Environmental Fate and Safety Management of ... - ACS Publications

Chapter 28

Downloaded by COLUMBIA UNIV on September 7, 2012 | http://pubs.acs.org Publication Date: March 8, 2005 | doi: 10.1021/bk-2005-0899.ch028

Advances in Pesticide Applications and Their Significance to the Agrochemical Industry Servicing Tropical Farming William Taylor and Per Gummer Andersen Hardi International A/S, HelgeshojAlle38, Taastrup, DK 2630, Denmark (www.hardi-international.com)

Pesticide application has benefited from many advances in key areas that are associated with machine design and use. Field efficiency, drift control, safety whilst loading products and in use, the cleaning of internal and external surfaces, being some examples. The spurs for these activities are diverse, but legislation that demands improved water quality, lower operator risks, reduced Plant Protection Product use, and improved operator productivity, have been vital. To make, monitor and claim the many potential gains that were needed, has been stimulated by the activities of internationally agreed Standards. These are protocols that describe what needs to be considered and how performance should be measured as well as threshold limits that need to be reached. Although many of these activities are intended for field crop sprayers, or those used with air assistance in tree and bush crops, sprayers carried by operators and are manually operated, are also included. The application of pesticides as sprayed drops in the open environment of fields and plantations has also triggered Standards that define how drift is to be assessed, the categorisation of low drift equipment as well as protocols that may fully account for the fate of all the active ingredient within and beyond the treatment zone. Communication and training are equally critical; approved courses for operators, the periodic testing of sprayers both monitor and help sustain high standards on farms and plantations as well as ensuring effective transfer of knowledge. All countries and crops are likely to benefit from these broad initiatives that encourages more responsible Plant Protection Product use. This paper will focus on these advances - using tropical crop sprayers and spraying methods as examples that will illustrate what has been achieved and where advances still await.

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© 2005 American Chemical Society In Environmental Fate and Safety Management of Agrochemicals; Clark, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

321 Introduction


Pesticide application has benefited from many advances in key areas that are associated with machine design and use. These advances can be grouped into those aspects of design that have improved the safe use of the equipment, the loading of Plant Protection Products [PPP] into the sprayer, the application of a diluted solution for optimal effects, drift containment to the treated zone and the cleaning of internal and external surfaces. Spray machinery design has also been influenced by its needs to meet the interests of Regulatory Bodies who may wish to improve safety in a more general way - such as drift control or may require a specified product to be loaded into the machine in a particular manner.

Safe use Sprayers - in almost every country of the world - are getting larger, are fitted with wider booms, are spraying at faster speeds to meet the pressures introduced with the growth in farm size and the reduction of available labour. Tank capacities that exceed 4000 litres and booms that reach beyond widths of 38 metres and spraying at speeds in excess of 15 km.hour are no longer unusual. .These changes further increase the needs for engineered controls on these more sophisticated machines Engineering control systems that protect the operator from physical injury as well as reduce the threat of exposure to PPPs are in common use. Thus, hydraulic mechanisms to fold and raise booms both avoid the physical demands on the operator but also discourage him from making contact with contaminated surfaces on the machine and those he may have just sprayed. Tank drainage is remotely controlled without having to get under the machine to unscrew a plug whilst induction bowls avoid the need for the operator to climb up on top. Bayonet fixing nozzles reduce potential exposure since the time required to change nozzles is afractionof that demanded from the older screw fittings. Multi-turreted nozzle bodies can be used to replace blocked nozzles instantly in the field without having to remove them for cleaning. Clean water supplies are carried on the machine and are conveniently located to where the operator works. Spillage onto, for example, gloves or nozzle-blocking debris can be quickly removed. Modern filtration systems - coupled to improved formulations - are now so effective that nozzle blockage or disturbances to their patterns are rare. The occasions that operators find themselves making running repairs or adjustments - are very rare. Most modern sprayers have their functions remotely controlled from within the protected environment of the driving cab; a control area that is ideally pressurised to stop the ingress of particles. Research has shown that cabs with windows or doors open and not sealed - readily permit particulate ingress irrespective of wind direction.

