Equipment and consumption rates
Mikhail Evgenievich DANILOV, Avgusta's Director for Marketing and Sales, continues his story about the influence of various factors on the effectiveness of pesticides. Previous publications have discussed the effect of water quality and weather conditions on spray performance and droplet behavior during spraying. Now we will talk about the equipment used to apply pesticides.
For the bulk of crops, a boom sprayer is most often used. This is the "weapon" from which we will either hit the target accurately and in time, or we will miss. And therefore, the effectiveness of pesticides is highly dependent on its characteristics and state of use.
PREPARATION OF THE SOLUTION
The first stage of the sprayer, before the start of the actual treatment, is the preparation of the working solution. And our task is to make the working solution so that the preparation is evenly distributed throughout its volume, does not accumulate in the stagnant zones of the sprayer, does not form precipitation or clots of inverse emulsion, etc.
The key phrase in the description of the preparation of the working solution is “when the mixer is running (turned on)” in various variations (the mixer can be described as “mechanical”, “hydraulic”, “working well” or “constantly working”).
Recently, the fleet of sprayers in many farms has been renewed, however, their variety in terms of quality is still great. And in my practice, I have met sprayers (I will not do advertising or anti-advertising to anyone), where a mechanical agitator starts to work only when the sprayer is moving, and therefore the procedure for preparing a solution "with the agitator on" is simply impossible. To reduce the risk of sedimentation of poorly soluble drugs (in the form of SP or WDH, for example), in such circumstances it makes sense to prepare a mother liquor.
In addition, it should be borne in mind that when a similar sprayer is added to the tank, many drugs, due to their density, which is greater than that of water, will sink to the bottom. And this, in the case of preparation of tank mixtures, can lead to the formation of a hardly soluble sediment. The subsequent cleaning of the apparatus becomes a very difficult task. Somehow I personally witnessed the torment with such a sprayer when trying to make a tank mixture of the "August" Tornado and Herbitox: the "concrete" formed at the bottom of the sprayer could not be stirred with a stirrer that turns on only when driving.
It is important to remember that when preparing a working solution, the amount (unlike mathematics) depends on the permutation of the terms in the equation. For example, many formulations in the form of emulsion concentrates (EC) tend to form a so-called inverse emulsion. Simply put, when we add a drug to water, then small droplets of the formulation in water are formed - an emulsion that we are striving to obtain, but if you pour water into the drug, then you get small droplets of water in the drug, that is, an inverse emulsion. It can be extremely thick and stable and can be extremely difficult to emulsify by adding water and stirring. Moreover, this process is accompanied by the clogging of everything and everyone in the sprayer with the corresponding comments of the machine operators and agronomists to the developers. The danger of "inverse emulsions" must be borne in mind, as the variety of sprayers with different possible loading methods can lead to unpleasant surprises.
Continuing the conversation about the amount that changes from the permutation of the terms, tank mixtures of drugs must be prepared in the sequence (as a rule, from less soluble to more soluble), as recommended by the manufacturers, adding each subsequent drug after the previous one is completely dissolved. Only the drug itself or its stock solution is filled through the pre-tank, but not water. And in order to reduce the possibility of "surprises" already in the sprayer, it is necessary to first check the pesticides for compatibility (especially when it comes to products from different manufacturers and combinations unfamiliar to you from experience).
SPRAYER CONDITION
We assume that by the beginning of spraying, all the mechanisms of the sprayer, from the pump, pipelines, filters and directly to the spray nozzles, are in good working order, the pressure in the system is maintained at the required level, nothing flows, and the spread of the liquid flow rate in the spray nozzles during the test does not exceed 10 %. If the nozzles were previously cleaned with an awl, a screwdriver or a metal brush and one can only dream of 10% spread and a uniform spray, then they are replaced with serviceable sprayers.
What happens if you ignore the injectors? Once we got questions from a client about the strong aftereffect of the herbicide Lapis Lazuli on barley sown after potatoes. We arrived at the place, and the field seemed to be combed with a comb with rare teeth, and every meter with a little - neat parallel strips of bare earth with a complete absence of seedlings. And nearby there is a “handmade” sprayer with low-volume electric nozzles, each of which produces not only a “cloud” of spray, but also a trickle of working solution. It turned out that this particular sprayer was used in a potato field in the same way last year. And he, of course, introduced the metribuzin norm for each nozzle many times higher than all the regulations. That's why the barley turned out to be "combed".
