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Optimal spraying speed

28. 11. 2016

Do You think You could drive faster, but don't know how this would affect, the deposit on plants? Read our findings based on TESTS which were carried out

Orchard farmers wonder how does the increase of driving speed affect the quality of deposit of PPP and efficiency of PPP.  However, there is not much literature about this topic.
Suppression of harmful organisms in orchards is still based on protection with PPP. Their efficiency depends on quality of application of spraying agent. What is more the quality of application has a huge impact on quality of end product – fruits.
Increase of agricultural areas, stricter conditions of production economics, decreasing of production costs and very narrow time window for spraying, all result in a need for higher spraying speeds.
Because of different types, forms and measurements of plantations make it difficult for farmers to find the best setting of sprayer and to define the best working speed. In order to achieve the best deposit of protection agent on the plant it is crucial to optimise air capacity and to direct the airstream. Next important topic is to find working speed which is the most suitable for plantation.
We carried out test in two different types of plantations, with two different driving speeds. The primary speed was 6 km/h and the increased driving speed was 9 km/h. The fact is that because of various factors (terrain, form of plantation) it is not always possible to work with 9 km/h or more.
With higher driving speed we can shorten the time needed for application of PPP.  Furthermore, our response time to suppression of harmful organisms is also shorter with higher driving speeds.
Every year the need of shorter response time becomes more important. The farmers aim to bigger cultivations which can become a problem. Higher driving speeds are one of solutions for effective work on bigger cultivations. But we have to be careful that the driving speed is still safe – we cannot drive faster if our cultivation and agricultural equipment doesn't allow this. In cultivations which allow higher driving speeds we can save time and we all know that time is money.
We chose the cultivation with GALA and Jonagold apples. The cultivations were very different. Gala cultivation had a shape of »narrow spindle« and 1 m of between trees in a row. The Jonagold cultivation had a shape of “modified wider spindle” with 1,5 m between trees in a row. Both cultivations had 3,5 m row width, were covered with anti-hail net and were trimmed with machines. The cultivations were connected with each other so we drove from one cultivation into another without changing the driving speed. We carried this test in beginning of August, when the apples were already fully formed and the “green wall” had a full volume.

The theoretically primary driving speed was 6 km/h and the increased driving speed was 9 km/h. The realistically measured speed differed a little bit from the plan, because of different gear ratios. So we achieved the primary speed 6,48 km/h and increased speed 9,28 km/h.
The speed of the tractor adapts to the terrain. The speedometers of tractors usually aren’t exact so it is recommended to control them.  We do this by 100 m test: this means that we drive 100 m with working speed and working turns and we measure the time needed for doing this. It is important to have full working speed at the start of 100 m.
We used trailed sprayer with 1500 l tank and axial fan. The machine used for test was a modern sprayer, with 18 nozzles, 2 fans with diameter 500 mm and 600 mm and it sucks air from the back and front.
We used following nozzles: at 6 km/h yellow Albuz ATR nozzles and at 9 km/h orange Albuz ATR nozzles. We also carried out separated test with 6 km/h where we used anti drift nozzles Albuz TVI green.
We chose 4 most typical trees which didn’t differ from each other. All of this 4 trees were marked with 6 spots for sampling. Spot 1 was on the outer side of the crown on the bottom, spot 2 was inside the crown, spot 3 was on outer part of the crown in the middle, spot 4 was in the middle of the crown, spot 5 was on the top of the crown and last 6th spot was inside the crown on the top.


Each of this spots had clipped 4 clippers. One of them held 2 water sensitive papers, which were positioned to one another. Other 3 clippers held each 3 apple tree leaves, which were torn away in the same cultivation, far from the spot where we carried out the test.




Deposit of spraying agent Quality Analysis with coloured tracker.


In the picture you can see 3 clippers, each with 3 apple leaves.
Three leaves were clipped in each of the clippers. The clippers were clipped in six points in the crown of the tree. The leaves were clipped on the peduncle. When test spraying was finished we removed the leaves and put them in PVC bag and store them in a cooling bag, so that no light could access them. Laboratory analysis followed 20-26 hours after the bags were stored. We exchanged the leaves for every version of spraying test with new ones, so that we had 9 clean leaves, which were taken from the same tree type in orchard.
We got analytic solution of tartrazine which was washed from the leaves by pouring the PVC bag with 9 leaves with 100 ml of distilled water and with shaking of the bag for 30 seconds. We achieved effective dissolution of tartrazine deposit. After this we vacuumed 20 ml of liquid with help of a modified filter. We injected this solution into cuvette for readout in photo spectrum Varian Carry 50 (Varian Inc., USA). The Tartrazine dye readout was carried out at wave length absorbance 430 nm.  Because of the fact that the PVC bags were poured with 100 ml of water, we could calculate how much of tartrazine was in each PVC bag (micro grams). When we divided the total quantity of tartrazine with the surface of all 9 leaves we got the information about micro grams of tartrazine on cm2 (leaves surface).
 
