In agriculture, just as with sprayers, herbicide units are also essential to protect cropland from the presence of soil-damaging pests. These tools enable the combination of water and agrochemicals to eradicate pests, plant and animal, from crops.
This group of tools falls into the category of mechanical pressure sprayers, or commonly called classic sprayers. This term is attributed to all those spraying machines that use a pump to distribute the product of water and pesticide.
In addition, weed control includes all operations that are carried out through the use of sprayers on field crops, such as:
-
- cereals
-
- tomatoes
-
- vegetables
A separate category of trailed and carried sprayers are those equipped with an air sleeve, where the fan apparatus, as well as for sprayers, allows for a more homogeneous and effective spraying of plant protection products on the fields. In this case, the fan jet allows its parallel thrust with more uniform droplet sizes.
The nature of the spray pattern allows for quick release of the pesticide through the nozzles, but with droplets of widely varying diameters. The diameters of the liquid particles, in fact, predominantly presents a diameter between 300 and 600 μm but much larger or much smaller droplets can be found.
This size variation may depend on:
Type of chemical used
Pressure
From the type of nozzle used
type of mixture
The categories of commercially available weed control groups.
There are two broad categories of products on the market:
Carried weed control units have a three-point tractor attachment and consist of a tank, a low-pressure pump, a mechanical or hydraulic type weed control boom and possible lance attachment for cleaning the sprayer at the end of work. Generally, the capacities of these pulverizers range from 400 liters up to 1800 liters.
Trailed weed control units, on the other hand, generally have larger dimensions than carried units and are attached to farm tractors through hooks, eyes or articulated drawbars of various types. In fact, this tool features a rubberized trolley that supports the tank and its weed control bar.
How a weeding group is composed
All pulverizers are composed as follows:
- frame
- pump
- tank
- distributors or controls
- bars
Frames are usually made of hot-dip galvanized steel. Some companies make them in powder coating.
Tanks
The tanks are made of polyethylene and consist of a main tank and two independent tanks, of which one is for operator cleaning and the other for circuit flushing.
They have a capacity between 200 and 1,500 liters for carried versions, and between 1,000 and 3,000 for trailed versions.
Pumps
The pumps used are low-pressure diaphragm pumps whose parts in contact with the liquid are made of polyamide or plasticized aluminum. The maximum operating pressure of these pumps does not exceed 20 bar.
Distributors or controls
Distributors, or controls, can be of various kinds and are divided into:
Manual controls can be three, four or six-way; they are generally used with mechanical booms or hydraulic booms up to 15 meters.
There are, in addition, proportional manual controls that allow the same amount of liters per hectare to be distributed when opening and closing one or more boom sections, as long as the speed of the tractor is constant.
Electric controls can be three-, four-, five-, or six-way and are distinguished by on/off switching of individual sections, and in volumetric. The latter make it possible to distribute the same amount of liters per hectare when opening and closing one or more boom sections, as long as the speed of the tractor is constant.
A separate topic is the computer, which allows the same amount of liters per hectare to be distributed as the speed, pressure, and opening and closing of one or more boom sections change.
The bars
castings
Jets can be of various kinds; the most commonly used are:
Hydraulic bars are made of hot-dip galvanized steel, are equipped with stainless steel pipes and their respective castings, and range in size from 12 to 24 meters.
There are several models of bars on the market that can be grouped as follows:
Hydraulic cross-locking booms have a working width of 12 to 15 meters and are mostly combined with carried sprayer.
In contrast, those with side closure, which have working widths exceeding 18 meters are mainly used on trailed sprayers.
What is the recommended combination of bars
Tentatively, the ideal choice of pulverizer might follow the pattern below:
- With 400- to 600-liter carried sprayers: 6- to 12-meter bars
- With carried sprayers from 600 to 1200 liters: bars from 10 to 15 meters
- With carried sprayers from 800 to 1200 liters: bars from 12 to 18 meters
- With carried sprayers from 1200 to 1800 liters: bars up to 27 meters
- With trailed sprayers from 1000 to 1500 liters: bars from 12 to 15 meters
- With trailed sprayers from 20 to 40 quintals: bars up to 27 meters
Setting up the sprayers
Sprayers are highly customizable equipment depending on the type of crops, crop extension, and type of tractor (equipped with parallel guidance, isobus). In fact, the distribution of plant protection product could be done through the use of manual, volumetric-manual, volumetric-electric, electric on/off, and computer controls.
To these can be added countless accessories such as:
- nozzle type
- shock absorbers bar
- hydraulic correctors
- hydraulic lifters
- air sleeve
- computer with GPS receiver
- tracefile
- filling meter
- self priming pump
- electrohydraulic systems
- seletron jets
Proper pesticide treatment depends on spray homogeneity and delivery stability. This last factor is most important because a bar that is not perfectly parallel to the ground can be the cause of:
- drift
- overdose of plant protection products
- Insufficiently sprayed areas
Other factors that influence to the proper phytosanitary treatment result from:
- bar height above the ground
- Speed of work execution (must be constant)
- nozzle flow rate
- correct speed in relation to the nozzles used
- agitation system (mixing of plant protection products)
- filters (blocking function for particles that may occlude or change the amount of product dispensed per hectare)
In addition to these factors are elements inherent in safeguarding the environment and the operator.
BEST WEEDING PERIOD
In the agribusiness sector, weed control is vital to protect crops from pests, weeds, and weeds that undermine crops, which is why it is important to understand the best time to carry out this procedure.
