Research Approach

The field experiment was conducted at Champaign, Illinois on a Drummer Flanagan silty clay loam, planted on April 28th, 2016 over 4 replicated blocks of 13th year continuous corn and 1st year corn in a corn-soybean rotation (Figure 1A and 1B) using two commercial hybrids.  The factors evaluated were:

1) Residue Management:

Mechanical residue treatments were implemented during the
previous harvest by a combine head equipped with:

• Calmer’s BT Choppers® (residue sized 3-4 cm in length; Figure
  2A), vs.
• Standard Stalk Rollers (residue not sized; Figure 2B).

2) Agronomic Input Level:

Standard
• One week prior to planting, nitrogen was applied at 202 kg N ha
-1
as UAN.
• Soil test values for P and K were in the optimal range and no
additional fertility was applied.
• Plots were planted to achieve a final stand of 79,100 plants ha-1
(32,000 plants ac-1
; to simulate a standard producer practice).
• No fungicide was applied.
High Input
• A base rate of 202 kg N ha-1 as UAN was applied preplant with an
additional sidedress of 67 kg N ha-1 as urea (46-0-0) at V5 (269 kg
N ha-1 total).
• Phosphorus was banded preplant at 112 kg P2O5 ha-1 as Mosaic’s
MicroEssentials® SZTM (12-40-0-10S-1Zn) and potassium was
broadcast at 84 kg K2O ha-1 as Mosaic’s Aspire® (0-0-58-0.5B).
• Planted to achieve a final stand of 111,200 plants ha-1
(45,000 plants ac-1 ; as an intensive practice).
• Plots received a foliar fungicide application of BASF’s Headline
AMP® at plant growth stage VT/R1.

RESULTS AND DISCUSSION

Mechanical residue management showed visual differences after harvest (Figure 2A and 2B), and in-season (Figure 2C and 2D).
• On average, residue decay was increased by sizing the residue (50% reduction in residue when chopped compared to a 43% reduction with
the standard stalk rollers) (Figure 3).
• Seedling emergence in continuous corn was significantly delayed during the first 5 days of emergence (3-26% delay across harvest method; P = 0.007) compared to corn in rotation with soybean. Stand establishment was reduced in corn on corn vs. corn following soybean (94% vs. 97%, respectively) (Figure 4).
• Visual growth differences between continuous corn and rotated corn (Figure 1A, and 1B), translated into a CCYP of 0.6 Mg ha
-1 across treatments (Table 1); the greatest yields were achieved in the corn/soybean rotation with the enhanced agronomic system (i.e., additional
plants, added fertility, side dressed nitrogen, and a foliar fungicide application).
• The high input level improved plant growth (Figure 5) and grain yield across rotations by 2.1 Mg ha -1 (Table 1; P = < 0.001). Across harvest method, the CCYP was lessened by 56% with the high input level (penalty of 0.4 Mg ha -1 ) vs. the standard input level (penalty of 0.7 Mg ha -1 ), suggesting enhanced agronomic management as a method to alleviate the CCYP.

Figure 3. Effect of mechanical residue management on percent overwinter residue degradation across rotations. Data represents dry matter weight reduction of residue subsamples from the initial previous season post harvest vs. remaining preplant in field-located mesh bags.

Figure 2. Mechanical residue management in corn on corn the previous fall (A and B) and at the R3 growth stage the following growing season (C and D): Standard stalk rollers (A and C) and Calmer’s BT choppers (B and D) .

Figure 1. Late-season differences between 13th year continuously grown
corn (A) and 1 st year corn in a corn-soybean rotation (B). | A B | A B C D

Figure 5. Early-season differences between standard (left) and high input (right) agronomic systems.
• Across agronomic input level, chopped residue harvest increased continuous corn yields by 0.5 Mg ha
-1 compared to standard harvest and reduced the CCYP (0.8 Mg ha
-1 with the standard stalk rollers vs. 0.3 Mg ha
-1 with sized residue) (Table 1).