Tillage Is Recreational, Fertilizer Is Essential: Economic Analysis over 44 Years of a Tillage x Fertility Corn and Soybean Trial in Southern Illinois.

Input costs for diesel, machinery use, herbicide, and fertilizer can fluctuate greatly over time and determine relative profitability of different agricultural production practices. This study uses historical data from a 44-year tillage x fertility field trial of continuous-corn (1970-1990) and corn-soybean (1990-2013) in southern Illinois to reconstruct partial annual budgets for the entire time series for different fertilizer/tillage combinations.  Tillages included moldboard plow, chisel plow, no tillage, and alternating tillage.  Fertilizer regimes included no fertilization, N-only, and NPK.  Historic records of yield, field activities, and crop inputs along with price records and indices for corn and soybeans, fertilizers, herbicides, fuel, and machinery operations were used to reconstruct a partial budget of income and costs in each tillage x fertilizer combination in each year.  Estimated net profits for each year showed a large impact due to fertilizer treatment, with highest annual profits in plots receiving NPK fertilizer.  There was little difference in profits based on tillage.  Seedbed preparation costs were higher in tilled systems compared to no-till, but overall impacts on average net profits were minimal.  In contrast, fertilizer was a relatively major annual cost but offered a large return on investment in terms of improvement of yield and income.  Returns for use of nitrogen fertilizer were larger than further additional returns for application of P and K.  Our findings suggest that in southern Illinois no-till corn/soybean production under full fertility management carries the same potential for profit as other tillage systems based on historical prices.