**3. Fungicide application techniques**

Nowadays, Asian soybean rust (ASR) deserved special attention due to its severity and difficulty of control, since it develops in the aerial part of plants, damaging the physiology and contributing to a drastic reduction of grain yield. For efficient control and cost-cutting, spray techniques and spray equipment must be improved. Studies show that the use of air assistance in the sleeve boom, connected to the hydraulic system of the tractor, can reduce the drift, increase droplet penetration into the plant canopy and improve the spraying distribution (Bauer & Raetano, 2000; Cooke et al., 1990; Taylor et al., 1989; Taylor & Andersen, 1991).

#### **3.1 Air assistance delivery system in boom sprayers**

The use of air assistance in phyto-sanitary product application is very old. However, the enthusiasm in using this spray technology started in 1980, as reported by Robinson (1993). Four years later, the Degania Sprayers Company in Israel developed a sprayer, revolutionary at the time, equipped with air assistance on the spraying sleeve boom. However, only since the end of the 1980s and the beginning of the 1990s has air assistance been effectively adopted in sleeve boom sprayers. In Europe, this technology was introduced by Hardi, and in Germany, in 1996, seven manufacturers exhibited equipment with air assistance in the *Agritechnica* agricultural trade show (Koch, 1997). At that time, the Brazilian industry also incorporated this technology to tractor-driven trailing sleeve boom sprayers. The incorporation of this technology to sleeve boom sprayers was an attempt to improve spraying penetration in the target culture, reduce drift and the number of applications required, increase the time available for carrying out the spraying and enable changes to the spraying height over the culture (DEGANIA SPRAYERS Co., s.d.). For

easily settle on the top leaves. The influence of the size of droplets from different nozzles on soybean spray coverage was studied by Antuniassi et al. (2004). The authors verified that very fine quality spray obtained with hollow cone TX VK6 nozzle and Twinjet flat fan TJ 60 11002 nozzle, and fine quality spray with a flat fan pattern XR 11002 nozzle, provided greater coverage in middle and bottom parts of the soybean plants when compared to the extremely coarse spray quality produced by air induction flat fan nozzles. The effects of spray nozzles (flat fan pattern, pre-orifice flat fan, air induction flat fan and air induction twin flat fan) and volume rates (115 and 160 L ha-1) on chemical control of rust and the deposition of tebuconazole fungicide sprayed on soybeans of the Emgopa 313 variety, were studied by Cunha et al. (2006). The results showed that, despite the fact of the volume rate of 160 L ha-1 and of the use of pattern flat fan nozzles, they provided larger fungicide distribution uniformity in the plant canopy. There was no influence of the nozzle type neither of the application volume in the control of the rust, as well as in the soybean yield. In part, the results described by Raetano & Merlin (2006) ratified those observations that have been made by Cunha et al. (2006). The experiments were conducted in 2004/05 and 2005/06 seasons, using soybean, IAC-19 variety, with the same sprayer equipment and near application volumes (99 and 143 L ha-1; 100 and 150 L ha-1). The values of spray deposition were less influenced by nozzle type (hollow cone, flat fan and twin flat fan), both with fine spray quality. It is recommended for Asian soybean rust control that droplets have a size of 200 to 300 µm (OZKAN, 2005), but droplets smaller than 100 µm can be used with drift

control in spraying with air assistance delivery systems near to the sleeve boom.

Nowadays, Asian soybean rust (ASR) deserved special attention due to its severity and difficulty of control, since it develops in the aerial part of plants, damaging the physiology and contributing to a drastic reduction of grain yield. For efficient control and cost-cutting, spray techniques and spray equipment must be improved. Studies show that the use of air assistance in the sleeve boom, connected to the hydraulic system of the tractor, can reduce the drift, increase droplet penetration into the plant canopy and improve the spraying distribution (Bauer & Raetano, 2000; Cooke et al., 1990; Taylor et al., 1989; Taylor &

The use of air assistance in phyto-sanitary product application is very old. However, the enthusiasm in using this spray technology started in 1980, as reported by Robinson (1993). Four years later, the Degania Sprayers Company in Israel developed a sprayer, revolutionary at the time, equipped with air assistance on the spraying sleeve boom. However, only since the end of the 1980s and the beginning of the 1990s has air assistance been effectively adopted in sleeve boom sprayers. In Europe, this technology was introduced by Hardi, and in Germany, in 1996, seven manufacturers exhibited equipment with air assistance in the *Agritechnica* agricultural trade show (Koch, 1997). At that time, the Brazilian industry also incorporated this technology to tractor-driven trailing sleeve boom sprayers. The incorporation of this technology to sleeve boom sprayers was an attempt to improve spraying penetration in the target culture, reduce drift and the number of applications required, increase the time available for carrying out the spraying and enable changes to the spraying height over the culture (DEGANIA SPRAYERS Co., s.d.). For