The method for determining the quality of deposit using water-sensitive papers (WSP)

This method is more known to You
After the end of each test we took water sensitive papers from the tree. We stored them in envelopes in dry place and analysed them with help of Image analyser device. This was carried out in IHSP Žalec. The device analysed three spots of 1cm2 on each of the leaves in order to determinate the density of drop hits (n/cm2) and cover rate (%) and calculated statistical average value of the two studied parameters mentioned above.
Both methods complement each other. Analysis of quality of the spray mixture deposit, gives us information in which spots the deposit is OK, the method for determining of the quality of deposit with WSP tells us whether the deposit is better on upper or lower side of the leaves.

The structure of “green wall” in Gala and Jonagold cultivations differed a lot, this is the reason that the coverage percentages were also very different. The picture bellow shows different coverage rates of WSP (water sensitive papers) positioned on different parts of the tree in cultivation Gala. The upper leaves were turned upwards (in the direction of the sky), the ones below are those which were turned downwards. Left picture shows primary driving speed (6km/h) and the right picture shows increased driving speed. The first glance on the picture bellow allows us to visually claim that the deposit in both cases is good, but on the other hand we can see some differences.

What follows is a statistic analysis of data gathered from WSP (%).  According to the opinion of some researchers for average effect of protection agents, 15% of target area should be covered, which means to have 85 droplet prints per cm2 (Deveau 2013). This applies only for foliar application of agents, which have a good secondary distribution.

The deposits were compared to each other with help of statistical software SPSS, which allowed us to prepare an analysis of interaction between deposit in different parts of trees with different driving speeds. Small letters beside the data of deposit are helpful for comparison of deposit of dye in spots of trees in same cultivation and a driving speed. Capital letters show differences in deposit between trees of the same shape (in same spots) in case of different driving speeds.
Results Gala cultivation:
Deposit quality analysis results with coloured tracer analysis.


Normalized deposit (Gala, double axial ventilator, left tree 6km/h and right 9 km/h). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different driving speeds.
The Gala cultivation was sprayed with primary speed of 6,48 km/h (left) and increased speed of 9,28 km/h (right) and shows to a higher normalized deposit (Spot 5) in case of increased driving speed or the same in all other spots. Both speeds show a better deposit inside the crown.
 
Deposit results with use of water sensitive papers (WSP).

 
WSP Coverage rate (%) data. (Gala cultivation, double axial ventilators, left tree 6 km/h, right tree 9 km/h, lower set of data -bellow, upper set of data above). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different driving speeds.
 
When comparing both working speeds it is interesting that all upper spots (spots 3,4,5,6) in average had a slightly worse or the same deposit (all A) in comparison with lower spots (3,4,5,6 - all B). The deposit in spots 1 and 2 was a lot better (upper and lower side of WSP) with higher driving speed. The Gala cultivation sprayed with primary speed 6 km/h had a very good optimal allocation (almost all spots above 15%) except in spot 1 in the part bellow. Increased spraying speed resulted in some minor changes in spots 3, 4, 5 where the result just slipped under 15%.  This information refers that increasing of working speed in cultivation Gala spoiled the quality of deposit. But the truth is that the air capacity used with higher working speed was too low and 300 turns of P.T.O. shaft per minute are not enough for optimal results.  For optimal quality of deposit 350 – 380 turns of the P.T.O. shaft would be needed.
Increased working speed (from 6km/h to 9 km/h) in our case didn’t cause significant deterioration of spray deposit quality. This is shown by very small differences in different spots of the tree.
The decision of increasing the working speed when spraying depends on interactive effect between sprayer characteristics, airstream produced by the sprayer, tree shape and nozzles used. When increasing spraying speed, we should also adjust the capacity of the fan. Increased spraying speed needs also higher air capacity, except if it is already too high in the beginning.

The structure of “green wall” in Gala and Jonagold cultivations differed a lot, this is the reason that the coverage percentages were also very different. The picture bellow shows different coverage rates of WSP (water sensitive papers) positioned on different parts of the tree in cultivation Jonagold. The upper leaves were turned upwards (in the direction of the sky), the ones below are those which were turned downwards. Left picture shows primary driving speed (6km/h) and the right picture shows increased driving speed. Because of the bush tree crowns in Jonagold cultivation the coverage is slightly different than in Gala cultivation, but also here we cannot find major differences.

