1. UNIVERSITY OF ZAMBIA
SCHOOL OF AGRICULTURAL SCIENCES
Department of Soil Sciences
PROGRAMME: MSc of Integrated Soil Fertility Management (ISFM)
by Charles Bwalya. Chisanga
Plant Nutrition
Nutrition of Potato (Solanum tuberosum) and Sugar-cane (S. officinarum)
24th September 2012
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2. 1. Introduction
Plant nutrition is the study of the chemical elements that are necessary for growth. According to
Westermann (2005) only relatively few chemical elements are necessary for plant growth. To be
an essential chemical element from the perspective of plant nutrition (a) it must be present for the
plant to complete its life cycle, (b) its metabolic role cannot be replaced by another chemical
element, and (c) it is directly involved in a metabolic process within the plant, either having a
direct role in the process or as a compound component involved in the process. The 16 chemical
elements that fulfill these criteria are carbon (C), hydrogen (H), oxygen (0), nitrogen (N),
potassium (K), phosphorus (P), sulfur (S), calcium (Ca), magnesium (Mg), zinc (Zn), manganese
(Mn), iron (Fe), copper (Cu), boron (B), molybdenum (Mo), and chloride (Cl). The plant obtains
C, H, and O, from air and water, while the remaining 13 are obtained from soil and fertilizer
sources. Nitrogen can also be obtained from the air by symbiotic organisms for use by legumes
and other plants. This paper discusses the nutrition and water requirements, climatic condition
and soil types of potato (Solanum tuberosum) and sugar cane (Sugar officinarum).
2 Potato (Solanum tuberosum)
The area of primary domestication for the potato is believed to be South America and
specifically in the high plateau of Bolivia and Peru around Lake Titicaca (Ministry of
Agriculture, Food and Fisheries, 1997). Haifa (2011) reported that the potato (Solanum
tuberosum) belongs to the family solanaceae which includes such other plants as tobacco,
tomato, eggplant and pepper. It is an herbaceous annual plant that grows up to 100 cm tall and
produces tubers, which are botanically thickened stems that are so rich in starch that they rank as
the world's fourth most important food crop, after maize, wheat and rice. S. tuberosum is divided
into two subspecies: andigena, which is adapted to short day conditions and is mainly grown in
the Andes, and tuberosum, the potato now cultivated around the world, which is believed to
descend from a small introduction to Europe of andigena potatoes that later adapted to longer
day conditions. It is one of the most important starchy foods in Zambia.
2.1 Climatic conditions and soil
Potato grows best on slightly to moderately acid soils although it can grow successfully in soils
with a wide pH range (Roy et al., 2006). Potato is a cool season crop that can be successfully
grown in all agro-ecological zones of Zambia. The optimum planting time is cool dry season.
Rainy season planting is possible, also in hot dry season but the production is low due to pests
and high temperature that inhibit tuberisation. Ideal soil for potato growing is deep, well-drained
and friable. On the other hand, light soils that are rich in humus are preferred for potato
production. Bohl and Johnson (2010) reported that potatoes grow well on a wide variety of soils.
In some areas where potatoes are commercially grown the soils are acid, whereas, in others they
are alkaline.
2.2 Potato nutrient requirements
Nutrition of the potato crop is characterized by its shallow rooting habit and rapid growth rate.
Therefore, high yields necessitate an adequate supply of nutrients throughout the growth period
(Roy et al., 2006). According to Ministry of Agriculture, Food and Fisheries (1997) potatoes are
heavy feeders, requiring large quantities of nutrients, partly on account of their shallow fibrous
root system and because they have to bulk up yields within a short time. The most important
nutrients for optimum growth and maxmizing yields in potatoes are high nitrogen, posphorus and
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3. potassium (Vander Zaag, 1981 and Dufour et al., 2009) and Mg. These can be met by using
manures, compost and crop rotations. Bulky organic manures and green manures have an
important place in the nutrient management of potato. Potatoes utilize both ammonium and
nitrate N, but show a preference for ammonium, especially in the early stages of growth. They
add nutrients and also improve the physical environment for better plant and tuber growth (Roy
et al., 2006). In spite of their low nutrient content, they help in fertilizer economy. It is
recommended in Zambia to apply compound “C” 2500 kg/ha, compound “V” 2000kg/ha for
poor soils and to top dress with 150 kg/ha in soils rich in phosphate and potassium. All
compound fertilizers should be applied before planting. Top dressing not exceeding 150 kg/ha
should be applied (ibid). Lack of nutrients results in retarded growth and reduced yield.
