Long-run return impacts for corn-soybean planting
In many areas of central Illinois, corn-after-corn yields were substantially below corn-after-soybean yields in 2010 and 2011. These yield drags, along with large increases in corn costs, have led some farmers to reevaluate corn-soybean cropping decisions.
For land productivities that predominate in Illinois, corn-after-corn and continuous corn usually have higher budgeted returns than soybeans. However, more intense corn rotations reduce corn-after-soybeans acres, often some of the most profitable acres on a farm. Reduction in corn-after-soybean acres will impact returns in future years.
Budgets for central Illinois are shown in Table 1 for high-productivity farmland. Budgets are given for corn-after-soybean, corn-after-corn, continuous corn, soybeans-after-corn, and soybeans-after-two-years-corn.
Yields differ for the different budgets. Corn-after-soybean yield is 198 bushels. Compared to corn-after-soybeans, corn-after-corn is 10 bushels less at 188 bushels per acre and continuous corn is 18 bushels less at 180 bushels per acre. Soybeans-after-corn has a 56 bushel per acre yield. Soybeans-after-two-years of corn have 3 bushels higher yield at 59 bushels per acre. Differences in yields in these budgets reflect research conducted at the University of Illinois. Emerson Nafziger reported some of the corn yield research in a 2012 Corn & Soybean Classic Proceedings entitled “Fixing What Ails Continuous Corn” (Department of Crop Sciences, University of Illinois).
Non-land costs for corn-after-soybeans are $505 per acre. Non-land costs for corn-after-corn and continuous corn are $15 per acre higher at $520 per acre, reflecting higher fertilizer and pesticide use. Costs in Table 1 do not include more tillage for corn-after-corn and continuous corn. If more tillage is used, costs would increase by $12 to $15 per tillage pass.
Operator and land returns are:
$578 for corn-after-soybeans,
$510 for corn-after-corn,
$467 for continuous corn,
$390 for soybeans-after-corn, and
$425 for soybeans-after-two-years-corn.
Not that all corn budgets have higher returns than soybean budgets. For the coming year, budgets suggest that returns are maximized by planting all corn.
Longer run implications of current year cropping decisions can be analyzed by calculating rotation returns given stable rotations. Rotation returns for three rotations are calculated:
1.Corn-soybeans. This rotation has 50% of its acres in corn and 50% in soybeans. The rotation is one year corn and the next year soybeans. Given a stable cropping rotation over time, corn-soybeans has an average return of $484 per acre, the average of $578 for corn-after-soybeans and $390 for soybeans after corn (i.e., ($578 + $390) / 2).
2. Corn-corn-soybeans. This rotation has 2/3 of its acres in corn and 1/3 in soybeans. The rotation is corn in a field for two years, followed by a year of soybeans. Given a stable cropping rotation, corn-corn-soybeans has an average return of $504 per acre (i.e., ($578 corn-after-soybeans + $510 corn-after-corn + $425 soybeans-after-corn) / 3).
3. Continuous corn. Continuous corn has a return of $467 per acre. This assumes that yield reductions relative to corn-after-soybeans have occurred and corn averages 180 bushels per acre over time.