With the development of applied science, agricultural sprayers have become a key equipment in crop production.

How to choose a suitable sprayer is a topical issue for growers. It is, in fact, the first step to improve the usage rate of pesticides and fungicides, a smart way to save farm management cost. Growers, however, may try to select innovative adjuvants to adequately protect crops.

According to a crop production costs report from the Manitoba province of Canada¹, the Total Operating Cost of crop production was US$226.33 per acre in 2016. As much as 8.05 per cent of this was the cost of fungicides, the third largest costs item after seed and fertilizers. It cost $18.22 per acre.

In 2016 wheat farming summary by USDA², the operating costs in the United States were $115.30 per acre and the chemicals costs were $14.37 per acre. In 2002, CropLife Foundation published a farming value report³, which reported that net value had increased by 14.60 per cent. Partial crops such as artichoke and sweet pepper had nearly 60 per cent increase in value return after using fungicides. Thus, it can be seen that the use of fungicides in crop production is a pragmatic decision.

Agricultural Aerial Application

On-land sprayers or Ag aircrafts can be chosen for agricultural spraying work. On-land sprayers mainly include self-propelled sprayers, integral sprayers, and pull-type sprayers. The swath width can be extended to more than 18m (about 59ft). Ag tractors are easy driving, spraying, and maintaining. They are farming around the world. But Ag tractors leave deep ruts when they are spraying and are also restricted by hilly and mountain terrain.

Agricultural planes, helicopters, fixed wings drones, and multi-rotor drones are some choices for aerial application. UAV technologies are the new trend in recent years. Traditional fixed wings and helicopters have been servicing for more than a half century. Many countries have provided a full agricultural solution by aerial application and built a complete training system. Today in America, 65 per cent of agricultural chemicals are sprayed by aircrafts and 88 per cent of spraying is done by fixed-wing planes.

There are some issues that the farm owners need to face. On the one side, the market needs to build a successful business model in the country, on the other side, the precise aerial Ag-spraying is affected by many aviation factors, such as flight speed, crosswind, nozzle type, or nozzle pressure. All factors can cause the Vapor Drift. In China, to protect the environment and improve the precision of aerial spraying, the droplet size is controlled at 80 to 400 microns⁴.

The UAV technology is based on GIS system. Compared with Ag planes, the drones have been equipped with the new visual sensor and 3/5 band sensor for crop protection. Growers can analyze the data using professional software5, such as Plant Health Indices, Measure Chlorophyll to Assess Plants, Drought Stress Identification, and Disease Pressure Mapping for Precision Farming Management.

A New Choice for Agricultural Aerial Spraying

Benefits of using drones to protect crops:

• Rapid reaction ability
• Safe ultra-low volume spraying
• Vertical airflow of UAV rotor improves the penetration ability of spraying

Due to the less flight speed of drones, the vapor drift of fungicides is less than planes spraying, which has a higher settling efficiency. A test6 results show, at 34m/s of crosswind speed condition, the nozzles of single-rotor drones adjust to 350μm droplet size and have a good spraying effect. As much as 90 per cent of the drift volume was dropped into the target area within 8 metre range.

Spraying droplet size directly influences drift distance and settlement volume of fungicides. The finer size is smooth but evaporates easily. The coarser size will increase the bounce time of fungicides on the blade surface, and effect a stronger penetration on canopy of crops.

Table 1 Color codes for droplet size. by Jim Wilson, PhD. Source: Pesticide Environmental Stewardship

PINEYE™ EC emulsion is a nonionic type of adjuvant for fungicides. It has a sticky and wetting feature. It is a new choice for aerial agricultural spraying. Based on past farming experience, the pilots reduce turbulence by controlling flight height or speed or adjusting nozzles. PINEYE™ EC emulsion has a film-forming feature and extension properties. It affects the dynamic surface tension of molecules. In the medium droplet size condition, the active ingredients improve adhesion performance of fungicides and reduce contact angle between leaf surface and farm chemicals. Fungicides and pesticides find it easier to stick to the crops, reducing bounce on the blade surface and preventing fungicides loss.

When the droplet size is adjusted to fine condition (about 80 to 150 microns), spraying by the right nozzle type is important. Nozzles can change droplet size directly by adjusting the sprayer pressure. PINEYE™ EC emulsion affects the waxy blade surface and improves critical surface tension of crops so that the fungicides and pesticides are sprayed more evenly over the canopy. If growers blend PINEYE™ EC emulsion according to the mixing ratio, it even affects potentiating and releases control function.

1. Guidelines for Estimating Crop Production Costs 2016 in Manitoba
2. Recent Costs and Returns: All commodities, Wheat 2015-16, USDA
3. The Value of Fungicides In U.S. Crop Production, Leonard P. Gianessi, Nathan Reigner, 2005, CropLife Foundation
4. 中国农业航空作业质量技术指标（The operative indices of quality and techniques of agriculture and forestry aviation, Spraying operation）MH/T 1002.1-1995
5. The smarter agriculture package, PrecisionHawk
6. 单旋翼无人机航空施药效果分析与试验研究，王森，2016