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1. WO1997016964 - A SPRAY SYSTEM FOR NEED DOSAGE

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A spray system for need dosage

The present invention concerns a spray system for need dosage for use in agriculture.

Today, plant protection agents are applied to cultivated land with an even dosage over the entire area. This means that too great amounts of plant protection agents are ap-plied to some areas, while others receive a too low concentration.

Great variation may occur between and within the shifts at a farm when it comes to state of culture, yield of crop and topographical conditions. Crop variations of 40% have been recorded with the same strain and cultivation technique during tests on sloping ground.

Today, the same dosage of plant protection agents is gen-erally used on the entire field. The consumption of plant protection agents becomes greater than necessary. Research results suggest that the consumption of plant protection agents may be reduced by up to 50% with variable dosage, i.e. by using need dosage.

New techniques for regulating delivery and accurate localization permit adjustment for variations in the field. With such an optimum spreading of plant protection agents, the composition and dosage may vary during travel according to the real needs in the field. Further, the drift may be kept at minimal level. Where desirable, the spray quality may be varied without affecting the dosage. Variations in travel speed will have no influence on the dosage.

Of the annual plant protection agent consumption in Norway of about 1,000 tons of active substance, about 90% is spread with the 20 - 25,000 field sprayers which are available. About 80% of the plant protection agents is herbicides. Traditionally, the entire field is treated with the same dose. This is done although the need should be adapted locally in the field according to the type of harmful organisms (weed, fungus, insect), according to the amount of harmful organisms and growth stage. Fur-ther, the dose should be adapted to prevailing spray conditions (temperature, air humidity, wind, etc.). This means that the dose should be varied during spraying, adapted to the biological needs and spray conditions without impairing the spray effect. Also, the need varies much within the individual field. The weed flora is stronger along the edges of the field because of weed seeds from weeds outside the field in ditch edges and the like. The same applies where the cultivated plants do not compete so well with the weed, e.g. on water-logged soil, depressions and boggy soil. The plant protection need is smaller on hill tops, and where the presence of weed is smaller. The need for plant protection agents varies with different local variations of weed in the field, such as e.g. density, fertility, type and number. For example, it is very unfortunate to spray with growth regulating chemicals on grain on hill tops where the soil is dry during almost the entire growth season and results in reduced growth.

The drift, which takes place particular with wind and evaporation, is frequently a problem. Drift-reducing agents may be added to spray liquids, but this is not done because they involve further costs, and because the consumption becomes excessively great when the same dose must be used over the entire field, even though the drift is just locally a problem.

It is recommended in Norway that the fields should not be sprayed when the wind is stronger than 3 m/s, at worst never over 5 m/s. The alternative is to lower the spray boom, but this results in poor liquid distribution. To reduce the pressure is not a good solution either, as it affects the dosage. With the technology of today, the travel speed must be kept approximately constant in order not to change the drop picture or pattern. Cleaning of equipment results in pollution of the environment and of the ground water. The working environment in the handling of the agents is not good enough at present, since the surroundings tend to be easily soiled when the sprayers are filled, emptied and cleaned.

In traditional spray equipment using water and preparation in the same tank, the dosage can just be varied to a minor extent, and this is done by changing the working pressure (the nozzle pressure) . Changes in pressure have a great impact on the drop size. It is agreed interna-tionally that the pressure must not vary more than +/-25%, which corresponds to an about +/- 12% change in liquid flow. There is a need for reasonable equipment with a good operational reliability where the active preparation may be added from a separate container to the water flow during spraying, and where the dosage can be varied in a simple manner without changing the drop picture. Active use of control parameters for the spraying is not used very much, e.g. travel speed, wind meter and weed sensor. Some of these parameters will be simple to use, others are more complicated. The drop size should be adapted to the harmful organisms and varying spray conditions. For example, larger drops may be used, independent of dosage changes, where the risk of drift is great.

Economically and environmentally, there is a strong need for a more correct use and utilization of plant protec- tion agents . The environmental authorities and public opinion make ever stricter demands on the spray methods today. Warning service for spray time against diseases has been introduced. The actual preparations have been developed such that they are more active and have less negative environmental impacts . The actual spreading and formation of drops using hydraulic nozzles on ordinary field sprayers are a simple, reasonable and effective method which will be dominating also in the years to come. What is missing, on the other hand, is a more flexible and need-adapted utilization of the spray method such that the consumption of agents may be reduced considerably.

Several countries have realized the advantages of using spray equipment with need control. Consequently, intensive research is being carried out in many countries regarding development of need-controlled dosage equipment. The systems which are being tested or are commercially available are based on a tank containing pure water, while one or more other smaller tanks contain one or more plant protection preparations in a pure concentrate. As the dosage of preparation in agriculture is generally from 2 to 500 g (ml) per daa (20 to 5000 g (ml) per ha), this means that from the preparation tanks:

very small amounts are to be discharged,
different amounts are to be discharged for different preparations used,
- the properties of the preparations have a great influence (volatility, miscibility, foaming, etc.)
mixing is impeded, as the concentration proportion between the liquids in the two tanks is very high; as much as 0 to 100% (in the system of the present invention just 0 to about 1%),
cleaning of the dosage unit is difficult, regulation of the dose will easily be inaccurate and incorrect dosage may occur,
the operational reliability is poor,
the dosage unit is very expensive.