Craighead and Martin (1999) reported that a potato crop has been variously quoted as removing
approximately 3-5 kg nitrogen (N), 0.4-0.8 kg phosphorus (P) and 4-6 kg potassium (K)/tonne of
tubers (Allison et al., 1999; Perrenoud, 1983). Roy et al. (2006) reported that in potato, harvested
tubers account for 80, 83–88 and 70–78 percent of total N, P and K absorbed, respectively.
Potato plants well supplied with K have been found to withstand frost better than plants low in K
(ibid). Yields range from 15-50 t/ha for early season and seed potatoes to 40-80 t/ha for table and
process potatoes, hence there is a large variation in the nutrient demands of each crop. Lang et al
(1981) reported that nitrogen is required in large amounts to maintain optimum shoot and tuber
growth. Nitrogen may be supplied by residual soil nitrogen reserves, mineralized soil nitrogen,
nitrogen in irrigation water, and fertilizer application.
Haifa (2011) revealed that phosphorus plays a critical role in root development and overall plant
health, which is directly related to yield. However, once phosphorus levels are at concentrations
which adequately support plant health, large increases in phosphorus application rate to support
increased yields are unnecessary. For maximum tuber yields, phosphorus should be mixed into
the seed bed prior to planting to support: early shoot and root growth (stage I), tuber initiation
(stage II), and tuber bulking (stage III). Plant phosphorus levels in mid- and late-season (stages
III and IV) may be raised by applications of phosphorus using foliar sprays, application through
irrigation water, or soil applied phosphorus followed by irrigation (ibid). The daily requirements
of potato tubers during the critical bulking stage are 4.5 kg/ha N, 0.3 kg/ha P and 6.0 kg/ha K
(ibid). Potassium requirements of potato tubers during the bulking stage are very high as they are
considered to be luxury consumers of potassium (Haifa, 2011 and Ministry of Agriculture, Food
and Fisheries, 1997). Daily yield increase during the critical tuber bulking stage can reach 1000 -
1500 kg/ha/day. Therefore, it is important to supply the required plant nutrients during the tuber
bulking stage in right N-P-K ratio and in ample quantities. According to Ministry of Agriculture,
Food and Fisheries (1997) the ration of N:P2O5:K2O on normal soils may be 1:1:2 or 1:2:3.
Westermann (2005) reported that potassium and nitrogen are found in the largest amounts in a
potato plant, followed by Ca and Mg. Most of the phloem-mobile nutrients will be in the tubers
at harvest while the immobile nutrients will be in the residual vegetative portions of the plant.
Total uptake amounts are site-specific since plants generally take up more nutrients than required
if available. Nutrient uptake is nearly complete when the majority of tuber growth ends since
little additional uptake occurs during the maturation growth stage (Westermann 1993). Potatoes
require high levels of potassium in concentrations which are comparable to or greater than
nitrogen (Tindall, 1992; Tindall and Westermann, 1994; Tindall et al., 1993; Westermann et al.,
1994a). Potassium is taken up from the soil solution as the potassium ion (K+) which is
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4. replenished predominately from the exchange sites on soil colloids. Therefore, soil extracted K+
(reported in ppm) provides an index of soil potassium supplying ability.
Roy et al. (2006) reported that soil application or foliar sprays are the widely used methods for
supplying micronutrients. The micronutrient needs of potato can also be met simply by soaking
the seed tubers in nutrient solutions. The non-dormant seed tubers are soaked in 0.05-percent
micronutrient salt solutions for three hours. Dipping seed tubers in 2-percent zinc oxide
suspension is also effective for meeting the Zn needs of the crop (Grewal and Sharma, 1993).
The high seed rate of potato makes it possible to supply the micronutrient needs of the crop
through soaking. The deficiencies of Cu and Mn are controllable by soil or foliar application.
The storage life of potatoes can be reduced where there is a B deficiency. Potato cultivars can
differ markedly with regard to their sensitivity to micronutrient deficiencies.
2.3 Irrigation of potato
Haifa (2011) indicated that water requirements in potatoes vary with different stages of the crop.
Planting to emergence is a very sensitive and most risky period for a potato crop. The soil should
neither be dry nor wet, but just moist. Wet soil conditions lead to tuber decay and dry conditions
may lead to either delayed/uneven emergence or tuber decay where soil temperature is high
(ibid). During bulking up, water requirements rise sharply up to the peak (Ministry of
Agriculture, Food and Fisheries, 1997). Additionally, water requirements during this period vary
from 25-30 mm every three days on light soils and 35-40 mm every four days on heavy soils. A
day of water stress is a loss in production for good. It has been estimated that the bulking up rate
for a fully grown crop may be as high as 600-700 kg/ha per day (ibid). Insufficient or irregular
irrigation during this period leads to loss in production, misshapen tubers and growth cracks.
