Date of Award


Document Type


Degree Name

Master of Science (MS)


Plant and Environmental Science

Committee Member

Michael T Plumblee

Committee Member

John D Mueller

Committee Member

Jeremy K Greene

Committee Member

Kendall R Kirk


New innovative precision technologies are changing the way farmers are producing crops across the world. This research looked at two row crop technologies (planter downforce and spray droplet size) that directly impact the entire production system through crop establishment and pest management. The objective of this research was to determine the implementation and profitability of these technologies for farmers to understand and use on their farms in South Carolina. The first study, planter downforce, was conducted at the Edisto REC near Blackville, SC, and at the Piedmont REC near Pendleton, SC. Four-row plots were arranged within a split-split plot experimental design, where tillage (conventional/strip-till at EREC and conventional/no-till at PREC) was the main plot factor, gauge wheel (normal and narrow) was the sub-plot factor, and downforce (target gauge wheel load) was the sub-sub-plot factor. Seven different downforce settings (0.0 to 136 kg in 22.7 kg increments) were compared in soybean planted in each tillage system at each location. The second study, spray droplet size, was conducted between 2019 and 2020 at the Edisto REC in Blackville, SC. Three separate fields were used, where 1-2 leaf cotton was sprayed with Orthene 97SG (Acephate) applied at a rate of 197 g ai ha-1 targeting thrips. This study was arranged in a randomized complete block design with treatments consisting of 150, 300, 450, 600, 750, and 900 µm droplets applied on four row plots. Results from the downforce study resulted in decreased emergence when downforce was applied over 90.7 kg as compared with 0, 22.7, 45.4, and 68.0 kg at EREC. Downforce rate influenced plant emergence at 2, 3, and 4 DAE at PREC, where rates over 68.0 kg resulted in greater emergence than 0 and 22.7 kg. As downforce increased across treatments, the depth at which soybean seeds were placed also increased up to 35%. No significant differences in yield were observed as a function of tillage, gauge wheel, or downforce rate at EREC. However, at PREC, significant differences in yield were observed in 2020, where tillage type influenced soybean grain yield. Results from the spray droplet size study found that in 2019, acephate applied at a droplet size of 450 microns resulted in the greatest number of thrips on cotton 3 DAA when compared to all other droplet sizes. Visual injury ratings 3 DAA were greater on cotton where acephate was applied at 300-micron droplets when compared to other droplet sizes. In 2020, acephate applied at a droplet size of 150 microns resulted in the lowest number of thrips on cotton 14 DAA when compared to all other droplet sizes. Even with significant differences in thrips counts among treatments during 2019 and 2020 neither year resulted in yield differences between droplet size treatments or the untreated check. Continued research on the impacts of planter downforce and spray droplet size on agronomic and economic factors are needed in row crop production in South Carolina.



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