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INVESTIGATOR: Williams, P.

PERFORMING INSTITUTION:
CLEMSON UNIVERSITY
CLEMSON, SOUTH CAROLINA 29634

DEVELOPING A SENSOR-BASED, VARIABLE-RATE NUTRIENT MANAGEMENT TECHNIQUE FOR CENTER PIVOT IRRIGATION SYSTEMS

NON-TECHNICAL SUMMARY: Crops in the Southeastern USA are produced in fields with significant variation in soil texture, soil type, and other factors which have a major impact on crop fertilization strategies. In this region, yield response to nitrogen application varies significantly across the production field. Therefore, blanket application of N fertilizer over the entire field can be both costly and environmentally unsound. Scientists at Clemson have successfully developed cost-effective sensor-based nitrogen application systems designed specifically for Coastal Plain region. During the past 10 years, irrigated crop acreages have increased significantly in South Carolina. However, currently there are no practical decision making tools or equipment available for variable-rate application of nitrogen through center pivot irrigation systems. Therefore, the primary goal of this project is to develop technologies for a sensor-based, variable-rate nutrient management program for center pivot irrigation systems, to provide site-specific application of fertilizers only where needed within individual fields. The tools developed/refined under this project are designed to lower fertilizer use, optimize farm profits, and minimize the effect of production practices on the environment. This Pre-doctoral project will help to develop the technical and academic competence of the doctoral candidate. Working with a group of multi-disciplinary mentors, this project will provide hands-on experience to him in basic and applied research. Also, demonstrating this technology to producers will help him to develop oral communication skills.

OBJECTIVES: To modify variable-rate irrigation application equipment (developed at Clemson) to allow for site-specific nitrogen management.To adapt our sensor-based nitrogen recommendation algorithm from single side-dress application to multiple split-applications through a center pivot.To develop correlations between NDVI measured using a commercially available optical sensor (such as GreenSeeker or Crop Circle) and those measured by an aerial platform (UAV) and low cost optical sensors (LCS) developed at Clemson.To compare sensor-based (GreenSeeker, UAV, and LCS) and conventional nutrient management methods in terms of nitrogen use efficiency (NUE) and crop responses on three soil types.To conduct training programs for growers, county Extension agents, and technology providers during field days and workshops at the Edisto REC.

APPROACH: This project will be conducted on a representative coastal plain soil. The test field is equipped with a variable-rate center pivot irrigation system and will be mapped for variation in soil texture, using a commercially available soil electrical conductivity (EC) meter. This field will be divided into management zones based on soil EC and soil texture. The treatmentswill be replicated five times in each management zone using a randomized complete block experimental design. The technology developed for variable-rate irrigation (VRI) system at Clemson, will be modified for variable-rate nitrogen (VRN) application to match fertilizer rates with field variability and crop needs. The controller system for VRN will be independent of the VRI system and can be retrofitted to any exiting overhead irrigation system. The Clemson sensor-based nitrogen recommendation algorithms will be modified for multiple applications of nitrogen through a center pivot during the time window for side-dress nutrient application, and will be compared to single-application method based on sensors and also growers' methods. Intensive NDVI data will be collected during 2016 and the first year of this proposed project (2017) from cotton and corn fields, utilizing a spray mounted multi-sensor GreenSeeker, UAV equipped with NDVI cameras, and Clemson low cost sensor (LCS) mounted on the irrigation system. These data will be used to develop correlations between NDVI measured using these three sensors and to calibrate the UAV and LCS systems against commercially available optical sensors. The calibration equations will be incorporated into Clemson site-specific nitrogen algorithms and will be adapted for use with center pivot irrigation systems. Replicated tests will be conducted to compare sensor-based (GreenSeeker, UAV, LCS) and conventional nutrient management methods in terms of nitrogen use efficiency (NUE) and crop responses on different soil zones as identified by EC and soil texture. Crops will be harvested at maturity, using a spindle picker or a grain combine, both equipped with AgLeader yield monitors. Plant and soil data will be collected during growing seasons. The sensor-based variable-rate nitrogen management technologies for center pivot irrigation systems will be showcased during the Edisto REC growers' field days (two/year) and hands on training workshops (one/year). The pre-doctoral fellow will be responsible for project evaluation tasks. The criteria for evaluating the data generated with the VRN application system for irrigated crops will be based on the ability of equipment to correctly apply nitrogen where it is needed and the amount needed. Modifications and fine-tuning of the system will be conducted as performance is assessed. Major events and deliverables will be compared with the project milestones to verify that the project is on schedule and each task is completed successfully. The educational activities of the PD will be evaluated by his successful completion of coursework (approved in his GS2 from), research and Extension activities, publication of project results, and completion of his dissertation. Workshops and field days will be evaluated for value and benefit using standard Cooperative Extension Service evaluation forms. The evaluations will be conducted after each event, and results will be used to improve delivery and impact of subsequent training workshops. Successful implementation of this project will enhance nitrogen use efficiency and farm profitability while substantially reducing nitrogen use and its adverse impact on ground and surface water quality by applying fertilizer at optimum rate. Reduction in nitrogen use due to VRN application technology would be one indication of the success of this project.

PROGRESS: 2017/02 TO 2019/01
Target Audience:During the course of this project, 5 training field days and workshops were offered to farmers, county extension agents, crop consultants, graduate students, and agricultural-related businesses at geographically diverse locations in South Carolina. In addition, results were presented to other scientists at national, regional, and local meetings. Efforts: On-farm demonstrations were combined with a regional education and promotion program which provided information directly to growers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two undergraduate students were trained under this project. In addition, this project provided training to crop consultants, technology providers, and county Extension agents. The results of this project were incorporated into two graduate courses at Clemson University. How have the results been disseminated to communities of interest?The results of this project have been presented to other scientists at national meetings (4). Demonstration and training activities (5 field days and workshops) were conducted to familiarize stakeholders with the benefits of these technologies. Also, results were presented to graduate students at Clemson University during Fall and Spring semesters. What do you plan to do during the next reporting period to accomplish the goals?This is the Final report for this project. However, another graduate student will continue to further refine this technology, so it could be easily used by growers.