**3. Fungicide application techniques** 

**3.1 Air assistance delivery system in boom sprayers** 

Andersen, 1991).

applying phyto-sanitary products on low-stem cultivation, the spraying sleeve booms equipped with air assistance appeared as the ideal tools to improve application quality (smaller droplets, in higher numbers), increase productivity (lower volume and replenishment, higher displacement speed and extended spraying times), reduce drift (the machine's wind speed is greater than the environmental wind) and exposure to these products (Sartori, 1997). After twenty years of using air assistance in sleeve boom sprayers, a great deal of information must still be clarified about the interactions between air volume and speed which are more appropriate for different cultures, the angle of the nozzles on the boom in relation to the air, spraying height and displacement speed, amongst other factors which enable wider spraying coverage and lower losses.

#### **3.1.1 Characterisation of the technology**

Tractor-driven sprayers with air assistance can be coupled to the tractor's hydraulic power take-off (third point) (those with lower capacity tanks or of the trailing type). These sprayers are equipped with one or two fans, usually axial, positioned near the centre section of the spraying sleeve boom, which distribute a very high air volume in an inflated duct assembled over the boom and nozzles (Matthews, 2000). The speed of the air generated may vary with the fan rotation (rpm), and generally it does not follow a linear relationship. Also, air speed variations could occur along the boom, at the ends, when compared to the speed achieved in its centre section (Raetano, 2002). The established standards for evaluating with accuracy the speed of the air generated by sleeve boom sprayers equipped with air assistance was necessary to standardise the measuring distance in relation to the air exit opening, as well as to specify anemometers that are able to record high air speeds (30-40 m s-1). Thus, Kunz (2010) developed two methods for air speed and volume measuring in spray booms equipped with air assistance. In the first method, a wooden mould was placed at the outlet of the air curtain, in a vertical position, in the direction of the air flow, and measurements were taken with the anemometer at pre-established distances. This form of measuring became know as the "ruler method". This method makes it very difficult to determine the main vector of the air flow that comes out in a continuous manner through the rectangular opening on the lower part of the inflated sleeve, which makes it difficult to measure the air speed with precision. New air-speed readings are now taken beforehand, using a nylon thread fixed to the air outlet, to indicate the point of air flow displacement vector, which substitutes the ruler method. In this way, it makes it very much easier to identify the main air flow and increases the precision and uniformity of speed values obtained with the anemometer. In a similar manner to the ruler method, pre-defined distances are marked off on the nylon thread, so that measurements can be taken with greater ease and accuracy. This procedure is called the "thread method" (Figure 1). Due to the dynamic behaviour of the air flow, it becomes difficult to identify the vector of the air flow that comes out under high speed from the system, principally at distances of 0.25 and 0.50 m, which causes a great variation in the speed data obtained with the ruler method, as can be seen in Table 2. The air speed values obtained with the thread method present greater uniformity in relation to the ones obtained with the ruler method, especially at distances of 0.25 and 0.50 m from the air outlet. This can be observed through the variance values (%) of the data, which were smaller with the thread method (Table 2). The average values of the air speed obtained with the thread method were greater, probably due to the correct identification of the main air flow vector when measured by this method. Measuring the air speed, therefore, becomes more precise and easier, especially at longer distances in relation to the air flow at the spray boom.

Fig. 1. "Nylon thread method" for measuring air speed in a sleeve boom sprayer.


\*Values expressed in km h-1.

Table 2. Descriptive statistics of the air speed data obtained along the spray boom with different evaluation methods.

#### **3.1.2 Air speed on spray deposition**

Raetano & Bauer (2003) evaluated the effects from air speed variation (50%, 75% and 100% of the maximum fan rotation capacity) on the spraying sleeve boom, when depositing phyto-sanitary products on bean culture. Forty-eight days after sprouting begins, 200 g of copper oxide per 100 L of water were applied with AXI-110015 tips at 206.7 kPa and JA-1 at 1,033.5 kPa, either with air assistance or not, using a Model Falcon vortex sprayer. The broth volume was 100 L ha-1 in both operational conditions. The air speed variation did not influence the deposit levels in the culture, but the use of air assistance, operated at full fan capacity, resulted in better deposit levels on the abaxial surface of the leaflets positioned in the lower portion of the plants. Cereal-cultivated soil contamination can be reduced to

becomes more precise and easier, especially at longer distances in relation to the air flow at

Fig. 1. "Nylon thread method" for measuring air speed in a sleeve boom sprayer.

