Nov 14, 2011

Occasional light tillage may benefit asparagus fields

Michigan’s asparagus industry began experimenting with the no-till system of production in the 1970s and since that time the system has been nearly universally adopted by our state’s growers. There is a very sound theory behind the no-till system: Tillage activities cut and damage the asparagus crowns opening them up to opportunistic diseases like Fusarium crown and root rot and destroying feeder and storage roots needed by the crown for high production.

But are there times when tillage, at least an occasional light tillage, is warranted? While there is no definitive research to answer that question, many growers are coming to the conclusion that the answer to that question is “yes.”

Why might it be appropriate to consider giving your asparagus field an occasional light tillage? One consideration might be nutrient stratification as the result of surface applications and the cycling of nutrients to the surface in the fern that dies each year (see Michigan State University Extension Bulletin E-471, “Lime for Michigan Soils”). This is especially true for pH where acid soil conditions at the surface can even affect the performance of herbicides. Periodic tillage will enhance decomposition of the fern residue and the release of nutrients back into the soil.

Oddly enough, disease control is another area where tillage might prove helpful. While tillage has the potential to open crowns up to injury from soil borne diseases, burying of previous years’ fern residue that may have been infected by foliar diseases such as rust or purple spot could reduce the frequency of those diseases during the growing season. This is particularly true of suppressing the spear-infecting stage of purple spot, which has no chemical control during the harvest season. Following a year when purple spot was so severe during harvest, this may be of special interest to Michigan growers.

If you plan to try tillage on your asparagus, take time to consider how deeply and how often you want to apply this procedure. Since crowns are planted 8 to 10 inches deep, shallower tillage in the 2- to 3-inch range runs the least chance of damaging crowns, especially in the early years of a field. Tillage probably does not need to be applied every year, as it takes several years for nutrients to stratify and disease-infected residue to build up. Ideally, growers should coordinate lime application with tillage for disease control, thereby reducing the frequency of tillage. Unfortunately, opportunities to till asparagus while minimizing damage are generally limited to periods of dormancy. Early spring is probably the preferred time since fall and winter tillage leaves soils more exposed to wind and water erosion.

By Norm Myers, Michigan State University Extension