LIMING AND FERTILIZING BURLEY TOBACCO
J.L. Sims and K.L. Wells
Burley tobacco is a billion-dollar
crop in Kentucky. One of every 14 jobs in Kentucky, directly or indirectly,
exists because of tobacco. The effect of the more than $200 million in
taxes generated annually in Kentucky by the tobacco industry is felt throughout
The dry matter removed by a burley
tobacco crop can put a lot of stress on soil to provide the necessary nutrients
for such intensive production during the 85-95 day growing period in the
field. A good crop of burley can remove about 200 lb nitrogen, 35 lb phosphate,
and 240 lb potash/acre while producing 2.5 to 3 tons of dry matter during
this relatively short growing period.
1 shows the rate at which growth (dry matter accumulation) and nutrient
uptake occurs during the season. These data, from University of Kentucky
research, show graphically that only about a third of the dry matter and
nutrient uptake takes place during the first half the season. To ensure
that fertilizer is unlimiting, Kentucky burley producers have traditionally
used a ton or more of mixed fertilizer (usually a 1-2-3 ratio) and 500
to 900 lb of ammonium nitrate/acre, all broadcast and plowed under or disked
in before transplanting.
Continual use of such heavy fertilization
has often led to early season growth problems which result in reduced yields,
particularly for producers not routinely liming their fields. Good fertilizer
management practices should ensure that by mid-season plants will be sound,
healthy, and fast-growing, capable of maximizing yield and nutrient uptake
during the last half of the season when about two-thirds of growth and
nutrient uptake occurs.
During recent years another concern
has been the crop's production costs, of which fertilizer makes up 15-20%.
Many producers, attempting to cut total production costs, try to provide
only the minimum amounts of lime and fertilizer necessary to produce a
good crop. This approach is often workable because many tobacco fields
have very high soil test levels of phosphate and potash having been over-fertilized
in the past. In fact, soil test results often indicate no need for phosphate
and/or potash to produce a high yielding burley crop. About two-thirds
of the tobacco field soil samples sent to UK's Soil Testing Laboratory
indicate no need for phosphate, one-third need no potash, but about half
need lime to adjust soil pH to desirable levels.
Determining Lime and Fertilizer Requirements
Determining lime and fertilizer needs
for burley in a particular field requires knowledge of that field's fertility
status. Analysis of a representative soil sample taken from the field is
the best way to get this information. Because of the high crop value and
because pH levels and nutrient content can change following each production
year, soil samples should be taken from tobacco fields every 1-2 years.
The best time to take soil samples is immediately following harvest. This
schedule allows enough time to get the results back from the testing laboratory
so that when lime, phosphate or potash is needed, it can be broadcast and
disked into the soil prior to seeding the cover crop. The amount of lime,
phosphate and potash needed is dependent on the soil's residual status
as determined by a good soil test.
UK does not offer a soil test for nitrogen
since seasonal nitrogen availability is so difficult to estimate. Instead,
nitrogen recommendations reflect the influence of past cropping history
on the amount of residual soil nitrogen available for plant uptake.
Additionally, internal drainage characteristics
of the soil, that is, how fast water percolates through the rooting zone,
and data from field experiments testing nitrogen rates are incorporated
into nitrogen fertilizer recommendations.
Lime and Fertilizer Recommendations
Limestone should be applied in the
fail and thoroughly mixed with the soil. While applying agricultural limestone
several months before transplanting tobacco is preferable, it can be applied
in the spring if it can be thoroughly mixed into the plow layer by turning
about 1/2 under with the cover crop and disking 1/2 into the surface when
smoothing the field before transplanting.
Rates--If a soil buffer test has been
made (soil buffer pH), use the amount of limestone indicated to raise soil
pH to 6.6 (see Table 1). If a soil buffer test is unavailable, follow the
rates shown in Table 2.
Table 1. -- Rates of Agricultural Limestone Needed to Raise Soil
Water pH to 6.6 as Influenced by Soil Buffer pH.
Soil Buffer pH Reading 1
Agricultural Limestone Needed (tons/A)
1 Soil buffer pH is measured in the UK Soil Testing Laboratory
only when soil water pH is less than 6.0. If soil water pH is 6.0 to 6.6,
apply 1-2 T Agricultural Limestone/acre.
Table 2. -- Rate of Aglime When Buffer pH is not Available.
Rates -- Nitrogen fertilization
rates depend primarily on the field cropping history and the type of soil.