Ruler method of measurement

(m) Average\* S.D. Variance CV % Min\* Max\* Amplitude\* 0.0 70.14 10.00 100.05 14.26 53.40 97.20 43.80 0.25 41.71 5.70 32.55 13.68 31.20 54.00 22.80 0.50 29.49 8.20 67.27 27.81 20.50 51.80 31.30 Nylon thread method of measurement 0.0 71.57 10.09 101.83 14.10 59.50 93.60 34.10 0.25 43.64 4.04 16.33 9.26 36.60 51.00 14.40 0.50 35.26 3.53 12.47 10.01 28.80 41.90 13.10

Table 2. Descriptive statistics of the air speed data obtained along the spray boom with

Raetano & Bauer (2003) evaluated the effects from air speed variation (50%, 75% and 100% of the maximum fan rotation capacity) on the spraying sleeve boom, when depositing phyto-sanitary products on bean culture. Forty-eight days after sprouting begins, 200 g of copper oxide per 100 L of water were applied with AXI-110015 tips at 206.7 kPa and JA-1 at 1,033.5 kPa, either with air assistance or not, using a Model Falcon vortex sprayer. The broth volume was 100 L ha-1 in both operational conditions. The air speed variation did not influence the deposit levels in the culture, but the use of air assistance, operated at full fan capacity, resulted in better deposit levels on the abaxial surface of the leaflets positioned in the lower portion of the plants. Cereal-cultivated soil contamination can be reduced to

the spray boom.

Distance

\*Values expressed in km h-1.

different evaluation methods.

**3.1.2 Air speed on spray deposition** 

approximately 40% when using 50% of the maximum speed of the air generated by the fan in a sprayer equipped with air assistance on the sleeve boom, when compared with conventional application (without air), as reported by Taylor & Andersen (1997). The deposit and losses of spraying broth in the cultivation of bean (*Phaseolus vulgaris*), 26 days after sprouting, and using sprayers equipped with air assistance on the sleeve boom and conventional sprayers (without air) and volumes of 60 and 100 L ha-1, have been evaluated by Raetano & Bauer (2004). The higher volume resulted in greater deposits, but high losses to the soil (above 60%) have been noted, even when using air assistance with air speed corresponding to 50% of the maximum fan rotation. In part, such results have been assigned to 40% of the soil bare of vegetation at this growth stage of the culture. The air volume generated may vary from 0 to 2000 m3 per hour per boom, depending on the number and power of the fans distributed on variable-size booms that could reach 30 m in length. The air distributed in the inflated duct is forced to pass through a continuous or intercalated opening, in a perpendicular direction to the one in which it has been generated, in a descending direction. The effects of chemical control of the rust and deposition fungicide sprayed under four speeds (zero, 9, 11 and 29 km h-1) by a spray boom on soybean crop were evaluated by Christovam (2008) and Prado et al. (2010). Significant differences were obtained in the lower part of the plants for spray deposition using higher speed of air assistance. On the top part of the plants, greater levels of deposition were seen when spraying without air assistance was carried out. The rust severity was more intense in treatments without air assistance. Raetano & Bauer (2003) evaluated different velocities of air assistance near the spray boom and concluded that air assistance, with maximum air speed generated by the fan (29 km h-1) and a flat fan nozzle (AXI 110015 type), provided greater spray deposition on the abaxial leaf surface, on the bottom part of the bean plants. The data of the soybean crop yield at different air speeds using an air-assisted sprayer for Asian soybean rust management was compared in the 2006/07 (Christovam et al., 2010a) and 2007/08 (Prado et al., 2010) seasons (Figure 2). Air speeds used in both studies were zero, 9, 11 and 29 km h-1.

Fig. 2. Effect of the air speed on soybean crop yield, 2006/07 and 2007/08 agricultural season using a sleeve boom sprayer. Botucatu, SP, Brazil.

There is a positive correlation between air speed and soybean crop yield. When compared, the soybean yield using the maximum air speed generated by the fan (29 km h-1) in conventional spraying (without air), increases of 31.9% and 17.1% can be seen in the 2006/07 and 2007/08 seasons, respectively. As can be verified, in the last agricultural season, the increase in soybean yield was lower, due the higher severity of ASR on the Conquista variety (Figure 2). The effect of different air speeds (0, 9, 11 and 29 km h-1) in chemical control of pests on soybean crop, Conquista variety, was evaluated by Prado (2009), after insecticide spraying using an air-assisted sprayer. The use of air speed generated by the fan in the maximum rotation (29 km h-1) provided greater control of the lower velvetbean caterpillar (*Anticarsia gemmatalis*). This effect was not observed with longer caterpillars (> 1.5 cm) because the lowest caterpillars are more easily located in the lower part of the soybean plants. Thus, the lower caterpillars received an additional amount of insecticides due the effect of air assistance with maximum air speed into the canopy. In general, there was not a statistically significant difference between air speeds on stink bug control after insecticide spraying on soybean culture.

