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Competency Area 8: Cropping Systems

PO 35 Compare and contrast different residue management systems for corn on:
A. Yield
B. Structure
C. Soil water and nutrient status
D. Insect pests
E. Pathogens
F. Weeds
G. Economics

A. Yield
Corn generally yields better under high-tillage systems on droughty soils that have low water holding capacity. Conversely, corn usually yields lower on poorly drained soils that are cool in the spring under high residue systems because high residue keep soil cool and wet longer.

B. Structure
High residue management systems on corn generally improve soil structure because increased residue increases aeration, infiltration, and water-holding capacity of these soils. But under very dry spring conditions, silt and clay loam soils can have higher bulk densities under high residue systems (i.e. no-till) and make it difficult for root penetration. Timely rains in June or July alleviate this problem.

C. Soil water and nutrient status
High corn residue soils can initially result in less N availability because of immobilization of N under these high C:N ratio conditions. High residue conditions with alfalfa or soybean does not cause this problem. High residue conditions can also result in stratification of P and K in the upper soil zones because of the lack of incorporation. High residue conditions, however, reduce runoff of P during high rainfall events resulting in greater P in the soil over time. Finally, high residue conditions can result in macropores in the soil profile so during high rainfall events some N or P can be leached.

D. Insect pests
Generally, high residue conditions increase the incidence of insect pests, especially soil insect pests. High residue conditions, especially from green manure crops or sod, encourage greater wireworm, cutworm, and white grub problems.

E. Pathogens
High residue systems, especially in a continuous corn or second-year corn crop, can increase occurrence of the leaf blights, eye spot, gray leaf spot, and anthracnose.

F. Weeds
High residue systems typically encourage more perennial weeds such as dandelions or quackgrass but over time less annual weeds, such as pigweed or lambsquarter.

G. Economics
There are not clear-cut economic outcomes on residue management systems of corn. High residue systems greatly reduce fuel, labor, and machinery costs but can increase seed costs and drying costs of the grain. Sometimes high-residue management systems may increase pest control costs but not always. Yields can be higher or lower under different management systems and that also tends to greatly influence the economics of corn residue management systems.