Continuous corn and corn–soybean profits over a 45-year tillage and fertilizer experiment

Abstract

Studies comparing profitability of tillage systems oft en examine narrow historic windows or exclude annual price fl uctuations. This study uses a continuous corn (Zea mays L.) (CC; 1970– 1990) and corn–soybean [Glycine max (L.) Merr.] (CS; 1991– 2014) Tillage × Fertilizer study in somewhat poorly drained soils in southern Illinois to reconstruct partial annual budgets with historical prices for crops, fertilizers, lime, herbicides, fuel, labor, and machinery. Combinations of tillage (moldboard plow [MP], chisel tillage [ChT], alternate tillage [AT], and no-till [NT]) and fertilizer (Control, N-only, N+NPK starter, NPK+NPK starter, and NPK broadcast) treatments were evaluated. The CC profits were highest in NPK-applied treatments followed by N-only and Control. The MP treatments were similar to ChT and more profitable than NT, while AT fell between. In CS, NPK-applied treatments were similar regardless of tillage. Combined costs for herbicide, machinery, labor, and diesel were higher in MP and ChT systems than AT and lowest in NT, but were a small percentage of total costs (26.6, 26.0, 21.5, and 18.2%, respectively). Nitrogen fertilizer offered a return on investment of 396% in CC and 133% in CS while P & K returned 78% in CC and 109% in CS. Sensitivity analysis in CS showed that NT would be less profitable than MP if herbicide costs increased 850%. A 300% machinery cost increase would have made MP less profitable than NT. These findings suggest that since 1991 CS under NT carried the same potential for profit as other tillage systems under full fertility management.