Since losses of fertilizer nitrogen may occur on sandy soils or on soils
with poor internal drainage, splitting nitrogen applications on these soils
is helpful. Apply 1/3 to 1/2 of the nitrogen before transplanting and the
remaining nitrogen 2 to 3 weeks after transplanting.
• For soil with low N levels (problem soils as mentioned above, or the
first year of tobacco following a poor sod crop), use 250-300 lb of N/A.
• For soil with medium N levels (first year of tobacco following a
good grass or grass-legume sod), use 200-250 lb of N/A.
• For soil with high N levels (first year of tobacco following a good
legume sod or legume cover crop), use 150-200 lb or N/A.
• For continuous tobacco, add 50 lb of N/A to the amount shown above.
Time and Method -- Currently,
most nitrogen fertilizer is broadcast within 4 weeks of transplanting with
some side-dressed 4 to 5 weeks after transplanting. Since Kentucky usually
has large rainfall amounts during April and May, applying the broadcast
nitrogen as near to transplanting (10 days to 2 weeks before) as possible
will significantly lessen the chances for losses of applied nitrogen. Apply
the nitrogen after plowing and disc into the surface soil.
Further efficiencies in nitrogen use,
decreased manganese toxicity and increased early growth may be obtained
by banding all the nitrogen (sidedress) after transplanting. These bands
should be applied 10 to 12 in. to the side of the row in either 1 or 2
bands, and at depths of 4 to 5 in. The nitrogen should be banded all within
10 days after transplanting or in 2 applications, 1/2 within 10 days and
1/2 at 4 or 5 weeks after transplanting.
Phosphate and Potash
Rates -- Phosphorus and potassium fertilizer
additions should be determined by soil tests. Based on these tests, apply
the amounts shown in Table 3.
Table 3. -- Rates of Phosphate and Potash at Different Soil Test
Soil Test Level
Lb/A to Apply Burley
P 2O 5
Very high (above 80 P, 450 K)
High (80-60 P, 300-450 K)
Medium (60-30 P, 200-300 K)
Low (below 30 P, 200 K)
Secondary and Micronutrients
Sulfur -- Sufficient sulfur
is available in soils from atmospheric fallout and from sulfate of potash
used for tobacco. No additional sulfur fertilizer is needed.
Calcium -- Residual levels of
available calcium in Kentucky soils, even when acid, are high enough for
good burley production. Application of calcium solely for use as a plant
nutrient is not recommended.
Magnesium -- Levels in Kentucky
soils range from very high (chiefly the loess-derived soils), to somewhat
low (primarily some of the sandstone-derived soils). Soil test levels are
rarely low enough to justify use of magnesium as a fertilizer. UK soil
test levels and the recommended amounts, are shown in Table 4.
Table 4. -- Rates of Magnesium at Different Soil Test levels.
Soil Test Level
Low (below 40)
High (above 81)
1 These rates may be applied when no lime is needed or where dolomitic lime cannot be
obtained. When lime and magnesium are needed,
the addition of dolomitic lime is preferred.
Molybdenum is recommended for use on
burley tobacco either as a broadcast soil application or as a mixture in
transplant setter water when the soil pH is less than 6.4. Recent research
and field trials have shown that setter water applications are as effective
as broadcast applications for supplying molybdenum to the crop. Molybdenum
may be purchased in dry solid form or as a liquid. Either source is satisfactory
when molybdenum is needed and may be applied either broadcast or in the
1. Soil Broadcast -- Apply one lb of sodium molybdate (6.4 oz
of molybdenum)/acre. Dissolve this amount of dry sodium molybdate (or 2
gal of 2.5% Mo liquid product) in 20 to 40 gallons of water and spray uniformly
over each acre. Apply prior to transplanting and disc into the soil. Since
sodium molybdate is compatible with many herbicides used on tobacco, it
may be mixed with herbicides normally applied as a spray in water to save
application costs since only one trip over the field is necessary. It is
recommended that not more than 2 lb of sodium molybdate (12.8 oz of molybdenum)/acre
be used during a 5-year period.
2. Setter Water -- Use 1/4 to 1/2 pound sodium molybdate (1.6
to 3.2 oz of molybdenum)/acre. If dry sodium molybdate is used, divide
the total recommended amount (1/4 to 1/2 lb/A) equally among the number
of 52 gal barrels of water used/acre. For example, if 8 barrels of water/acre
are used, add 1/8 (0.2 to 0.4 oz sodium molybdate) of the total recommended
amount to each barrel and fill the barrel with water. Adding the dry material
prior to filling the barrel will help it dissolve and mix. If a 2.5% liquid
source of molybdenum is used with 8 barrels of setter water/acre, add 1/2
to 1 pt (1 to 2 cups) of the liquid product/barrel prior to filling the
barrel with water.
