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The differences in the growing conditions and the cotton varieties used in the cotton-growing areas in Xinjiang and theYellowRiver Basin result in different operating parameters required for unmanned aerial vehicle (UAV)-based plant spraying operations in the two regions. In this experiment, a multi-rotor plant protection drone was used for the application of cotton defoliant in theYellowRiver Basin to determine the optimum dosages of the defoliant ethepon. The experiment consisted of six treatments;40 g of thidiazuron, 1 mL of an additive, and different amounts of ethephon (50, 70, 90, 110, and 130 mL) were applied. The defoliation rate was measured on the 5, 10, 15, and 20 days after the chemical application and the correlation between the ethepon concentration and the defoliation rate as well as the cotton boll opening rate was determined. The results showed that the application of 90 mL ethephon resulted in the optimal defoliation effect and ripening of the cotton on 5 and 15 days respectively after the chemical application. It was found that the ethephon application had a larger effect on the cotton defoliation than the ripening rate. The results of this study provide reference data for the use of a plant protection drone for applying cotton defoliants in theYellowRiver Basin. Keywords: drone, UAV, cotton defoliant, ethephon, defoliation rate,Shandong DOI:  10.33440/j.ijpaa.20190201.0016  Citation: Han X, Yu J Y, Lan Y B, Kong F X, Yi L L.  Determination of application parameters for cotton defoliants in theYellowRiver Basin.  Int J Precis Agric Aviat, 2019; 2(1): 51–55.

Defoliants spraying is necessary to facilitate mechanized cotton harvesting. However, traditional uniform spraying usually decreases the defoliation effects and increases the costs. In order to address this problem, a variable rate spraying strategy was designed in the context of cotton defoliation. UAV multispectral imagery was collected in a cotton filed ofYellowRiver BasininChina, and the imagery was mosaicked into an ortho-photo. The indexes of NDVI and GNDVI were calculated, and the index maps were generated and later transformed into grid maps. A plant protection UAV was used for variable rate spraying, with the chemical dose proposed by the grid maps. Ground investigation before and after the spraying were conducted carefully to verify the defoliation effects. Investigation results showed that the proposed variable rate spraying strategy yielded satisfactory results with less defoliants, which demonstrated that this technology has potential in the cotton defoliation applications. Keywords: multispectral remote sensing, cotton, defoliation, UAV DOI:  10.33440/j.ijpaa.20190201.0018  Citation: Yi L L, Lan Y B, Kong H, Kong F X, Huang H S, Han X.  Exploring the potential of UAV imagery for variable rate spraying in cotton defoliation application.  Int J Precis Agric Aviat, 2019; 2(1): 42–45.

The method for UAV spraying of cotton defoliating agent in theYellowRiver basin was investigated in this study through comparison of a one-time pesticide application experiment and a two-time pesticide application experiment. The experiment was carried out using a Jifei P30 multi-rotor electric UAV. The experiment was divided into five different treatments, the first treatment was the one-time pesticide application to Jinfeng 103 cotton, the second treatment was the two-time pesticide application to Jinfeng 103 cotton, the third treatment was the one-time pesticide application to Lumianyan 37 cotton, the fourth treatment was the two-time pesticide application to Lumianyan 37 cotton, and the fifth treatment was blank test.  The cotton plant defoliation and opening of bolls were observed at 5, 10, 15, and 20 days under five different treatments, and statistical analysis was conducted to analyze variations in wadding and defoliation rate for the different treatments. The results showed that the effects of defoliation rates and vomiting rates were better than those of the control group, and the effect of the two-time pesticide application of the same variety of cotton was better than that of the one-time pesticide application. By observing defoliation and wadding after applications, the defoliation effect was determined to be faster than the wadding effect. The costs of one-time pesticide application and two-time pesticide application were also compared, and the cost of the two-time pesticide application was approximately 1.58 times as much as the cost of the one-time pesticide application. Therefore, it is suggested to select the two-time pesticide application mode when spraying defoliant agent on cotton. Keywords: cotton, defoliation, defoliant agent, wadding, UAV, plant protection DOI:  10.33440/j.ijpaa.20200301.65  Citation: Kong H, Yi L L, Lan Y B, Kong F X, Han X. Exploring the operation mode of spraying cotton defoliation agent by plant protection UAV.  Int J Precis Agric Aviat, 2020; 3(1): 43–48.