Excess water on the other hand, leads to enlarged lenticels or tuber decay. The water
requirements of a potato crop tapers off towards maturity. Excess water during this period leads
to poor quality potatoes. It is essential to test water used for irrigation to determine the level of
soluble salts (Haifa, 2011 and Ministry of Agriculture, Food and Fisheries, 1997).
3 Sugar-cane (S. officinarum)
Sugar cane varieties are species and hybrids of the genus Saccharum which in turn is of the
family Gramineae in the tribe Andropogoneae (Blackbwin, 1984). Sugar cane (Saccharum
officinarum L.) is a tropical, perennial grass that tillers at the base to produce multiple stems,
three to four metres high and approximately five centimetres in diameter. Its composition varies
depending upon the climate, soil type, irrigation, fertilizers, insects, disease control, varieties,
and the harvest period (Meade and Chen, 1977 and Perez, 1997). Furthermore, Blackbwin (1984)
reported that for centuries S. sinense has been grown in China and S. barberi in India, but it was
the increased planting of the noble cane, S. officinarum, which caused the sugar industry to
spread throughout the tropics and subtropics. It is thought that the S. officinarium oringinated in
the South Pacific area, probably in New Guinea.
3.1 Climatic condition, soil and water requirements
Sugarcane is grown in the world from alatitude 36.7° N and 31.0° S, from sea level to 1000m of
altitude or little more. It is considered as essentially a tropical plant and is a long duration, high
water and high nutrient-demanding crop. Sugarcane is grown under wide range of climate,
ranging from sub-tropical to tropical conditions. Temperatures above 50oC and below 20oC are
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5. not suitable for its growth. For optimum productivity it requires 750-1200 mm of rainfall during
its entire growth period. Well drained alluvial to medium black cotton soils with neutral pH (6.0
– 7.0) and optimum depth (>60 cm) are good for sugarcane growth.
Soil is as a medium for plant growth provides nutrients, water and anchorage to the growing
plants. Maintenance of proper physical, chemical and biological conditions of the soil is
necessary for realizing higher growth, yield and quality of sugarcane. Sugarcane does not require
any specific type of soil as it can be successfully raised on diverse soil types ranging from sandy
soils to clay loams & heavy clays. Sugar cane requires a well-drained, well-aerated, porous soil
with pH range of 4.5 to 8.5 (Roy et al., 2006 and Ethiopian Investment Agency, 2008). A well
drained, deep, loamy soil with a bulk density of 1.1 to 1.2 g/cm3 (1.3-1.4 g/cm3 in sandy soils)
and total porosity, with an adequate balance between pores of various sizes, is higher than 50%;
ground water table below 1.5 to 2.0 m from soil surface and an available water holding capacity
of 15% or more (15 cm per meter depth of soil is considered ideal for sugarcane cultivation).
Compacted soils (> 1.6 to 1.7 g/cm3) affect root penetration, water and nutrient uptake. The crop
is moderately sensitive to soil salinity (Roy et al., 2006). The planting pattern is dual or paired
row and spacing adopted (1.4m + 0.4m) is 0.15m under drip irrigated conditions, while sowing
depth is generally 10cm. The crop is grown by vegetative propagation and requires 40,000 two-
bud1 or 30,000 three-bud setts 2 per hectare in order to maintain a desired millable stalk
population target of 130,000/ha (ibid).
3.2 Nutrient Requirements for sugar-cane
According to Miller and Gilbert (2009) the essential elements for a healthy sugarcane crop
include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, boron,
chlorine, copper, iron, manganese, molybdenum, sulfur and zinc. Silicon, although not strictly
needed for the sugarcane plant to complete its life cycle, may enhance sugarcane production
significantly. Sugar cane suffers growth reduction under conditions of low Si availability (Roy et
al., 2006). An over-abundance of one element may cause a deficiency or toxicity of another.
Hence, there is a need for a good nutritional balance to produce the healthiest plants. Since
relatively large quantities of N, P, K, S, Mg, and Ca are needed by the plants, these are referred
to as macronutrients (Miller and Gilbert (2009). The remainders of the elements are usually
called micronutrients. Although nitrogen constitutes only a fraction of one per cent of the total
dry matter of a mature sugarcane plant, it plays an important role as C, H and O, which together,
form more than 90 percent of the dry matter. Nitrogen deficiency is common in sandy soils and it
is uncommon in organic soils. Nitrogen has the greatest influence on cane ripening of all the
nutrient elements. Sugarcane will store a higher percent of sucrose when nitrogen is limited 6 to
8 weeks prior to harvest.