SELECTION OF NOZZLES
The registration documents for any pesticide always indicate the rate of application of the working fluid per hectare for a given crop. It can fluctuate widely depending on the drug, its mechanism of action, the main location of the target object along the profile of the vegetative mass, the usual density of its canopy, and so on. Due to the peculiarities of the registration process in the Russian Federation, for most manufacturers and pesticides, these norms usually start from 200 l / ha. And for contact preparations, they end up with multiples of large norms - 400 l / ha, and for some perennial tall crops they can exceed 1000 l / ha.
The application rate is derived from the caliber (size) of the sprayer, the distance between the spray nozzles on the boom, the operating pressure, and the spray rate. By virtue of the prevailing ISO standards, the nozzle caliber is generally understood to mean the nozzle flow rate in US gallons per minute at 40 psi operating pressure. This means that caliber 01 is an outflow of 0,1 US gallons (one gallon equals 3,785 liters) at 2,8 bar. Caliber 02, 03 or 04 means 0,2, 0,3, or 0,4 gpm at 2,8 bar. Sprayers of the same caliber are usually painted in the same colors to reduce possible confusion.
But all this math and American gallon-lb-inch specifics do not need to dive into. Because the corresponding calculators for the selection of nozzles are available in the mobile applications of many pesticide manufacturers (for example, in the mobile application "Augusta"), sprayers or sprayers that can be downloaded from the Google Play and App Store. And in them everything can be counted based on the kilometers, meters and liters we are used to. Having given such a program the required consumption of the working solution per hectare, the distance between the nozzles of the sprayer and the estimated speed of its movement, we get a set of possible nozzles.
An important characteristic of the atomizer is the size of the drop it forms. Let me briefly recall the droplet classes according to the ISO 25358 standard: VF / very fine - very fine; F / fine - fine; M / medium - medium; C / coarse - large; VC / very coarse - very large; XC / Extremely coarse is extremely coarse and UC / Ultra coarse is ultra coarse. A detailed description of the classes (so far only in English) can be found in the new Lechler catalog: www.lechler.com/fileadmin/media/kataloge/pdfs/agrar/EN/lechler_agriculture_catalogue_2020_en.pdf.
The quality of processing, as we wrote earlier, is significantly influenced by the weather - first of all, the temperature and humidity of the air, as well as the wind speed. At the same time, these factors affect the efficiency of spraying in different ways, depending on the characteristics of the nozzles (the size of the drop they form) and the application rate. So, small-drop spraying in conditions of high relative humidity, moderate temperatures and wind should lead to a more complete coverage of the treated surface, which is extremely important for contact and local systemic preparations. But at the same rate of consumption, but in dry, hot and windy weather, small droplets will be susceptible to drying and drift to neighboring fields, therefore, in such conditions, coarse-droplet application is preferable (especially with the use of injection nozzles, which reduce the risk of falling droplets bouncing off the treated surface) ... Now drift has become the most important characteristic, and droplets less than 150 microns in size are absolutely drift, which can lead to the death of adjacent crops. Within the framework of this short article, it is not possible to describe all the variety and features of spray nozzles. Detailed characteristics of specific nozzles, based on their size (caliber), the type of spray they form, droplet size, drift hazard, suitability for systemic or contact pesticides, as well as important recommendations regarding the height of the sprayer boom above the object being processed depending on the angle of the spray pattern and the distances between the nozzles are in the materials of the companies "Lechler" and "TeeJet". This information should be looked for on the sites www.lechler.com/fileadmin/media/kataloge/pdfs/agrar/RU/lechler_agrar_broschuere_feldbau_ru.pdf и www.teejet.com/ru/spray_application/nozzles.aspx
There are also programs for the selection of nozzles that take into account weather conditions. This is, for example, the Jacto Smart Selector mobile application from one of the world leaders in the production of sprayers - the Jacto company, also available for installation in the Google Play or App Store. In addition to weather, this program also takes into account the characteristics of the pesticide - herbicide / fungicide / insecticide and systemic / contact / soil.
