‘Costs precision spraying in soybean and maize crops 2.3 times lower than conventional’

The researchers from the Grosso State University in Brazil and the Federal University of Mato Grosso do Sul emphasise in their study ‘Reduction of pesticide application via real-time precision spraying’ that the majority of crop prices vary depending on supply and demand on the market. “The only way for farmers to increase profitability is to decrease production costs, without compromising crop yield”, they say. Precision spraying is a way to lower costs, the study suggests.

The researchers analysed data from pesticide applications (herbicides, insecticides, and fungicides), sprayed on soybean and maize on two farms, and two crop seasons in the municipality of Mineiros in the state of Goiás, Brazil. Both farms were cropped with a no-tillage system. The region has an average annual rainfall of 1600 mm. Data were collected from a total of 22 fields from both farms.

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John Deere 4730

During the experiment, spraying applications were conducted in the entire field. A self-propelled sprayer, a John Deere 4730, was used on each farm. The sprayer was equipped with a spray boom of 36 m and a hydraulic stainless flat fan nozzle (Teejet 4003).

The nozzle spacing was 0.3 m, and the spray speed was 5.6 m s−1. This specific nozzle can apply a flow rate of 1.1 L min−1 at a hydraulic working pressure of 2.8 bar (280 kPa). For the precision spraying , a Weed-it (Smart Sensing) spraying system, with real-time sensors for detecting plants, was assembled on the sprayer.

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Highest averages pesticide reduction

The Weed-it system had 36 sensors installed on, with a spacing of 1 m. Each sensor had five independent detection channels, which controlled five independent spray nozzles. The sensors operated at a height of 0.60–0.80 m from the crop canopy.

The real-time sensors facilitated the system by detecting the plant, which is followed by instantaneous spraying by opening and closing pulse width modulation (PWM) valves. Each PWM valve controlled each spray nozzle on the sprayer boom.

The researchers found that desiccation and pre-planting applications showed the highest averages of pesticide reduction

The experiment was performed with 721 spray applications over 3,702 ha of land, across two years. The spraying applications were classified into four types of operations for each crop. For the soybean crop those applications were: weed desiccation, crop pre-planting, first post-emergence application, and crop defoliation (pre-harvesting). For the maize crop, the applications were: the first, second, third, and fourth applications of post-emergence herbicides.

The researchers found that desiccation and pre-planting applications showed the highest averages of pesticide reduction, close to 76.0% and 72.1%, respectively, in the soybean crop. These spraying applications occurred before sowing. The sprayed applications after crop sowing showed a lower average reduction in the volume of the pesticides, with an average reduction of 51%. Such a decrease in reduction can be attributed to the fact that these applications were made during soybean cultivation, with the row spacing almost closed by plant leaves.

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Volume reduction pesticides maize crop

The volume reduction of pesticides applied to the maize crop ranged from 53.7% to 36.6%. The results from the first, second, and third spray applications did not differ significantly from each other. The results from the fourth spray application showed an average of 37% volume reduction of pesticide application. By then, the crop developed and increased the foliage, covering the soil on the row spacings.

The researchers explain that several other studies that have evaluated real-time precision spraying systems to manage weeds, achieved a significant reduction in herbicide usage levels of approximately 30% to 40%. “This technology facilitates the use of a practical alternative approach that focuses on precision spraying in the context of environmentally friendly pesticide application”, they point out.

“Further investigation is required to determine the extent to which these results can be expanded to other crops, varieties, and types of applications. Other pesticide applications, as well as herbicide applications (for weed patch control), with this site-specific technology, must be studied. Recently, studies on insecticides have gained attention. A study with aphids and ladybird beetles in cereals indicated that site-specific spraying with sensor technology could reduce insecticide use by 13% on average.”

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Long-term perspective

When all costs were added together, the conventional application by total area spraying was noted to have a cost per hectare of US $ 418.71, whereas the use of the specific spray application had a total cost of US $ 183.50 per hectare. So, the experiment resulted in reduction of 56.16% (2.3 times lower costs). In these cost calculations, fixed costs (depreciation and interest) were also included.

Under the experimental conditions applied, there were no differences in the yields of soybean and maize crops, obtained using the precision spraying technology, compared to the historical yield of soybean and maize crops.

Potential profitability

The researchers point out that the potential profitability of precision technologies will depend on many variables such as farm and field size, crop, soil type, degree of specialisation, on-farm labour costs, and access to finance.

Implementation of precision spraying requires capital investment

“In addition, individual farmers may decide on adoption, depending on their current investments in machinery and the expected time of replacement. Other elements that may hinder or promote adoption are access to training and extension services related to precision farming.” Implementation of precision spraying requires capital investment, they say, and farmers should keep in mind a long-term perspective when adopting this technology.