#### **3.1.3 Nozzle angle on spray deposition**

The positioning angle of the spraying nozzle in relation to the air curtain (Figure 2), generated by the equipment (vertical, descending), as well as the nozzles and air curtain, simultaneously, in relation to the vertical position, may significantly influence the deposit levels and the spraying distribution. Nowadays, in sleeve boom sprayers equipped with air assistance, the angle variations of the nozzles and air curtain, in relation to the vertical position, pro or against the tractor-sprayer assembly displacement, are made simultaneously clockwise or counterclockwise, with the single-cylinder command. The results research carried out under controlled conditions and in the field have shown that the positioning of the nozzle at 30° forward of the displacement in conventional sprayers (without air) provides a significant increase in deposits on the leaf surface of different vegetal species: *Cyperus rotundus* (Silva, 2001), *Brachiaria plantaginea* (Tomazela, 2006) and *Glycine max*  (Bauer, 2002). In England, research carried out in wind tunnels with plants cultivated on trays have confirmed that the spraying angle forward of the displacement, in the presence of air assistance, increased deposit on cereals and reduced soil contamination (Hislop et al., 1995). Nowadays, one may position the spraying nozzles and air curtain at angles of 15° and 30° in relation to the vertical position in sleeve boom sprayers equipped with air assistance, made in Brazil. The use of air angled forward of the displacement with fine droplets could substantially increase spraying deposit levels on vertical targets. These results were obtained from practical experiences published by the Hardi Int. Tech. Reports in potato culture which indicated that spraying penetration and retention are greater with air assistance positioned at an angle forward of the displacement on the leaves in the lower portion of the plants. In the upper portion, the retained broth volume was virtually not influenced by the air exit angle, pro or against the equipment displacement (Taylor & Andersen, 1997). The effect of the nozzle angle and air-jet parameters in an air-assistance sprayer on the biological effects of ASR chemical protection was studied by Christovam et al. (2010b). Four air levels (0, 9, 11 and 29 km h-1) were combined at two nozzle angles 0° and 30° for the sprayings using flat fan AXI 110015 nozzles. The spraying with triazole fungicide was realised in R2 and R5.2 growth stages of soybean at 142 L ha-1 of volume rate. For the evaluation of spray deposition, a cupric tracer was used. At the bottom part of the plant, spraying with maximum air speed Air Speed (km h-1)

126 Soybean Physiology and Biochemistry

There is a positive correlation between air speed and soybean crop yield. When compared, the soybean yield using the maximum air speed generated by the fan (29 km h-1) in conventional spraying (without air), increases of 31.9% and 17.1% can be seen in the 2006/07 and 2007/08 seasons, respectively. As can be verified, in the last agricultural season, the increase in soybean yield was lower, due the higher severity of ASR on the Conquista variety (Figure 2). The effect of different air speeds (0, 9, 11 and 29 km h-1) in chemical control of pests on soybean crop, Conquista variety, was evaluated by Prado (2009), after insecticide spraying using an air-assisted sprayer. The use of air speed generated by the fan in the maximum rotation (29 km h-1) provided greater control of the lower velvetbean caterpillar (*Anticarsia gemmatalis*). This effect was not observed with longer caterpillars (> 1.5 cm) because the lowest caterpillars are more easily located in the lower part of the soybean plants. Thus, the lower caterpillars received an additional amount of insecticides due the effect of air assistance with maximum air speed into the canopy. In general, there was not a statistically significant difference between air speeds on stink bug control after

