DD ~L'- 4 POTATO INVESTIGATIONS LABORATORY
Mimeo Report POL 66-4 October 1, 1965
LIMING RECOMMENDATIONS FOR POTATOES
D. R. Hensel, Associate Soils Chemist & Head
Reasons for Liming
Most virgin and cultivated sandy soils in the Hastings area are naturally acid
or have a low pH. This is due to the nature of the parent material from which they
are formed Ind also to the soil-forming process in the humid climate which leached
cut the basic elements such as sodium, potassium, calcium and magnesium. Perio,'i-.
i cming as indicated by a pH test is necessary to replace the calcium -.nd magnesia
taken up by the potato crop and lost by leaching, neutralize the acidifying effBI:
of fertilizers, make the nutrients in the soil and fertilizer more available to the
pl-nts, reduce the leaching loss of ammonical nitrogen by heavy rains, reduce the
av .ilbility of aluminum, end improve structure of soil. Liming also increases
nutrification which is a precautionary measure against nutritional leaf roll of
Soil samples for pH determinations in indicating liming requirements should be
collected on old land in the fall immediately after the summer cover crop has been
turned under and on new land as soon as the land has been cleared and leveled but
before the cover crop is planted. However, if nutritional leaf roll has occurred in
potatoes grown on old land, the soil should be sampled in the spring soon after the
potatoes have been dug. In all cases, lime should be applied as soon as possible
after the soil samples have been collected and the pH determined in order to provide
additional time for the lime to react.
It is extremely important to obtain a representative soil sample from the field
being sampled. A tube, auger, or spade may be used to collect the sample. Each
type of soil should be sampled separately by taking from eight to ten plugs or
slices of the surface six inches over the area and mixing them together to make one
sample. Several such samples should be taken from each field, usually about one or
two per ten acres.
Soil Acidity (pH)
Until recently, a soil pH of 5.5 was recommended for potato production in the
Hastings area. However with good management, the pH may be maintained at 6.0.
At this pH, seed free of scab should be used. If scab becomes a problem the pH
of the soil should be lowered to 5.5 for a few seasons until scab no longer exists.
At a higher pH than 6.0, certain microelements such as boron, copper, manganese,
and zinc become less available. Liming above 6.0 should be avoided.
Kind of Lime
Dolomite is preferred for general use to maintain proper soil pH for potatoes
because of the magnesium it contains. High calcic limestone isal&fpE ed where more
rapid correction of acidity is desirable. H. ydra Ie Mg; -fx ster correc-
tion of acidity but is more costly and diffi d usd in emergen-
cies where liming of new lands or those subj t to leaf roll has been delayed until
late fall. r i i
SF.A.S. Unv. o Florida
150 copies FA..