Iron, Copper, Zinc, Manganese, Boron -No need for these micronutrients
has been found for burley production in Kentucky.
Selecting Lime and Fertilizer Materials
Agricultural limestone is the most
economical source of lime. If it meets the minimum requirements of the
Kentucky Lime Law, its purity will be no less than 80% (calcium carbonate
equivalent); would pass a 10-mesh screen; and at least 35% would pass a
50-mesh screen. Such a product will have a relative neutralizing value
of 50%. UK lime rate recommendations are based on use of agricultural limestone
with a relative neutralizing value of 67%. County agricultural agents have
up-to-date information on the relative neutralizing value of agricultural
limestone produced by quarries in the state, most of which exceed the minimum
Finely ground limestone, commonly sold
at farm supply stores throughout Kentucky's burley growing area, can be
broadcast and disked in just before transplanting. Pelleted lime is another
fast reacting product manufactured by granulating very fine lime to make
it more easily handled. Both bagged, fine lime and pelleted lime will be
considerably more expensive than regular agricultural limestone. Their
best use is for situations where a relatively rapid neutralization of soil
acidity is desired. Both of these fast-acting lime sources can also be
used in "rescue" procedures to alleviate manganese toxicity after transplanting.
A broadcast application of about 1000 lb/A, followed by a cultivation to
work it into the soil, sometimes relieves manganese toxicity symptoms of
To supply the needs for good burley
production based on soil test results, some combination of straight materials
(those guaranteeing only one nutrient such as ammonium nitrate, triple
superphosphate, or sulfate of potash) and/or mixed materials (those containing
more than one nutrient such as a 5-10-15 or 10-20-20 grade) will be required.
Although many burley growers commonly use mixed fertilizer of a 1-2-3 ratio,
there is no agronomic basis for a 1-2-3 ratio of N:P 2O 5:K 2O
being best suited for burley production. If mixed fertilizer is needed
as determined by a soil test, the ratio of the grade purchased should reflect
the amount of fertilizer recommended. With the high levels of fertility
currently existing in many burley fields, grades of a 1-2-3 ratio many
times do not supply phosphate and potash in the ratio really needed.
1. Straight Materials
Nitrogen Sources -- All commonly available
N sources can be used satisfactorily on tobacco, particularly on well-drained
soils where a good liming program is followed and soil pH is maintained
in the range of 6.0 to 6.5. Table 5 compares the effect of acid-forming
and non acid-forming nitrogen fertilizers on soil pH.
Table 5. -- Effect of Liming an Acid Soil Prior to Use of Acid Forming
(Urea) and Non-Acid Forming (Sodium Nitrate) Sources of Fertilizer
Rate of Lime Tons/A
Soil pH 2
1 Both N sources applied at 225 lb N/A pre-plant.
2 Soil pH (water) measured at midseason of each year.
Soil pH before liming was 5.4.
The greatest difference in yield occurred when no lime was used. In
that case, soil pH dropped to 4.7 during the growing season where urea
was used, but hardly changed where the non-acid forming all-nitrate N source
was used. When the soil was limed to offset the acid-forming potential
of urea, no significant difference between N sources existed. These data
also show that leaf concentration of manganese (Mn) was greatly increased
when urea was used without liming the initially acid (pH 5.4) soil. Leaf
concentration of molybdenum (already deficient) correspondingly dropped
to even lower levels. But with use of lime, urea performed agronomically
as well as the nitrate source of N. If soil pH is moderately to strongly
acid (pH 6.0 or below) and no lime is applied, using a non-acid forming
source of N (sodium nitrate, calcium nitrate or nitrate of soda-potash)
will lower the risk of manganese toxicity. Use these sources (or ammonium
nitrate or potassium nitrate) for side-dressing since nitrate is more mobile
in soil than ammonium nitrogen. If tobacco is grown on sandy soils or soils
which tend to waterlog, regardless of pH, using ammonium sources (urea,
ammonium nitrate, ammoniated phosphates, ammonium sulfate, nitrogen solutions)
will lower the risk of leaching and denitrification losses. Nitrogen content
of sources commonly used for burley in Kentucky is shown in Table 6.
Table 6. -- Nitrogen Concentration of N Fertilizer Sources.
