Andrew Landers

Cornell University,

Department of Agricultural and Biological Engineering

Riley Robb Hall, Ithaca, NY14853-5701

1. Introduction

Farmers are under great pressure when applying pesticides. The increasing awareness of environmental pollution, along with worries about pesticide residues on food has resulted in increased legislation concerning pesticide use. The decrease in profit margins requires closer attention to the production costs. Traditionally, farmers have used pesticides to 'blanket' spray the whole field. The advent of direct injection sprayers and computer based information systems will allow them to spot treat patches of weeds or disease.

2. Direct injection crop sprayers

A conventional crop sprayer is fitted with an injection system comprising one to four pumps which dispense pesticide at a known rate into the water stream within the sprayer pipeline. The main tank of the sprayer holds clean water only. The pesticide is mixed with the water, either in a manifold or at the main water pump and the resultant mix flows to the booms and nozzles.

An electronic controller adjusts the pesticide injection pump according to changes in operating requirements, e.g. changes in application rate and pesticide requirement. The major advantages of injection sprayers are:-

i) reduction in environmental pollution due to the elimination of tank and pipeline washing.

ii) reduction in the operator contamination which occurs with conventional sprayers. Ideally the pesticide would arrive on the farm in large returnable and refillable containers and be connected directly to the pesticide injection pumps. The resulting closed system reduces operator contamination.

iii) the use of an electronic controller which allows each pesticide pump to deliver a specific product. The injection pumps can be switched on / off, as and when required, to spray various patches of weeds.

iv) the amount of pesticide applied ( dose rate ) can be adjusted on the move, allowing a higher dose rate to be applied to a high infestation of weeds or disease and vice-versa.

3. Computer-assisted information gathering and application

Information technology can be used to help farmers gather information about the health status of their crop and compare field conditions with a computer model. The resulting farm management information can be used to develop a crop spraying programme based on field observations of soil type, weed and disease status, crop response to pesticides and crop yield.

Pesticide requirement varies from one soil type to another, certain pesticides are used at different rates on organic soils compared to sand soils, and weed growth is often more vigorous on organic soils compared with other soil types.

A hand held data logger can be used with a position indicator so that weed or diseased patches can be identified and located for spot treatment. The data can be downloaded into an office computer so that an informed spray programme may be devised.

'Smart card' and disc systems have been developed which allow information to be downloaded from the office computer into the sprayer controller. The card or discs contains information about weed and disease status and its position in the field. As the injection sprayer drives towards a patch of weeds or diseased area the vehicle position indicator informs the sprayer controller and switches on a particular injection pump. A patch of weeds or disease can be spot treated with pesticide as the sprayer passes. As the weed infestation is passed the sprayer can be switched off. Satellite positioning would indicate the grid reference. The 'smart card' contains information on the level of infestation, allowing the pesticide to be applied at varying levels according to the degree of infestation.

The controller of the injection sprayer enables the farmer to carry out these functions manually or, if fitted with a GPS receiver, automatically. A printer can be installed to allow the farmer to know the exact quantities of pesticide applied and the area sprayed which would enable precise financial control to be retained.

Current research, based on real-time sensors, is developing techniques for the discrimination and quantitative registration of weed populations. Different spectral information of the plant and soil is used with a video camera to deliver separate image signals to an electronic controller.

4. Conclusions

i) Direct injection sprayers enable farmers to rationalize their pesticide use, reduce environmental pollution and reduce operator contamination.

ii) Variable rate application of pesticides along with GPS will result in more appropriate use of pesticides and rates being used, with an overall reduction in application rates, thereby satisfying environmentalists, legislators and farmers.

iii) Information technology systems already exist to allow computer aided pesticide application technology to be developed. The new systems will enable farmers to be better informed regarding their pesticide application strategy and improve their decision-making skills.