Another interesting mobile application developed by the Department of Agriculture and Food of Western Australia is called "SnapCard" https://link.springer.com/article/10.1007/s13593-015-0309-y... It calculates an estimated coverage ratio (with different experimental model tolerances, of course) depending on weather conditions for three calibers (02, 03, 04) and four varieties of TeeJet nozzles - TT, TP, XK and AIXR. The program also provides for the use of water-sensitive paper: by taking a photo of it with a smartphone, you can determine the percentage of surface coverage with a working solution.
Inquisitive technicians can use water-sensitive paper to compare calculated coverage with actual results to determine how well Western Australian approaches correlate with local conditions.
Let's repeat: many factors affect any spraying. Among them are the flow rate of the working solution, the type of nozzle (operating pressure, spray pattern, droplet size and characteristics, angle of attack), the distance between the nozzles, and the height of the boom. Temperature, humidity, air pressure, wind speed and sprayer travel speed are important. What matters is the density of the vegetative mass, the location of the target object, the angle of inclination of the treated surface to the ground, the properties of the treated surface. Let's not forget about concentration, surface tension, viscosity of the working solution, and so on. At the same time, many factors act in different directions, and for different modes of operation of the sprayer "go" either in the plus of efficiency or in the minus. Additionally, it should be borne in mind that the use of various tank mixtures can lead to an increase in the concentration in the working solution of not only active substances, but also solvents and adjuvants, which can cause phytotoxicity.
WHERE IS THE NORM?
Numerous experiments carried out by both independent and dependent organizations on manufacturers or technology or pesticides, often do not give an unambiguous answer which regime is better. Too much depends on specific weather conditions, stage or degree of crop / weed / pest / disease development. As a result, in one season we can see a significant difference in the spraying efficiency at 100 and 150 l / ha, and in the other we can not see the difference between 25 and 200 l / ha.
What can we say about the personal experience of practicing agronomists? One will be foaming at the mouth to prove that any drug works great at a rate of 25 l / ha (some clever Frenchman said that he always does this), and the other with the same ardor will tell the story of how in heat and drought burned winter wheat with a small-droplet sprayer with a mixture of preparations based on 2,4-D, florasulam, propiconazole with cyproconazole and lambda-cyhalothrin. And both will be right, because this is a personal experience of each associated with a specific application of a specific product in specific conditions, and not a meta-study.
In addition, even the most remarkable experiments from the point of view of the method of field experience have a significant drawback. They are carried out almost simultaneously, and therefore do not take into account such a factor as the time required for processing, and give an answer only to the question of which spraying mode is better right now and for a specific situation on the field. And a practicing agronomist who does not conduct research, but works in real time - organizational problems, weather "windows", lack of machine operators and breaking equipment - there is a difficult choice. Which is better - taking into account the existing set of sprayers and the logistics of supplying water, spraying in seven days with the recommended rate of application of 200 liters per hectare or in four to five days at the rate of application of 100 l / ha? Or maybe to process everything in three days with a consumption rate of 50 l / ha? Indeed, in many cases it is better to work less efficiently in terms of the degree of coverage, but on time than qualitatively, but late - for overgrown weeds, insensitive stages of the pest, or at such a phase of the disease when even the most effective treating can no longer cure it and an eradicating drug.
Of course, from general considerations, if you have a sprayer for your 10 - 15 - 30 - 50 hectares (as is the case with farmers in Europe), and the water is not hard, salty and not dirty, then you can work at a rate of 200 - 300 - 400 l / ha, and think of seconds (time spent on processing) downright. But when you have one sprayer at your disposal for hundreds (or even thousands) hectares, then the time should be treated with much more reverence.