Different coverage rate with help of WSP in Jonagold cultivation (left 6 km/h, right 9 km/h)
What follows is a statistic analysis of data gathered from WSP (%).  According to the opinion of some researchers for average effect of protection agents, 15% of target area should be covered, which means to have 85 droplet prints per cm2 (Deveau 2013). This applies only for foliar application of agents, which have a good secondary distribution.
The deposits were compared to each other with help of statistical software SPSS, which allowed us to prepare an analysis of interaction between deposit in different parts of trees with different driving speeds. Small letters beside the data of deposit are helpful for comparison of deposit of dye in spots of trees in same cultivation and a driving speed. Capital letters show differences in deposit between trees of the same shape (in same spots) in case of different driving speeds.
 
Results Jonagold cultivation
Deposit quality analysis results with coloured tracer analysis.

 
Normalized deposit (Jonagold cultivation, double axial ventilator, left tree 6km/h and right 9 km/h). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different driving speeds.
Results (see picture left and right) show, that the coverage of spots 1, 3, 5 on the external side is better at increased speed (9km/h) than at primary working speed (6km/h). The results in spots 2,6 are statistically the same, the only spot with worse result at increased working speed was in spot 4, which was still reasonably high (61%). Gathered data shows that air resistance of the tree crown in cultivation Jonagold, was higher than in Gala cultivation, which caused bigger airstream bending and resulted in better deposit on outer parts of tree crown and a slightly worse result inside the tree crown.
 
Deposit results with use of water sensitive papers (WSP).

 
WSP Coverage rate (%) data. (Jonagold cultivation, double axial ventilators, left tree 6 km/h, right tree 9 km/h, lower set of data -bellow, upper set of data above). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different driving speeds.
Pictures ( left and right) show spraying results in Jonagold cultivation at 2 different spraying speeds.  At higher spraying speed statistically worse deposit can be seen in spot 6 and on lower points (5, 3, 2) which are marked with letter B.                       
 WHY did this happen? The machine produces a slightly different airstream which is whirling, this is the reason that the sprayer is a little more sensitive for increasing of speed. This can especially be seen in cultivation Jonagold, because of lush tree crown. To achieve better results at increasing speed we should also increase the airstream capacity and turns of P.T.O. shaft.
Generally, the sprayer did a very good job, because in majority of spots it achieved normalised deposits, which were higher than 0,5, which grants good impact of protection agents. Results in terms of normalised deposit show better performance than the result of WSP coverage.
 
The decision of increasing the working speed when spraying depends on interactive effect between sprayer characteristics, airstream produced by the sprayer, tree shape and nozzles used. When increasing spraying speed, we should also adjust the capacity of the fan. Increased spraying speed needs also higher air capacity, except if it is already too high in the beginning.
 

Comparison of nozzles in cultivation Gala


Pictures (left and right) show WSP in cultivation Gala at working speed 6,4 km/h. Left tree represents WSP with use of ATR yellow nozzle, right picture represents WSP with use of anti-drift nozzle Albuz TVI green. Anti-drift nozzles produce bigger droplets, which can be seen in the picture on the right. In both cases we can see a high number of droplets on WSP, which indicates that the deposit is very good.
Comparison of deposit quality with analysis of coloured tracer.

 
Normalized deposit (Gala, double axial ventilator, left tree ATR nozzle right tree TVI nozzle). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different nozzles.
The best deposit when using ATR nozzles in cultivation Gala (left) was achieved in spot 6, all other spots also had a very good deposit. The deposit was also the best in spot 6 when using TVI anti-drift nozzle (right), spots 1 and 2 also had a very good deposit. The worst normalized deposit was in both cases achieved in spot 5. Statistical comparison showed that the deposit with anti-drift nozzle was slightly better. In other cases, statistically there was almost no difference between both type of nozzles.
According to achieved normalized deposit, we can state, that in the settings of the sprayer were optimal (air capacity) and prevented drift from the outer part of tree crown.
 
Deposit results with use of water sensitive papers (WSP).

 
WSP Coverage rate (%) data. (Gala cultivation, double axial ventilators, left tree yellow ATR nozzle, right tree green TVI anti-drift nozzle, lower set of data -bellow, upper set of data above). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different nozzles.
Picture (right) shows good coverage on the upper side of WSP in spots 2 and 4 (inside the tree crown), spot 1 is also very good. The lower part of WSP has also a good coverage in spot 2. The worst coverage can be found in spot 5.
When comparing statistical results achieved with both nozzles, we can state that the normal nozzle (ATR) achieved better results in all spots monitored. Our test also showed that with use of anti-drift nozzles we can achieve a similar deposit as with normal ATR nozzles. In case of a “green wall” with lower density the deposit is a little bit worse.
When using anti-drift nozzles with increased speed we have to pay attention to weather conditions, temperature, wind, humidity. With all this factors in mind we can achieve even better results.
 

