**TECHNICAL NOTES**

**USDA-Natural Resources Conservation Service**

**Boise, Idaho**

TN AGRONOMY NO. 30 January 1994

By Floyd G. Bailey, State Conservation Agronomist, Boise, Idaho.
Information for this Technical Note was gathered from successful
Chisel-Plant Residue Management Potato Growers across southern Idaho.

**USING CHISEL-PLANT RESIDUE MANAGEMENT SYSTEMS TO IMPROVE**

**POTATO QUALITY AND PROTECT THE ENVIRONMENT**

Most of Idaho's famous potatoes are grown on soils with high potential
for soil erosion or soil compaction and water intake problems. During
recent years, a number of growers have found when they maintain a
blanket of crop residue on the soil surface during the potato crop they
produce better quality potatoes and protect the quality of the soil,
water and air resources associated with their farms.

In order to maintain crop residue on the soil surface, they have
abandoned the moldboard plow and switched to Chisel-Plant Residue
Management systems for potato seedbed preparation. Commonly used
rotations consist of potatoes in rotation with small grains. In the
Chisel-Plant Residue Management System, chisels are the primary tillage
implement used to prepare the seedbed for potatoes.

Small grains generally produce four to six tons of straw per acre.
Historically, small grain stubble has been fall moldboard plowed to bury
the straw. Once the soil has been plowed, several additional tillage
operations are needed to reduce clods and prepare the potato seedbed. It
is common to use eight to ten tillage operations after plowing, leaving
soils in a condition that is highly erodible and restricts water intake
and plant root development.

Chisel-Plant Residue Management Systems reduce tillage, provides an
improved growing environment for the potato and protects the soil
against wind and water erosion. The following steps can be used to guide
producers into successful implementation of a Chisel-Plant Residue
Management System.

**Step One**

It is important that straw be well-spread before tillage begins.
Windrows and large clumps of straw plug chisels and planters. Combines
should be equipped with straw spreaders. If the combine doesn't spread
the straw, use a field chopper or other suitable equipment that will
evenly spread the straw over the field.

**Step Two**

Fields should be irrigated soon after grain harvest to maximize
germination of volunteer grain and weeds before fall tillage begins.

**Step Three**

Fall tillage should be done with high clearance chisels. The chisel may
be equipped with straw choppers or a light disking used when heavy
residues are present. When a disk is used, it should be set to chop
straw with little residue burial.

Most producers chisel twice in the fall with the second opera­tion at
right angles to the first. The object of the chisel operations is to get
about half of the straw mixed into the soil to start decaying during the
winter. The remaining straw should be maintained on the soil surface.
The goal should be to keep about 80 percent of the soil surface covered
with residue during the winter to reduce soil erosion, trap winter
moisture and reduce evaporation. When conditions permit, it is best if
fields are bedded in the fall.

**Step Four**

Fields not bedded in the fall will have to be bedded in the spring.
Spring tillage should be kept to a minimum because it exposes soils to
wind erosion. The best rule of thumb is, "If it is not needed, don't do
it." When spring weeds are present, control with a burn down herbicide.

**Step Five**

Where fields have been fall bedded, most producers prefer to inject
fertilizer, plant potatoes, incorporate pesticides and hill up the
potatoes all in one operation. Straw plugging of the planter is
generally not a problem where the straw has been properly spread. If
problems are encountered, a coulter should be placed in front of the
planter to cut straw and allow it to flow around the planter. It is best
to maintain at least 70 percent of the soil surface covered with residue
after planting.

**Step Six**

Cultivation during the potato growing season should be kept to a minimum
to reduce residue burial. The goal should be to main­tain at least 60
percent of the soil surface covered with residue during the growing
period. This will moderate soil temperatures and moisture evaporation
during the crop growth period, reducing plant stress and helping produce
better quality potatoes.

**Step Seven**

While the crop is growing, fertilizers, pesticides and irrigation water
should be applied through the sprinkler when possible.

Producers using Chisel-Plant Residue Management Systems claim they
harvest better quality potatoes, their potatoes grow larger and more
uniform in size and have significantly fewer knobs. Reducing plant
stress also helps the potato resist insect and disease infestations that
reduce plant growth and potato quality.

Chisel-Plant Residue Management Systems have many advantages. They
control soil erosion and help growers meet the requirements of the Food
Security Act (FSA). They also produce a significant change in soil
organic matter and soil tilth. Soils become mellow and easier to work.
Clods are softer and break down easier during harvest, resulting in
cleaner potatoes and less tare. Production costs are reduced because
time and machinery requirements are less than in moldboard plow systems.

Idaho growers have also found that with careful management they can
maintain grain straw on the soil surface completely through the potato
year to reduce soil erosion during the critical erosion period following
potato harvest.

Growers not already using a Chisel-Plant Residue Management System
should be encouraged to do so. It is best if they start with a small
acreage. Once they experience the many benefits, they will find ways to
expand Chisel-Plant Residue Management systems to the rest of the farm.