GB2170981A - Spraying of agricultural chemicals - Google Patents

Abstract

A dense canopy of crop foliage can prevent even the wrap-round action of electrostatic sprayers being effective. An air-blast (A) positioned away from the spray (S) can be directed to open the crop canopy to penetration by the charged spray. The charged spray can be forced down toward the crop by a charged plate(G). <IMAGE>

Description

SPECIFICATION Spraying of agricultural chemicals This invention relates to the spraying of agricultural chemicals onto crops as charged partices or droplets.

Agricultural chemicals include fungicides, pesticides and herbicides, among others, used in farming, horticulture, fruitgrowing and other activities.

The effective distribution of such chemicals into the foliage and branches of a crop (which may be a plant, a bush or a tree) is an important aspect of spraying the chemicals. Adequate penetration is not always achieved even when electrostatic charging of spray used. Although charged particles of spray can get round to the back of an individual leaf a dense canopy of leaves can form a barrier even to charged spray.

It is an object of the invention to improve the delivery of agricultural chemicals by spraying.

According to the invention there is provided a method of spraying agricultural chemicals onto a crop as charged particles or droplets of liquid including providing a charged spray of chemical, moving the spray over the crop, providing a blast of air and moving the blast of air over the crop with the spray but spaced therefrom to open the crop to penetration by the charged spray, and electrostatically forcing the spray toward the crop.

The spray may be directed into the open crop. The spray may be blown by the air blast into the opened crop. The air-blast may be in front of or behind the spray.

According to the invention there is provided an apparatus for spraying crop with electrostatically charged liquid including a support, a spray-forming and charging means and an airblast-forming means, the support carrying at least one means to deliver said liquid as charged spray and electrostically force the spray toward the crop together with spaced from said delivery means at least one means to direct said air blast to open crop to said charged spray.

The apparatus may be a vehicle-mounted boom supporting a plurality of spray-delivery means and air-blast-delivery means spaced in respective spaced rows together with an airdelivery duct for the air-blast and a liquid-delivery conduit for the spray liquid.

The air-blast and spray delivery means may alternate along the boom in their respective rows. The spacing of said rows and the means in the rows may be adjustable. The airblast delivery means may end in a tapering part changing from a delivery duct cross-section to a slot aligned along the boom length.

The spray-delivery means may be electrostatic sprayers including at least one charged plate to force spray towards the crop.

The air-blast may be directed perpendicularly to the surface of the crop or at the other angles thereto. The spacing of the air-blast from the spray can be adjustable for different crops. The speed over the crop can be similarly adjustable. The angle, the spacing and the speed can be altered relative to one another for different crops.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic perspective view of a tractor mounted apparatus embodying the invention.

Figure 2 shows tables of results of comparative tests of sprayers.

In the drawings Fig. 1 shows a boom B of any suitable form. Conveniently this is a triangular section lattice construction to permit the mounting of items on the boom spaced at intervals along it and spaced into two rows.

The items are in one row electrostatic sprayheads, S, and in the other row air-blast nozzles, A. A tractor to carry the boom is indicated at T. The tractor also carries an aircompressor, C, and a plenum chamber, P.

Ducts D connect the plenum chamber to individual nozzles A. Electrostatic, electrical and liquid feeds for the spray heads are carried along boom B but are not shown. The electrostatic sprayers can be fitted with extra, charged, guard plates G to keep spray off the sprayer and boom, and modify the spray pattern if required. In particular the charged plates push the spray down by electrostatication.

The construction of the boom and electrostatic sprayers will be readily apparent to those skilled in the art and, apart from the extra weight of the air-blast arrangement, should not be critical. The spacing between the rows of sprayheads and nozzles is about a half a metre and this should not be a difficult mechanical problem.

The air-blast nozzles are spaced to provide a substantially continuous air-blast "curtain" along the boom and directed towards a crop traversed by the boom B on tractor T. Conveniently four nozzles each with an outlet slot about 500 millimetres by 6 millimetres are spaced to cover a swath about 3 metres wide. The sprayers S are in a row spaced about 400 millimetres from the row of nozzles A and approximately at each gap between the nozzles. The sprayheads are arranged to pass about 250 millimetres above the crop. The nozzles are a little above the level of the sprayheads. The three sprayheads together provided a substantially continuous spray across the 2 metre swath. Figure 1a shows in outline the relative positions with the air curtain behind the sprayheads opening the crop P to the spray.Dimension x is the air nozzle row to sprayer row spacing and dimension y the height of the sprayer above the crop.

Clearly the spacing of the devices in a row as well as the row spacing can be adjustable if required. The angle of the air curtain can also be adjusted. Angles of up to 40 mayprove useful for certain crops, or conditions. The airblast disturbs and opens the canopy to penetration by the charged spray.

For the arrangement just described the compressor had a five horse power drive to a centrifugal fan. Each nozzle received about half a cubic metre of air per second through a 100 millimetre flexible duct D. The plenum chamber P was constructed to supply a higher pressure in the lower half, where the ducts to the more remote nozzles were connected, than in the upper half for the nearer nozzles. This produced a fairly even air curtain along the boom.

