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Watch for pH problems in older asparagus


December 14, 2011
By Norm Myers Michigan State University Extension

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asparagusfernNEWS HIGHLIGHT

Watch for pH problems in older asparagus

Most commercial asparagus growers have their fields on a regular
soil-testing program. Usually that is once every two years, but is sometimes
yearly. Unfortunately, even when growers are regularly soil testing and
following the soil test recommendations, pH problems can develop as a field
ages.

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December
2, 2011 – Most commercial asparagus growers have their fields on a regular
soil-testing program. Usually that is once every two years, but is sometimes
yearly. Unfortunately, even when growers are regularly soil testing and
following the soil test recommendations, pH problems can develop as a field
ages.

The wide
spread use of the no-till system of production can speed development of pH
problems in asparagus fields. Most nitrogen fertilizers are acid-forming by
nature and in no-till systems where these materials are applied to the surface
once or twice per season, acid layers can develop two- to three-inches below the
surface.

 asparagusfern 
  

Another
cause of rapid development of low pH spots in asparagus fields is the sandy
texture of soils planted to the crop. The pH drops quicker in sandier, lower
organic matter soils. Where the texture varies within a field, look for pH
problems to develop first on the sandiest spots.

Growers
often notice asparagus fern growing on these sandier spots is shorter and there
are fewer ferns per crown. Developing pH problems are often easiest to notice
from a “High-boy”-type sprayer. If the person in charge of spraying is not also
the person in charge of soil testing, it may make sense to have the soil
testers ride the sprayer once during fern season to spot these problems.
Flagging tape or GPS positioning units can be used to mark these problem spots,
and separate samples should then be taken to check the pH of the problem spots.

Another,
more expensive way, to identify these spots is to employ precision farming
techniques where samples are taken on small grids, or in small zones,
decreasing the chances of missing isolated pH problems. Once the low pH spots
have been identified, separate lime applications can be made to these problem
spots.

It is
better to detect isolated pH problems early. Asparagus is a no-till crop in
most of Michigan, and lime is applied to the surface and not incorporated after
application. This means that to bring up pH after it has dropped will take
longer because rainwater or irrigation must solubilize and move the lime into
the soil, which is a slower process than when lime is incorporated.


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