IMPACT: 2017/02 TO 2019/01
What was accomplished under these goals? A variable-rate fertigation system (VRFS) was developed which applied different rates of N fertilizer through an overhead irrigation system, using a pulse width modulation technique. The VRFS utilized the Clemson Lateral Irrigation Control software which controlled the solenoids in each zone by turning the N supply on and off (pulsing) for each zone. Tests were conducted to 1) Determine the uniformity of the VRFS; 2) The uniformity of nozzle flow at different irrigation system travel speeds; 3) The uniformity across the length of the irrigation system; and 4) The accuracy of the map-based controller system for applying variable rate N. The results showed that the pump output had a linear slope relationship and was the same for water and N. There was a strong correlation (R2 = 0.9998) between irrigation system speed and N rate. The nozzle pulsing produced an overall average error of 0.1% across all N rates. The system accurately applied N based on prescription maps with an error of less than 1.8%. In summary, the VRFS applied the correct amounts of N within each zone by either manually controlling the pulsing mechanism or utilizing a prescription map to apply different rates throughout the field. Also, field tests were conducted on cotton during the 2016 and 2017 growing seasons to 1) adapt the Clemson sensor-based N recommendation algorithms from a single side-dress application to multiple applications through an overhead irrigation system; and 2) to compare sensor-based VRFS with conventional nutrient management methods in terms of N use efficiency (NUE) and crop responses on three soil types. The results showed that the multiple applications of N compared to the grower's conventional methods (even though less N was applied) had no impact on yields in either growing season. Applying N in three or four applications, statistically increased yields compared to single or split applications in 2016. Applying N in four applications, statistically increased yields compared to single, split or triple applications in 2017. The sensor-based N applications reduced fertilizer requirement by 69% in 2016 and 57% in 2017 compared to grower's conventional methods. When comparing N rates among the four sensor-based methods (three or four) applications, increased N rates by 22 kg/ha in 2016 and 26 kg/ha in 2017 compared to single or split applications but in-creased the cotton lint yields by 272 and 139 kg/ha, for 2016 and 2017, respectively.

PUBLICATIONS (not previously reported): 2017/02 TO 2019/01
1. Type: Theses/Dissertations Status: Published Year Published: 2018 Citation: Development of a Sensor-Based, Variable-Rate Fertigation Technique for Overhead Irrigation Systems
2. Type: Journal Articles Status: Published Year Published: 2017 Citation: Khalilian, A, Nicholas Rogers, Phillip Williams, Young Han, Ali Mirzakhani Nafchi, Joe Maja, Michael Marshall, Jose Payero. (2017) Sensor-based algorithm for mid-season nitrogen application in corn; Open Journal of Soil Sciences, Vol. 7, No. 10, pp. 278-287. https://doi.org/10.4236/ojss.2017.710020
3. Type: Journal Articles Status: Published Year Published: 2017 Citation: Nafchi, A.M., Maja, J.M., Khalilian, A., Han, Y., Rogers, N., Payero, J.O., Marshall, M.W., Williams, P.B. and Fox, J. (2017) An Electro-Mechanical Controller for Adjusting Piston Pump Stroke On-the-Go for Site-Specific Application of Crop Nutrients. Agricultural Sciences, Vol.8, No. 9, pp. 949-959. https://doi.org/10.4236/as.2017.89069
4. Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Williams, Phillip, Ahmad Khalilian, Ali Nafchi, Joe Mari Maja, Jonathan Fox, Haibo Liu, Dara Park, Michael Marshall, 2018, A variable-rate nutrient management technique for overhead sprinkler irrigation systems. Proceedings of the Beltwide Cotton Conferences, National Cotton Council of America, Memphis, TN. http://www.cotton.org/beltwide/proceedings
5. Type: Journal Articles Status: Published Year Published: 2018 Citation: Williams, P.B., Khalilian, A., Marshall, M.W., Maja, J.M., Liu, H.B., Park, D. and Nafchi, A.M. (2018) Development and Testing of a Variable Rate Nitrogen Application System through an Overhead Irrigation System. Journal of Water Resource and Protection, 10, 994-1011. https://doi.org/10.4236/jwarp.2018.1010058
6. Type: Journal Articles Status: Published Year Published: 2019 Citation: Williams, P.B., Khalilian, A., Marshall, M.W., Maja, J.M., Liu, H.B., Park, D. and Nafchi, A.M. (2019) Cotton Response to Variable Nitrogen Rate Fertigation through an Overhead Irrigation System. Agricultural Sciences, 10, 66-80. https://doi.org/10.4236/as.2019.101006
7. Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Nicholas G. Rogers, Phillip B. Williams, Ali Mirzakhani Nafchi, Young J. Han, Joe Mari Maja, Jose Payero, and Ahmad Khalilian. 2017. Development of a sensor-based algorithm to determine the mid-season nitrogen requirements in deficit irrigated corn production. 2017 American Society of Agricultural and Biological Engineers, Annual International Meeting, Paper No. 1700849, pages 1-7 (doi: 10.13031/aim.201700849).
8. Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Khalilian, Ahmad, Michael Marshall, Joe Maja, Ali Mirzakhani Nafchi, Jose Payero, Phillip Williams, 2017. Site-specific Nitrogen Management for Crop Production in Coastal Plain Soils, Abstract ID: 166, Soil and Water Conservation Society.