RULES AND EXCLUSIONS
With a high load on the sprayer, pushing to go beyond the limits of the registered norms, we can briefly advise the following. When it comes to systemic herbicides (these include, for example, glyphosate, 2,4-D, dicamba, MCPA, sulfonylureas, florasulam, clopyralid, picloram), for which the degree of coverage and penetration into the lower layer of the weed are not so important due to their movement along the phloem, then for increasing productivity (of course, taking into account the danger of drift), you can work with reduced rates of consumption of the working solution. Even medium-sized annual weeds with a relatively large irregularity of coverage when using coarse-droplet nozzles will be destroyed by glyphosate better than overgrown ones due to their higher specific surface area. For such preparations, consumption rates up to 100 l / ha are quite acceptable. And if we look at the situation with the registration of such products in countries where gallons and acres are used, then there it often starts with a rate corresponding to values of just under 50 l / ha.
However, lowering the recommended application rates requires great care. The fact is that any formulation is developed for use in the form of an emulsion or suspension at a certain concentration. With a decrease in the rate of water consumption at times, you can get an unstable working emulsion or suspension.
For anti-grain herbicides the situation is even more complicated. The leaves of cereals are always closer to the vertical, and in addition, they are often less wetted than the leaves of many dicotyledonous crops (not all, of course). Therefore, although there is also a successful experience of using modest flow rates of working fluid for anti-cereal preparations, it is still not worth reducing the flow rate below 100 l / ha.
A separate question - soil herbicides... Often, the recommendations indicate that they need to work so as to cover the soil well, and therefore only very high rates of consumption of the working solution are permissible (we are talking about regulations that do not require the incorporation of the drug into the soil after spraying). But here, too, everything strongly depends on the ability of the herbicide to move, in this case, not in the plant, but in the soil. If we talk about pendimethalin, then it does not move in the soil and in plant residues - where it fell, it fixed there. And chloroacetamides (C-metolachlor, propisochlor, acetochlor) and triazines (prometrine, metribuzin, terbutylazine) have a relatively high mobility, and therefore very high consumption rates of the working solution required by pendimethalin are not necessary for them.
Well, as for contact herbicides (bentazone, desmedipham, fenmedipham), then it is preferable for them to spray with a high degree of coverage, which is achieved primarily by higher rates of the working solution and small-drop spraying.
For fungicides and insecticides coverage, bottom-tier and leaf-back are much more important than systemic herbicides. This requirement for contact drugs is clear to everyone, but it is also important for systemic ones. Systemic fungicides and insecticides are either locally systemic (they can penetrate through the leaf or move along its surface, slightly moving through the vapor phase), or xylem-systemic (some triazoles, strobilurins, succinate dehydrogenase inhibitors), that is, they can move through the plant only acropetally, upwards. And unlike glyphosate, they, once on the upper tier of the plant, cannot end up in its lower part or in the roots. Therefore, if possible, it is worth using insecticides or fungicides with a working solution rate of at least 100 l / ha. And it is even better to use at least the lowest recommended rate for processing (if, of course, the technical equipment and the availability of water with appropriate logistics allow).
There are situations when the rate of the working solution has to be increased and not spare external surfactants. For example, it is worth doing this when fighting the cabbage moth, which lives on the back of a slippery and thickly waxy rape leaf.
But again - "the theory is dry, my friend, and the tree of life is magnificently green." The effectiveness of fungicides, when the disease "leaves" for the middle of the incubation period, sharply decreases. And the incubation period for brown rust on cereals, under favorable conditions, can be within one week. Therefore, sometimes you have to work not so efficiently (reducing the rate of the working solution), but on time, since doing the treatment three to four days earlier becomes, as the classic used to say, “paramount”.
In addition, some fungicides (for example, systemic triazoles) at their high concentration in the working solution (and even in mixtures with herbicides, which is not uncommon), especially when applied in small droplets in dry and hot weather (when the drop on the way to the target object has time to dry out and still increase the concentration) may exhibit phytotoxicity. It is, of course, influenced by the peculiarities of the culture and varietal sensitivity, but if the manifestations of such phytotoxicity do not often occur on cereals and slightly affect the yield, then it can be dangerous on various "delicate" vegetables or potatoes.
To be continued
Prepared by Elena POPLEVA
Photo Lechler и Amazon
Contact Information
Mikhail Evgenievich DANILOV
Tel .: (495) 787-08-00