The positioning angle of the spraying nozzle in relation to the air curtain (Figure 2), generated by the equipment (vertical, descending), as well as the nozzles and air curtain, simultaneously, in relation to the vertical position, may significantly influence the deposit levels and the spraying distribution. Nowadays, in sleeve boom sprayers equipped with air assistance, the angle variations of the nozzles and air curtain, in relation to the vertical position, pro or against the tractor-sprayer assembly displacement, are made simultaneously clockwise or counterclockwise, with the single-cylinder command. The results research carried out under controlled conditions and in the field have shown that the positioning of the nozzle at 30° forward of the displacement in conventional sprayers (without air) provides a significant increase in deposits on the leaf surface of different vegetal species: *Cyperus rotundus* (Silva, 2001), *Brachiaria plantaginea* (Tomazela, 2006) and *Glycine max*  (Bauer, 2002). In England, research carried out in wind tunnels with plants cultivated on trays have confirmed that the spraying angle forward of the displacement, in the presence of air assistance, increased deposit on cereals and reduced soil contamination (Hislop et al., 1995). Nowadays, one may position the spraying nozzles and air curtain at angles of 15° and 30° in relation to the vertical position in sleeve boom sprayers equipped with air assistance, made in Brazil. The use of air angled forward of the displacement with fine droplets could substantially increase spraying deposit levels on vertical targets. These results were obtained from practical experiences published by the Hardi Int. Tech. Reports in potato culture which indicated that spraying penetration and retention are greater with air assistance positioned at an angle forward of the displacement on the leaves in the lower portion of the plants. In the upper portion, the retained broth volume was virtually not influenced by the air exit angle, pro or against the equipment displacement (Taylor & Andersen, 1997). The effect of the nozzle angle and air-jet parameters in an air-assistance sprayer on the biological effects of ASR chemical protection was studied by Christovam et al. (2010b). Four air levels (0, 9, 11 and 29 km h-1) were combined at two nozzle angles 0° and 30° for the sprayings using flat fan AXI 110015 nozzles. The spraying with triazole fungicide was realised in R2 and R5.2 growth stages of soybean at 142 L ha-1 of volume rate. For the evaluation of spray deposition, a cupric tracer was used. At the bottom part of the plant, spraying with maximum air speed

insecticide spraying on soybean culture.

**3.1.3 Nozzle angle on spray deposition** 


0 1.2425 a A 0.6962 b AB 0.6585 a A 0.2444 b B 9 0.6997 a A 0.9865 a AB 0.3621 a A 0.4527 a B 11 1.147 a A 0.6395 b B 0.4651 a A 0.3292 a B 29 0.6287 b A 1.2663 a A 0.4904 b A 0.8552 a A

generated by the fan and nozzles angled at 30°, it was essential to promote doubled deposits on the abaxial leaf surface (Table 3). Maximum air speed (29 km h-1) and nozzles angled at 30° resulted in an increase in spray deposits on adaxial surface of leaves in the bottom part of the plants (Table 3).

The same larger letters in the column, did not differ by the Tukey test (p<0.05).

DMS Angle 0.46 0.24 DMS Air speed 0.62 0.33 CV (%) 34.17 34.16

Table 3. Average values of deposits of the copper tracer in an artificial target (filter paper) on leaf surfaces, in the bottom part of the soybean plants, Conquista variety, in relation to different spraying angles. Botucatu, SP, 2006/2007.

Nozzles angled at 30°, in the same direction of the sprayer displacement, combined with air assistance (29 km h-1 of air speed) positively influenced the control of disease as well as the yield of the Conquista variety crop. This fact confirms the importance of spraying performed with nozzle angles in the same direction of the sprayer movement, which can contribute significantly to Asian soybean rust control, considering the disease epidemiology. The choice of the best combination of air speed and nozzle angle in air-assisted sprayers is influenced by architecture and growth stage of the plants to obtain a desirable biological effect in soybean Asian rust chemical protection with this technology. Conventional spraying (without air) and air-assistance at 0º (vertical) and 30º (forward to displacement of the equipment) are shown in Figures 3A, 3B and 3C, respectively. The spray boom angle interference, with or without air assistance near the boom, on spray deposit levels were studied by Scudeler & Raetano (2004) in potato culture. The higher deposits were evidenced with nozzles positioned at 0º and 30º, with the presence of air assistance, both at the top and bottom part of the potato plants. The lower spray deposits were obtained with nozzles positioned at 30º in the opposite direction to the displacement of the sprayer. In addition to the volume rate, generated air speed and nozzle angle in air-assisted sprayers, other factors, such as displacement speed of the tractor-sprayer assembly, presence of vegetal coverage in the area or not, vegetal coverage type (monocotyledonous or dicotyledonous, plant density, architecture and plant cuticle characteristics), positions of insect pests and plant pathogens, agrochemical product characteristics, droplet size and environmental conditions, especially wind speed, may influence the efficacy of phyto-sanitary control. It is necessary to develop studies with variations in air speed combined at different angles of spray nozzle on spray deposition and coverage. Dynamic systems for air speed evaluation combined at different nozzle angles and the performance of these in spraying could be better studied.

Fig. 3. Air-assisted sleeve boom sprayer in the following operation modes: A – conventional spraying (without air); B – spraying with air assistance at 0º (vertical) and C – spraying with air assistance angled at 30º forward to the displacement of the tractor-sprayer assembly on soybean crop.