% Total N
LB/N per Ton Material (approximate)
45 to 46
33.5 to 34.5
28 to 30
20 to 21
15 to 16
Nitrate of soda-potash
Phosphate Sources -- Triple superphosphate
is the most commonly used straight phosphate material. It contains 44 to
46% available phosphate and has no agronomic limitations. Other sources
sometimes used are ordinary superphosphate (20% available P 2O 5)
and ground, raw rock phosphate. Although ground rock phosphate has a relatively
high content of total P 2O 5 (27-41%), its availability
to plants is quite low. Phosphate fertilizers can safely be applied in
the fall by disking in just before seeding the winter cover crop.
Potash Sources -- Because a
large price difference has recently developed between the preferred source
of potash for tobacco (sulfate of potash) and the other widely available
source (muriate of potash), there has been great interest in the cheaper
source (muriate of potash). Recent research at the University of Kentucky
has shown that spring applications of chloride- containing fertilizers,
such as muriate of potash (KCI), above 50 lb of chloride/ acre, leads to
excessive levels of chloride in the cured leaf of burley tobacco, increased
curing and storage problems, decreased combustibility of leaf and ultimately
greatly reduced quality and usability of cured leaf.
Although several field experiments
have shown a yield increase to spring applications of muriate of potash,
chloride content of the leaf lamina, particularly at the higher rates of
application, is increased. Such increased chloride levels are usually associated
with lower leaf grades. Table 7 shows the effect of fail and spring application
of muriate of potash on leaf concentration of chloride. Consequently, sulfate
of potash (K 2SO 4) should be the major source of potassium
if applied in the spring. Because animal manures contain chlorine, applications
of manure should not exceed 10 tons/acre and should not be applied with
potash fertilizer other than sulfate of potash in the spring.
Fall application of chloride-containing
fertilizers (prior to January 1 of the production year) will greatly minimize
increases in chloride concentration of cured leaf but may lead to somewhat
higher levels than spring applied sulfate of potash. Neither source of
potassium (KCI or K 2SO 4) should be applied in the
fall on sandy soils since the potassium will leach out of the soil over
the winter. Research to date indicates potassium does not leach appreciably
during winter and spring when applied in the fall to silt loam or other
fine textured soils in Kentucky.
Table 7. -- Effect of Rate of Muriate of Potash and Date of Application
on Chloride Concentration of Cured Leaf Lamina.
Rate of KCI lb/A
Leaf Position on Stalk
2. Mixed Materials
Liquid vs. Dry Fertilizer --
Fluid fertilizers in various forms (clear liquids or suspensions), grades
and ratios are an important segment of fertilizer usage in Kentucky. They
represented 15% of total fertilizer tonnage used in 1981-82 and 10% of
total fertilizer tonnage used in 1982-83. However, most of this fluid tonnage
is nitrogenous material (anhydrous ammonia and UAN solutions). About 4%
of the total mixed fertilizer tonnage used during 1981-82 and 1982-83 was
in fluid form. Solid fertilizers are currently the most commonly available
form in Kentucky, either as materials or mixtures. However, fluid mixtures
are available in some Kentucky localities, and fluid materials are generally
Fluid mixed fertilizers have been shown
in numerous field and laboratory tests to be equivalent to dry mixed fertilizers.
For this reason, agronomists generally have no basis to predict any difference
between the agronomic effectiveness of fluids or solids when applied in
the same manner at the same rate of actual nutrients. A producer should
determine whether or not to use fluid or solid mixed fertilizer by considering
only such factors as convenience, how it fits into his program, cost, and
To determine the plant food content
of some volume of fluid fertilizer, the weight of that volume must first
be determined. Generally speaking, fluid fertilizers weigh 10-12 lb/gallon,
depending on the product. Once gallons are converted to pounds, plant food
content is calculated just as with dry fertilizers since the guaranteed
fertilizer analysis is on a percent-by-weight basis.
Organic Sources of Nutrients
-- Many growers apply animal manures, tobacco stalks or tobacco stems to
fields. Such practices add nutrients to the soil and fertilizer rates should
be reduced accordingly as shown in Table 8.
Table 8. -- Nutrient Content of Organic Sources.
For each ton/A of material applied, reduce fertilizer
rates (lb/A) as follows:
P 2O 5
Dairy cattle (80% water) 11
Hogs (75% water)
Poultry (55% water)
Horses (60% water)
Sheep (65% water)
1For tobacco production, do not apply more than 10 T/A of animal
manure because of high chlorine content.
