Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/8/2003
Publication Date: 6/1/2004
Citation: Heatherly, L.G., Spurlock, S.R., Elmore, C.D. 2004. Deep and shallow fall tillage for irrigated soybean grown with different weed management systems in the midsouthern USA. Agronomy Journal. 96:734-741. Interpretive Summary: The Early Soybean Production System (ESPS) is a high-yield, high-profit system when coupled with irrigation in the midsouthern USA. Level of profit is affected by management inputs such as tillage and weed control that are not related to the cost of irrigation. Tillage costs can be affected by the use of either minimum (shallow) or intense (deep) tillage methods that are usually applied in the fall. Weed management costs can be controlled by using either glyphosate-resistant (GR) or non-GR cultivars and manipulating herbicide inputs and application timing. Use of shallow tillage vs. deep tillage resulted in $15/acre average lower costs and nearly identical profits. Using non-GR cultivars and non-glyphosate herbicides resulted in $28 to $47/acre greater profit than using GR cultivars with glyphosate herbicide. Use of postemergent weed management vs. weed management that contained a preemergent component resulted in greater profits. These results indicate that the investment in equipment for deep fall tillage for irrigated ESPS planting is not justified. Also, cultivar type (GR or non -GR) and weed management system (pre- plus postemergent vs. postemergent only) will affect profits from irrigated soybean plantings.
Technical Abstract: Management inputs that maximize economic return from Early Soybean Production System (ESPS) plantings in the midsouthern USA have not been evaluated fully. The objective was to determine effect of different weed management systems on yield and net return from irrigated ESPS planting of glyphosate (GR) and non-GR soybean cultivars following deep (DT) and shallow (ST) fall tillage. Adjacent experiments receiving either DT or ST were conducted in 1999 and 2000 on Sharkey clay (very-fine, smectitic, thermic Chromic Epiaquert) near Stoneville, MS (lat. 33 degrees 26 minutes N). Weed management systems were 1) preemergent broadleaf followed by (fb) postemergent grass weed control (WMS 1), 2) postemergent broadleaf and grass weed control (WMS 2), and 3) preemergent broadleaf fb postemergent broadleaf and grass weed control (WMS 3). Fall DT was more expensive than ST, but resulted in taller soybean plants and less weed cover at harvest. However, yields and net returns from DT and ST were not significantly different. Use of WMS 2 was cheaper for both non-GR and GR cultivars. Use of WMS 2 with GR cultivars resulted in greater yield and net return. Use of all WMSs with non-GR cultivars resulted in similar yields, but net return to WMS 2 was greater that that from WMS 3. Under the conditions of this study, use of non-GR vs. GR cultivars resulted in greater profit. These results indicate that the investment in equipment for deep fall tillage for irrigated ESPS planting is not justified.