The negative effects of weeds on crops include: competition for production factors (light, water, nutrients) and/or allelopathy (interaction of organic substances secreted by plants at the root level). The competition that weeds exert on fruit species over production factors will be greater in newly established plantations or young orchards.
An optimal weed control strategy in cherry trees must initially consider prevention and eradication, and subsequent weed management, which must consider all cultural practices (manual and mechanical methods), physical, biological and chemical methods, aimed at reducing their incidence, minimizing the damage that weeds can cause in agricultural farms.
Chemical control offers effective, timely and, often, more economical weed control when compared to other control methods. Of course, herbicides are excellent tools that must be used appropriately, taking care of the environment and avoiding possible phytotoxicity problems that their misuse could cause (Integrated weed control in cherry trees March 30, 2023, https://smartcherry.cl/noticias/control-integrado-de-malezas-en-cerezos/)
In industrialized countries herbicides are applied to 85-100% of all major crops. Finney (1988) predicted that the need for agricultural intensification, as a result of high levels of population growth, will increase herbicide use. Used judiciously, within an integrated weed management system, herbicides are safe for the farmer and pose minimal risk to the environment (Source: Food and Agriculture Organization of the United Nations). https://www.fao.org/3/t1147s/t1147s0e.htm)
Herbicides may be applied to foliage or to the soil. Herbicides applied to foliage and affecting only the treated part are described as contact herbicides, while those that move from treated foliage to a point of action elsewhere on the plant are called systemic herbicides. Soil-applied herbicides that generally affect germinating weeds must persist for some time to be effective and are called residual herbicides. Some residual herbicides have contact action and affect roots and stems as they emerge from the seed, while others enter the root and underground parts of the plant and are translocated to their point of action.
The treatments of pre-emergence are always carried out before the weeds emerge. The treatments of post-emergence They are applied after the crop and (usually) weeds have emerged.
Two of the most important factors determining spray effectiveness are the range or spectrum of droplet sizes and the coverage of the target by the spray.
Small droplets produce very good coverage and adhere well to hard-to-wet surfaces such as waxy grass leaves, but are subject to drift and evaporate rapidly, especially at low relative humidity. Larger droplets tend to bounce off "hard-to-wet" surfaces, but drift and evaporation are less of a problem here. A broad range or spectrum of droplet sizes is best for good coverage of these diverse targets, and proper spray nozzle selection generally meets this requirement (Source: Food and Agriculture Organization of the United Nations). https://www.fao.org/3/t1147s/t1147s0e.htm).
Herbicide application equipment in fruit growing
There are various types of equipment used in fruit growing to apply herbicides. Among them we can find: "pumps" or backpacks, application bars with hydropneumatic equipment (suspended or dragged), application motorcycles with electric bars and pumps, among others.
Nozzles for herbicide application
The nozzle functions to divide the liquid into droplets, form the spray pattern and control the flow or rate of the liquid. The most commonly used nozzles for weed control are fan nozzles. The most common are: flat fan nozzles with an application width of 110° or 90° (tip nozzles) and “mirror” nozzles that can generate an application width from 130 to 160°.
Within both types of nozzles we have those with air injection (anti-drift effect) and those without air “injection”. There are various brands on the market and it is recommended to invest in those that guarantee their manufacturing components and their technical qualities, such as the indicated flow rate according to working pressure.
In general, for applications with booms, it is recommended to space the nozzles between 50 and 60 cm on the application boom and the recommended application height is 50 to 60 cm.
Spray quality, or droplet size range, becomes finer as the fan nozzle orifice size is reduced, and the nozzle angle and application pressure are increased. Conversely, spray quality becomes coarser as the orifice diameter is increased and the nozzle angle and application pressure are reduced.
The quality of the application, as with foliar applications, will depend on 3 components described in Figure 1.
Figure 1. Responsibility of the factors in the effective control of an application.
1.- Choose a good herbicide product (active ingredient and effective formulation), with sufficient support, a reasonable cost for its objective, ideally with low environmental impact and always consider its dose range.
2.- Use agrochemical products in a timely manner depending on the development stages of our crop and the weeds to be treated.
3.- Finally, use application equipment that is always in good maintenance condition, clean and optimally calibrated to develop applications in a wide range of water volumes or “application rate”.
Herbicide applications can be carried out at different speeds and will depend on several factors, however, we must always choose the maximum possible transit speed in orchards depending on the topography and the equipment available for this. The application speed ranges (we will give them only as a reference) can be wide from 3.6 (backpack pumps) to 5.5 km/hour in suspended hydropneumatic equipment with bars and motorcycles with electric pumps with bars.
Do we apply 100% of the surface or a proportion of it?
We can carry out weed control on the entire surface of a hectare or only on a proportion of it (most frequent recommendation), leaving a central strip of plant cover in the center of the rows which is generally 50% of the surface.
Whatever the choice of weed control management and “vegetative cover” management, herbicide doses are expressed in dose/ha (kg or L).
The recommended water volumes for applications vary and depend on the type of herbicide to be used. As an example, some recommendations are between 100 and up to 300 L/ha.
If we consider an application at 50% of the surface (on row) and the recommendation of the commercial product is 2 L/ha with an application volume of 100 L/ha; we should use in a “physical” ha only 1 L and with a volume of 50 L of “wetting”.
The above example may seem like “common sense”, however, we find inappropriate uses or overdoses of some herbicides because the doses calculated, purchased and applied are the “total” doses per ha.
Following the example and considering an orchard with a planting distance of 4 meters between rows, to apply 100% to the surface (recommended on the labels) with a boom with nozzles spaced 50 cm apart; we must have 8 nozzles to cover the width of the rows.
The arrangement of the nozzles must consider an “overlap” between their fans as described in the following diagram:
If we consider an application speed of 5.5 km/hour, the time we have to apply “within the crop (without the turns) is 27.27 minutes.
The nozzles we can choose for this recommendation are: AVI 11001 Orange at 4 bar pressure (unit flow rate of 0.46 L/minute). Total nozzles: 8.
To cover just 50% of the surface we can do this by simply “eliminating” 4 of them (central) and leaving 2 at each end of the herbicide bar.
It will always be It is recommended to maintain an application height of 50 to 60 cm (maximum) to achieve the width of the trail and a uniform deposit.
Timely and effective weed control will always be part of the profitable outcome of cherry and other fruit tree cultivation. Don't neglect it.
In order to develop effective and efficient application management plans, we must have previously diagnosed equipment in all its components, repaired and replaced its critical elements, perform annual and periodic maintenance, permanent cleaning and have highly trained personnel to develop the applications that will translate into the success of our crop at harvest with the least impact on the environment and people.
