The present invention relates to improvements in or relating to crop spraying or assessment operations.

It is now common practice to use aircraft in the spraying of crops, this spraying operation being achieved by the aircraft provided with crop treatment fluid flying over the crop in a series of passes at a relatively low height and discharging the treatment fluid into the crop by means of nozzle discharges. Previously in the spraying of crops by aircraft, the fluid discharge from the aircraft has not been of great accuracy and consequently the spread of the fluid on the crop during a pass has not been very uniform. To cater for this problem a generous overlap between passes has been employed, but this has had the disadvantage of requiring the usage of greater quantities of treatment fluid and also increased cost of aircraft operation due to the increased number of passes required. However, there has recently been proposed an improved method of spraying crops from an aircraft which gives a considerably more uniform width of spraying band. It is an object of the present invention to enable a more economic application of treatment fluid to a crop, especially when the aforementioned improved more uniform crop spraying method is employed.

According to one aspect of the present invention there is provided a method of detecting irregularities in horticultural or agricultural treatments or in crop growing comprising moving sensing means in at least one pass over field or ground areas where gound or crop treatments have been applied or crop growing is occurring and continuously monitoring the ground by said sensing means during said pass to sense thermal differentials at the ground thereby detecting irregularities in the crop or ground treatment or crop growing. Preferably the sensing means are moved over he ground by an overflying operation.

Preferably he monitoring comprises infra-red sensing.

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According to a second aspect of the present invention apparatus for carrying out the aforesaid inventive method comprises ground monitoring means adapted for support at a suitable location or locations on carrying means, said monitoring means serving to sense thermal differentials on the ground during movement of the carrying means over the ground. The carrying means preferably comprise an aircraft.

In accordance with a further aspect of the present invention, there is provided in a crop spraying or crop assessment operation means for sensing wetted (or non- wetted) areas of the crop. More especially the monitoring sensing means can comprise an infra-red sensing device.

In a preferred embodiment, the sensing means are linked to navigational equipment of a crop spraying aircraft.

Preferably the monitoring or sensing means comprises infra-red radiometers adapted for external location on the carrying means or aircraft, the radiometers working in combination to detect temperature differentials. In particular, the radiometers can be located adjacent the wing tips of an aircraft.

In an alternative embodiment the monitoring or sensing means comprises an infra-red camera and this camera will be set to scan the ground below and preferably slightly forward of the aircraft. The monitoring and sensing means can include a visual display unit (screen) . V.D.U. arranged for convenient viewing within the aircraft, the V.D.U. providing a thermal (differential) image of the scanned ground.

The V.D.U. preferably links with aircraft navigational equipment so that the aircraft flight path is also registered on the V.D.U. Screen.

The viability of the infra-red sensing device as the sensing means of the invention results from the fact that when a crop is sprayed, the temperature of the sprayed area of the crop is reduced due to the evaporation of the spraying liquid (water) from the crop or from the ground: Lhis reduced temperature condition would be present when the

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crop is still wet and for a period thereafter. The infra¬ red sensing device would detect the reduced temperature area and consequently the wetted area of the crop.

In addition to use in guiding crop spraying operations, the present invention could be used in other agricultural or horticultural assessmemt operations such as for example: a) Identification o blocked spray heads from the air in systems of large area drip irrigation. b) Identification of crop areas where the plant metabolism is weak due to inadequacies of water, fertilisers and other causes; c) Identification of areas of plants where earlier emergence and other causes can be detected by higher levels of infra-red radiation; d) Detection of areas of crop disease or pest infestation by virtue of differences in temperature. e) Detection of areas of mis-application of fertiliser or irrigation.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings wherein Figs. 1(a) and 1(b) show schematic views of an aircraft crop spraying operation, embodying the present invention; Fig. 2 shows a similar view to that of Fig. 1 but according to another embodiment of the present invention; and Fig. 3 shows a schematic view of a visual display unit (V.D.U.) used in the embodiment of Fig. 2.

Referring to Figs. 1(a) and 1(b) , a crop spraying aircraft 1 has a pair of infra-red temperature sensing devices (radiometers) 2 located at respective wing tips of the aircraft, and the devices 2 are linked to a visual (warning light) or aural indicator (bell) 3. The arrangement is such that when the radiometers 2 indicate a temperature difference greater than a predetermined amount (i.e. T > X° C) then the indicator 3 isε ies a warning signal. The above apparatus is intended ^~ o distinguish

the boundary B between sprayed 4 and unsprayed zones 5 of the crop in a fairly straightforward crop spraying operation.

As explained previously, the temperature of a fairly recently sprayed crop zone will be less than the adjoining non-sprayed zone. Thus if the aircraft 1 is positioned as shown in Fig. 1(b) the radiometers will detect a distinct temperature difference and the indicator 3 will issue a warning signal so that the pilot may effect an appropriate adjustment in the aircraft flight path i.e. towards the position shown in Fig. 1(a) where the starboard radiometer 2 (for aircraft motion out of the paper) is located substantially above the boundary B at which position the warning signal will cease. During each pass, the pilot will know of course, which side of the pass has already bee.:: treated (sprayed) so he would readily recognise the required movement when a warning signal issues; i.e. towards the unsprayed side. A suitable spraying technique could involve the flight path being deliberately set initially so as to be partially over the sprayed zone, and the pilot then quickly adjusting the flight path (aided by the indicator 3) so as to fly substantially as shown in Fig. Ka) .

In the embodiment shown in Fig. 2, a scanning infra-red camera 6 is used instead of infra-red radiometers 2. The infra-red camera 6 is mounted on the aircraft 1 so that it views the ground below and preferably slightly forward of the aircraft, and the view scanned by the camera is reproduced on a visual display unit 7 (Fig. 3) mounted in the aircraft cockpit so that it can be continuously monitored by the pilot. The sprayed and unsprayed areas 4, 5 will show up as different tones on the screen of the display unit 7, e,g, as represented by the diagonal and horizontal hatching 4', 5' respectively, and the boundary B' between the zones will be indicated. The aircraft flight path can be represented by a vertical dashed line 8 and this car- be compared with the line B' to ascertain if an ac-u≤tment of the flight path is required.

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In a further embodiment (not shown) , a linear infra-red scanner is used as opposed to an area infra-red scanner, and the linear scanner would be adapted to scan below and forward of the aircraft on a line perpendicular to the aircraft flight path and the scanned line would be displayed on a suitable visual display unit, with the actual flight path again superimposed on the V.D.U. screen.

The actual scanning and monitoring arrangement used will of course be compatible with the type of spraying apparatus fitted to the aircraft. This spraying apparatus may comprise feed conduits extending over the length of the aircraft wingspan with downward discharge nozzles spaced along the conduits. By way of example the crop spraying apparatus can advantageously be that described in the present applicants' co-pending PCT Application filed of ever.- date: thus the spraying apparatus can comprise a spraying device 10 on at least one wing including discharge nozzles 10A. Alternatively the spraying apparatus may simply comprise discharge nozzle means on the aircraft fuselage.

Further variations are possible in the scanning and monitoring apparatus, and the apparatus could be used with crop spraying machines other than aircraft. Additionally, the monitoring apparatus could be used to assess other agricultural or horticultural conditions such as the conditions (a) to (e) described above, instead of being utilised solely in crop spraying operations.

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