POTATO INVESTIGATIONS LABORATORY
Mimeo Report 57-6 October 1, 1956
RECOMMENDATIONS FOR LIMING AND FERTILIZATION OF POTATOES*"
Donald L. Myhre
Most virgin and cultivated sandy soils in the Hastings section are naturally
acid, due to the nature of the parent material from which they were formed and also
to the soil-forming process in a humid climate which leached out the basic elements
such as sodium, potassium, calcium and magnesium. Periodic liming as indicated by
a pH test is necessary to replace the calcium and magnesium taken up by the potato
crop and lost by leaching, neutralize the acidifying effect of fertilizers, make
the nutrients in the soil and fertilizer more available to the plants, and make
aluminum more unavailable. Liming also increases nitrification which is a pre-
cautionary measure against nutritional leaf roll of potatoes.
Soil Sampling.- Soil samples for pH determinations in indicating liming re-
quirements 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.
Each type of soil should be sampled separately by taking about eight plugs of
the surface six inches over the area and mixing them together to make one sample.
Several samples should be taken from each field.
Soil Acidity (pH)t- A soil pH of 5.5 is currently recommended for growing
potatoes- n the Hastings section. Potatoes will grow at a higher pH than is recom-
mended for them, but generally scab is less troublesome in aicd soils below pH 5.5.
For average soils lime may be used on the basis of 200 pounds per acre of ground
limestone (dolomite or high calcic limestone) or 120 pounds per acre of hydrated
lime for each 0.1 pH below 5.5, as shown in Table 1.
*Revision of Mimeo Report $5-1, September 22, 1953, as prepared by Drs.
G. M. Volk and Nathan Gammon, Jr., Department of Soils, Gainesville, Florida.
TABLE 1.- Amount of Lime Required to Adjust Soil pH to 5.5.
Original Pounds per Acre Lime Required to
Soil pH Adjust Soil pH to 5.5
Dolomite or High Calcic Hydrated
4.3 2400 1i44
4.4 2200 1320
4.5 2000 1200
4.6 1800 1080
4.7 1600 960
4.8 140o 840
4.9 1200 720.
5.0 1000 600
5.1 800 480
5.2 600 360
5.3 0oo 240
5.4 200 120
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 is preferred where more rapid correction of acidity is
desirable. Hydrated lime gives still faster correction of acidity but
is more costly and difficult to use. It may be used in emergencies where
liming of new lands or those subject to leafroll has been delayed until
Amount of Fertilizer.- About 2,500 pounds per acre of 6-8-8 ferti-
lizer is currently recommended for growing potatoes in the Hastings
section. Proportionately less of higher analysis materials can be used.
Contents of Fertilizer.- All fertilizers should contain about 2 per-
cent soluble~ e agnesia. For average conditions, one fifth of the nitrogen
should be nitrate itrogen. For new lands or where leaf roll has been
prevalent, Te-' trate nitrogen can be increased up to one third of the
total nitrogen present. Generally, the use of more than one unit of
nitrogen from insoluble sources cannot be justified for potato fertili-
zers."The chlorine content should be not more than 3 percent, the lower
the better If E r season is encountered.
Side Dressing.- New lands or ones previously showing leaf roll
should be sidedressed with about 150 pounds of nitrate of soda-potash
or its equivalent per acre at about 40 days after planting. This side-
dressing is also recommended after heavy leaching rains have occurred.