In Environmental Fate and Safety Management of Agrochemicals; Clark, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

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PPP loading Perhaps the quickest and most rapid uptake of any new sprayer technology - has been the speed with which operators have recognised the need for - and used - induction bowls to load the undiluted product into the main tank. These devices are fitted to the sprayer in a position that the operator can safely reach from the ground in order to both avoid spillage and time [Fig 1]. Almost every formulation can be loaded into the sprayer with ease; liquids, WDG, sachets are sucked into a pipe that directs the product into a violently agitated zone of the main tank. Although, induction bowl use was encouraged by safety needs operators must not be encouraged to climb up onto sprayers especially when carrying product - their popularity was gained by the speed with which they could now load the bigger sprayers and the increased quantities of product loaded each time; a trend that still continues as water volumes come down and hence, product concentration, increases. Loading speed is limited only by the time it takes the operator to open the package and release its contents.

Fig 1 : Operators can load sprayers quickly and safely using facilities such as this induction bowl with its container cleaning facility, PPP store and work area


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Optimising nozzle use PPP are almost always diluted with water before use and sprayed using hydraulic [often flat fan] nozzles that break this liquid up into drops. Both the volume of spray solution and the drop size can be changed and this facet is used to optimise retention on target plant surfaces, disperse more product to preferred locations on a plant or within a leaf canopy. In some instances, the same mechanism may be used to gain crop selectivity by discouraging retention by the crop yet enhancing the same spray on weeds. These efficacy driven needs for a range of nozzles to meet each and every situation is now extended to meet further - environmentally driven - demands [Fig 2]; but the same volume rate/drop size approach is being used to reduce drift beyond the treatment zone - a move that may jeopardise product performance. Regulators may also influence the final advice on how a product should be applied. Some products are approved for use with a stated maximum concentration to protect operators from inadvertent exposure. This concentration will then define a lower volume rate for that active which may restrict the operators nozzle range. Similarly, Regulators may require that some products specify a larger drop size than that needed for its optimal efficacy to limit the risk of drift or operator inhalation. In addition to all these interests that advise on how a product should be applied - there are those the operator may also wish to exploit. In his wish to increase field timing - critical when optimising biological responses - he will exploit faster work rates by using lower water volumes [that will avoid time wasted in transporting water or going to its source] and he may use a coarse drop sizes to keep spraying when wind speeds may be restrictive. The trend now in Northern Europe is to spray at volumes of 100 to 1501/ha using speeds of 10 to 15 km/hour rather than 200 to 4001/ha at 6 to 8 km/hour. In reality, many compromises between conflicting needs are made but a range of nozzle sizes and types have to be considered when meeting all these demands; demands originally imposed by the product but now conditioned by other needs.

Fig 2: Nozzle selection tables need to describe not just physical performance but also likely uses and restraints


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Drift control Larger less drifting drops have been traditionally generated by increasing the size of the nozzles orifice; an option that increases liquid throughput as well as coarsen the resultant drop size. Such drops were also faster and entrained air; features that further increase drift reducing benefits. However, the higher water volumes that then have to be used are at variance with field work rates, efficacy and other demands. New nozzle designs evolved from these conventional, high output, flat fans to those with a pre-orifice and now a type that induces air to generate coarser sprays but at low liquid throughputs [Fig 3]. Sprays which are Coarse, Very Coarse and Extra Coarse can be applied at low volumes. Thus, for those products that will tolerate large widely dispersed drops on the target surfaces, there are great user benefits to be gained. Not surprisingly,

Fine spray

Coarse spray

Coarse spray with Buffer Zone

Fig 3: The most appropriate nozzle choice now has to consider - not just the needs of the target plant and/or best but - environmental interests too; especially the need to reduce contamination - of those areas beyond the treatment zone - by drift

many foliar applied products show less than optimal biological effects from these applications. These products can be applied in low volumes offinersprays - and with low drift hazards - by using well designed air assistance that entrains the drops immediately after the full swath across the boom has been formed.

In-field cleaning Carry over of spray liquid from one crop type to another -risks crop damage and spurred the original interest in better sprayer hygiene. Recently, surface water contamination by pesticides has been attributed to inappropriate sprayer cleaning too. If internal residues are discharged at a point - for example that is close to surface water or onfreelydraining soil, the resultant, localised but very high dose exceeds that for which it is approved - to increase this hazard. Today, dried spray deposits on the outside of the sprayer have also been associated to the same problem as well as posing exposure risks to operators and bystanders.