The nozzles can be set at various angles to the vertical to produce an air curtain directed over a range of angles which can be either side of the vertical. The air curtain can be behind or in front of the spray. As the charged spray can have a direction not controlled by the canopy-opening air-blast the wrap-round action of the charged spray is not constrained to the direction of the air-blast, which merely opens a channel through the canopy for the spray liquid to expoit. In contrast an hydraulic spray would not be able to "wrap-round" once it was inside the opened canopy. Ciearly the air-blast can assist the spray if required while retaining the electrostatic action.

A range of air speeds from the nozzles could be selected by controlling the compressor. Convenient values were 30 metres/second and 15 metres/second.

In one embodiment the sprayheads were of the rotary, electrostatically inductively charged type based on a Micron Micromax (RTM) CDA atomiser operated at about 30 kV and 4,500 r.p.m. to deliver between 5 and 10 litres/hectare at a volume median diameter (VMD) of about 80 micrometres. This sprayhead is known as JUMBO. In another embodiment electrostatically charged rotary sprayheads applying between 2 and 5.6 litres/hectare at a VMD of 100 micrometres were used. This sprayhead is known as APE. Hydraulic sprayers were used as a basis for comparison.

These used Lurmark (RTM) jets with a supply pressure of about 300 kPa to give either about 200 litres/hectare or 380 litres/hectare.

Table I shows the result of a test using the JUMBO sprayheads to deposit tracer chemicals on spring barley at growth stage 37 to 39. In the table L1 indicates the uppermost leaf, L2 the next leaf from the top and L3 the leaf below L2. The columsn E, E+A1, E+A2, and H show the deposit, in micrograms per gram of leaf, for various sprayers. Column E is for the JUMBO electrostatic sprayer alone.

Column E+A1 is for air assistance at 15 m/s, column E+A2 is for air assistance at 30 m/s, in each case on the spacings outlined above.

Column H is the hydraulic sprayer. The final column (SED) is an indication of the statistical quality of the results. The results show that by using air assistance at 30 m/s the distribution from an electrostatic sprayer can be changed to greatly increase the deposit on lower leaves to the revel attained with an hydraulic sprayer, which typically uses 20 times the flow rate (in litres per hectare).

Table II shows the results of applying TILT TURBO (RTM) at growth stage 41 with the APE sprayer to control mildew in spring barley. The "%" column shows the percentage of leaf area with mildew, the DEP column the actual chemical deposit in micrograms per gram and the YE column the yield in tonnes/hectare. In the table row H is the result for the hydraulic sprayer, row E for the electrostatic sprayer, row E+A for air assisted electrostatic sprayer and row U for the untreated crop. Row SED indicates the statistical quality of the results. The use of air assistance increases the yield for electrostatic spraying by about 8%.

The above test show that although the addition of air assistance complicates an electrostatic sprayer the results can be as good as for an hydraulic sprayer, bearing in mind the higher application rate for hydraulic sprayers.

Other sprayheads, e.g. the vertical disc type, can be used.

Claims (13)

1. An apparatus for spraying a crop with electrostatically charged liquid including a support, a spray-forming and charging means and air-blast-forming means, the support carrying at least one means to deliver said liquid as charged spray and electrostatically force the spray toward the crop together with spaced from said delivery means at least one means to direct said air-blast to open the crop to penetration by said charged spray.

2. An apparatus according to Claim 1 including a vehicle-mounting boom supporting a plurality of spray-dispersing means and airblast-delivery means spaced in respective spaced rows together with an air-delivery duct for the air-blast and means to supply the spray liquid.

3. An apparatus according to Claim 2 in which said spray means and an air-blast delivery means alternate along the boom in their respective rows.

4. An apparatus according to Claim 2 or claim 3 in which the air-blast delivery means includes a tapering part changing from a delivery duct cross-section to a slot aligned along the boom length.

5. An apparatus according to Claim 1 in which the spray means is at least one electrostatic sprayer including at least one charged plate to force spray towards the crop.

6. An apparatus according to Claim 1 in which the air-blast is directable at the crop at an angle to the surface of the crop.

7. An apparatus according to Claim 6 in which said angle is the perpendicular to the surface of the crop.

8. An apparatus according to Claim 2 including means to adjust the spacing of said rows and the means in the rows to different arrangements.

9. A method of spraying agricultural chemical onto a crop as a spray of charged particles of droplets of liquid including providing a charged spray and an air-blast stream, spacing the air-blast from the spray, moving the spaced spray and air-blast over a crop and directing the air-blast stream to open the crop to penetration by the charged spray and electrostatically forcing the spray toward the crop.

10. A method according to Claim 9 in which the air-blast stream is directed at an angle to the surface of the crop.

11. A method according to Claim 9 in which a plurality of sprays and air-blast streams are provided spaced from one another.

12. Spraying apparatus substantially as herein described with reference to the accompanying drawings.

13. A method of spraying substantially as herein described with reference to the accompanying drawings.