In addition, the control to be performed by the user must be carried out using the preparation, which is unfortunate in terms of the working environment and takes a great deal of time. The calibration must frequently be performed, since the regulation of the dose can easily be incorrect and change undesirably over time.

As a result of these drawbacks, the systems commercially available today have not been successful in practice. Examples of systems and patents where active preparation is present in concentrated form in one tank and water in another, and where said drawbacks can easily occur, include:

US Patent No. 4 925 096, European Patent No. 0 201 981, Agri Futura Dose 2000, Mid-West Technology CCI-2000, Vi-con Injection System, Direct Injection Closed System at the Silsoe Research Institute and MSR Ciba Geigy Agro inject .

In all these systems, the preparation is present in a concentrated form in one tank, while pure water is contained in another. This means that with the concentrations at which the plant protection agent is to be mixed with water, just a slight incorrect dosage of the concentrate may result in great differences. This may be caused by measurement errors, deposits in ducts or conduits or the properties of the plant protection agent.
The present invention aims at mixing finished spray liquid in the usual manner in a tank in a concentration which corresponds to normal dosage at e.g. maximum travel speed. This corresponds to maximum dosage equal to 100%. Water is fed in a variable amount from another tank, which is filled with pure water, to the mixing chamber, when it is desired to reduce the dose and/or the travel speed changes and it is desirable to keep the dose constant. Since the liquid amount out through the nozzles is constant in order not to affect the drop picture, this means that the liquid amount from the first tank must simultaneously be reduced in the opposite proportion.

This provides the following advantages:

The dosage may be changed without changing the liquid amount fed to the spray boom, i.e. the drop pic- ture/spray quality are maintained (like for other spray equipment with need control).

The dose is the same even if the travel speed varies (like for other equipment with need control).

The drop picture may be changed without the dose being changed (like for other equipment with need control) .

The spray system for need control according to the present invention additionally provides the following advantages:

Low concentration difference between plant protection agent and water simplifies and ensures a better, safer and quicker mixing of the two liquids.

The control by the user is quick and simple and can be performed accurately using simply pure water in both tanks.

The dosage unit will be extremely reasonable and operationally reliable because of the following circumstances :
only pure water is to be added additionally to a greater or smaller degree, i.e. always the same liquid properties and unharmful liquid, the dosage accuracy is improved, since large water amounts have to be added to regulate the dose. For example, a water amount equal to 10 1/min in case of normal spraying must be added to halve the dose, while with addition of pure preparation, it may be matter of a preparation amount which is 40 to 10 000 times smaller. The latter makes metering of correct dose much more complicated and easily results in incorrect dosage when using a concentrated preparation,
great security, since it is impossible to overdose above 100%, which can easily happen when addinng concentrated plant protection agent (such overdosage is prohibited),
may be used for powder-formulated preparations.

Also the water tank has many advantages, such as:
cleaning of spray tank (will presumably be re- quired in new spray equipment in ISO and CEN) .

Here, pure water is pumped from water tank 2 into tank 1 to a washing nozzle which flushes the tank internally. Pure water is also flushed through spray boom and nozzles. The flushing water is sprayed on the crop which is treated. water accessible for hand washing (requirement in Norway, Sweden and Germany) .

Reasonable and operationally reliable spray equipment for need control.

The invention will be explained more fully below by means of five figures, which show different ways of regulating the supply of plant protection agents and water.

In the simplest model, which is shown in figure 1, the operating pressure is first regulated in the nozzles on spray boom 9 by control of a pressure reduction valve 8, which is positioned after the mixing chamber 7. The pressure reduction valve provides a constant pressure to the nozzles. The tank 1 is filled with plant protection agent diluted to the maximally permissible concentration, while the tank 2 is filled with pure water.

The pressure at the pressure restriction valve 5a must be set slightly higher than the pressure at the pressure reduction valve 8. The difference depends somewhat on the sensitivity of the pressure reduction valve, pressure loss in hoses and desired pressure at the nozzles, but is just set once before spraying is begun.

If the pressure restriction valve 5b is throttled, the pressure increases somewhat in front of the pressure reduction valve 8. As a result, the pressure restriction valve 5a automatically opens correspondingly. Increased water supply from the tank 2 results in reduced supply of liquid from the tank 1. The system also works conversely. If the valve 5b opens, the pressure drops somewhat, and the valve 5a automatically closes correspondingly. This provides a system in which the supply of liquid is in-versely proportional to the supply of water. The spray picture, drop size, operating pressure and liquid amount out through the nozzles 9 remain the same. On the other hand, the concentration of plant protection agent in the liquid changes in a controlled manner, so that the dose is adapted to the spray conditions, as desired. Incorpo- rated non-return valves 6 protect against backflow of undesired liquid to the tanks.