325 In-field cleaning encourages the following of a routine that ensures all the product is removed and confined to the intended treatment zone [Fig 4]. Equipment that makes this possible has to encourage the operator to do this extra task frequently; a goal that has to be reached with ease and at speed. Modern sprayers have fewer hold back points for residual liquid; better sumps, non-stick build surfaces and bleeding control valves are some advanced features. Dedicated tanks carry clean water to the field where - after spraying isfinished- can be pumped through sprinklers to rinse internal main tank surfaces, flush all control pipe work and still be retained for it to be sprayed out. Field areas preferred for this discharge are those that have not been treated or exposed to less than the full approved dose. Advanced internal field cleaning is so efficient that the volume of clean water used for internal use is reduced- allowing some to be retained for external use. High pressure hoses effectively remove external deposits with lower rates of water use. Operators know where deposits are likely to be greatest and can focus the time spent at the more critical areas. Appropriate in-field cleaning techniques may do more to remove hazards of ground water contamination from pesticide use than any other single development.

Fig 4: Cleaning internal and external surfaces of the sprayer - when done in the last field of use -safeguards the safety of other crops, the environment and the machine - but does so, whilst still containing all the PPP to its approved area of use.


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Regulation Sprayers - just as with pesticides - are subjected to independent scrutiny and controls. International Standards encourage a minimal level of performance or a common identity that avoids confusion. Thus, colour coded nozzles convey to the operator that if all his nozzles are one colour then all flow rates will be the same and thus the dose across the boom will be uniform. Pictograms used to show operator functions are common to all conforming manufacturers and will convey the same message to the operator irrespective of whether he is literate or not or his native language. Standards describe protocols on how to make performance measurements and set threshold limits that must be reached. Internal residual volumes within sprayers are specified. For example, field crop sprayers require such volumes to be < . These control measures are welcomed and encouraged by leading manufacturers as they seek the means for improvement in pesticide use. Until quite recently, little supportive data was needed to back commercial claims made by manufacturers of sprayers or nozzles. This situation is changing with some Regulators demanding that low drift equipment be independently approved and listed as a prerequisite for some specified pesticide uses. Today, sprayers are tested in the EU before and during their use; tested to meet requirements that ensure the PPP is applied with the greatest care and accuracy. Condition of pipes, effectiveness of gauges and uniformity of nozzle output are just some criteria that are examined.

Record keeping for crop assurance/tracking interests Calibration for dose, water volume and drop size is now much easier to achieve. Nozzle selection guides help select most appropriate types and tractors - or prime mover - more readily attain, hold and record - spraying speeds. Electronic monitors can record total spray liquid emission, volumes of product used as well as the area treated and when. GPS based systems are recording where the product has been applied; many developments that make PPP use fully accountable and traceable [Fig 5].

Communication and training Sprayers and spraying is a far more sophisticated technology today then it was just a few years ago. The modern sprayer is an advanced piece of equipment that is expected to complete - efficiently, effectively and safely - a vitally important task; a task that has a high public profile. To meet that challenge, training takes place at every level - from the operator to the machinery deak who helps to advise on the purchase. Whilst instruction books remain essential, the



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Fig 5: Sprayer calibration and recording is much eased with devices such as this nozzle selection device and in cab controller operator is further supported with CDs, active flow charts, moving images and devices to help ensure accuracy of adjustment and recording [Fig 5]. Web sites such as that used by Hardi International A/S [www.hardi-international.com] make a wealth of information immediately available too. Users can interact with the site as well be updated on recent developments. Courses for all spraying needs are available; operators may wish to attend locally held events whilst specialist interests are also met. Week long Application Technology Courses are held on application technology; an activity that attracts university, regulatory, agrochemical folk from around the world.

Conclusion The sprayer remains one of the most important farm machines. However, to meet current needs for efficiency as well as safety, it has evolved into larger more complex designs. Modern manufacturers are meeting today's challenges by introducing technological advances that both meet these demands but doing so in a manner that encourages the operator to understand and adopt the required improved practice.


Environmental Fate and Safety Management of ... - ACS Publications

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