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Some of our sky-blue waters turned brown during the past two growing seasons.  Fueled by heavy rains over much of the southern part of the state, soil loss has, obviously, been substantial.  Most growers clearly understand the importance of keeping the highly fertile top soil on the landscape.

Past research has also shown that use of some type of conservation tillage system will reduce soil loss.  Yet, adoption of the systems that have the greatest potential for reducing soil loss has been, at best, slow.  Over three years, there have been several explanations for the slow adoption rate.  Many are no longer valid and it's time to take a new look at planting systems that will keep soil loss to a minimum in the corn-soybean rotation.

Although a conservation tillage system can be described as any practice that leaves a certain percentage of crop residue on the surface after planting, the three generally accepted conservation tillage systems used in the northern and western corn belt are no-till, ridge-till, and strip-till.

Comparing Yields

Researchers have not ignored these systems.  Active research projects have compared various tillage systems that might be used for corn and soybean production.   Results of research with a silty clay loam in Indiana are summarized in Table 1.   Closer to home, a summary of research conducted at the Southwest Research and Outreach Center at Lamberton is provided in Table 2.

Table 1.  The effect of various tillage systems on yield of corn and soybeans in Indiana.

*Soil Type = Chalmers silty clay loam.

In this study on a soil with a texture very similar to many soils in southern Minnesota, yield of both corn and soybean crops was lower when the no-till planting system was used.   Results from several studies which have compared various tillage systems lead to the general conclusions that yields are reduced where no-till is used when soils are cold and wet in the early part of the growing season.

Table 2.  Comparison of three conservation tillage systems used for the corn-soybean rotation at the Southwest Research and Outreach Center.

*Average yield for 1999, 2000, and 2001. Source: N. Eash and B. Potter.


The high average yield for the strip-till system is attributed to a high yield in 2000.   In 1999 and 2001, corn yields resulting from the use of these three systems were nearly equal.  Soil at this experimental site is moderately well drained and probably warms more rapidly than many other fine textured soils.  When the results of several comparisons of tillage systems are considered, there is a general conclusion that the lowest amount of  risk  is associated with the ridge-till and strip-till planting systems.

Thinking About Fertilizer Use

The switch from conventional to conservation tillage planting systems requires some changes in our thinking about fertilizer use.  Recommended rates of nitrogen needed to achieve the expected yield do not change.  However, broadcast applications that remain on the soil surface are not a good option.  Research has shown that broadcast N (wether fluid or dry) that remains in contact with crop residue is subject to loss.   The mechanism for loss is thought to be volatilization.  Nevertheless, fertilizer N applied in a conservation tillage planting system should be placed below the crop residue.

For application of phosphate, potash, and other immobile nutrients our thinking should shift from broadcast to banded applications.  There are several choices for a banded application.  Most ridge-till farmers have adopted the idea of placing the band in the center of the ridge at a depth of 4 to 6 inches in the fall of the soybean year.   This deep band is used effectively by young corn plants.  The yield summarized in Table 3 show the importance of the deep band.  The deep band also eliminates the need for the use of a starter fertilizer. 

The use of deep band has another advantage.  Rates of phosphate and potash needed can be reduced considerably when compared to broadcast applications in conventional planting systems.

The placement of the phosphate fertilizer in a band below the soil surface also reduces the potential for loss of phosphorus from the landscape thereby causing an increase in algae populations.  The use of the deep land is evidence that farmers who use conservation tillage planting systems are concerned about the environment.

Table 3.  Corn yield in a ridge-till planting system as affected by fertilizer placement.

Economic Comparisons are Positive

The soil conservation positives of conservation tillage planting systems are widely recognized.  The economic advantages of these systems, however are frequently overlooked.  A survey was conducted in the summer of 2001 to document the positive economics of the ridge-till planting system.  The results were convincing.

To complete the survey, several ridge-till farmers were asked via personal interviews to provide their production costs for corn and soybeans as well as their yields for each crop.  Neighbors who farmed a similar number of acres with conventional tillage were asked the same questions.

Average corn yields for the conventional and ridge-till planting systems were 144.9 and 149.0 bu. per acre respectively.  For soybeans, the average yield of 41.5 bu. per acre from the conventional system can be compared to 43.7 bu. per acre for the ridge-till planting system.  So there was no reduction in yield for growers who used the ridge-till planting system.

There was, however, a substantial difference in cost of production when the two planting systems are compared.  Those who used the conventional system had a cost of production of $1.94 per bu. of corn.  With the ridge-till planting system, the cost of producing a bushel of corn was reduced to $1.52 per bu.  For soybean production, the cost of production was $4.13 and $3.69 per bu. for the conventional tillage and ridge-till planting systems respectively.

In general, lower production costs in the ridge-till system were associated with fertilizer, herbicides and fuel.  These actual costs and associated yields reported by farmers illustrate the economic benefits of conservation tillage planting systems.

Equipment Options Are Not a Concern

In the past, many growers have been reluctant to explore a switch to conservation tillage planting systems because of a rumor that these systems are best suited for small equipment.  The source of these rumors is not known; but the perception persists.

Crop producers in Iowa and Minnesota who use the ridge-till and strip-till planting systems have clearly shown that these rumors are false.  The photo that accompanies this article shows a 16-row ridge-till planter working in southern Minnesota.  The use of the ridge-till and strip-till planting systems does not place a limit on the size of equipment.  As with conventional tillage systems, choice of equipment for conservation tillage is an individual grower decision that is influenced by many factors.

Summary

When evaluated from agronomic, environmental, and economical perspectives, the adoption of conservation tillage planting systems is a win-win situation for everyone.   Results of various research projects conducted by Land Grant universities, as in the past, continue to document the positive effects of planting systems.

When viewed from an agronomic perspective, crop yields are not reduced when the conservation tillage planting systems are used.  With the new systems, care must be taken to place the nitrogen below crop residue and the  immobile  nutrients should be applied in a band either in the previous fall or near the seed at planting time.

The subsurface banded application of phosphorous has very positive environmental consequences.  This placement provides for the most efficient use of this nutrient while substantially reducing the loss from the landscape.

Farmer records document the positive economical advantages, with no reduction in yield and lower costs, the potential for profit increases.