CORESTA Meeting, Agronomy/Phytopathology, 2023, Cancun, APPOST 16

Fungicide and starter fertilizer placement at transplanting

North Carolina State University, Department of Crop & Soil Sciences, Raleigh, NC, U.S.A.

Starter fertilizer and fungicide products are commonly included in transplant water solutions. It has been hypothesized that a different placement strategy is needed in order to minimize chemical and soluble salts injury. Research was initiated in 2022 to compare the efficacy of traditional in-furrow fungicide and fertilizer placement versus that of a sidedress placement. Two placement techniques were evaluated, a traditional in-furrow application that places solution in the planting furrow and a sidedress application that places the solution 5 cm away from seedlings. Within each placement technique three treatments were subsequently evaluated: oxathiapiprolin (0.07 kg ai/ha) + mefenoxam (0.21 kg ai/ha), 9-45-15 starter fertilizer (12.4 kg/ha), and oxathiapiprolin + mefenoxam + 9-45-15. A non-treated control was included for comparison (935 L water/ ha only). In-furrow placement was delivered in 935 L water/ha, while sidedress placement was delivered with 187 L water/ha. Two weeks after transplanting, visual injury (45-48 %) and chemical residues were highest in treatments receiving oxathiapiprolin + mefenoxam in-furrow. Sidedress placement of this fungicide combination reduced injury to 16 and 5 % and residues of mefenoxam to < 20 mg/kg. Oxathiapiprolin residues were below the Limit of Quantification. In the same measurement interval, the non-treated plots contained the largest plants based on dry mass and stem height measurements. Plant recovery was observed four weeks after transplanting, as chemical injury was not visible and in-furrow placement of starter fertilizer resulted in plants that were taller with a higher dry weight mass than the fungicide only treatment or any treatments that were applied sidedress. By six weeks after transplanting there were no differences in growth or biomass accumulation recorded across treatments. Preliminary results indicate that sidedress applications of fungicides and starter fertilizers may reduce injury; however, plant assimilation of those inputs may be delayed relative to in-furrow placement. Moreover, the addition of 9-45-15 in-furrow may promote plant recovery from fungicide injury. Results from 2023 field trials will be included in this presentation.