Generally speaking, but it is not a fixed rule, the best time to use sprayers and spray booms is from spring onward. This is because most plant protection agents work best at temperatures between 10 and 25 degrees.
However, the correct answer to the best time to carry out herbicide operations is: when needed. This may seem a trivial answer, however, activities and crops are different and occur at different times of the year.
For example, vegetables are grown throughout the year, requiring constant herbicide intervention in order to protect the agri-food product.
However, depending on the different periods, activities with sprayers and spray booms are always carried out by the farmer. This is because many pathogens, especially animal pathogens, tend to form after rains and periods of high humidity. Moisture, in fact, tends to promote the establishment of grass and insect larvae.
The grass, in order to feed itself, risks depriving fruit trees of water and nutrients from the soil. Insects, also in the business of feeding, are likely to attack the fruit on the tree, bringing potential disease and damage to the produce.
What is the best time for weeding activities?
Weeding can be done in two distinct stages:
- Pre-emergence
- Post-emergency
Pre-emergence activity, which often coincides with pre-seeding, is an operation designed to disinfest cropland from weeds that, by arising, could create damage to the future fruit plant. A preventive treatment promotes the elimination of competing grasses and reduces the risk from insect attacks.
Post-emergency treatments, on the other hand, should be carried out when weeds or animal hazards, are already present in the soil. In general, these treatments are carried out after planting during particularly rainy and/or wet periods, especially to defend fruit plants from insects.
If the pre-emergence activity is easily scheduled, the post-emergence activity can be predicted by keeping abreast of weather conditions, however, sudden rains dictate that the level of attention must be kept very high in order not to waste part of the investment.
In addition, knowledge of the phenological cycle of agribusiness products helps to study the best activities to preserve one’s crops.
In general, the following outline can be followed for guidance on when to weed:
- Fruits: from February to August
- Vegetables: year-round depending on the crop planted
- Cereals: March to May (pre- and post-transplant herbicide treatments are generally done in February)
NOZZLE TYPES
Agricultural spraying machines, whether sprayers or weed control units, owe the successful distribution of pesticides to a small but vital component: the nozzle.
The nozzle is the terminal on the machine that distributes the pesticide and converts the energy that the fluid possesses into kinetic energy. The nozzles, if well calibrated allow for minimal drift, that is, the plant protection solution not hitting the target.
Well-calibrated, therefore, allow both reduced economic expenses and potential risks to the environment and people.
What is the right nozzle for your farm machinery?
The nozzle, like any component in agricultural production, requires of the right choice in order to achieve the desired result by the farmer.
Its function of creating droplets of water/agropharmaceutical solution comes from its mechanism of producing droplets to be distributed on plants in order to carry out treatment.
The choice of nozzle depends on the type of application the farmer intends to make. In fact, for field crops there are a wide variety of nozzles that can be used depending on the types of treatments:
- herbicides
- fungicides
- insecticides
For each of these categories, there are additional variables that intervene when contact treatments or systemic treatments are given.
This also applies to the choice of nozzles to be used on atomizers.
Commercially available nozzles
There are different types of nozzles on the market, depending on the mechanism, but four macro categories are generally given:
- spray nozzles by pressure or hydraulics
- pneumatic spraying diffusers
- rotary nozzles (centrifugal pulverization)
- atomizers or foggers (thermal spraying)
The hydraulic spray nozzle turns liquid into spray by passing the solution through spray tip. It is also divided into: threaded body, filter, spray tip and locking ring.
Its operation is simple: the greater the pressure, the smaller the outlet orifice, the finer the droplets distributed.
Several categories of these nozzles are found on the market:
- slotted
- turbulence
- mirrored
- full cone
The choice of these nozzles varies according to the type of crop, the amount of liters per hectare to be distributed, the speed of the tractor machine, the type of pressure and the type of treatment.
For the purpose of product distribution per hectare we will provide mathematical formulas, which are easy to understand, to better understand the choice of the right nozzle for one’s needs.
To calculate the formula for herbicide groups, the steps below should be followed.
If we want to obtain the liters per hectare that the sprayer distributes at a given pressure, at a given speed, and with a given type of nozzle, we must use the following formula:
Liters per hectare (lt/ha) = 60000*lt/min (per nozzle) all divided by kilometers per hour(km/h) and distance (L) in centimeters, between nozzles.
Example:
60000= fixed number
1.82= lt/m AITTJ60 nozzle at 4 bar (TEEJET anti-drift nozzle)
5 km/h=speed of the tractor
50 cm= L (distance between one nozzle and the other)
60000 *1.82/ 5*50= 436.80 lt/ha
If, on the contrary, we intend to calculate the gallons per minute of each individual nozzle, the mathematical formula to be used will be as follows:
Lt/ha*Km/h*L
_____________ = 500*5*50/60000= 2,08
60000
Data taken with bar height from the ground of 50 centimeters.
Pneumatic spray diffusers the spray is generated by the collision between the transmitted fluid and a high-speed air stream produced by a fan. The higher the air velocity, the finer the droplets will be.
Rotary nozzles consist of a by a toothed rotating disc that rotates by a motor while liquid is conveyed at low pressure to the center of the disc. Finally, the indentation of the disc contributes to the creation of the drops. Fineness is derived from the speed of the disk: higher speed creates smaller droplets.
In Nebulizers, or foggers, the mixture is pulverized by the stream of hot gases that are produced by combustion of a small engine.
