FIELD OF INVENTION

[1] This invention relates to agriculture, and more particularly to foliar spraying of plants.

BACKGROUND

[2] Foliar spraying is one way to deliver fertilizer to plants. Essential elements can be absorbed by the plants through stomata on their leaves, or even across the cuticle and through the epidermis of the leaves. Recently, water infused with CO2 or ammonia has also been used in foliar spraying, so as to improve the delivery of CO2 or nitrogen, respectively, to plants.

[3] For indoor plants, including in greenhouses, drip irrigation, booms, or hand watering is used for the foliar spraying. For outdoor plants and crops, spray tractors or hand spraying is used.

[4] Each of these methods of application has drawbacks. Foliar spraying by hand is slow, and is in fact impractical for large fields of crops. Drip irrigation and booms require that infrastructure be installed, and this can be costly to replace or even adjust as plants grow or as plants are changed due to crop rotation. Spray tractors are expensive, and costly to adjust (if even possible) for different height plants or as the plants being sprayed grow. An example of the latter occurring is cannabis, which can grow from a few inches high to six feet tall.

[5] It would be desirable to be able to conduct foliar spraying using devices which were not permanent installed, were cost effective to operate, and flexible enough to adapt to different plant species or stages of growth. SUMMARY

[6] According to one embodiment of the invention, a method of foliar spraying plants is provided. Gas, such as ammonia or CO2, is infused into water to create gas- infused water. The gas-infused water is loaded into a tank of a drone. The drone uses the gas-infused water in the tank to foliar spray plants in an area. The drone preferably conducts foliar spraying by producing water droplets by spraying the plants with water droplets having a diameter of about 50 pm to about 150 pm.

[7] In one embodiment, after foliar spraying the plants the drone returns to a refilling station. Additional gas-infused water is then loaded into the tank, the drone flies to a different area of plants and foliar sprays the plants in the different area using the gas-infused water in the tank.

[8] A method is also provided for foliar spraying plants. Gas, such as ammonia or CO2, is infused into water to create gas-infused water. The gas-infused water is passed through a nozzle so as to create water droplets of gas-infused water each with a diameter between 50 pm and 150pm. Plants are then foliar sprayed with the water droplets of gas-infused water.

[9] By using drones to effect the foliar spraying over large areas, expensive infrastructure is avoided. Use of drones also provides great flexibility in foliar spraying as plants grow or as different species of plants are subject to the foliar spraying. The latter allows the same foliar spraying equipment to be used throughout crop rotation without hardware adjustment to the equipment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[10] Broadly, a gas is infused into water to create gas-infused water. The gas-infused water is loaded into a tank of a drone. The drone uses the gas-infused water in the tank to foliar spray plants.

[11] According to one embodiment of the invention, water is infused with a gas, such as but not limited to CO2 or ammonia, to create gas-infused water. The gas is infused into the water using hollow carbon fibers. Hollow carbon fibers create very small bubbles, or nano bubbles, on the order or 0.2 mhi in diameter. The small surface area of the gas nano bubbles allows very quick and efficient gas adsorption into the water.

[12] The gas-infused water is then placed into a tank carried by a drone. The tank preferably has a capacity of about 15 to about 20 liters. The tank contains baffles to reduce movement of the gas-infused water during flight of the drone. The tank is not pressurized, but is equipped with a pump and sprayer nozzle that allows the drone to spray the gas-infused water at water droplet sizes of 50 to 150 pm diameter.

[13] The drone with the tank then flies to an area of plants. The plants are preferably of the class of broad-leafed plants or grasses, so that the gas-infused water is able to cover a large number of stomata.

[14] The flight path is preferably pre-programmed so as to avoid obstacles and to maximize efficiency and duty -time, but may alternatively the drone may be fully controlled by a control person. Even if the flight path is pre-programmed, however, there is a control person. The drone then carries out foliar spraying of the plants with the gas-infused water in the tank.

[15] In one embodiment, when the tank is empty or close to empty, the drone returns to a refilling station where more gas-infused water is added to the tank. During refilling of the tank, the battery of the drone can be replaced with a fully charged battery. The switching of batteries is preferably on the order of seconds rather than minutes, so as to increase the duty time of the drone. Additional replacement fully charged batteries can be on hand, and depending on the recharging time of the batteries, some may even be recharged while the drone is in flight. The drone then flies to a different area of plants. The drone carries out foliar spraying of the plants in the different area with the gas- infused water in the tank.

[16] The invention has been described as using hollow carbon fibers to infuse the gas in the water. Alternatively, other gas infusion methods can be used, such as the use of air stones. But depending on the method of gas infusion used, large quantities of gas can be lost to the atmosphere as large bubbles of gas rise through the water before being adsorbed. The use of hollow carbon fibers and the resulting nano bubbles increases the amount of gas adsorbed by the water. [17] The invention has been described using a tank with a capacity of 15 L to 20 L tanks. Alternatively, larger or smaller tanks could be used. However, as the size of the tank increases the length of time spent foliar spraying by the drone increases, and the gas can gradually be lost to the atmosphere. More powerful drone is also needed, increasing capital cost. As the size of the tank decreases, escape of the gas from the water is less of a concern, but the drone must spend a larger fraction of its airborne time returning to the refdling station rather than spraying. A tank size of about 15 L to 20 L balances these two concerns.

[18] The invention has been described in which the foliar spraying is done with water droplets of 50 to 150 pm diameter. Other water droplet sizes may be used, but these are less efficient as they may not form a complete film around a leaf of the plant. If the water droplet is too small, then the water can drift in the wind and not all of it will reach the leaf, or the gas leaves the solution because there is too high a drop in pressure as the water passes through the nozzle, or both. If the water droplet is too large then the water droplet may not adhere to the leaf because the water droplet bounces off or rolls off the leaf, and a film of gas-infused water does not cover the leaf. In either case (too small droplets or too large droplets), transfer of the gas into the leaf through the stomata or epidermis is less effective when foliar spraying is carried out with the gas-infused water. This effect occurs in all types of foliar spraying with gas-infused water, not just with drones. The effectiveness of gas delivery to plants, such as delivery of CO2 or ammonia, by foliar spraying with gas-infused water with or without drones is reduced if the water droplet size of gas-infused water being sprayed onto the plants is less than

50 pm in diameter or greater than about 150 pm in diameter.

[19] The embodiments presented are exemplary only and persons skilled in the art would appreciate that variations to the embodiments described above may be made without departing from the spirit of the invention. The scope of the invention is solely defined by the appended claims.