Location: Crop Production Systems Research2011 Annual Report
1a. Objectives (from AD-416)
Objectives are: 1) Control off-target drift and enhance penetration of active ingredients, such as fungicides and biological control agents, into crop canopies; and 2) Develop remote sensing methods, utilize and evaluate Global Positioning Systems (GPS), develop methods amenable to rapid image processing, and evaluate flow control systems to support variable rate aerial application.
1b. Approach (from AD-416)
This project seeks to advance application technology through improvements in 1) drift management technology, 2) technologies for improved within-canopy deposition, 3) use of low-altitude remote sensing to identify stressed plants, and 4) performance of variable rate aerial application systems. While drift management is a concern for all pesticide applications, it is of particular concern for aerial applications. The potential for drift is greater for aerial application due to higher altitudes of spray release and greater air turbulence in the wake of the aircraft. Determination of optimal spray release height will be a goal, as the effect of this variable on within-canopy deposition and off-target drift has not been considered adequately. Experiments for both drift and deposition will attempt to reduce confounding of treatment data with environmental effects, preserving statistical precision of the experiments. Penetration of sprayed material to the lower portions of the canopy is critical for control of fungal spore diseases like Asian Soybean Rust (ASR). Studies will compare nozzle types paired with carefully selected formulations and tank mixes for spray penetration. The deleterious effects of off-target herbicide drift to cotton will be detected using hyperspectral, multispectral, and thermal remote sensing techniques. Evaluation of variable rate aerial application systems will be continued and improvements will be made through interaction with system component manufacturers. Experiments are also proposed to demonstrate the validity of techniques developed.
3. Progress Report
Experiments were completed to determine the effects of formulation, relative humidity (RH), ambient temperature, and droplet volume on the size of droplet stains applied to water sensitive paper (WSP) used in spray drift and deposition studies. This experiment was conducted to improve spread factor equations for more accurate representation of droplet diameter. A model was developed to determine these effects on droplet diameter. A 0.24% increase in droplet stain area per 1% increase in RH was determined, which translates to a 5% increase over the range of relative humidity normally encountered in the field. In practice, this was not seen to be significant enough to measure and compensate for when using WSP for drift and deposition studies. Use of a surfactant increased average stain diameter on WSP by as much as 40% over the application of water alone. Data were analyzed for a study that quantified the effects of application height on spray drift and in-swath deposition of spray. A new method to account for wind direction and calculate the effective distance to the drift samplers was implemented by an M.S. student at Mississippi Valley State University as part of her thesis fulfillment. Results showed deposition of tracer material applied from the 3.7m application height to be up to three times the deposition of material from either the 4.9 or 6.1m heights on samplers closest to the spray swath. These differences decreased with distance from the spray swath. The deposition of material at 4.9 and 6.1 spray heights were comparable. A greenhouse study was conducted to characterize soybean plant injury due to varying rates of applied glyphosate in a spray chamber. Each of the two rates, 0.086 kg active ingredient/ha (ai/ha) and 0.86 kg ai/ha, was applied to four potted plants, and four were used as control. A hyperspectral imaging system, spectroradiometer, and chlorophyll fluorescence meter were used to measure plant responses to applied glyphosate 1, 2 and 3 days after spray. Data for this study are being analyzed. A field study was conducted to characterize corn, soybean and cotton plant injury due to varying rates of glyphosate applied from a ground sprayer. Each rate was applied on four plots of plants, which were randomly distributed in a crop field and compared with data from control plots. A hyperspectral imaging system was used to measure the plant responses in 1, 2 and 3 weeks after treatment. Plant injury was assessed visually and biological responses were measured as dry weight, plant height, and chlorophyll. Hyperspectral image processing methods were developed in collaboration with Mississippi State University via Specific Cooperative Agreement. Significant bands are being identified and correlated with plant rating to establish the relationship between spectral range and plant injury.
1. Crop spraying guidelines to prevent off target movement of spray. Aerial Applicators should not spray during unfavorable atmospheric conditions, which include atmospheric temperature inversions and stable atmosphere. Spraying should be avoided under these conditions to prevent crop damage and environmental hazards caused by long distance off-target movement of spray. Times of the day and weather conditions were documented in the Midsouth U.S. under which aerial applicators should not spray, and it was found that spraying should not occur when wind speed was less than about 3 mph and when there was less than 3 to 4°F temperature rise from the morning low. An important finding was that the time window during which spraying was permissible was shortened by about two hours under cooler weather conditions. This research has resulted in two invited talks to Agricultural Aviation Associations in Louisiana and Alabama.
2. Early detection of the onset of the crop stress is needed for effective crop production management. Hyperspectral imaging provides a technique for early detection of crop injury with great potential. A visible near infrared hyperspectral imaging system was successfully employed by ARS researchers at Stoneville, Mississippi, in collaboration with Geosystems Research Institute of Mississippi State University, to determine herbicide-induced crop response to applied glyphosate at different application rates. Use of this system will allow specific spectral bands to be determined that indicate onset of crop stress due to herbicide induced damage, nutrient deficiency, and water deficiency.
Huang, Y., Thomson, S.J., 0rtiz, B.V., Reddy, K.N., Ding, W., Zablotowicz, R.M., Bright Jr, J.R. 2010. Airborne remote sensing assessment of the damage to cotton caused by spray drift from aerially applied glyphosate through spray deposition measurements. Journal of Biosystems Engineering. 107:212-220.