Transplant-Water Fertilization --
Although somewhat unclear, research on N-P 2O 5-K 2O
fertilizer in the transplant water finds the practice questionable when
N-P 2O 5-K 2O fertilizer has been broadcast
and disked in before transplanting. Best results are likely to result when
this practice is combined with a post-transplant band application of fertilizer,
because small transplants need only a small amount of nutrients in the
transplant water. The slight decline of soil pH around the roots will not
suppress root development until roots are able to reach the post-applied
band application of N-P 2O 5-K 2O. It is
generally agreed that transplant water fertilizer should contain a much
higher proportion of phosphate than nitrogen and potash. Some UK research
has shown that 3 gal/acre of a 7-14-7 grade liquid fertilizer mixed with
the transplant water is effective for transplant water fertilization.
As discussed under micronutrients,
molybdenum in transplant water is an efficient way of applying it when
needed (soil pH below 6.4).
Foliar Fertilization -- University
of Kentucky research has shown no value to foliar application of fertilizer
Broadcast vs. Band Fertilizer
Generally, research has shown that
only 1/2 to 2/3 as much fertilizer is required to produce maximum crop
yields when properly banded as when it is broadcast. However, the magnitude
of plant response to banding compared to broadcast applications varies
widely with soil nutrient levels, soil temperature, soil pH, and the mobility
of the nutrient being applied. Greatest benefits from banding result from
(a) applications to soils having low or very low soil test levels of the
nutrient in question, (b) applications to crops grown in cool soil, (c)
applications to either acid or alkaline soils, and (d) applications of
nutrients designated as being immobile in soil. In contrast, broadcast
and band applications have about equal efficiencies on soils with medium
to high soil test levels, neutral pH, high temperatures, and when the nutrient
is considered to be a mobile nutrient in soil. Because of the potential
for greater efficiency from banded fertilizers, banding may be one way
to lower fertilizer costs under certain conditions.
In addition to banding's potential
for more efficient nutrient use, recent University of Kentucky research
has suggested other advantages including less manganese toxicity, improved
early growth, fewer days to maturity and increased cured leaf yields (Table
9). These advantages occur primarily because the fertilizers are placed
between the rows allowing transplants to become established before roots
permeate the fertilized soil zone. High rates of commercial fertilizers
applied to tobacco soils through commonly used broadcast methods greatly
increase the salt concentration of the soil solution and decrease soil
pH 0.5 to 1.0 pH unit. Such changes in the soil may result in damage to
plant roots, cause nutrient toxicities or deficiencies and adversely affect
plant growth and yield. Banding of the fertilizer appears to alleviate
many of these problems. Research on the best system for banding continues
to proceed along several avenues.
Table 9. -- Effect of Broadcasting and Banding Fertilizer on Burley
Leaf Manganese (ppm) 45 days after transplanting
Early season growth dry wt (g/plant) of all above-ground portion of
plant 45 days after transplanting 50
Days from transplanting to flowering
Cured leaf yield (lb/A)
1 Fertilizer was placed in a band 12 in. from the row, 4
to 5 in. deep, 5 days after transplanting.
Steps in Developing a Good Fertilizer Program For Growing Burley Tobacco
1. Soil test each year immediately after
harvesting so that any needed lime, phosphate and potash can be spread
onto fields before they are disked and seeded with a cover crop.
Seed a cover crop after harvest each
year to prevent erosion and conserve soil nutrients.
Minimize the likelihood of manganese
toxicity by liming burley fields to pH 6.6 (this will prevent the normally
occurring pH drop after fertilization and plowing from getting low enough
to release large amounts of soil manganese).
Use only the amount of phosphate and
potash indicated by soil test results. Application of needed kinds and
amounts is much more important than using a specific fertilizer grade.
Time nitrogen application to soil
type. All nitrogen on well drained soils can be broadcast and disked-in
just ahead of transplanting. For soils which waterlog or percolate water
slowly, apply no more than 1/3 to 1/2 the total N ahead of transplanting
and sidedress the remainder (this minimizes fertilizer nitrogen losses
from such soils). Do not apply nitrogen fertilizer in the fall in Kentucky.
Apply molybdenum in the transplant
water on soils testing less than pH 6.4
Do not use muriate of potash on tobacco
fields after January 1 since it will result in elevated leaf chloride levels
and can lower quality.
Rotate tobacco with a sod crop (clover-grass
mixture) every two years if possible. This will help maintain good physical
condition of the soil.
Do not plow or disk fields when they
are too wet.