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CDA Aerial application in Brazil

Micronair AU5000 magnifying glass Micronair AU5000

Low volume aerial applications typically at 5-15 l/ha (0.5-1.5 US gallons/acre) with rotary atomizers are not new in Brazil but recent developments have seen a renewed interest in this technique. Low volumes offer operators improved productivity and reduced operational costs, particularly as the majority (75-80%) of the Brazilian Agaviation fleet of 1000 aircraft are of the Ipanema type that has a hopper capacity limited to 200-400 US gallons.  For more than three decades, for example, Micronair rotary atomizers have been used throughout Brazil in a range of diverse cultures such as soyabean, corn, sugar cane, beans, rice, wheat, cotton and bananas. Products applied have usually been insecticides, fungicides, growth regulators and some foliar fertilizers where the biological performance of the Micronair system with it’s control of droplet size was often superior to conventional high volume sprays with hydraulic nozzles.

One perceived limitation of the technique, however, was the inability to use rotary nozzles for herbicide applications due to the need for use of larger spray droplet sizes often in excess of 250um in diameter. Most rotary atomizers have to date not been suitable for use with herbicides particularly on faster fixed wing aircraft as the choice of droplet size was limited in the range 50-200um VMD (Volume Median diameter). Concerns about spray drift when using smaller droplets, particularly along field margins have also been a restriction to further uptake of the technique by aerial operators.

Aerial herbicide applications have also increased markedly over the years and operators have been required to use higher volume applications and larger droplets to compensate for reduced spray quality and drop size control.

An example of this is in  Rio Grande do Sul, Brazil’s southernmost state where around 90% of aerial applications are made on flooded rice and soybean crops. In some regions of the state, crops of rice and soybean coexist side by side. In rice crops, of which there are around 1 million ha in Rio Grande do Sul alone, the main aerial applications are of herbicides (50% of the applied area) followed by  fungicide, insecticide and granulated fertilizers. In  soybean crops, applications of insecticide, fungicide and herbicide (particularly crop dessicants such as  glyphosate) are routinely used.

During the season 2003/2004, the Brazilian company Agrotec Ltda conducted a series of spray trials in southern Brazil on Rice crops applying herbicides with the newly developed Micronair AU5000LD low drift rotary atomizer. Spray applications were also made using  fungicides in soya crops to target the recently discovered serious disease ‘Asian leaf rust’ Phakopsora pachyrhizi.

In conjunction with local aerial operators Julio Kampf, owner and pilot of the company Terra Aviação Agrícola Ltda, of Cachoeira do Sul, and his colleagues Vitor Hugo Nitz and Valdomiro Schramm, owners and pilots of the company Nitz Aviação Agrícola, in Pântano Grande, Agrotec equipped a number of Ipanema fixed wing aircraft with the new atomizers. The objective was to achieve:-

  1. To use the same rotary atomizers for all applications (fungicides, insecticides and insecticides).
  1. To reduce drift when using herbicides by reduction in the small droplet fraction below 150um in size
  1. To use the optimal droplet size according to target, product and environmental conditions for the particular application by simply changing the blade angle setting on the atomizers.

The Micronair AU5000LD atomizer assembly consists of a stack of precision moulded discs with serrations on the disc edge to improve droplet size control at the high flow rates required for aerial application. The diameter of the discs is only 65mm reducing the tangential velocity at the disc edge as the atomizer rotates compared with the standard AU5000 metal gauze atomizer. This together with an air deflector to prevent drops shattering as they are released into fast moving airstream reduces the small droplet fraction and hence off target drift. The AU5000LD atomizer assembly is inter changeable with the standard Micronair AU5000 gauze by simply removing three screws and is capable of selecting droplet sizes in the range 80um VMD up to 400um VMD depending on application by simply changing the blade angle setting and hence rotational speed of the atomizer from say 5000 rpm (100 -150um for insecticides)  down to 1500 rpm for large drops (around 300-400um in size for herbicides).

A set of 8 atomizers were installed on a Ipanema EMB 201A, from Terra Aviação Agrícola as well as two more sets of atomizers installed on two Cessna Agtruck aircraft, from Nitz Aviação Agrícola.

For the full anaylsis report download the pdf below.

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