Interactions of Nitrogen Fertilizer, Cotton Seeding Rate, and Late Season Insecticide for Tarnished Plant Bug Control in Midsouth Cotton

Peanut production has expanded across eastern Arkansas and SE Missouri cotton production areas in the past 5 years. Practical questions from cotton growers with a peanut rotation includes how best to take advantage of resulting opportunities associated with the new crop. Some producers manage to reduce inputs in the year following peanuts with lowered N fertilizer and pesticide (for nematodes) inputs. There are questions from high input producers about whether they might take advantage of improved fertility and push the crop to increase yield. The high input approach could lead to an excess of soil N, which often results in cotton maturity delays. In the midsouth, a late crop often leads to increased late-season pest pressure from tarnished plant bug, Lygus lineolaris. More bugs typically means more costly insecticides for crop protection. An important cultural control tactic in cotton IPM is judicious use of N fertilizer.

To address these questions, we initiated an on-farm study in 2020 to validate Extension recommendations to reduce N fertilizer from standard 100 to 120 lb N/ac down to 80 units N in the year following peanut. Our experiment focused on the soil fertility question, but we also examined multifactor effects that included a range of low to high production inputs. The experiment included 4 fertilizer treatments, 2 seeding rates, and 2 late season insecticide regimes.  The 4*2*2 factorial experiment (3 replications) was located in a commercial field in Mississippi County, AR. Plots were 150 ft long, 12 rows wide with at least 24 rows separating plots. All applications were made using the cooperating producer’s equipment. We conducted extensive pest and plant monitoring through the season. Yield analysis of yield monitor data included treatment effects as well as effects relative to different soil textures in the spatially variable field. Results also include budget data.