine whether the measurement value exceeds a predetermined threshold and to transmit a signal signalling an outcome of the determination.

7. A system according to claim 6, wherein each gas sensor unit is configured to transmit the signal signalling an outcome of the determination in response to a positive determination.

8. A system according to claim 6 or 7, wherein each gas sensor unit is configured, in response to receiving a control signal from the base station, to configure the signalling signal.

9. A system according to any preceding claim, further comprising: a base unit comprising a computer system configured: to receive a value of measurement from at least one of the one or more gas sensors units; to determine whether the measurement value exceeds a predetermined threshold; and in response to a positive determination, to signal the positive determination.

10. A system according to claim 9, wherein the computer system is configured: to receive an outcome of a determination whether the measurement value exceeds a predetermined threshold from at least one of the one or more gas sensors units, and in response to the determination being a positive determination, to signal the positive determination.

11. A system according to claim 9 or 10, wherein the computer system is configured: to transmit a control signal to the gas sensor unit(s) comprising instructions for configuring the gas sensor unit(s).

12. A system according to any preceding claim, comprising: a base unit comprising a computer system configured: to receive an outcome of a determination whether the measurement value exceeds a predetermined threshold from at least one of the one or more gas sensors units, and in response to the determination being a positive determination, to signal the positive determination.

13. A system according to any preceding claim, wherein at least one of the one or more gas sensor units is portable.

14. A system according to claim 13, wherein portable gas sensor units is a hand-held gas sensor.

15- An installation comprising: a storeroom; and a system according to any one of claims l to 12, wherein the set of one or more gas sensor units are installed in the storeroom.

16. An installation comprising: a transportation container; and a system according to any one of claims 1 to 12, wherein the set of one or more gas sensor units are installed in the transportation container.

17. An installation comprising: a bed or field; and a system according to any one of claims 1 to 12, wherein the set of one or more gas sensor units are installed in the bed or field.

18. A method of gas monitoring of an agricultural product and/or of the environment in the vicinity of the agricultural product, the method comprising: sensing gas(es) and/or volatile organic compound(s) generated by the agricultural product or provided to treat the agricultural product using a set of one or more gas sensor units disposed in a storeroom, a transportation container or a bed or field, wherein the one or more gas sensors units each comprise at least one respective gas sensor, wherein the gas sensor(s) comprises metal-oxide gas sensor(s), electrochemical gas sensor(s), conducting/composite polymer gas sensors(s), photoacoustic gas sensor(s), piezoelectric gas sensors(s), infrared gas sensor(s) or photoionization detector gas sensor(s).