Tillage Best Management Practices for Water Quality Protection in Southeastern Minnesota

Long-term Research in Southeastern Minnesota

Loess soils over glacial till

Two long-term tillage experiments on continuous corn and corn-soybean rotations have been conducted on loess-cap soils over glacial till at the Iowa State University Northeast Research Center, Nashua, Iowa. Because tillage studies have not been conducted on these soils in Minnesota, data from somewhat poorly drained, high organic matter, glacial till soils at Waseca, which are somewhat similar to the Kenyon-Floyd soils, will be cited. Results from the Waseca studies are likely quite appropriate for the more poorly drained soils in the loess-cap area over till in southeastern Minnesota.

Continuous Corn

Summary:

Yield penalties of 10 bu/A or more are frequently found for ridge-till and no-till systems compared to moldboard and chisel systems on loess-cap soils with poorer internal drainage.

Discussion:

A 15-year study conducted on a Kenyon silt loam soil at Nashua, Iowa compared moldboard plow (MP+), chisel plow (CP+), ridge tillage (RT) and no tillage (NT) (Table 13). The yield average was greatest for moldboard plow (134 bu/A), intermediate for chisel plow (130 bu/A) and ridge tillage (124 bu/A), and lowest for no tillage (121 bu/A). This ranking of yields is very similar to some of the long-term data obtained on the Nicollet and Webster soils at Waseca.

Table 13. Continuous corn yield as influenced by tillage on a Kenyon silt loam in Northeastern Iowa, 1978-92. ^1/

^1/ Personal communication, Ramesh Kanwar, 2000.

Corn after soybeans

Summary:

Results from four studies on poorly drained soils consistently show slightly lower corn yields (3 to 8%) with no tillage compared to chisel plowing, the highest yielding treatment. Very small differences occurred among the chisel, strip-till and field cultivation systems.

Discussion:

A 15-year corn-soybean study conducted at Nashua compared the same tillage systems as the above continuous corn study. Corn yields averaged across the 15-year period were not greatly affected by tillage, ranging from a high of 145 bu/A with chisel tillage to 139 bu/A for ridge tillage (Table 14). A 30-inch row spacing was used for all treatments. A 6-year study conducted from 1993-1998 showed a 10 bu/A advantage for a single, spring field cultivation (FC) prior to planting corn (128 bu/A) compared to no tillage (118 bu/A).

Table 14. Corn and soybean yields in rotation as influenced by tillage on a Kenyon silt loam in Northeastern Iowa. ^1/

1/ Personal communication, Ramesh Kanwar, 2000.
2/ 15-Yr = 1978-92; 6-Yr = 1993-98.
3/ Tillage for corn = spring field cultivation (FC); tillage for soybean = fall chisel plow plus spring field cultivation (CP+).

At Waseca, tillage studies were conducted to compare nitrogen (N) and phosphorus (P) management strategies on chisel plow (CP+), strip-till (ST), field cultivation (FC) and no-till (NT) systems. The 3-year yield average ranged from 184 bu/A with chisel tillage to 176 bu/A with no tillage (Table 15). The optimum time for N application varied greatly from year to year. In 1997 and 1998, with normal rainfall amounts, yields were identical (188 bu/A) for fall and spring-applied anhydrous ammonia. However, in
1999 very wet and warm April and May conditions led to large losses of fall-applied N. As a result, corn yield was 36 bu/A less for fall-applied N compared to spring application, but was similar for all tillage systems. A 4-year study on high P-testing soils showed no yield difference between the chisel (CP+) and field cultivation (FC) systems, no yield difference between the strip till (ST) and FC systems, and lowest yields for no tillage (NT) (Table 16).

Table 15. Corn yield after soybean as influenced by tillage and time of N fertilizer application on a Nicollet-Webster clay loam soil complex at Waseca, 1997-99.

^1/ As anhydrous ammonia at 110 lb N/A.

Soybeans after corn

Summary:

Results from three studies show very little yield penalty (maximum of 5%) for no tillage when soybeans follow corn.

Discussion:

Tillage studies conducted in Nashua, Iowa show no difference in soybean yield averaged across 15 years among moldboard plow (MP+), chisel plow (CP+), ridge-till (RT) and no-till (NT) systems (Table 14). Similar results were obtained during a 6-year period when chisel plow was compared to no tillage (Table 14).

At Waseca, 3-yr yield averages show significantly higher yields (56 bu/A) when some tillage was performed after corn—either chisel plowing (CP+) or spring disking (SD) of the corn stalks compared to no tillage (53 bu/A) (Table 16).

Table 16. Corn and soybean yields in rotation as influenced by tillage system on a Nicollet- Webster clay loam soil complex at Waseca.