Most growers who've adopted continuous corn understand it's more difficult to obtain maximum yields with this practice. In fact, a recent study in Illinois finds continuous corn yields 25 bushels per acre less than a traditional rotation.
The study identifies 3 key factors that limit continuous corn yields:
A yield drag
Numerous studies have documented yield reductions when corn follows corn rather than soybeans. The results persist even when it appears all yield-limiting factors have been adequately addressed.
A recent study in east-central Illinois compared corn-after-corn and corn-soybean systems over a period of 6 years ("Identifying factors controlling the continuous corn yield penalty," F. Gentry, M.L. Ruffo, and F.E. Below, 2013, Agronomy Journal 105:295-303). The study used the same high-yield management practices for both systems. Only nitrogen (N) fertilizer rates varied.
On average, continuous corn yields were 25 bushels per acre lower than a corn-soybean rotation and required 10 pounds per acre more N to achieve optimum yields (in this case, optimum for continuous corn being lower than optimum for a corn-soybean rotation).
The authors evaluated 11 potential yield-limiting factors. 3 of the factors collectively explain more than 99% of the difference between continuous corn and corn-soy results.
Here's a look at the top 3 factors:
While many growers report continuous corn yields approach corn-soybean yields over time, this study found the yield penalty increased with more years of continuous corn production. One explanation: Growers generally improve management as they gain experience with continuous corn; however, the Illinois study used relatively constant management practices.
The yield decrease over time likely reflects the effects of corn residue accumulation over time. Corn residues impede nutrient cycling, early-season soil warming and moisture. They also increased disease pressure over time
The yield penalty for continuous corn was greatest in years when environmental conditions limited soil N availability in continuous corn more than in a corn-soybean rotation. Continuous corn is generally more sensitive to these negative weather effects.
Growers should consider numerous factors to maximize continuous corn yields: hybrid selection, tillage, soil fertility, weed control and insect control. However, according to this Illinois study, the lion's share of the yield differences between continuous corn and a traditional corn-soybean rotation are due to N supplies, continuous corn field history and Mother Nature.
The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.