According to Blackbwin (1984) sugar is a carbohydrate meaning it contains compounds of
carbon, hydrogen and oxygen. Miller and Gilbert (2009) indicated that N, P and K requirement
of sugarcane is quite large – an average of 100, 60 and 225 kg N, P2O5 and K2O per hectare is
actually used up by the crop to produce around 100 tonnes of cane yield. Nitrogen is the key
nutrient element influencing sugarcane yield and quality. It is required for vegetative growth, i.e.,
tillering, foliage formation, stalk formation, stalk growth (internode formation, internode
elongation, increase in stalk girth and weight) and root growth. Since vegetative growth is
directly related to yield in sugarcane, the role of nitrogen is paramount to build yield. Deficiency
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6. of nitrogen causes paleness of foliage, early leaf senescence, thinner and shorter stalk, and longer
but thinner roots (Gilbert, 2009 and Blackbwin, 1984). Normal cane development depends
greatly on the presence of phosphates in soluble, plant absorbable form in the soil. Phosphorus
requirement is relatively less than N and K. According to Anderson (1990) in other areas of the
world, sugarcane production may also be markedly enhanced by the application of Si. This
element qualifies as a "functional" or "beneficial" element since, in the absence of Si (Elawad et
al., 1982), the plant can still complete its entire life cycle, although production and general vigor
may be reduced. Additionally, elements that are of nutritional concern include N, P, K, Mg, B,
Cu, Fe, Mn, Si, and Zn. A deficiency or over-abundance of one or more of the above elements
may limit yields. Growers striving to produce high crop yields should pursue management
strategies that deliver a balanced supply of nutrients to the plant.
Phosphorus plays a very significant role in sugarcane production. It stimulates root growth and is
required for adequate tillering. It interacts with nitrogen and thus influences ripening. Deficiency
of phosphorus leads to reduced tillering, delay in canopy closure and thus leads to greater weed
infestation and stalk elongation is also affected (Gilbert, 2009). Potasium requirement by the
crop in general is greater than nitrogen or phosphorus. For sugar synthesis and its translocation to
the storage tissue, potassium is highly important. Potassium gives resistance to sugarcane against
pests and disease attack and lodging. It helps sugarcane under moisture stress by maintaining cell
turgidity. It has a balancing effect on both nitrogen and phosphorus.
Roy et al. (2006) observed that under Brazilian conditions, the nutrient uptake per tonne of cane
yield is as follows (IFA, 1992): macronutrients (kg): N 0.8, P2O5 0.30, K2O 1.32, MgO 0.50,
CaO 0.42 and S 0.25; micronutrients (g): Zn 4.5, Mn 11, Cu 2.0, B 2.0 and Mo 0.01. Under
Indian conditions, a crop yielding 100 tonnes of cane per hectare absorbed 130 kg N, 50 kg P 2O5
and 175 kg K2O. Even on a per-unit cane basis, nutrient uptake varies considerably depending on
the climate, cultivar and available nutrient status even at comparable yields (Hunsigi, 1993).
Sugar-cane trash is particularly rich in K (3 percent K2O) (ibid). Deficiencies of Zn, Cu and Mn
and lime-induced iron chlorosis can occur in sugar cane. These can be controlled by application
of deficient elements as their sulphate salts or chelates. Iron chlorosis can be corrected by
spraying 2.5 kg of ferrous sulphate in 150 litres of water twice at fortnightly intervals. Sugar
cane, like rice, reacts favourably to soluble silicates on some soils, which probably also releases
soil P (Roy et al., 2006). To correct Zn deficiency, soil application of zinc sulphate at a rate of 25
kg/ha can be made on coarse-textured soils (Roy et al., 2006).
4 Conclusion
Both the potato and sugar-cane require carbon, hydrogen and oxygen. Additionally, for the
potato the most important nutrients required for optimum growth and maxmizing yields are high
nitrogen, posphorus and potassium and Mg. Potatoes are heavy feeders, requiring large quantities
of nutrients, partly on account of their shallow fibrous root system and because they have to bulk
up yields within a short time. The potato is an annual crop although it can persist in the field
vegetatively from one season to the next. It is one of the most important starchy foods in Zambia.
The essential elements required for a healthy sugarcane crop include nitrogen, phosphorus,
potassium, calcium, magnesium, boron, chlorine, copper, iron, manganese, molybdenum, sulfur
and zinc. Silicon may enhance sugarcane production significantly.
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