Comparison of nozzles in cultivation Jonagold


Pictures (left and right) show WSP in cultivation Jonagold at working speed 6,4 km/h. Left tree represents WSP with use of ATR yellow nozzle, right picture represents WSP with use of anti-drift nozzle Albuz TVI green. Anti-drift nozzles produce bigger droplets, which can be seen in the picture on the right. Similar as in cultivation Gala (ISSUE nr. 6) also here the deposit is good, but, we can already sense it visually that the deposit with the same nozzles in cultivation Gala was better.

Comparison of deposit quality with analysis of coloured tracer.

Normalized deposit (Jonagold, double axial ventilator, left tree ATR nozzle right tree TVI nozzle). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different nozzles.

The anti-drift nozzle TVI had the best result in spot 4, good result in spots 2 and 6 (in the middle of the crown). Comparison between ATR and TVI nozzle didn't return significant statistical differences, except in spot 5, where TVI nozzle showed a little better percentage of spray concentration.
The use of anti-drift nozzle TVI also caused equalization of normalized deposits in different spots of tree in cultivation Jonagold. This is an essential effect for functioning of protection agents, because it minimizes the spots where harmful organisms could burst out.

Deposit results with use of water sensitive papers (WSP).

WSP Coverage rate (%) data. (Gala cultivation, double axial ventilators, left tree yellow ATR nozzle, right tree green TVI anti-drift nozzle, lower set of data -bellow, upper set of data above). Small letters represent values in different spots of tree with the same working speed, which differ from each other according to the Turkey HSD test (a < 0,05). Capital letters with different fonts represent significantly different values in the same spot of the same tree with 2 different nozzles.

Statistical data on the upper side of WSP (picture right) show the best deposit in spot 2, all other spots have also a very good deposit. The most important thing is that the deposit of all spots is almost equal. The lower part of WSP also doesn't indicate any difference between different spots (parts of trees), the same applies for the ATR nozzle.
During test in Jonagold cultivation (picture left and right), we could sense differences between deposit of both nozzles only in 2 spots. In spot 1 on lower side of WSP, the ATR nozzle had worse deposit in compare with TVI nozzle. On the other hand, in spot 4, conversely the ATR returned better deposit. In Jonagold cultivation, the TVI nozzle didn’t have so big difference in results in comparison with Gala cultivation.
During our test we also learned that we can achieve similar deposit with anti-drift nozzles as with normal (ATR nozzles). In case of green wall with smaller density the deposit quality is a little lower but on the other hand in case of green wall with higher density the effect is reverse. The TVI nozzles aren’t a good choice when spraying with lower air capacity.
When using anti-drift nozzles with increased speed we have to pay attention to weather conditions, temperature, wind, humidity. With all this factors in mind we can achieve even better results.


When browsing literature about spraying speeds we found this interesting statement: »Speed doesn’t kill, but time is money. « It is very important to find optimal speed which still allows us good results and combine it with right timing for spraying. This is a combination which will give us successful and effective plant protection (Niederholzer 2015).

Summary

Increased working speed (from 6 km/h to 9 km/h) didn't worsen the deposit in monitored parts of the tree. Furthermore, in some points of the tree the deposit was even better than in case of working with lower speed. This is shown by small differences in normalised deposit in different spots of the tree, after spraying with 6km/h or 9 km/h.

We cannot increase the working speed endlessly. We can increase it only to the speed which still allows enough penetration through the crown of the tree (some specialist say that the minimum speed of the airstream in the tree crown should be between 3 and 4 m/s). The experiment showed that the effect depends on adjusted airstream capacity to the air resistance and volume of the green wall.
The decision of increasing the working speed when spraying depends on interactive effect between sprayer characteristics, airstream produced by the sprayer, tree shape and nozzles used. When increasing spraying speed, we should also adjust the capacity of the fan. Increased spraying speed needs also higher air capacity, except if it is already too high in the beginning.

Based on many years of our experience, we can state that the majority of fruit farmers is spraying with too high airstream and too low spraying speed.

Every year the need of shorter response time becomes more important. The farmers aim to bigger cultivations which can become a problem. Higher driving speeds are one of solutions for effective work on bigger cultivations. But we have to be careful that the driving speed is still safe – we cannot drive faster if our cultivation and agricultural equipment doesn't allow this. In cultivations which allow higher driving speeds we can save time and we all know that time is money.
During our test we also learned that we can achieve similar deposit with anti-drift nozzles as with normal (ATR nozzles). In case of green wall with smaller density the deposit quality is a little lower but on the other hand in case of green wall with higher density the effect is reverse. The TVI nozzles aren’t a good choice when spraying with lower air capacity.
When using anti-drift nozzles with increased speed we have to pay attention to weather conditions, temperature, wind, humidity. With all this factors in mind we can achieve even better results.
Like we already stated: »Speed doesn’t kill, but time is money It is very important to find optimal speed which still allows us good results and combine it with right timing for spraying. This is a combination which will give us successful and effective plant protection (Niederholzer 2015).