Fertilizer management for conservation tillage
Farmer interest in conservation tillage for crop production is expanding. Research has shown that use of one or more conservation tillage systems will work on most soils in Minnesota. The system, to be successful and profitable, must be modified to fit soil texture. There is no “one size fits all” conservation tillage system. Each system (no-till, strip-till, ridge,till) has unique advantages and the preference among crop producers varies across the state.
A conversion from full width to conservation tillage requires some changes in use of traditional management practices. This is especially true with fertilizer use. Therefore, a description of fertilizer management practices that should be used in conservation tillage systems will be summarized in the paragraphs that follow.
NITROGEN USE: Results of research conducted to date lead to the conclusion that there is no need to change rate of applied fertilizer N when there is a switch from full width to conservation tillage systems. The current concept that addresses rate of applied N that is used throughout the Corn Belt is appropriate for both full width and conservation tillage production systems.
Timing of the fertilizer N is flexible in both tillage systems. Growers usually develop a preference for time of N application. Best Management Practices (BMP’s) that pertain to N timing have been developed for several region of Minnesota when corn is planted with full width tillage. These BMP’s are also appropriate for corn planted in conservation tillage systems.
However, special consideration should be given to placement. Results of various research trials conducted across the Corn Belt lead to the conclusion that fertilizer N should be placed below the crop residue—not in contact with residue on the soil surface. Efficiency of N use by corn is reduced substantially if fertilizer N remains in contact with crop residue.
There is no indication that source of N should be changed if there is a switch to conservation tillage. All N sources are equal if applied so that loss of N is minimized. This statement is appropriate for both full width and conservation tillage systems.
PHOSPHATE APPLICATION: Research and grower experiences have produced the same conclusion. Placement of phosphate fertilizer in a band is one of the keys to profitable production from a conservation tillage planting systems in Minnesota. There are several options for the location of the band. Placement of fertilizer to the side of and below seed level at time of planting works for all soil textures. Except for sandy soils (loamy sand, sandy loam), phosphate fertilizer can be placed in contact with the seed (pop-up) and this has become a very popular practice.