Figure II is identical with figure I, but additionally incorporates a velocity meter 10. Signals from the velocity meter 10 and the volume flow meters 13a and 13b are received in a control box 12, which regulates the dose by operating the pressure restriction valve 11. The pressure restriction valve is driven e.g. by an electric motor such that the dose continues to be independent of the travel speed. The water supply is changed in inverse proportion to the travel speed, which means that the plant protection agent amount is changed in proportion to the travel speed, as desired.

Figures I and II have simple solutions to keep the pressure constant, while the dose is changed. The equipment may be adapted in a simple manner to standard pump types on existing field sprayers. The mixing chamber 7 is po-sitioned near the nozzles 9 to reduce the reaction time from when dose regulation takes place until desired concentration in the liquid spray after the nozzles is achieved. The liquid flow to the nozzles is adapted such that the change in concentration takes place simultane-ously in all the nozzles to the greatest extent possible.

In figure III, signals from the velocity meter 10 and the volume flow meters 13a and 13b are received in the control box 12 like in figure II, such that the dose will be the same irrespective of the travel speed.

The control box 12 may also be constructed such that the drop picture may be changed without the dosage of the plant protection agent being changed. For example, when the wind is rising, the drop size may be increased (the pressure is reduced) so that the deposition increases and the drift is reduced. This takes place in that 100% dosage is set with supply of spray liquid just from the tank 1 at the highest predicted velocity and lowest operating pressure at the nozzles (1.0 bar). The pressure is re-duced by reducing the water supply from the tank 2, while the liquid supply from the tank 1 is the same so that the dose is constant. The pressure at the nozzles decreases and the drop size increases. Conversely, the drop size is reduced by increasing the water supply from the tank 2. A similar system may also be incorporated in figure II.

The control box 12 also regulates the liquid flows from the pumps 4a and 4b so that the dose is adapted to the biological needs. This may be done e.g. in that the pres-sure restriction valve Ila is always regulated in inverse proportion to the pressure restriction valve lib, which means that the liquid amount to the spray boom 9 is constant. The spray quality remains the same. The pressure restriction valves are regulated e.g. by means of elec-trie motors. The liquid is mixed well in the mixing chamber 7 before it reaches the nozzles on the spray boom 9. The pressure reduction valve 8 in figures I and II is not necessary here.

In figure IV the signals are received in the control box 12 similar to the system in figure III. On the other hand, liquid from the tank 1 and the tank 2 is conveyed forwardly to the nozzles where they are mixed in a small prechamber 15. This minimizes the reaction time from de-sired dose regulation to completed dose regulation. As the concentration difference between the spray liquid from the tank 1 and the water from tank 2 is small compared with systems using the preparation in concentrated form, the liquids are simply mixed in one or more mixing chambers, e.g. a small mixing chamber positioned in front of each nozzle 15.

Both in figure III and in figure IV, the liquid amount may alternatively be regulated directly e.g. by using adjustable pumps or by changing the number of revolutions of the pumps .

Figure V shows a more detailed and further developed system from figure III. Here, also a directional valve 14 is shown. When water is passed from the tank 2 to one or more washing nozzles in the tank 1, the sprayer is cleaned internally in a simple manner in the field. Flushing water is pumped through i.a. the pump 4a, the valve Ila and out through the nozzles on the spray boom 9.

The spray apparatus with need control of the present invention may be provided with additional equipment. Several liquid volume meters, e.g., may be incorporated for direct reading of liquid flow. Pressure sensors may be incorporated in the existing system.

The system may be extended with several tanks for use of several agents. A third tank may be filled with e.g. a drift-reducing substance which may be injected when de-sired. Here, a great dosage accuracy is not required, and such substance may be used when needed (drift likely) .

A chemical filler device with a graded scale should be mounted for simple and safe filling and subsequent flush-ing of both liquid and powder-formulated preparations.

Level sensors may be incorporated in the liquid tanks and thus indicate the remaining volume and amount of consumed liquid at any time.

A computer may be incorporated for calculation of consumption, sprayed area, dosage, automatic storage of liquid and preparation consumption on data cards and for optional connection to GPC (Global Position System) .

Regulation of the dose may take place steplessly or in several steps manually, but may also be performed automatically, based on sensors for harmful organisms, previous experience, data cards, etc.

The possibilities of regulating dose according to local needs as well as constant dose independent of the travel speed are combined in figures II, III, IV as well as V.

The use of the system of the invention allows effective, need-dosed spraying of an agricultural area. It results in a more environmentally sensible use of plant protection agents and chemicals, and it enables differentiation of the added amount of plant protection agent.